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Reasoned fertilization practices promote fertilizers formula adjusted to the crop's needs and increase production and income. In this study, two agronomic tests were carried out on two sites named Tabligbo (site 1) and Djikame (site 2) on degraded sandy loam soils situated in the south of Togo using inorganic and organic fertilizer quantities obtained from reasoned fertilization. An indigenous variety of Abelmoschus esculentus was used and five treatments were applied: T2: mineral fertilizer (667 kg/ha), T3: waste compost (6126 kg/ha at Tabligbo and 7260 kg/ha at Dzikame), T4: mineral (333.50 kg/ha) + compost fertilizers (3063 kg/ha for site 1 and 3630 kg/ha for site 2), control (T0) and smallholder farmers' old fertilization practices (T1). At Tabligbo, treatments T2 and T4 stimulated quick growth (74,5 ± 03.50 cm) and the highest number of fruit was obtained on T4 treatment (102 ± 09). At Djikame, treatments T2 and T3 presented the highest growth (65.82 ± 2.51 cm) and the T4 treatment gave the best number of fruits (72 ± 4.00). Economic Efficiency and Cost-Value Ratio were high on the T4 formula on Tabligbo soil (53.48% and 1.85). At Djikame, treatment T2 presents the highest value of economic parameters (24.52% and 01.35). Among treatments tested, T4 (compost + mineral fertilizer) is the effective treatment on Tabligbo sandy loam soil for okra production while the T2 (mineral fertilizer) option is the best for okra production on site 2 due to the low content in nitrogen increasing C/N ratio. The effective fertilizer formulas discovered in this study will be shared with farmers in the study areas in order to improve market garden crop production in South Togo. [ABSTRACT FROM AUTHOR]

Controlled release fertilizers (CRFs) mitigate negative effects of high nitrogen (N) fertilization rates, such as N toxicity and soil N loss. However, it is unknown if potentially toxic rates of CRF and quick release fertilizer differentially affect soil bacterial communities. To examine potential N toxicity effects on soil microbial communities, we grew tomato (Solanum lycopersicum "Rutgers") for eight weeks in soils that were fertilized with high levels of quick release or controlled release urea and in soils with either low or high initial microbial N competitor populations. In both soils, we observed N toxicity in urea-fertilized tomatoes, but toxicity was ameliorated with CRF application. Controlled release fertilization increased soil N retention, thereby reducing soil N loss. While N toxicity symptoms manifested in the plant, the soil microbiome was only minorly affected. There were subtle differences in soil bacterial populations, in which nitrifying bacteria accumulated in soils fertilized at high N rates, regardless of the type of N fertilizer used. Ultimately, CRF reduced plant N toxicity symptoms but did not change the soil microbiome compared to quick release urea. These results show that while there are clear benefits of CRF regarding N toxicity tolerance on crops, the soil microbiome is resilient to this abiotic stressor. [ABSTRACT FROM AUTHOR]

In a field experiment from 2020-2023 on the southern chernozems of the Odessa region of Ukraine, we studied the effect of the doses and timing of mineral nitrogen application when growing winter peas on the tuberization process and crop productivity. Mineral nitrogen in doses of 30, 45 and 60 kg/ha in the form of ammonium nitrate was applied in different development phases of winter peas under seedbed cultivation: foliar top dressing with urea solutions during the resumption of spring vegetation, the budding phase and the beginning of grain filling. Winter pea of the Enduro variety was sown annually on October 20, with a row spacing of 15 cm and a rate of 1.2 million germinating seeds per hectare. The previous crop was winter wheat. The conditions of the Southern Steppe of Ukraine for winter sown peas were shown for the first time. The introduction of mineral nitrogen at a rate of 30-60 kg/ha into the soil during sowing inhibited the formation of nodules from the active spring growth phase. The mass of nodules on the roots of pea plants decreased by 30-50% compared to the control variant without nitrogen application. The same norms of mineral nitrogen introduced in early spring during the resumption of vegetation on the leaf in the form of aqueous solutions did not have a negative impact on tuberization. The correlation coefficient between the dose of mineral nitrogen and the number and weight of nodules did not exceed 0.37, indicating a weak relationship between these indicators. The share of influence of mineral nitrogen norms did not exceed 13.7%. With this method of application, the nitrogen content in the vegetative mass of winter peas exceeded the control variant by 18-27%. [ABSTRACT FROM AUTHOR]

Studies have been performed on the sod-podzolic medium loamy soil of the Middle Cis-Urals for determining the mineral nutrition factors to ensure obtaining the yield of the Accord rape seeds of at least 1. 50 t/ha. In 2018 - 2019, the introduction of calculated doses of nitrogen (N60-80) fractionally (½ before sowing and ½ as top dressing) in the phase of three to four leaves, followed by subsequent foliar fertilization with the ZnSO4 micronutrient fertilizer (162 g/ha) in the budding phase, helped to obtain the planned yield by increasing the rape plant stand density by 8 plants/m² and the rape plant productivity by 0. 45 g. Improvement of mineral nutrition has increased the area of plant leaves of the crops in the budding phase to 27, 000 m²/ha. With the seed yield of 1. 53 t/ha, rape has ensured the gross fat yield of 687 kg/ha and the protein yield of 320 kg/ha; it has also showed the efficiency of cultivation -- the energy efficiency coefficient of 1. 64 with the cost of 10, 413 rubles per ton of seeds. [ABSTRACT FROM AUTHOR]

Abstract The VegSyst model, initially developed for nitrogen (N) and irrigation recommendations for greenhouse-grown vegetable crops, was adapted for outdoor conditions, for lettuce, spinach and processing tomato. The major change introduced into the existing VegSyst model was to include evaporative demand, as transpiration use efficiency (TUE), as an additional determinant of dry matter production (DMP); PAR radiation being the other determinant. For daily simulation of DMP, VegSyst-Outdoors selects the smallest of the two DMP values calculated using both approaches. Data from studies conducted in different locations and years were used for calibration and validation. For lettuce, data from crops grown in California and Spain were used, for three lettuce types – Crisphead, Romaine and Batavia. One crop of each lettuce type was used for calibration. Different crops of Crisphead and Batavia lettuce were used for validation; no data were available for validation of Romaine lettuce. For spinach, calibration was conducted with data from a winter-grown crop grown in Spain, and validation was done with data from a spring-grown crop in Spain from a different region and year. For processing tomato, the calibration crop was grown in Spain, and validation was conducted with data from 10 different crops from California, Italy and Spain, and from different years. Radiation-use efficiency (RUE) values ranged from 2.1 to 2.8 g MJ−1 PAR for the three lettuce types, and were 2.2 and 2.3 g MJ−1 PAR for spinach and processing tomato, respectively. TUE was different among lettuce types, being 3.8 g kg−1 for Crisphead, 5.0 g kg−1 for Romaine, and 5.4 g kg−1 for Batavia. TUE values for spinach and processing tomato were 5.0 and 5.6 g kg−1, respectively. Following adaptation to outdoor conditions, crop DMP, crop N uptake and crop evapotranspiration (ETc) were accurately simulated in most of the validation crops. The diversity of sites and years of the crops examined demonstrated the robustness of the VegSyst model when adapted to outdoor conditions. Highlights • The VegSyst model for greenhouse crops was adapted for outdoor conditions. • Daily dry matter production (DMP) based on either TUE or RUE. • Adapted model calibrated and validated for lettuce, spinach and processing tomato. • DMP, N uptake and ETc accurately simulated in most validation crops. • Diversity of validation crops demonstrated robustness of adapted model. [ABSTRACT FROM AUTHOR]

Abstract During the past twenty years, the Nordic countries (Denmark, Sweden, Finland and Norway) have introduced a range of measures to reduce losses of nitrogen (N) to air and to aquatic environment by leaching and runoff. However, the agricultural sector is still an important N source to the environment, and projections indicate relatively small emission reductions in the coming years. The four Nordic countries have different priorities and strategies regarding agricultural N flows and mitigation measures, and therefore they are facing different challenges and barriers. In Norway farm subsidies are used to encourage measures, but these are mainly focused on phosphorus (P). In contrast, Denmark targets N and uses control regulations to reduce losses. In Sweden and Finland, both voluntary actions combined with subsidies help to mitigate both N and P. The aim of this study was to compare the present situation pertaining to agricultural N in the Nordic countries as well as to provide recommendations for policy instruments to achieve cost effective abatement of reactive N from agriculture in the Nordic countries, and to provide guidance to other countries. To further reduce N losses from agriculture, the four countries will have to continue to take different routes. In particular, some countries will need new actions if 2020 and 2030 National Emissions Ceilings Directive (NECD) targets are to be met. Many options are possible, including voluntary action, regulation, taxation and subsidies, but the difficulty is finding the right balance between these policy options for each country. The governments in the Nordic countries should put more attention to the NECD and consult with relevant stakeholders, researchers and farmer's associations on which measures to prioritize to achieve these goals on time. It is important to pick remaining low hanging fruits through use of the most cost effective mitigation measures. We suggest that N application rate and its timing should be in accordance with the crop need and carrying capacity of environmental recipients. Also, the choice of application technology can further reduce the risk of N losses into air and waters. This may require more region-specific solutions and knowledge-based support with tailored information in combination with further targeted subsidies or regulations. Highlights • The four Nordic countries have different approaches on agricultural N flows and mitigation measures. • Most countries will need new actions if National Emissions Ceilings Directive targets are to be met. • A solely voluntary and economic approach may not promote the necessary changes needed. • Tailored information and support in concert with targeted subsidies and regulations may be required. • It is important to apply the most cost effective mitigation measures. [ABSTRACT FROM AUTHOR]

Highlights • The amount of nitrogen in the substrate increases, the spawn running period of shiitake is shortened. • The yield is not directly correlated with the N, lignin, cellulose content and cellulose:lignin ratio of the substrate. • Shiitake prefers substrates containing a moderate amount of N, hemicellulose and lignin. • The N content of the substrates increases with time. • The amount of lignocellulosic content was reduces in the substrate during the life cycle of mushroom. Abstract The study assessed the changes in digestibility of some agricultural wastes such as chickpea straw (CPS), corn stalk (CS), alfalfa hay (AH) and sunflower head residue (SFH) during the spawn running period and fruitbody production of Lentinula edodes (Berk.) Pegler (shiitake) to better understand the nutritional needs of this mushroom species. In addition, the effects of these wastes on some productivity features of shiitake cultivated under laboratory conditions were evaluated. Oak awdust (OS) was used as a control substrate. The substrates were analyzed for nitrogen (N), cellulose, hemicellulose and lignin content at three different growth stages. Morever, the effect of agro-wastes on spawn run time, time to first primordia initiation, time to first harvest, yield, biological efficiency (BE) and average mushroom weight were evaluated during the cultivation cycle. Among the five substrates, the SFH exhibited maximum productivity, followed by CPS (233.7 g/kg and 228.1 g/kg, respectively). No correlation was found between the shiitake yield and the N or lignocellulosic content of the growing substrates. On the other hand, the shiitake consumed hemicellulose during the spawn running period, whereas the consumption of cellulose and lignin occured during the pinheading and fruiting formation stages. The hemicellulose, cellulose and lignin contents in the spent substrate were 36.5–51.9%, 5.3–27.0% and 24.0–36.8% lower, respectively, than in the initial substrates, while the N content in the mushroom substrate was increased by 10.3% (CS)−97.1% (OS) after shiitake cultivation. In conclusion, shiitake mushrooms had a preference for substrates containing a moderate amount of N, hemicellulose and lignin, and having a low cellulose:lignin ratio. Morever, the chemical composition of the growing substrates changed during the life cycle of the mushroom and the protein content increased with time, while the amount of lignocellulosic content in the substrates was reduced, making it more digestible. [ABSTRACT FROM AUTHOR]

Highlights • Most of the growth parameters were greater in vermiculite than in rockwool. • Dissolved oxygen concentration decreased sharply in rockwool but slightly in vermiculite. • The growth of wasabi plantlets is depressed at low dissolved oxygen concentrations. • A hydroponic system incorporates a 50% or 100% nutrient concentration and vermiculite. • The above-hydroponic system allows high-quality wasabi plantlets. Abstract The growth of wasabi (Wasabia japonica Matsumura) plantlets was compared in four concentrations of standard Enshi nutrient solution (25%, 50%, 100%, and 150%) and two kinds of supporting materials (rockwool and vermiculite) using an in vitro hydroponic culture system for photoautotrophic micropropagation. After 28 days of culture, most of the growth parameters such as fresh weight and dry weight, shoot/root dry weight ratio, and leaf area ratio were highest in wasabi plantlets grown in 50% or 100% nutrient solution, and this enhancement was greater in vermiculite than in rockwool. Dissolved oxygen concentration decreased sharply in rockwool but only slightly in vermiculite during the course of the experiment, resulting in a dissolved oxygen concentration of 8 mg L−1 in the vermiculite and 6 mg L−1 in the rockwool. The highest root nitrogen concentration was observed at a nutrient concentration of 100% in vermiculite and rockwool. The highest net photosynthetic rates were observed on day 28 in vermiculite at nutrient concentrations of 50% and 100%. The growth of wasabi plantlets is depressed through a decrease in root water and nutrient uptake caused by low dissolved oxygen concentrations. These findings clearly demonstrate that a hydroponic system that incorporates a 50% or 100% nutrient solution concentration and vermiculite will allow high-quality wasabi plantlets to be propagated rapidly under photoautotrophic conditions. [ABSTRACT FROM AUTHOR]

Herbivore damage by chewing insects activates jasmonate (JA) signalling that can elicit systemic defense responses in rice. Few details are known, however, concerning the mechanism, whereby JA signalling modulates nutrient status in rice in response to herbivory. (15NH4)2SO4 labelling experiments, proteomic surveys, and RT‐qPCR analyses were used to identify the roles of JA signalling in nitrogen (N) uptake and allocation in rice plants. Exogenous applications of methyl jasmonate (MeJA) to rice seedlings led to significantly reduced N uptake in roots and reduced translocation of recently‐absorbed 15N from roots to leaves, likely occurring as a result of down‐regulation of glutamine synthetase cytosolic isozyme 1–2 and ferredoxin–nitrite reductase. Shoot MeJA treatment resulted in a remobilization of endogenous unlabelled 14N from leaves to roots, and root MeJA treatment also increased 14N accumulation in roots but did not affect 14N accumulation in leaves of rice. Additionally, proteomic and RT‐qPCR experiments showed that JA‐mediated plastid disassembly and dehydrogenases GDH2 up‐regulation contribute to N release in leaves to support production of defensive proteins/compounds under N‐limited condition. Collectively, our results indicate that JA signalling mediates large‐scale systemic changes in N uptake and allocation in rice plants. Exogenous methyl jasmonate applications significantly inhibited N uptake in rice roots and N‐assimilating enzymes, mediated plastid disassembly, and reduced N translocation from roots to leaves. Jasmonate signalling mediates large‐scale systemic changes in N uptake and allocation in rice plants. [ABSTRACT FROM AUTHOR]

Highlights • N supply promoted broccoli growth by improving LAI, rather than RUE. • N crop demand and RUE were assessed close to 186 kg ha-1 and 3.2 g MJ-1. • 'Naxos' and 'Parthenon' were more stable than 'Ironman' between years. • Two N critical curves are proposed to be selected on the base of cultivar stem size. Abstract Adequate nitrogen (N) availability must be ensured in broccoli as it is a high N demand crop, however the N not taken up may cause ground and surface water pollution. Both species-specific growth and N demand predicting models could be useful for rational N fertilization management. Two field experiments were conducted on three broccoli cultivars grown at different N fertilization levels [0 (N 0), 75 (N 75), and 100 (N 100) kg ha−1] and under Southern Italian/Mediterranean conditions (i) to study the growth and the N uptake and (ii) to determine the critical N dilution curve for this crop. Nitrogen fertilization prompted crop growth during the linear phase (growth rate ∼9.0 g m-2 d-1 of dry weight - DW) as a result of the enhancement of the intercepted photosynthetically active radiation (IPAR) and of the efficiency in using IPAR for producing dry biomass (RUE). However, the effect of N fertilization on final aboveground dry biomass production (ADW) (∼4.6 Mg ha-1) was affected by the cultivar specific response to the seasonal variability of the temperature time course. In the 'Ironman' cultivar, N nutrition was less effective under suboptimal temperatures, in enhancing ADW and N uptake, because of the reduced leaf growth and IPAR. On the contrary, in 'Naxos' and 'Parthenon' N fertilization was more effective in limiting the effect on plant growth of the sub-optimal temperatures. Under such conditions, despite a slow reduction in IPAR, both cultivars enhanced RUE, with a concomitant increase in specific leaf N. 'Naxos' and 'Parthenon' gave higher and more stable yields, ADW, harvest index (HI) and N uptake over the two seasons. Among the N rates, the best N use efficiency in terms of yield (Partial Factor Productivity) and head dry weight gain (Agronomical NUE) per unit of applied N fertilizer, was obtained with the rate of 75 kg ha-1. At the highest N rate, ADW and yield slightly increased, with no effect on HI. Hence, this rate might be considered close to the optimal under the conditions of the experiment. Two cultivar-specific N dilution curves for broccoli have been proposed to account for the difference which emerged between' Parthenon' and the other broccoli cultivars mainly for the differences related to the proportion of stems on ADW. Both curves underline that this crop maintains a relatively high fraction of photosynthetically active tissue approaching the harvest compared to other brassicas. [ABSTRACT FROM AUTHOR]

For 50 years, UC Agriculture and Natural Resources (UC ANR) has contributed to dairy water quality policy in California and helped, with partner organizations, to implement it in the dairy industry. When conditional waivers for waste discharge requirements expired in 2003, UC ANR shared research and best professional practices as regional water quality control boards developed new orders. UC ANR academics then worked with water quality control boards' staff and dairy industry representatives to develop feasible, staged implementation plans. Collaboratively, more than 50 hours of workshop curriculum were developed and disseminated, helping dairy producers to accept scientifically sound management practices that are more protective of groundwater. Research by UC ANR to better understand system dynamics, nitrogen management and practices to minimize the impact of manure application on groundwater quality continues, as does a program in environmental stewardship. [ABSTRACT FROM AUTHOR]

A field experiment was carried out during the two successive winter seasons of 2014/2015 and 2015/2016 at a private farm in El-Tour region, South Sinai Govemorate, Egypt, to study the effect of planting dates, nitrogen sources and their interactions on dry weight, yield and its components and nitrogen use efficiency (NUE) of garlic (Balady cultivar) grown in sandy soil conditions using drip irrigation system. The obtained results could be summarized as follows: The interaction between planting dates on 15th Oct. or 1th Nov. and fertijizing plants with 100% of the recommended rate (RR) of N as poultry manure (PM) or and 50% RR ofN as ammonium sulphate (AS)+50% RR of N as PM gave the highest values of each of dry weight of bulbs, leaves, and total dry weight/plant at 135 days after planting (DAP), N and P uptake by bulbs and leaves and total uptake of them by plant. yield of grades 1,2, exportable, marketable, total yield, average bulb weight and the highest values of nitrogen use efficiency (NUE). Whereas, the interaction between planting on 15th Oct. and fertilizing plants with 50% RR of N as AS + 50% RR of N as PM gave the highest values of K uptake by bulbs and leaves as well as K total uptake by plant. [ABSTRACT FROM AUTHOR]

Nutrient loss reduction strategies have recently been developed in the U.S. Midwest to decrease the environmental footprint associated with nitrogen (N) fertilizer use. Although these strategies generally suggest decreasing N rates and shifting the timing of N application from fall to spring, the spatiotemporal impacts of these practices on maize yield and fertilizer N use efficiency (NUE, kg grain yield increase per kg N applied) have not been assessed at the watershed scale using crop simulation models. We simulated the effects of N fertilizer rate (0, 168, 190, 224 kg N ha-1) and application timing [fall-applied N (FN): 100% N applied on 1 December; spring-applied N (SN): 100% N applied 10 days before planting; split N: 66% N applied on 1 December + 34% N applied 10 days before planting] on maize grain yield (GY) across 3042 points in Illinois during 2011–2015 using the DSSAT-CERES-Maize model. When simulations were scaled up to the watershed level, results suggest that increases in average maize GY for SN compared to FN occurred in years with higher than average winter rainfall (2011, 2013), whereas yields were similar (+/- 4%) in 2012, 2014, and 2015. Accordingly, differences in NUE for SN compared to FN were small (0.0–1.4 kg GY/kg N) when cumulative winter rainfall was < 300 mm, but increased to 0.1–9.2 kg GY/kg N when winter rainfall was > 500 mm at both 168 kg N ha-1 and 224 kg N ha-1. The combined practice of reducing N fertilizer amounts from 224 kg N ha-1 to 190 kg N ha-1 and shifting from FN to SN resulted in a wide range of yield responses during 2011–2015, with the probability of increasing yields varying from <10% to >70% of simulation points within a watershed. Positive impacts on both GY and NUE occurred in only 60% of simulations for this scenario, highlighting the challenge of simultaneously improving yield and NUE with a 15% N rate reduction in this region. [ABSTRACT FROM AUTHOR]

The effects of different nitrogen application rate on the physical characteristics and anatomic structure of rice stems were investigated with rice cultivars Guangliangyou 1128 (with high resistance) and Zhunliangyou 527 (with low resistance) as materials. The results showed that, firstly, plant height, gravity center height and basal internode length of the 2 rice cultivars increased with the increase of nitrogen application rate, while wall thicknees and internode fiiling degree decreased. The breaking-resistance strength per stem and thrust-resistance strength of plants declined with the increase of nitrogen application rate. Secondly, as nitrogen input increased, the number of vascular bundles and the area of vascular bundles increased between the 2 rice cultivas. Thirdly, with the increase of nitrogen application rate, the stem section area of Guangliangyou 1128, which had strong lodging resistance, graduHy increased, while that of Zhunliangyou 527 increased firstly and then decreased. The maximum application amount of nitrogen was 240 kg/hm2. Nitrogen fertilizer mainly affected the relative gravity center height, stem WXI thicknees and internode fiiling degree of the 2 cultivars, thereby reducing the basal stem breaking resistance and plant thrust-resistance strength. [ABSTRACT FROM AUTHOR]

Use of chemical agricultural inputs such as nitrogen fertilisers (N) in agricultural production can cause diffuse source pollution thereby degrading the health of coastal and marine ecosystems in coastal river catchments. Previous reviewed economic assessments of N management in agricultural production seldom consider broader environmental impacts and uncertain climatic and economic conditions. This paper presents an economic risk framework for assessing economic and environmental trade-offs of N management strategies taking into account variable climatic and economic conditions. The framework is underpinned by a modelling platform that integrates Agricultural Production System sIMulation modelling (APSIM), probability theory, Monte Carlo simulation, and financial risk analysis techniques. We applied the framework to a case study in Tully, a coastal catchment in north-eastern Australia with a well-documented N pollution problem. Our results show that switching from managing N to maximise private net returns to maximising social net returns could reduce expected private net returns by $99 ha −1 , but yield additional environmental benefits equal to $191 ha −1 . Further, switching from managing N to maximise private returns in years with the highest profit potential (hereafter, good years ) to maximising mean social net returns could reduce expected private profits in good years by $277 ha −1 , but yield additional environmental benefits equal to $287 ha −1 . We contend that it is essential to incorporate farmer risk behaviour and environmental impacts in analyses that inform policies aimed at enhancing adoption of management activities for mitigating deterioration of the health of coastal and marine ecosystems due to diffuse source pollution from agricultural production. [ABSTRACT FROM AUTHOR]

In the Taihu region of China, overuse of chemical nitrogen (N) fertilizer is often associated with low nitrogen recovery (NRE) and leads to serious groundwater pollution caused by N leaching losses. Controlled-released nitrogen fertilizers (CRNFs) and mechanized deep placement are promising alternatives to broadcasting urea to increase crop yield and NRE in machine-transplanted rice production. However, their interactions with regard to soil N status, N leaching and crop performance are unclear. A two-year (2015 and 2016) field experiment was conducted in a randomized complete block using two fertilization techniques (broadcast and deep placement by mechanical side-dressing fertilization) and three CRNFs (sulphur-coated urea (SCU), polymer-coated urea (PCU) and a bulk blended mixture (BBF)). Conventional high-yield fertilization (four split applications of urea at 216 kg N ha −1 (CK)) and 0–N treatments were established as controls. The results showed that the variation in NH 4 + -N concentration in the percolation and surface water varied across the different CRNFs, irrespective of the techniques used. NO 3 − -N concentration in the percolation water varied with water conditions in the field. Deep placement with CRNF correspondingly increased mineral N concentration in percolation at depths of 20 and 60 cm but reduced it in the surface water compared to that of the broadcast, although the benefits varied depending on the CRNF type and growth stage. Deep placement of SCU and PCU significantly increased N leaching and the mineral N in the 40–60 cm soil layer compared to that of the broadcast, due to the intensive N release during tillering and ineffective stage when the rice plant had a weak N uptake capability. Deep placement of SCU had the highest N leaching of 6.65 and 5.34 kg N ha −1 during 2015 and 2016. In contrast, BBF exhibited the lowest N leaching, regardless of fertilization placement, which apparently synchronized N release rates with rice N uptake patterns. In the present study, BBF obtained higher rice yields and N recoveries, without significantly enhancing mineral N leaching losses, when compared to CK. Our results suggest that the use of BBF is a promising alternative to a conventional high-yield fertilization practice, especially if combined with deep placement. [ABSTRACT FROM AUTHOR]

Increasing nitrogen (N) application to croplands in order to support growing food demand is a major cause of environmental degradation. However, evaluations of suitable N application rates based on environmental benefit have rarely been carried out for paddy-rice at a national scale in China. To address this challenge, we investigated the current status of N management in 1531 counties, covering the primary agro-ecological regions of Chinese rice production in 2008, and conducted 12 field experiments with six N level practices for 3 years (2011–2013). Results showed that the highest yields for rice were 5.8–8.6 Mg ha −1 with N rates of 209.4–289.8 kg N ha −1 . Compared with the N rate for the highest yield (YHN), the environmentally optimal N rate (EnON) was lower by 20–39% and the corresponding N loss was reduced by 21–45%, while ensuring 95–99% of the highest crop yield. In China, the N inputs to paddy fields exceeded the YHN and EnON rates by 10% and 45%, respectively. After adjusting the N rate to paddy fields to the EnON rate, the N amount used in China and the corresponding N lost would be reduced by 0.9 and 0.5 Tg N yr −1 , respectively, which enable highly efficient production of food with the lowest N loss possible. Thus, we suggest that N use rates for 45% of rice paddy fields in China, for which N application rates exceed the EnON rate, need to be reduced to mitigate environmental damage, and this can be done while still meeting China’s food demand. [ABSTRACT FROM AUTHOR]

This work evaluated slow release fertilizers in basil cultivated in soil of Valle del Cauca (Colombia). A completely random design was established with 14 treatments in lysimeters and two fast liberation fertilizers (calcium nitrate and ammonium sulphate), urea coated with sulphur and two organic fertilizers (vermicompost and chicken manure) in different doses (100, 150 y 200 kg ha-1) were evaluated. At 96 days, measurements of nitrogen leached, dry mass, foliar nitrogen, pH, electric conductivity and soil organic matter were determined. In addition, apparent efficiency of recovery, internal efficiency of use and efficient use of water were calculated. The organic fertilizer caused changes in porosity, producing nitrogen leaching. The fast liberation fertilizers obtained better performance of percentage of dry mass, foliar nitrogen and efficiency of recovery, while slow release fertilizers did so in soil properties, internal efficiency of use and efficient use of water. [ABSTRACT FROM AUTHOR]

Quantification of soil organic carbon (SOC) pool fractions under different tillage systems is important in understanding SOC dynamics and storage. Two major pools of SOC that can be isolated are the light (LF) and heavy fractions (HF). Few studies have quantified the effect of tillage systems on the hydrolysable (HYF) and non-hydrolysable fractions (NHF) which comprise the HF. The objective of this study was to evaluate if there were significant changes in the quantity and δ 13 C of the HF, HYF, and NHF fractions of SOC after six years of no-tillage (NT), on arable soils that were previously under conventional tillage (CT). Our study used 13 C natural abundance (rotation of C 3 and C 4 crops) on a calcareous Typic Hapludalf soil in southern Ontario, Canada. The HF (>1.7 g cm −3 ) was isolated using density fractionation and separated into its HYF and NHF using acid hydrolysis (6 M HCl) for three soil depths: 0–10, 10–20, and 20–30 cm. The HF pool (90–93% of SOC) was significantly greater ( P  < 0.05) in the NT (28.9) than the CT system (25.5 Mg C ha −1 ) only for the 0–10 cm depth. The dominant SOC fraction from the HF pool was the NHF (62–65% of SOC) for both tillage systems. However, the HYF (25–30% of SOC) was significantly greater in the NT (9.3) than the CT system (7.0 Mg C ha −1 ) only for the 0–10 cm depth. Additionally, there was a significantly higher proportion of C 4 -derived C in the HF only at the 0–10 cm depth of NT soils. Differences in the δ 13 C of the whole soil and SOC fractions show a preservation of newly derived C in the HF, HYF and NHF of NT soils. We conclude that the adoption of NT systems on arable soils increases the quantity of HF and HYF in the 0–10 cm depth only, but there is no difference in carbon sequestration potential when treatments are compared over the 0–30 cm depth in the short-term. [ABSTRACT FROM AUTHOR]

We investigated the different functional strategies of N nutrition of cultivated and wild varieties of the legume Aspalathus linearis (N.L.Burm.) R.Dahlgren during wet and dry seasons in the Cape Floristic Region. The study addressed differences in soil and plant N cycling in cultivated and wild varieties of A. linearis . The seasonal variation in biological N 2 fixation (BNF), soil microbial activity, as well as N cycling strategies, were investigated in wild and cultivated varieties of the legume of A. linearis . Fresh leaf samples, leaf litter samples and soil samples were collected during dry and wet seasons for both cultivated and wild-growing A. linearis . Plant samples were analysed for δ 15 N and total N content. Percentage N resorption was calculated. Soil N, C, P, urease and β-glucosidase were determined directly at the rhizosphere and in bulk soil. During the wet seasons, wild plants had an increased reliance on biological N 2 fixation (BNF). This was attributed to an increase in soil microbial activity, which can lead to competition between roots and soil microbes for mineralized soil N. No trade-off between N sources in plants was found and plants tend not to rely more on BNF when microbial activity is low. Wild and cultivated A. linearis plants use different N cycling strategies, where wild plants are more reliant on biological N 2 fixation (BNF) whilst cultivated plants tend to retain N. [ABSTRACT FROM AUTHOR]

1. Compared to other plant life-forms, epiphytes remain understudied. Understanding the responses of epiphytes to changing environmental conditions is necessary to predict changes in ecosystem functioning especially in subtropical and tropical regions. 2. We investigated the functional traits of epiphytes along a large elevation gradient on Mount Kilimanjaro, Tanzania. We measured traits of co-occurring trees and terrestrial non-tree life-forms and compared changes in community-weighted means (CWM) of traits and trait spread, the range of observed trait values. We chose traits linked to growth and persistence: leaf area, specific leaf area, leaf dry matter content, stem specific density, plant height, leaf carbon, leaf nitrogen and leaf phosphorus. 3. For most traits, differences in CWM between life-forms exceeded differences within life-forms along the elevation gradient. Many CWM showed linear changes with elevation, but no response and unimodal patterns were also frequent. This was best explained by temperature, or a combination of temperature with precipitation or humidity, indicating effects of these factors on the distribution of epiphytic and non-epiphytic species. Trait spread did not change with elevation in nearly half of the traits, but hump-shaped patterns were also common, probably a result of weaker environmental filtering in the gradient centre. The magnitude of trait spread, that is, the variability between species of the same life-form within communities, was highest for terrestrial non-trees (TNT). Excluding ferns from the analyses lead to marked differences in trait patterns for epiphytes, as ferns made up 59% of the epiphytic species, while playing a minor role in the other groups. 4. The observed differences can be explained by a dichotomy in epiphytic life strategies, with tough-leaved xerotolerant species on one side and succulent soft-leaved species on the other. However, the influence of phylogeny was lower than expected from the taxonomic composition of the three life-form groups. 5. Our results emphasize that environmental constraints act upon functional traits of epiphytes, trees and TNT. The differences in trait expressions, arguably adaptations of the different life-forms, need to be taken into account in conservation contexts as well as when modelling the effects of global change on ecosystems. [ABSTRACT FROM AUTHOR]

Soybean, an important legume crop, serves as a good source of protein and oil with tremendous ability to fix atmospheric nitrogen for soil improvement. To study the genetic variability, genotypic, phenotypic and environmental coefficient of variation, broad sense heritability and genetic advance in soybean, a field experiment was conducted during Kharif 2013. The experiment, laid out in a randomized block design (RBD) with three replications, comprised of 24 genotypes and observations on 9 traits of soybean were recorded. In this experiment, analysis of variance indicated that significant variation were present among the different genotypes of the soybean for all the traits under study. The highest genotypic (GCV) and phonotypic coefficient of variation (PCV) were exhibited by the test weight, number of pods per plant, harvest index and plant height. The PCV was found higher than GCV which indicates the important role of environment in the expression of the characters. High heritability and high genetic advance were observed in the test weight, number of pods per plant, harvest index and plant height. The combination of the high heritability and high genetic advance provide the clear image of the trait in the selection process for crop improvement programme. [ABSTRACT FROM AUTHOR]

Accurate yield estimation and optimised nitrogen management is essential in agriculture. Remote sensing (RS) systems are being more widely used in building decision support tools for contemporary farming systems to improve yield production and nitrogen management while reducing operating costs and environmental impact. However, RS based approaches require processing of enormous amounts of remotely sensed data from different platforms and, therefore, greater attention is currently being devoted to machine learning (ML) methods. This is due to the capability of machine learning based systems to process a large number of inputs and handle non-linear tasks. This paper discusses research developments conducted within the last 15 years on machine learning based techniques for accurate crop yield prediction and nitrogen status estimation. The paper concludes that the rapid advances in sensing technologies and ML techniques will provide cost-effective and comprehensive solutions for better crop and environment state estimation and decision making. More targeted application of the sensor platforms and ML techniques, the fusion of different sensor modalities and expert knowledge, and the development of hybrid systems combining different ML and signal processing techniques are all likely to be part of precision agriculture (PA) in the near future. [ABSTRACT FROM AUTHOR]

Dissolved organic nitrogen (DON) is recognized as an important nitrogen (N) pool in soil N cycling, but its role in the N cycling of paddy soils, which are intensively fertilized, is not fully predicted. In this study, we investigated DON in flooded layer and soil solution along soil profiles with suction cups in fertilized paddy fields. The DON concentration showed a relative decrease in the deeper layer of paddy soil, while free amino acid N (FAA-N) exhibited a drastic increase along with nutrient profiles of soil. In the upper layer (0–20 cm), DON accounted for 54–64% of total dissolved N (TDN), but this value increased up to 63–97% in the deeper layer (40–60 cm). Low concentrations (9.6–15.0 μg L −1 ) of FAA-N and low percentage of FAA-N/DON (0.1–0.2%) were observed in the upper layer, but higher concentrations (111–307 μg L −1 ) and increased percentage (8–36%) were examined in the deeper layer. The high percentage of DON/TDN indicated that DON was the predominant N pool in the deeper layer. Concentrations of DON were significantly and positively correlated with organic matter, total N, and electrical conductivity (EC), while negatively related to soil pH. Additionally, capillary porosity, air porosity, bulk density and particle density were also found to be significantly associated with DON. We suggest the DON and FAA in the paddy field could be an important source for N leaching, which is most strongly related with soil nutrient profiles and physical properties. It is estimated that a total loss of 4.0 kg N ha −1  yr −1 is potentially linked to DON in the paddy field, which implied that ca. 3.35% of the applied N fertilizers could be lost via DON. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N) dynamics have considerable effects on the terrestrial carbon cycle, and land use changes could affect soil N through impacts on soil aggregate stability. This study selected nine sites including apple orchards of different ages and restored sites to explore the effects of soil aggregate stability on soil total N (STN), ammonium N (AN), and nitrate N (NN) following different stages of apple orchard on the Loess Plateau of China. The results showed that when compared with apple orchard sites, the restored sites had higher contents of STN and lower contents of AN and NN, but when compared with restored sites, inorganic-N storage played a more important role in the apple orchards. Following different stages of apple orchards, the STN, AN and NN contents and mean weight diameter (MWD) of soil aggregates were all improved. MWD had a negative effect on inorganic-N content at 10–30 cm soil depths but had a positive relationship with soil N at 0–10 cm soil depth. In addition, planting apple orchards destroyed soil aggregate stability in this erodible environment, but it could be restored soon after abandonment. Therefore, considering soil N and soil aggregate stability, it is feasible to plant apple trees in this area and we propose that the effects of trade-offs between soil aggregate stability and soil erosion on soil N in terraced agroecosystems should be a focus of future research. [ABSTRACT FROM AUTHOR]

Abstract: Phosphorus (P) often limits the biomass of primary producers in freshwater lakes. However, in unproductive northern lakes, where anthropogenic nitrogen (N) deposition is low, N instead of P can limit primary producers. In addition, light can be limiting to primary producers at high concentrations of coloured dissolved organic matter (cDOM), as cDOM is the major determinant of light penetration in these lakes. To address resource limitation of epilithic algal biomass, we repeatedly sampled epilithon (periphyton on stony substrata) in 20 lakes covering a large, correlated cDOM and N‐deposition gradient across boreal and subarctic Sweden. Across these lakes, pelagic total N (TN) and total P (TP) were positively correlated, and benthic light supply was negatively correlated, with cDOM. Microscopically determined algal biovolume and epilithic carbon (C), N and P were subsequently regressed against benthic light supply and pelagic TN and TP. Patterns in epilithic biovolume were driven by N2‐fixing cyanobacteria, which accounted for 2%–90% of total epilithic biovolume. Averaged over the growing season, epilithic algal biovolume, C and N were negatively related to TP and positively to TN, and were highest in the clearest, most phosphorus‐poor lakes, where epilithon was heavily dominated by potentially N2‐fixing cyanobacteria. A structural equation model supports the hypothesis that cDOM had two counteracting effects on total epilithic algal biovolume: a positive one by providing N to algae that depend on dissolved N for growth, and a negative one by shading N2‐fixing cyanobacteria, with the negative effect being somewhat stronger. Together, these findings suggest that (1) light and N are the main resources limiting epilithic algal biomass in boreal to subarctic Swedish lakes, (2) epilithic cyanobacteria are more competitive in high‐light and low‐nitrogen environments, where their N2‐fixing ability allows them to reach high biomass, and (3) epilithic N increases with N2 fixer biomass and is—seemingly paradoxically—highest in the most oligotrophic lakes. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N) fertilization is an indispensable agricultural practice worldwide, serving the survival of half of the global population. Nitrogen transformation (e.g., nitrification) in soil as well as plant N uptake releases protons and increases soil acidification. Neutralizing this acidity in carbonate‐containing soils (7.49 × 109 ha; ca. 54% of the global land surface area) leads to a CO2 release corresponding to 0.21 kg C per kg of applied N. We here for the first time raise this problem of acidification of carbonate‐containing soils and assess the global CO2 release from pedogenic and geogenic carbonates in the upper 1 m soil depth. Based on a global N‐fertilization map and the distribution of soils containing CaCO3, we calculated the CO2 amount released annually from the acidification of such soils to be 7.48 × 1012 g C/year. This level of continuous CO2 release will remain constant at least until soils are fertilized by N. Moreover, we estimated that about 273 × 1012 g CO2‐C are released annually in the same process of CaCO3 neutralization but involving liming of acid soils. These two CO2 sources correspond to 3% of global CO2 emissions by fossil fuel combustion or 30% of CO2 by land‐use changes. Importantly, the duration of CO2 release after land‐use changes usually lasts only 1–3 decades before a new C equilibrium is reached in soil. In contrast, the CO2 released by CaCO3 acidification cannot reach equilibrium, as long as N fertilizer is applied until it becomes completely neutralized. As the CaCO3 amounts in soils, if present, are nearly unlimited, their complete dissolution and CO2 release will take centuries or even millennia. This emphasizes the necessity of preventing soil acidification in N‐fertilized soils as an effective strategy to inhibit millennia of CO2 efflux to the atmosphere. Hence, N fertilization should be strictly calculated based on plant‐demand, and overfertilization should be avoided not only because N is a source of local and regional eutrophication, but also because of the continuous CO2 release by global acidification. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) play a critical role in agricultural production and cause many environmental disturbances. By combing life cycle assessment (LCA) method with the mass balance principle of substance flow analysis (SFA), this study establishes a nutrient-derived environmental impact assessment (NEIA) model to analyze the environmental impacts caused by nutrient-containing substances of agricultural production in China during 1978–2015. The agricultural production system is composed of crop farming and livestock breeding, and the environmental impacts include energy consumption, global warming, acidification, and eutrophication. The results show all these environmental impacts had increased to 8.22*10 9 GJ, 5.01*10 8  t CO 2 -eq, 2.41*10 7  t SO 2 -eq, and 7.18*10 7  t PO 4 3- -eq, respectively. It is noted the energy consumption and the climate change caused by the crop farming were always higher than those from livestock breeding, which were average 60 and two times, respectively. While the acidification and the eutrophication were opposite after 1995 and 2000, even they were similar. This was mainly due to the high N application including synthetic N fertilizer (from 1.33*10 9 GJ to 2.08*10 9 GJ), applied manure (from 4.94*10 8 GJ to 5.65*10 8  GJ) and applied crop residue (from 2.94*10 8 GJ to 5.30*10 9  GJ), while the synthetic N fertilizer was controlled and the livestock expanded rapidly after 1995. Among the sub-categories, the three staple crops (rice, wheat, and maize) contributed greater environmental impacts, which were about two to 10 times as other crops and livestock, due to their high fertilizer uses, sown areas and harvests. While the oil crops and fruit consumed the least energies because of their much lower fertilizer-use intensities. Pig and poultry especially pig also caused obvious effects on environment (even 20 times as other livestock) because of their large quantities and excretions, which emitted much higher N 2 O and P loss resulting in much higher climate change, acidification and eutrophication than other livestock. Then the study proposes the nutrient management in agricultural production by considering crop production, livestock breeding and dietary adjustment, so that some valuable experiences can be shared by the stakeholders in other Chinese regions. [ABSTRACT FROM AUTHOR]

Salinity is a common problem in arid and semi-arid regions, causing great damage to crop yields, and management strategies that reduce the effects of salt stress on plants are necessary. So, the aim of this study was to evaluate the interaction between salinity, nitrogen and phosphorus on water relations, gas exchange and chloroplastidic pigments of the West Indian cherry in the vegetative/reproductive phase transition. The cultivation was carried out in a greenhouse, in lysimeters filled with an Entisol of low phosphorus content. The experiment was arranged in a randomized complete block design, arranged in a factorial scheme with two factors, being five levels of electrical conductivity of irrigation water (ECw)(0.6, 1.4, 2.2, 3.0 and 3.8 dS m-1) and four P:N rates (100:100, 140:100, 100:140 and 140:140% of recommendation) with three replications and one plant per plot. The analysis of results indicated that the seedlings of West Indian cherry cultivar BRS 366-Jaburu, grafted on the Criolo rootstock from the EMBRAPA Agroindústria Tropical in Pacajus-CE were used. Irrigation with saline water of up to 3.8 dS m-1 does not affect the water status of the West Indian cherry. Increased salinity of irrigation water reduces gaseous exchange activity and increases the percentage of leaf cell damage in the West Indian cherry. The 40% increase over recommended level in nitrogen supply increases the synthesis of chlorophyll b and carotenoids in the West Indian cherry, when irrigated with saline water of up to 2.2 dS m-1. [ABSTRACT FROM AUTHOR]

This work aimed to evaluate the application effect of different dosages of nitrogen and potassium topdressing on mildew severity and on yield and fruit quality of melon. The three cultivars, Jangada, Gaucho Casca de Carvalho and Gaucho Redondo Cone Sul were evaluated in Cerrado (savannah) and floodplain areas. At 34 days after sowing (DAS) the topdressing treatments with different dosages of nitrogen and potassium were applied. The mildew severity estimation started at 56 DAS and was performed in five-days intervals until the harvesting of the fruits. The yield and physicochemical characteristics of the collected fruits were evaluated at harvest. There was no significative interaction among nitrogen and potassium topdressing, the cultivars and cultivated areas. However, there was significative differences when the factors were analyzed in separate. The cultivar Gaucho Redondo Cone Sul showed a significant linear increase in the area under the disease progress curve and higher productivity on cerrado compared to the remaining cultivars. The cultivar Gaucho Casca de Carvalho produced heavier and with higher °Brix fruits on cerrado. It is possible to conclude that the applied topdressings did not reduce the mildew severity in all tested cultivars, but they increased the yield in the floodplain area without modifying the physicochemical characteristics of the pulp on the evaluated melon fruits. [ABSTRACT FROM AUTHOR]

Constructed agricultural ponds and wetlands can reduce nitrogen loading from agriculture especially in areas where warm climate predominates. However, in cold climate temperature-dependency of microbiological processes have raised the question about the applicability of constructed wetlands in N removal. We measured in situ denitrification rates in a constructed agricultural pond using 15 N-isotope pairing technique at ambient light and temperature throughout a year as well as diurnally. The field IPT measurements were combined with a wide set of potentially important explanatory data, including air temperature, photosynthetically active radiation, precipitation, discharge, nitrate plus other water quality variables, sediment temperature, oxygen concentration and penetration depth, diffusive oxygen uptake and sediment organic carbon. Denitrification varied, on average, diurnally between 12 and 314 μmol N m −2  h −1 and seasonally between 0 and 12409 μmol N m −2  d −1 . Light and oxygen regulated the diel variation of denitrification, but seasonally denitrification was governed by a combination of temperature, oxygen and turbidity. The results indicated that the real N removal rate might be 30–35% higher than the measured daytime rates, suggesting that neglecting the diel variation of denitrification we may underestimate N removal capacity of shallow sediments. We conclude, that by following recommended wetland:catchment – size ratios, boreal agricultural ponds can efficiently remove nitrogen by denitrification in summer and in autumn, while in winter and in spring the contribution of denitrification might be negligible relative to the loading, especially with short residence time. [ABSTRACT FROM AUTHOR]

The excess use of nitrogen fertilizers causes many problems, including higher costs of crop production, lower nitrogen use efficiency, and environmental damage. Crop breeding for low-nitrogen tolerance, especially molecular breeding, has become the major route to solving these issues. Therefore, in crops such as barley (Hordeum vulgare L.), it is crucial to understand the mechanisms of low-nitrogen tolerance at the molecule level. In the present study, two barley cultivars, BI-04 (tolerant to low nitrogen) and BI-45 (sensitive to low nitrogen), were used for gene expression analysis under low-nitrogen stress, including 10 genes related to primary nitrogen metabolism. The results showed that the expressions of HvNIA2 (nitrite reductase), HvGS2 (chloroplastic glutamine synthetase), and HvGLU2 (ferredoxin-dependent glutamate synthase) were only induced in shoots of BI-04 under low-nitrogen stress, HvGLU2 was also only induced in roots of BI-04, and HvGS2 showed a rapid response to low-nitrogen stress in the roots of BI-04. The expression of HvASN1 (asparagine synthetase) was reduced in both cultivars, but it showed a lower reduction in the shoots of BI-04. In addition, gene expression and regulation differences in the shoots and roots were also compared between the barley cultivars. Taken together, the results indicated that the four above-mentioned genes might play important roles in low-nitrogen tolerance in barley. [ABSTRACT FROM AUTHOR]

This study exploits time, the relatively unexplored fourth dimension of gene regulatory networks (GRNs), to learn the temporal transcriptional logic underlying dynamic nitrogen (N) signaling in plants. Our "just-intime" analysis of time-series transcriptome data uncovered a temporal cascade of cis elements underlying dynamic N signaling. To infer transcription factor (TF)-target edges in a GRN, we applied a time-based machine learning method to 2,174 dynamic N-responsive genes. We experimentally determined a network precision cutoff, using TFregulated genome-wide targets of three TF hubs (CRF4, SNZ, and CDF1), used to "prune" the network to 155 TFs and 608 targets. This network precision was reconfirmed using genome-wide TF-target regulation data for four additional TFs (TGA1, HHO5/6, and PHL1) not used in network pruning. These higher-confidence edges in the GRN were further filtered by independent TF-target binding data, used to calculate a TF "N-specificity" index. This refined GRN identifies the temporal relationship of known/validated regulators of N signaling (NLP7/8, TGA1/4, NAC4, HRS1, and LBD37/38/39) and 146 additional regulators. Six TFs--CRF4, SNZ, CDF1, HHO5/6, and PHL1--validated herein regulate a significant number of genes in the dynamic N response, targeting 54% of N-uptake/assimilation pathway genes. Phenotypically, inducible overexpression of CRF4 in planta regulates genes resulting in altered biomass, root development, and 15NO3 - uptake, specifically under low- N conditions. This dynamic N-signaling GRN nowprovides the temporal "transcriptional logic" for 155 candidate TFs to improve nitrogen use efficiency with potential agricultural applications. Broadly, these timebased approaches can uncover the temporal transcriptional logic for any biological response system in biology, agriculture, or medicine. [ABSTRACT FROM AUTHOR]

Competition for nitrogen (N) and phosphorous (P) under potato-based intercropping systems decreases the level of nutrients available for potato and subsequently influences nitrogen and phosphorous use efficiency. A field trial was conducted for four consecutive seasons between 2014 short rains and 2016 long rains to assess the effect of incorporating legumes as intercrops into potato cropping systems on N and P uptake and uptake efficiency by the potato crop and nutrient use efficiency. The treatments included potato intercropped with either dolichos ( Lablab purpureus L.) (PD), garden pea ( Pisum sativum L.) (PG) or climbing bean ( Phaseolus vulgaris L.) (PB), and a pure stand of potato (PS). Intercropping potato with beans and peas significantly reduced its N uptake by 22 and 27% relative to PS, but the N uptake was not affected under PD. Phosphorous uptake was 2, 8 and 11 kg P ha −1 lower in PD, PB and PG, respectively compared with PS. Nitrogen use efficiency (NUE) was significantly higher in PD, PB and PG by 30, 19 and 9% compared with PS. Similarly, P use efficiency (PUE) was 6, 14 and 21% higher in PG, PB and PD, respectively than PS. The highest tuber yield recorded in PS (36 t ha −1 ) did not significantly differ from PD (34 t ha −1 ) whereas tuber yield was significantly lower in PB and PG as compared with PS. The study shows the great potential of dolichos as a promising intercrop that could be integrated into potato cropping systems without negatively affecting potato yield. [ABSTRACT FROM AUTHOR]

Availability of nitrogen and water are major constraints for crop yield, and their interactions are manyfold. Yield gap analysis in rainfed systems commonly uses water-limited yield potential (Y w ) as a benchmark; benchmarking against nitrogen-limited yield potential (Y N ) is less common. The aim of this study was to benchmark wheat yield against Y N in winter-rainfall regions of Australia. We established experiments, and sampled both farmers’ fields and National Variety Trials spanning wide ranges of soils, management practices, and water supply (seasonal rainfall + irrigation) from 153 to 759 mm in South Australia, and from 178 to 428 mm in Western Australia. We measured yield, quantified crop nitrogen nutrition index (NNI) at stem elongation, anthesis or both, derived boundary functions relating Y N and NNI, calculated yield gaps as the difference between Y N and actual yield, and explored the associations between yield gaps and environmental, crop and agronomic factors. In South Australia, NNI at anthesis ranged from 0.45 to 1.45 and yield from 0.9 to 8.9 t ha −1 ; in Western Australia NNI at stem elongation ranged from 0.27 to 1.16 and yield from 1.0 to 7.1 t ha −1 . Bi-linear boundary functions were fitted with a linear Y N – NNI phase up to a NNIx threshold (0.95 ± 0.134 in South Australia, 0.87 ± 0.145 in Western Australia), and a plateau reflecting yield potential (7.8 ± 0.38 t ha −1 in South Australia, 6.5 ± 0.52 t ha −1 in Western Australia). Similar bi-linear boundaries, with congruent NNIx (≈0.9), were found for grain number and shoot biomass at maturity. In South Australia, water supply explained 54% of the yield gap, which declined linearly from about 6 t ha −1 to zero with increasing water availability. Further, the yield gap correlated negatively with carbon isotope discrimination at anthesis, a direct measure of crop water status. In Western Australia, the direct association between yield gap and rainfall was weak, but there was an indirect agronomic link, where low seeding rate in low rainfall environments contributed to low biomass at stem elongation, which in turn explained a large part of the yield gap. In two out of five National Variety Trials, where the aim is comparing the yield of current and emerging varieties, crops were nitrogen deficient. This is a potential source of bias as some varieties were above and others below the NNIx threshold of nitrogen sufficiency. Supply of nitrogen in varietal comparisons needs attention. The approach advanced in this paper can be applied to benchmark yield against crop nitrogen status and identify causes of yield gaps, and for in-season quantification of crop nitrogen status to assist fertiliser decisions directly, or indirectly as a reference for spectral indices. [ABSTRACT FROM AUTHOR]

Protecting the environment and enhancing food security are among the world's Sustainable Development Goals and greatest challenges. International food trade is an important mechanism to enhance food security worldwide. Nonetheless, it is widely concluded that in international food trade importing countries gain environmental benefits, while exporting countries suffer environmental problems by using land and other resources to produce food for exports. Our study shows that international food trade can also lead to environmental pollution in importing countries. At the global level, our metaanalysis indicates that there was increased nitrogen (N) pollution after much farmland for domestically cultivated N-fixing soybeans in importing countries was converted to grow high N-demanding crops (wheat, corn, rice, and vegetables). The findings were further verified by an intensive study at the regional level in China, the largest soybean-importing country, where the conversion of soybean lands to corn fields and rice paddies has also led to N pollution. Our study provides a sharp contrast to the conventional wisdom that only exports contribute substantially to environmental woes. Our results suggest the need to evaluate environmental consequences of international trade of all other major goods and products in all importing countries, which have significant implications for fundamental rethinking in global policy-making and debates on environmental responsibilities among consumers, producers, and traders across the world. [ABSTRACT FROM AUTHOR]

Nitrogen (N) metabolism is of great economic importance because it provides proteins and nucleic acids which in turn control many cellular activities in plants. Salinity affects different steps of N metabolism including N uptake, NO3− reduction, and NH4+ assimilation, leading to a severe decline in crop yield. Major mechanisms of salinity effects on N metabolism are salinity-induced reductions in water availability and absorption, disruption of root membrane integrity, an inhibition of NO3− uptake by Cl−, low NO3− loading into root xylem, alteration in the activities of N assimilating enzymes, decrease in transpiration, and reduction in relative growth rate which results in a lower N demand. However, the effects of salinity on N metabolism are multifaceted and may vary depending on many plant and soil factors. The present review deals with salinity effects on N metabolism in plants, emphasizing on the activities of N metabolizing enzymes in a saline environment. [ABSTRACT FROM AUTHOR]

Increased cultivar tolerance to nitrogen (N) deficiency may increase productivity and reduce environmental impact of potato crops. In this study we screened 20 cultivars for the tolerance to N-deficient (0.05 mM nitrate) in comparison with N-abundant (7.5 mM nitrate) nitrate supply using plantlets grown for 15 days in a recirculating hydroponic system. Nitrogen deficiency increased the root-to-shoot ratio in 18 cultivars. Plant total dry weight (TDW) was reduced by an average of 61% under N-deficient nitrate supply. Tolerance to N deficiency was assessed as the TDW ratio (TDWR), calculated as the ratio of TDW under N-deficient to N-abundant nitrate supply. The cultivars Norland, Raritan, Nipigon and Langlade were significantly more tolerant to nitrogen deficiency (greater TDWR) than Eramosa, Carleton, and Epicure. The results indicate that the hydroponic system has capacity to rapidly screen a large number of cultivars for tolerance to N deficiency. [ABSTRACT FROM AUTHOR]

Summary: Boreal trees rely on their ectomycorrhizal fungal symbionts to acquire growth‐limiting nutrients, such as nitrogen (N), which mainly occurs as proteins complexed in soil organic matter (SOM). The mechanisms for liberating this N are unclear as ectomycorrhizal fungi have lost many genes encoding lignocellulose‐degrading enzymes present in their saprotrophic ancestors. We hypothesized that hydroxyl radicals (˙OH), produced by the ectomycorrhizal fungus Paxillus involutus during growth on SOM, are involved in liberating organic N. Paxillus involutus was grown for 7 d on N‐containing or N‐free substrates that represent major organic compounds of SOM. ˙OH production, ammonium assimilation, and proteolytic activity were measured daily. ˙OH production was strongly induced when P. involutus switched from ammonium to protein as the main N source. Extracellular proteolytic activity was initiated shortly after the oxidation. Oxidized protein substrates induced higher proteolytic activity than unmodified proteins. Dynamic modeling predicted that ˙OH production occurs in a burst, regulated mainly by ammonium and ferric iron concentrations. We propose that the production of ˙OH and extracellular proteolytic enzymes are regulated by similar nutritional signals. Oxidation works in concert with proteolysis, improving N liberation from proteins in SOM. Organic N mining by ectomycorrhizal fungi has, until now, only been attributed to proteolysis. [ABSTRACT FROM AUTHOR]

Summary: The classic model of nitrogen (N) flux into roots is as a Michaelis–Menten (MM) function of soil‐N concentration at root surfaces. Furthermore, soil‐N transport processes that determine soil‐N concentration at root surfaces are seen as a bottleneck for plant nutrition. Yet, neither the MM relationship nor soil‐N transport mechanisms are represented in current terrestrial biosphere models. Processes governing N supply to roots – diffusion, mass flow, N immobilization by soil microbes – are incorporated in a model of root‐N uptake. We highlight a seldom considered interaction between these processes: nutrient traverses the rhizosphere more quickly in the presence of mass flow, reducing the probability of its immobilization before reaching the root surface. Root‐N uptake is sensitive to the rate of mass flow for widely spaced roots with high N uptake capacity, but not for closely spaced roots or roots with low uptake capacity. The results point to a benefit of root switching from high‐ to low‐affinity N transport systems in the presence of mass flow. Simulations indicate a strong impact of soil water uptake on N delivery to widely spaced roots through transpirationally driven mass flow. Furthermore, a given rate of N uptake per unit soil volume may be achieved by lower root biomass in the presence of mass flow. [ABSTRACT FROM AUTHOR]

Due to its origin and hardiness, safflower is usually cultivated in low-fertility soils with few inputs and no irrigation. In Brazil, little is known about its response to nitrogen (N) and irrigation. This study was carried out near the city of Engenheiro Coelho, SP, Brazil, in 2014, in order to determine the effect of increasing nitrogen application rates (0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550 and 600 kg ha-1) on safflower cultivation under irrigation and rainfed conditions. The use of irrigation during drought periods allowed stress reduction and significantly increased yield components and grain yield. Safflower yield was influenced by the interaction between water regimes and nitrogen rates. Grain yield may vary depending on several factors, however, maximum yield was achieved with rates of 208 and 214 kg N ha-1 under irrigation and rainfed conditions, respectively. For oil yield, 200 kg N ha-1 were sufficient, regardless of the water regime. [ABSTRACT FROM AUTHOR]

One-year-old liners of Encore® azalea 'Chiffon' (Rhododendron sp.) were transplanted in Apr. 2013 into two types of one-gallon containers: black plastic container and paper biodegradable container. Azalea plants were fertilized with 250 mL of nitrogen (N) free fertilizer solution twice weekly plus N rate of 0, 5, 10, 15, or 20mM from ammonium nitrate (NH4NO3). All plants were irrigated with the same total volume of water through one or two irrigations daily. Plant growth and N uptake in response to N fertilization, irrigation frequency, and container type were investigated. The feasibility of biodegradable paper containers was evaluated in 1-year production of Encore® azalea 'Chiffon'. Paper biocontainers resulted in increased plant growth index (PGI), dry weights (leaf, stem, root, and total plant dry weight), leaf area, and root growth (root length and surface area) compared with plastic containers using N rates from 10 to 20 mM. Biocontainer-grown plant had more than twice of root length and surface area as plastic container-grown plant. Leaf SPAD reading increased with increasing N rate from 0 to 20 mM. One irrigation per day resulted in greater PGI, root dry weight, root length, root surface area, and root N content than two irrigations per day. Higher tissue N concentration was found in plants grown in plastic containers compared with those grown in biocontainers when fertilized with 15 or 20 mM N. However, N content was greater for plants grown in biocontainers, resulting from greater plant dry weight. The combinations of plastic container and one irrigation per day and that of 20mM N and one irrigation per day resulted in best flower production, 21.9 and 32.2 flowers per plant, respectively. Biocontainers resulted in superior vegetative growth of azalea plant compared with plastic containers with sufficient N supply of 10, 15, and 20 mM. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency of nutrient use whilst also meeting projected changes in the demand for food within China, new nutrient management frameworks comprised of policy, practice and the means of delivering change are required. These frameworks should be underpinned by systemic analyses of the stocks and flows of nutrients within agricultural production. In this paper, a 30-year time series of the stocks and flows of nitrogen (N), phosphorus (P) and potassium (K) are reported for Huantai county, an exemplar area of intensive agricultural production in the North China Plain. Substance flow analyses were constructed for the major crop systems in the county across the period 1983–2014. On average across all production systems between 2010 and 2014, total annual nutrient inputs to agricultural land in Huantai county remained high at 18.1 kt N, 2.7 kt P and 7.8 kt K (696 kg N ha − 1 ; 104 kg P ha − 1 ; 300 kg K ha − 1 ). Whilst the application of inorganic fertiliser dominated these inputs, crop residues, atmospheric deposition and livestock manure represented significant, yet largely unrecognised, sources of nutrients, depending on the individual production system and the period of time. Whilst nutrient use efficiency (NUE) increased for N and P between 1983 and 2014, future improvements in NUE will require better alignment of nutrient inputs and crop demand. This is particularly true for high-value fruit and vegetable production, in which appropriate recognition of nutrient supply from sources such as manure and from soil reserves will be required to enhance NUE. Aligned with the structural organisation of the public agricultural extension service at county-scale in China, our analyses highlight key areas for the development of future agricultural policy and farm advice in order to rebalance the management of natural resources from a focus on production and growth towards the aims of efficiency and sustainability. [ABSTRACT FROM AUTHOR]

Sowing nitrogen (N) fertilization can limit biological nitrogen fixation (BNF) reducing common bean yield. The aim of this study was to evaluate the effect of sowing N fertilization plus inoculation on the growth and yield of plants in the two seasons of cultivation in Brazil. In the dry season, N fertilization and inoculation promoted a greater shoot dry weight and higher pod number and yield than only inoculated. In contrast, in the rainy season, this treatment promoted no increase in shoot dry weight and yield compared with the inoculated alone. The number of nodules was greater for the inoculated alone treatment, but nodule weight was not affected by N fertilization in either season. Therefore, sowing N fertilization and inoculation can be an agronomic practice to achieve a higher common bean yield in the dry season, while in the rainy season, the inoculation without N fertilization can support a high yield at a lower cost. [ABSTRACT FROM AUTHOR]

The effect of nitrogen (N) application rate and sowing date on seed quality and pod production of four cultivars of okra (Abelmoschus esculentus L.) were examined. Seeds of four okra cultivars (cv. 'Boyatiou', 'Veloudo', 'Clemson', and 'Pylaias') were sown on 13 May (1st sowing) and 2 June (2nd sowing). Plants were subjected to three N levels: F1, F2, and F3 (150, 300, and 450 mg N L-1). The 2nd sowing improved flower induction and pod set, without however affecting pod size. The number of seeds per pod was not affected by sowing time, but the mean 100 seed weight was generally lower in the 2nd sowing. In all cultivars, except cv. 'Veloudo' germination increased in the 2nd sowing mainly as a result of lower seed hardness. Germination was also improved by increasing N levels, or by seed storage, acid scarification, or seed priming. [ABSTRACT FROM AUTHOR]

The current study aimed to verify the effect of the inoculant constituted by diazotrophic bacteria applied in different ways, associated to different nitrogen (N)-fertilizer doses, on the yield and N utilization efficiency of sugarcane ratoon. The use of inoculant did not affect the N content in leaves, the chlorophyll content, tiller number, stalk diameter, or any of the other assessed technological attributes. However, the use of inoculant associated to doses of 60 and 90 kg N ha-1 promoted increase in stalk yield, dry matter, and N accumulation and efficiency of N fertilizer, and, on the other hand, the association of inoculant with 120 kg N ha-1 caused reduction of these parameters. [ABSTRACT FROM AUTHOR]

Farmers, food supply-chain entities, and policymakers need a simple but robust indicator to demonstrate progress toward reducing nitrogen pollution associated with food production. We show that nitrogen balance--the difference between nitrogen inputs and nitrogen outputs in an agricultural production system--is a robust measure of nitrogen losses that is simple to calculate, easily understood, and based on readily available farm data. Nitrogen balance provides farmers with a means of demonstrating to an increasingly concerned public that they are succeeding in reducing nitrogen losses while also improving the overall sustainability of their farming operation. Likewise, supply-chain companies and policymakers can use nitrogen balance to track progress toward sustainability goals. We describe the value of nitrogen balance in translating environmental targets into actionable goals for farmers and illustrate the potential roles of science, policy, and agricultural support networks in helping farmers achieve them. [ABSTRACT FROM AUTHOR]