Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.07.005 Byline: Tessa Mills (a), Barbara Arnold (a), Siva Sivakumaran (a), Grant Northcott (b), Iris Vogeler (a), Brett Robinson (a), Cara Norling (a), Doris Leonil (c) Abstract: Pentachlorophenol (PCP) is a persistent organic pollutant (POP) previously used as a timber treatment chemical to prevent sap stain and wood rot. Commonly used in wood treatment industries for the last 50 years, there are now many sites worldwide that are contaminated with PCP. Although persistent, PCP is a mobile contaminant and therefore has a propensity to leach and contaminate surrounding environments. Both willow (Salix sp., 'Tangoio') and poplar (Populus sp. 'Kawa') growing in an open-ended plastic greenhouse were found to tolerate soil PCP concentrations of 250mgkg.sup.-1 or less and both species stimulated a significant increase in soil microbial activity when compared to unplanted controls. Both poplar and willow could not survive PCP concentrations above 250mgkg.sup.-1 in soil. Pentachlorophenol degradation occurred in both planted and unplanted pots, but a higher rate of degradation was observed in the planted pots. Soil contaminated by wood-treatment activities often contains co-contaminants such as B, Cr, Cu and As, that are also used as timber preservatives. An additional column leaching experiment, done along side the potted trial, found that PCP, B, Cr, Cu and As were all present in the column leachate. This indicates that although Cu, Cr and As are generally considered immobile in the soil, they were mobilised under our column conditions. If a contaminated site were to be hydraulically 'sealed' using plants, a reticulation irrigation system should be installed to capture any contaminant leachate resulting from heavy rains. This captured leachate can either be independently treated, or reapplied to the site. Our data demonstrate a reduction in soil hydraulic conductivity with repeated application of leachate containing PCP and metal compounds but the soil did not become anaerobic. This would need to be considered in site remediation design. Author Affiliation: (a) HortResearch, Sustainable Landuse Group, Private Bag 11030, Palmerston North, New Zealand (b) HortResearch, Ruakura Research Centre, Private Bag 3123, Hamilton, NZ (c) Universite de la Reunion, Maitrise sciences et techniques,Valorisation chimique et biologique du vegetal, Campus du Moufia, 15 avenue Rene Cassin, BP 7151-97 715 Saint-Denis messag cedex 9, France Article History: Received 16 December 2004; Revised 14 May 2005; Accepted 18 July 2005

To improve agricultural sustainability, alternative cultivation methods and assessment tools need to be developed. Integrating service crops (SC) can potentially increase cropping system multifunctionality and mitigate negative climate and environmental impacts of agriculture. (1) Calibrate oats, winter wheat and red clover SC, grown as sole crops and intercrops, in the cropping system model APSIM NG for northern Europe climate conditions. (2) Use the calibrated crop modules to assess ecosystem processes from an intercropping system. (3) Discuss the role of mechanistic crop models in assessing ecosystem services and disservices from complex cropping systems. The crops were calibrated with data from an oats-winter wheat cropping sequence at two field sites. Thirty weather datasets were created from historical weather data to generate weather-dependent variability in crop performance and related processes. The assessment compared two scenarios, with or without an intercropped red clover SC sown in oats and terminated the following spring in winter wheat. Outputs representing processes related to important ecosystem services were extracted from the simulations. Calibration of the three crops resulted in satisfactory biomass levels at the end of the growing season. Including a SC reduced oat yield, but increased winter wheat yield in two-thirds of simulations. Model outputs showed that including a SC resulted in 33–79% more fresh soil organic carbon, depending on site, compared with no SC. Nitrogen (N) uptake by both crops was highest in the SC scenario. In oats, N losses did not differ between the two scenarios, while in winter wheat the SC scenario had approximately 50% lower N leaching losses and 30% higher gaseous N emissions. However, in the fallow period from winter wheat harvest through to spring, both types of N losses were elevated in the SC scenario. The SC scenario had only a minor effect on water dynamics, causing a small reduction in soil water content. In this paper we give an example of how APSIM NG can be used to assess ecosystem services from complex agricultural systems using a case study with intercropping of cereals and leguminous SCs. APSIM NG was useful in providing a holistic assessment, and we show that intercropping with a SC can improve cropping system performance and reduce negative impacts, but long-term strategic management of N is required to prevent increased losses. To further improve simulation of intercrops more accurate simulation of early growth is needed for all crops included. [Display omitted] • Crop modules for oats, winter wheat and red clover were calibrated to simulate intercrops in Sweden in APSIM NG. • Effects of intercropping cereals (oats-winter wheat) and a legume service crop on cereals and soil processes were assessed. • Calibration resulted in satisfactory end-biomass, but poor simulation of biomass during leaf development and tillering. • Intercropping with a service crop had positive effects from an ecosystem service perspective. • Drawbacks were elevated N losses in winter wheat and fallow, indicating a need for long-term N management. [ABSTRACT FROM AUTHOR]

Highlights • A modelling approach was used to test different irrigation managements. • In a shallow soil more frequent irrigation resulted in a higher pasture production. • In deep soils pasture production was not affected by irrigation frequency. • Building up of soil water deficits in less frequent irrigation reduced N losses. Abstract While the benefits of irrigation for agricultural production are well established, the effects of irrigation management on production and environmental consequences are not well quantified. We used the APSIM (Agricultural Production Systems sIMulator) model to simulate the effect of six different irrigation management scenarios on pasture production and nitrogen (N) losses from both urine patches and non-urine affected areas using New Zealand farming systems as a test case. Nitrogen losses included nitrate (NO 3) leaching, and gaseous emissions via ammonia (NH 3) volatilisation and denitrification (nitrous oxide (N 2 O) and dinitrogen (N 2) emissions). The effects of different climate and rainfall regimes were simulated for three different soil types – deep, poorly drained (Otokia), deep, well drained (Templeton) and shallow, well drained (Eyre) soils, using 20 years of data from two climate stations with mean annual rainfall amounts of 600 and 800 mm. In the shallow soil with the least plant available water, more frequent irrigation with higher total annual amounts resulted in a significant increase in predicted pasture production compared with less frequent irrigation due to less plant water stress. However, predicted N losses through leaching, denitrification and N 2 O emissions also increased. In the deep soils pasture growth was not affected by the frequency of irrigation, whereas denitrification increased with higher frequency irrigation, especially in the poorly drained soil, leading to increased N 2 O emissions. Based on these modelling results, N losses can be reduced with little effect on production by irrigating less frequently and maintaining soil water deficits. [ABSTRACT FROM AUTHOR]

Nitrate leaching from urine deposited by grazing animals is a critical constraint for sustainable dairy farming in New Zealand. While considerable progress has been made to understand the fate of nitrogen (N) under urine patches, little consideration has been given to the spread of urinary N beyond the wetted area. In this study, we modelled the lateral spread of nitrogen from the wetted area of a urine patch to the soil outside the patch using a combination of two process-based models (HYDRUS and APSIM). The simulations provided insights on the extent and temporal pattern for the redistribution of N in the soil following a urine deposition and enabled investigating the effect of lateral spread of urinary N on plant growth and N leaching. The APSIM simulation, using an implementation of a dispersion-diffusion function, was tested against experimental data from a field experiment conducted in spring on a well-drained soil. Depending on the geometry considered for the dispersion-diffusion function (plate or cylindrical) the area-averaged N leaching decreased by 8 and 37% compared with simulations without lateral N spread; this was due to additional N uptake from pasture on the edge area. A sensitivity analysis showed that area-averaged pasture growth was not greatly affected by the value of the dispersion factor used in the model, whereas N leaching was very sensitive. Thus, the need to account for the edge effect may depend on the objective of the simulations. The modelling results also showed that considering lateral spread of urinary N was sufficient to describe the experimental data, but plant root uptake across urine patch zones may still be relevant in other conditions. Although further work is needed for improving accuracy, the simulated and experimental results demonstrate that accounting for the edge effect is important for determining N leaching from urine-affected areas. [ABSTRACT FROM AUTHOR]

To demonstrate the use of a previously developed fertilisation algorithm and to determine its potential effects on nitrogen (N) losses from grazed pastoral systems, a simulation study was performed using the Agricultural Production Systems Simulator (APSIM). The study considered a dairy system with irrigated ryegrass pasture on a silt loam soil in the Canterbury region of New Zealand. Firstly, the algorithm was parameterised for each month based on pasture yield and N contents from simulation run over 20 years using a wide range of N fertilisation rates. The algorithm was then used in the simulation of fertilisation management of a hypothetical dairy farm under different scenarios where its performance for increasing pasture yield with more efficient N use was tested. The scenarios were based on different yield targets for the proposed algorithm (50, 75, 90 or 100% of the average maximum yield) and included scheduled fertilisation to mimic more typical management. For more realistic evaluation, the simulations took into account changes in stocking rates and N flows in the farm resulting from the different fertiliser management. The simulations also considered the uneven return of urinary N by grazing animals, which are crucial to determine N losses in these systems. Both pasture yield and N losses were in general agreement with available measured data from similar systems and with comparable N inputs. Thus providing support for the simulation study as a valid way to demonstrate the potential effects of changing fertiliser management. The average of simulations run over 10 years showed that direct losses from the fertiliser were lower when the fertilisation was controlled by the proposed algorithm compared with scheduled fertilisation at similar N rates. However, with animals in the paddock and thus including the effects of urine patches, N losses were not significantly different. As there was an increase in pasture yield and consequent stocking numbers, the area receiving urinary N increased, counter balancing the increased N use efficiency when using the algorithm. Nonetheless, the larger yield lead to greater farm productivity, and this resulted in about 13% reduction in N losses per unit of milk production. [ABSTRACT FROM AUTHOR]

To investigate the potential use of diverse pasture swards to reduce nitrate leaching from intensive sheep and beef farms while maintaining economic viability, an integrated modelling assessment was conducted for the Canterbury region, New Zealand. The biophysical Agriculture Production Systems Simulator (APSIM) was used to obtain pasture growth curves for simple and diverse pastures over 10 different years, and the whole-farm system models FARMAX® and OVERSEER® were used to examine feed flow, nutrient balance, profitability, and nitrate leaching. The N leaching estimates obtained from OVERSEER® nutrient budget model ( Overseer ) were compared to estimates from APSIM. Five farm scenarios were explored, including three different proportions of the flat farm area under simple and diverse pastures (100% simple, 100% diverse, 50/50), two different stocking policies (without and with adjustment of livestock numbers), and three different years (an average, a best and a worst year, based on annual pasture yields). In the average year pasture growth was similar for the simple and diverse pasture swards, with annual pasture yields of 8.98 and 9.23 t DM/ha. The simple pasture had slightly higher growth in winter due to lower sensitivity to cold temperatures, whereas the diverse pasture showed higher growth during summer, which is frequently prone to water limitations. However, in the best year modelled pasture growth as well as profit were higher for the simple compared with the diverse pasture sward. Pasture N concentrations ranged from 2.5 to 3.5% of dry matter (DM) in the simple pasture, and from 2.2 to 3.1% in the diverse pasture sward, mainly due to a lower proportion of legumes. For the average year, having a diverse pasture on 50% of the farm area without changing the stocking policy of the farm, increased farm profit by 16%, due to the sale of surplus pasture. The total farm N leaching values predicted by APSIM, based on excretal N amounts obtained from Overseer , showed that the use of diverse pastures on 100% of the flat area decreased N leaching in an average year by 35%. In the worst year however, N leaching under the diverse pasture was slightly higher, and in the best year it decreased by 14% compared with the simple pasture. Corresponding reductions in N leaching estimated from Overseer were 6, 5 and 13% for the diverse pasture, primarily due to the lower N concentration of the diverse pasture. In contrast to APSIM, Overseer does not take into account the higher uptake of N of diverse pastures from the urine patches compared to simple pastures, which is mainly due to increased pasture growth in summer of the species included in the diverse pasture. This potential of diverse pastures to decrease N leaching needs to be evaluated via experimental studies, which should also include other aspects such as pasture persistence, and address the need for accurate model parameterisation. The modelling work also provided guidance for model refinement. [ABSTRACT FROM AUTHOR]

Catch crops have been proven effective in reducing nitrogen leaching in cropping systems due to their uptake of post-harvest soil mineral N prior to the main percolation season in winter. Information on the residual effect of catch crops, and their nitrogen fertilizer replacement value is scarce. To determine nitrogen fertilizer replacement values for different catch crops a field experiment was conducted over a four-year period on a sandy soil in Denmark, involving different catch crops and catch crop mixtures with non-legume and legume species. The residual effect of the catch crops was measured in spring barley grown in the residual year. For comparison, winter rye was also included. Over the four-year period the spring barley/fodder radish showed significantly lower leaching compared with the other catch crops, and the winter rye had the highest leaching. Regarding the residual effect, fodder radish and ryegrass, were most valuable, with nitrogen fertilizer replacement values ranging from 13 to 41 kg ha-1, based on fertilizer recovery efficiency of 50%. The process based APSIM (Agricultural Production Systems sIMulator) model was used to simulate the spring barley/catch crop rotations and the winter rye, and showed good model performance regarding N leaching and, crop yield and N uptake. The model was then run over a period of 20 years, to determine variations in N leaching and residual effects due to environmental conditions. The simulations showed that catch crops reduced N leaching by 38–64% when grown every year, and by 21–39% when grown only every second year. Nitrogen fertilizer replacement values ranged on average from 28 to 44 kg N ha-1, but showed high inter-annual variability. The nitrogen fertilizer replacement values showed only a weak relationship with the N uptake of the catch crop prior to termination, likely due to long term effects of N mineralisation from catch crop residues and pre-emptive competition for N by the catch crop. • Catch crops (CCs) were effective at reducing N leaching to or below that of the reduced N fertilizer treatment. • APSIM modelling indicates nitrogen fertilizer replacement values (NFRV) of catch crops ranging from 28 to 44 kg N ha-1. • APSIM modelling indicates that volunteers can be used as a low-cost alternative to CCs. • NFRVs showed high inter-annual variability and were not related to the CCs' N uptake. [ABSTRACT FROM AUTHOR]

Farm system and nutrient budget models are increasingly being used in analysis to inform on farm decision making and evaluate land use policy options at regional scales. These analyses are generally based on the use of average annual pasture yields. In New Zealand (NZ), like in many countries, there is considerable inter-annual variation in pasture growth rates, due to climate. In this study a modelling approach was used to (i) include inter-annual variability as an integral part of the analysis and (ii) test the approach in an economic analysis of irrigation in a case study within the Hawkes Bay Region of New Zealand. The Agricultural Production Systems Simulator (APSIM) was used to generate pasture dry matter yields (DMY) for 20 different years and under both dryland and irrigation. The generated DMY were linked to outputs from farm-scale modelling for both Sheep and Beef Systems (Farmaxx Pro) and Dairy Systems (Farmax® Dairy Pro) to calculate farm production over 20 different years. Variation in DMY and associated livestock production due to inter-annual variation in climate was large, with a coefficient of variations up to 20%. Irrigation decreased this inter-annual variation. On average irrigation, with unlimited available water, increased income by $831 to 1195/ha, but when irrigation was limited to 250 mm/ha/year income only increased by $525 to 883/ha. Using pasture responses in individual years to capturing the inter-annual variation, rather than the pasture response averaged over 20 years resulted in lower financial benefits. In the case study income from irrigation based on an average year were 10 to > 20% higher compared with those obtained from individual years. [ABSTRACT FROM AUTHOR]

Farm system and nutrient budget models are increasingly being used to inform and evaluate policy options on the impacts of land use change on regional environmental and economic performance. In this study, the common approach of up-scaling representative farm systems to a regional scale, with a limited input of resource information, was compared with a new approach that links a geospatial land resource information data base (NZLRI, Agribase™) that includes independent estimates of the productive capacity of land parcels, with individual farm-scale simulation (Farmax® Pro and Farmax® Dairy Pro) and nutrient budgeting models (Overseer®). The Southland region of New Zealand, which is currently undergoing enormous land use change, was used as a case study. Model outputs from the new approach showed increased profit of about 75% for the region if the current land area under dairying increases from 16% to 45%, with the shift to dairy constrained to high pasture production classes only. Environmental impacts associated with the change were substantial, with nitrate leaching estimated to increase by 35% and greenhouse gas emissions by 25%. Up-scaling of representative farm systems to the regional scale with limited input of resource information predicted lower potential regional profit and higher N leaching from dairy conversion. The new approach provides a farm scale framework that could easily be extended to include different systems, different levels of farming performance and the use of mitigation technologies. [ABSTRACT FROM AUTHOR]

Abstract: Elevated copper (Cu) concentrations have been shown to decrease the microbial activity in soils. Plants can have beneficial effects on the biological activity of soils mainly through their root exudates. In this study we investigated the impact of various plant species with different Cu tolerance levels on the microbial activity in two soils with low (10mg/kg) and high (180mg/kg) copper concentrations. The soil was a Kahangi Sandy Loam. Three different plants, Agrostis capillaris ‘Parys’ tolerant for Cu, Agrostis capillaris ‘Highland’ non-tolerant and Helianthus annuus tolerant and a hyper-accumulator for Cu were used. To increase the Cu availability to plants, EDTA was added to some of the pots 20days after sowing. The effect of Cu contamination on the biological activity of soil in the presence and absence of plant growth was evaluated by measuring the dehydrogenase activity, the microbial biomass, the basal respiration, and the potential nitrification. Results show that plants increased the microbial activity in the low Cu soil. In the high Cu soil the microbial activity seemed to be related to the plant health. With the Cu-tolerant Agrostis capillaris ‘Parys’, the microbial activity increased faster than with the other plant species. Up to 50days after sowing, the tolerant grass Agrostis capillaris ‘Parys’ had a higher plant biomass and was much healthier than the non-tolerant grass. Later on the growth of the non-tolerant Agrostis capillaris ‘Highland’ recovered, and the microbial activity of the soil reached close to those recorded for the soil treatments with the Cu-tolerant plant species. The addition of EDTA delayed the increase in microbial activity even further. The proportion of microbial biomass carbon in the organic fraction was higher in the low Cu soil than in the high Cu soil, with ratios ranging from 1.3 to 3.3 and from 0.5 to 1.7 respectively. The basal respiration rate in the original soil was significantly lower in the high Cu soil than in the low Cu soil, and was generally increased by the presence of plants. [Copyright &y& Elsevier]

Abstract: The use of chromated copper arsenate (CCA) treated timber posts as support structures in New Zealand vineyards has raised concerns regarding the release of heavy metal(loid)s from the treated timber into the environment. A laboratory experiment was set up to evaluate if post sealing by painting reduces the release rate of CCA metal(loid)s from timber posts. Three posts were painted (Gripset 38, Multi Purpose Bitumen Rubber) on the bottom part, submerged in freshwater, and the concentrations of copper (Cu), chromium (Cr) and arsenic (As) in the water were monitored over a period of 8 months. Three additional, unpainted posts were also used. The CCA contents in the water showed a clear difference between the painted and the unpainted posts, and painting the bottom of the posts reduced the release rate by 50–75%. To monitor the possible mobility of CCA from treated posts into grapevines further, an experiment with four-year-old grapevines planted into sixteen lysimeters was set up in a greenhouse. To half the lysimeters Cu, Cr and As were added to the soil surface at rates of 16, 20, and 12.5 mg/month from 15 November 2005 to 5 May 2006. The other lysimeters acted as a control. Soil solutions were collected at 50, 150 and 300 mm depths using suction cups after seven application of the CCA solution. The results showed that all the elements moved to a depth of 50 mm. Grape fruit, leaves and rachis were analysed for CCA metal(loid)s, but did not show any differences between the CCA-treated and control lysimeters. This indicated either that these metals were not taken up by grapevines or that their translocation from roots to the upper part of the vine was negligible. Further monitoring of CCA metal(loid)s in various parts of the grapevines, including roots, needs to be undertaken. [Copyright &y& Elsevier]

Abstract: A deterministic model for assessing the risk of groundwater contamination by nitrate from land-based sludge disposal was evaluated. A controlled large-lysimeter experiment was set up to monitor movement of nitrate through soil. Four large lysimeters of 900mm length were packed with Manawatu fine sandy loam (a Dystric Fluventric Eutrochrept), on top of which 200mm of municipal sewage sludge was applied. One of the lysimeters was planted with pasture (Lolium perenne and Festuca arundacea), one with a willow tree (Salix sp. ‘Tongoio’), another with a poplar tree (Populus sp. ‘Kawa’), and one was left bare. Bromide was used as a conservative tracer. Movement of bromide and nitrate was analysed in the effluent from the base of the lysimeters. The processes of water and nutrient transport were modelled using a mechanistic scheme based on Richards’ equation for water transport and the convection–dispersion equation (CDE) for nutrient transport. These equations were both linked to a sink term for plant uptake. The model simulated well the transport of water and movement of bromide in the four different lysimeters. The agreement between measured and simulated nitrate leaching was also reasonable considering the simplified model. Uptake of nitrogen by trees reduced the quantity of nitrogen available for leaching. The model could aid development of sustainable management of land-based sewage sludge disposal in terms of nitrate leaching. The next step will be to further develop the model for heavy metal movement, as heavy metals are common co-contaminants of sewage sludge. [Copyright &y& Elsevier]

Abstract: To study the effect of different soil tillage practices and the consequences of soil deformation on the functioning of the pore system, we performed unsaturated leaching experiments (by applying a suction of −10kPa) on undisturbed soil columns from the Ap-horizon of a luvisol derived from glacial till (agricultural site at Hohenschulen, North Germany). We compared two different tillage practices (conventionally tilled to 30cm depth, and conservational chiselled to a depth of 8cm-Horsch system) with respect to soil strength, pore connectivity and their effect on the fate of surface-applied fertilisers. The soil strength was measured by determining the precompression stress value (PCV). The conventionally tilled topsoil had a PCV of 21kPa at a pore water potential of −6kPa, while the conservation treatment resulted in a slightly higher PCV of 28kPa, suggesting a slowly increasing soil strength induced by the formation of aggregates under reduced tillage practice. The leaching experiments were modelled using the convection dispersion equation (CDE) and a modified version of the mobile–immobile approach (MIM), which included three water fractions: mobile, immobile and totally immobile water. From the CDE mobile water fractions (θ m) ranging from 47 to 67% were found, and θ m was slightly higher in the ploughed seedbed compared to the conservation-tilled one. This could be due to higher aggregation in the latter one. Dispersivities were relatively large, ranging from 44 to 360mm, but no difference was found for the treatments. The MIM could simulate the drop in concentration when leaching was interrupted, but overall did not improve the simulation, despite the larger number of fitting parameters. Compacting the soil with loads of 70kPa prior to the leaching experiment did not affect solute transport in the conservational tilled soil. In the conventional-tilled soil, however, the dispersivity decreased and the mobile water content increased compared to the non-compacted soil, suggesting that the former one is less prone to deformation by mechanical loads. [Copyright &y& Elsevier]

• Early sowing of winter cereals reduced N leaching compared with timely sowing. • Catch crops in spring barley reduced N leaching compared with bare soil. • Sowing time and catch crops did not affect grain yield or N concentration of grain. • In a wetter climate, early sown winter rye had similar N leaching as a spring barley/ryegrass. • In a drier climate, early sown winter wheat had higher leaching than spring barley/fodder radish. Sustainable management of intensively managed agricultural land requires high productivity with low environmental impacts. There is a lack of understanding concerning the effectiveness of early sowing of winter cereals compared with catch crops for reducing nitrogen (N) leaching losses. To test this, an experiment was conducted over three years (2016–2019) with different crop rotations and increasing rates of N fertilisation. The experiment was done at two contrasting sites in Denmark; one of the sites was at Foulum (FU) on a sandy loam in a wetter climate and the other at Flakkebjerg (FB) on a sandy loam soil in a drier climate. The main crops were either spring barley (SB), or winter rye (WR) at FU and winter wheat (WW) at FB. The SB received four different N fertilisation rates ranging from 0 to 200 kg N ha−1, and the winter cereals six different rates ranging from 0 to 255 for WR and from 0 to 300 kg N ha−1 for WW. In the SB treatments the soil was either left bare over winter, or sown with volunteer barley plants or catch crops. The catch crop used at FU was ryegrass, while fodder radish was used at FB. The WR and WW were either sown timely, according to common practice at the end of September or about three weeks earlier. Neither early sowing nor the use of a catch crop affected the grain yield or the grain N concentration. Nitrate leaching was reduced on both sites by early sowing and by the use of a catch crop. Early sowing of WR at FU reduced N leaching compared to timely sowing, and had almost the same N leaching as the spring barley/ryegrass rotation. At FB, early sowing of WW also reduced N leaching compared to timely sowing, but this was only significant in one of the three years, and leaching was much higher than in the spring barley/fodder radish rotation. Both early sowing of winter cereals and the use of a catch crop in spring cereals are mitigation options for reducing N leaching. [ABSTRACT FROM AUTHOR]

• the superiority of arable conventional or organic crop rotations regarding N leaching depends on the functional unit used. • organic arable crop rotations reduced the nitrate leaching loads per area significantly. • production related N leaching was 50 % lower in the conventional system. • all crop rotations exceeded the critical N load with respect to the EU-Nitrate directive threshold. • integrated approaches, which include crops with high N uptake efficiency in late autumn are needed to fulfill EU standards. Sustainable intensive agriculture requires enhanced nitrogen use efficiency and reductions in nitrogen (N) leaching losses. To investigate if organic farming systems have potential to achieve this, a comparison between conventional and organic arable farming was carried out over a two-year period. Two differently managed specialized organic arable crop rotations (low N-intensive (Ol), semi -N- intensive (Os)), and a typical N-intensive conventional crop rotation (Ch) were studied. The study was done under commercial farm scale conditions covering close to 400 ha in total (5−23 ha field sizes) in a highly productive arable region on fertile soils in northern Germany. Nitrogen leaching losses were measured using ceramic suction cups. Two functional units were used as indicators for eco-efficiency: N losses per area and per unit of grain equivalent (GE) produced. Results revealed that organic arable crop rotations reduced the nitrate (NO 3 -N) leaching loads per area significantly, with losses (kg NO 3 −-N ha-1 a-1) of 22.0 in Ol, 24.4 in Os and 35.1 in Ch. In contrast, when using the functional unit 'nitrate leaching per grain equivalent' as an indicator for eco-efficiency the conventional system resulted in 50 % lower N leaching loads per GE. This was due to the much higher land use efficiency of the conventional system (115 GE ha-1 vs 36 GE ha-1 for Ol and 38 GE ha-1 for Os), which resulted in N leaching losses (kg NO 3 -N GE-1) of Ch 0.32 for Ch, 0.64 for Ol, and 0.66 for Os. Regarding EU-Nitrate directive threshold for drinking water of 11.3 mg NO 3 -N l-1, all crop rotations exceeded the critical load. For the various main crop/preceeding crop sequences, the soil mineral N content at the end of the vegetation period and the autumn N uptake were the best predictors for N leaching, whereas for the aggregated effect across the various crop rotations within a farm system the N balance was the best descriptor. Considering N leaching loads our results show that both, specialized arable conventional and organic farming systems fail to meet the requirements of given environmental standards for water protection in the EU. This suggests that integrated approaches beyond such specialised systems are necessary, which are based on a balanced combination of forages (with two year leys), catch crops and cash crops. [ABSTRACT FROM AUTHOR]

Under favorable growth conditions cover crops are efficient tools to scavenge available nitrogen in the soil after the main crop and reduce nitrate leaching. However, their ability to reduce nitrate leaching is influenced by the available growth conditions after sowing and their characteristics to assimilate biomass and nitrogen (N). A flexible sowing time of cover crops without compromising their benefits to the environment implies knowledge of how the growth conditions after sowing of the cover crop affect leaching. Fodder radish, phacelia, and oats have different growth and N uptake characteristics, and their ability to reduce nitrate leaching depending on growth conditions after sowing may therefore differ. In this study, these three cover crops were evaluated, and their ability for taking up soil N and reducing nitrate leaching was quantified based on four sowing times from early August to early September with intervals of 7–11 days in 2019, 2020, and 2021 in Denmark. N uptake was measured in autumn each year and nitrate leaching measurements took place during the drainage period until the following spring. The N uptake decreased with subsequent sowing times across the cover crops and years. However, the decrease was different in different cover crops and different years. Nitrate leaching reduction also decreased with subsequent sowing times. On average, fodder radish reduced nitrate leaching by 64 kg N ha-1, significantly more than phacelia and oats with 47 and 44 kg N ha-1, respectively, across all sowing times and drainage periods. With an average reduction of nitrate leaching of 0.8 kg N ha-1 per day and no interaction of N uptake and cover crops, the ability of fodder radish, phacelia, and oats to reduce nitrate leaching was not significantly different. Fodder radish and early sowing was the most effective combination to obtain the maximum benefits of nitrate leaching reduction by a cover crop. • Delayed sowing time decreased the ability of cover crops to reduce nitrate leaching. • Nitrogen uptake differed in cover crops based on sowing time. • Nitrate leaching reduction was similar in cover crops based on the sowing time. • Average reduction per day with sowing time was same in cover crops. • Fodder radish and early sowing was an effective combination to reduce most leaching. [ABSTRACT FROM AUTHOR]

The relationships between dynamics and plasticity (ability of a hybrid to modulate its traits according to growing conditions) of agronomic and nutritional traits are unclear. Quantifying and characterizing these relationships can improve understanding of plant response mechanisms to growing conditions in short cropping periods at high latitudes. This study investigated the dynamics of key agronomic performance and forage quality traits and the importance of their mean values for expression of plasticity. Data were collected on eight sampling occasions during the cropping period in 2013 and 2014, using six phenologically different forage maize hybrids grown at three high-latitude locations. The dynamics of all traits studies were significantly affected by hybrid and environment (combination of location and year). Dry matter yield (DMY) and dry matter content (DM) were affected by interactions between hybrid, growing conditions on each sampling occasion, and overall growing conditions in the different environments. Neutral detergent fiber digestibility (NDFD), starch (STA) concentration, water-soluble carbohydrate (WSC) concentration, and organic matter digestibility (OMD) in the hybrids differed significantly over time across the environments. Early-maturing hybrids progressed faster in maturity based on DM content and had higher STA concentration, NDFD, and OMD at a given time than later-maturing hybrids. Similar DMY and higher NDFD and OMD in early-maturing compared with later-maturing hybrids, regardless of sampling occasion or environment, suggests that use of early-maturing hybrids is advantageous in the short cropping season at high latitudes. For most traits, plastic ability [plasticity of trait x/mean value of trait x, or ability to change expression of plasticity of a trait is based on the mean value of the trait] was dependent on the mean value of a trait and declined with increasing mean value. Plastic ability of DM, DMY and STA was higher at early developmental stages and decreased at later developmental stages, but the opposite was true for WSC and CP. Although the dynamics of trait development over time differed between the hybrids, the dynamics of plastic ability for four traits (DM, WSC, OMD, NDF) were similar in all hybrids. These maturity characteristics-based responses of the six hybrids in terms of trait dynamics and plastic ability, and the dependence of plastic ability on the dynamics of corresponding trait, can potentially be exploited in development of new variety/hybrid and prediction models for further improving the agronomic and nutritional value of forage maize crops at high latitudes. • Hybrid and environment affected dynamics of agronomic and nutritional traits. • Early maturing hybrids grew faster and had higher key nutritional trait quality. • Most plastic abilities were dependent on the mean dynamics of corresponding traits. • Hybrids had similar plastic abilities for half of the studied traits. • But they differed for the mean dynamics of the corresponding traits. [ABSTRACT FROM AUTHOR]