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The storage of carbon (C) in cultivated soils can be increased with the adoption of different practices. The objective of this study was to determine soil organic carbon (SOC) storage in the 0‐ to 90‐cm depth profile, in four different soil layers (0–15, 15–30, 30–60 and 60–90 cm) in a long‐term (29 years) experiment established in 1986 on a rainfed Mediterranean Vertisol in southern Spain. The treatments studied were: conventional tillage (CT) versus no‐tillage (NT); five 2‐year crop rotations (wheat–chickpea, wheat–sunflower, wheat–bare fallow, wheat–faba bean, and continuous wheat; and nitrogen (N) fertilizer applied to wheat at four rates (0, 50, 100 and 150 kg N ha−1). The SOC accumulation was higher in the 30–60‐cm layer (9.2 Mg ha−1) due to the size of the characteristic cracks of Vertisols under semiarid conditions. Over the 29‐year study period, the SOC in the 0–90‐cm layer increased by 23.6 Mg ha−1 due to the change in residue management. The NT treatment exhibited a higher mean annual rate of organic C accumulation compared with the CT treatment (1.0 and 0.66 Mg ha−1 year−1, respectively) due to the retention of the mulched residue. Additionally, crop rotation influenced the rate of organic C accumulation, with wheat‐faba bean, wheat‐sunflower and continuous wheat exhibiting the highest levels of C storage in comparison to the other treatments. In rainfed Mediterranean agriculture, the selection of no‐tillage along with a rotation with legumes is key to improving soil fertility and increasing C reserves and the rate of C accumulation by soil. Highlights: The SOC increase over the 29‐year study period was 23.6 Mg ha−1 in the 0–90‐cm soil profile.The characteristic cracks of Vertisol increase SOC stocks in deeper soil layers.No tillage accumulated 66.2% more SOC than conventional tillage in the 0–90‐cm profile.The wheat–sunflower rotation had the highest annual rate of C sequestration (1 Mg ha−1 year−1) and wheat–chickpea the lowest (0.6 Mg ha−1 year−1) over 29 years. [ABSTRACT FROM AUTHOR]

The objectives of this review are to analyse the potential of bioenergy crops development in European agriculture and to identify research objectives based on transformation technologies. Bioenergy is the chemical energy stored in organic material, which can be directly converted into useful energy sources by biological, mechanical or thermochemical processes. The substitution of food crops with energy crops and the demand for agricultural raw materials for liquid biofuel production will affect agriculture over the next decade and possibly beyond. It is expected that both second-generation biofuel production technology and energy crops used will be more efficient than first-generation. Nonetheless, there are still technical limitations for crop growth and fuel production from second-generation technology. In general, many of the crops that could supply the raw materials for second-generation biofuels are largely undomesticated and are in the first stages of development and management. The development of specific crops dedicated to energy has been proposed as a strategy to produce energy without affecting food security and the environment. The research seeks to develop enzymatic systems for the cost-efficient decomposition of cellulose into its molecular sugar components, which can then be fermented to produce ethanol. This biorefinery of crops into multiple products, including energy, chemical products and materials, will augment the overall value of the biomass. Clearly, multidisciplinary research is necessary to address sustainable biofuel production. [ABSTRACT FROM AUTHOR]

Highlights: [•] No-tillage registered higher water content in the soil at sowing than in conventional tillage. [•] Grain yield improved with no-tillage system. [•] Water use was superior in the no-tillage system than in the conventional tillage. [ABSTRACT FROM AUTHOR]

Abstract: Excessive application of fertiliser in agriculture can have detrimental effects, one of which is diffuse contamination with nitrates. An 18-year field study was conducted on a typical rainfed Mediterranean Vertisol to determine the effects of the tillage system, crop rotation and N fertiliser rate on the long-term NO3 −-N content in the soil profile (0–90cm). The experiment was designed as a randomised complete block with a split-split plot arrangement and 3 replications. The main plots tested the effects of the tillage system (no-tillage and conventional tillage); the subplots tested crop rotation, with 2-year rotations (wheat–wheat, wheat–fallow, wheat–chickpea, wheat–faba bean and wheat–sunflower); and the sub-subplots tested the N fertiliser rate (0, 50, 100 and 150kgNha−1). The nitrate content increased with time. The tillage system showed an inconsistent effect on nitrates, although, overall, nitrate levels were higher under conventional tillage than with no-tillage. The wheat–faba bean rotation induced a larger accumulation of soil nitrates. Nitrates usually accumulated to a greater extent in the 30–60-cm depth of soil. As a rule, farmers should know the amount of residual N existing in the soil prior to crop fertilisation in order to avoid over-fertilisation. [Copyright &y& Elsevier]

Abstract: The application of an adequate rate and splitting of nitrogen (N) is essential for the efficient use of N fertiliser and to maintain the economic sustainability of cropping systems. A 3-year field experiment was conducted on a Vertisol under Mediterranean conditions to determine the effect of tillage systems, crop rotation, and variations in N timing on the grain yield and N recovery of 15N-labelled fertiliser (N R) in hard red spring wheat (Triticum aestivum L.). The experiment was designed as a randomised complete block with a split–split plot arrangement and 3 replications. The main plots were tillage system (no-tillage [NT] and conventional tillage [CT]), and the subplots were the preceding crop with 2-year rotations (wheat–sunflower [WS], wheat–chickpea [WC], and wheat–faba bean [WFB]). Sub-subplots were the N timing (all at the same rate of 100kgNha−1), and the fertiliser was applied 50% at sowing and 50% at stem elongation and 50% at tillering and 50% at stem elongation. The area of each basic plot was 50m2 (5m×10m). The residual NO3–N content (0–90cm) was significantly higher in CT than in NT, the opposite occurring with grain yield. The N R of NT was greater than that of CT. According to the previous crop, the N R was WS>WFB=WC. The soil nitrate content was twice as much when the preceding crop was a legume compared with sunflower and the wheat yields were as follows: WFB>WC>WS. Although the N timing did not have an effect on overall grain yield, the interactions with year, tillage system and previous crop were significant. The average recovery of 15N fertiliser by wheat was 44.6%, with 33.7% obtained in the grain (41% in stem elongation, 32% in tillering and 27% in sowing). The habitual use of high rates of N fertiliser and the frequency of dry years in the agrosystem studied generated a progressive accumulation of residual in the soil profile. This can represent an important source of mineral N for the cereal and can reduce the need to apply N fertiliser to the crop. [Copyright &y& Elsevier]

Abstract: A well-developed root system is crucial for plant growth, especially under dryland farming conditions. A two-year field study (2003–2004 and 2005–2006) was conducted to determine the effects of the tillage system on root growth in chickpea (Cicer arietinum L.) grown in continuous rotation with wheat (Triticum aestivum L.) on a typical Vertisol in southern Spain as part of the long-term “Malagon” experiment begun in 1986. The tillage treatments were either no tillage (NT) or conventional tillage (CT), and the experiment was designed as a randomized complete block with three replications. Both soil cores and a minirhizotron were used to evaluate the root system. Measurements of the root parameters were performed at different depths and included the following: root length, root biomass, root nitrogen and root length density. Root length measurements were performed during five chickpea growth stages. The CT was more favourable than NT for chickpea root development (0.34mmcm−3 versus 0.18mmcm−3), which is one of the factors that induced higher yields during the drier year. The nitrogen content of the roots represented 15% of the total N extracted by the plant. The measured root lengths were larger when using the soil core method than with the minirhizotron (2.5mmcm−3 versus 1.3mmcm−3), which can be attributed to the cracks that occur in Mediterranean Vertisols that can separate the tube from the soil, resulting in the underestimation of the root length. [Copyright &y& Elsevier]

Abstract: Nitrogen fertilization is a key factor of the aesthetics and playability for golf greens. Nitrogen fertilization management is based on predetermined scheduled applications, set rates, or expected improvement in visual quality and green speed. As a consequence, the objective of this study was to obtain seasonal N application models (algorithms) based on remote sensing, optimizing playability and aesthetic quality. A 3-yr field study under Mediterranean conditions was conducted on an experimental ‘L-93’ creeping bentgrass (Agrostis stolonifera L.) USGA green, to examine effects of seasonal N fertilizer rates on color, clipping yields, and ball roll (green speed). The remote sensors used were a digital camera and reflectance meter (FieldScout CM1000 Chlorophyll Meter). From digital photographs, a dark green color index (DGCI) was calculated. All data were normalized (relative). For all seasons, a third-order polynomial response model was the best when using a CM1000 and a digital camera. Clipping yields and ball roll regressions were linear, increasing and decreasing when the N fertilizer rate increased, respectively. Ball roll and clipping relative values were correlated with both sensors. To fit a seasonal optimum N fertilizer rate model as a function of remote sensors and the other measured parameters, the intersection of models obtained from relative values of CM1000 and digital camera with ball roll and clipping was calculated, but ball roll was considered the most suitable. The model of the digital camera with automatic settings was less accurate and underestimated the optimum N rate. However, because the actual values of digital camera and CM1000 were correlated, converting DGCI values and applying CM1000 models enabled the obtaining of practically the same N fertilizer applications. A practical application procedure of these seasonal models for an entire golf course was also shown. Actual N recommendation applications with a quick remote diagnosis (CM1000) for creeping bentgrass golf green are feasible under similar management practices in Mediterranean environments. A digital camera can also be used successfully, but it should be better when its analysis is based on CM1000 models. [Copyright &y& Elsevier]

Abstract: Efficient management of legumes in order to maximize benefits depends on a correct field assessment of N2 fixation. A field experiment was conducted during a 6-year period (2001–2002 to 2006–2007) in Córdoba (Southern Spain) on a rainfed Vertisol within the wheat-chickpea and wheat-faba bean rotation framework of a long-term experiment started in 1986. The aim was to determine the effect of tillage systems [no tillage (NT) and conventional tillage (CT)] on chickpea and faba bean N2 fixation. Fixation was calculated using the 15N isotopic dilution (ID) and 15N natural abundance (NA) methods with the reference being the wheat crop. The strong inter-annual rain variation caused great differences in the behaviour of both leguminous plants with regard to grain yield, nodule biomass and N2 fixation. The NT system showed more nodule biomass than the CT system in both legumes. The ID method was more accurate than the NA method in determining N2 fixation. The average amount of fixed N in faba bean (80kgha−1 year−1) was much greater than that in chickpea (31kgha−1 year−1). The Vertisol under the NT system offered more favourable conditions for the stimulation of the N2 fixation, with fixed N values that were significantly higher than under CT. The N added to the system through N2 fixation was low in faba bean and virtually nonexistent in chickpea, only in terms of above-ground biomass. [Copyright &y& Elsevier]

Abstract: Studies on the growth of faba bean (Vicia faba L.) root systems in Vertisols under Mediterranean climates are practically non-existent. A three-year field study (2003–2004, 2005–2006 and 2006–2007) was conducted on a typical Vertisol (in southern Spain) to determine, using a minirhizotron system, the effects of tillage on root growth in faba bean grown in continuous rotation with wheat (Triticum aestivum L.) as part of the long-term “Malagón” experiment that started in 1986. Tillage treatments were no-tillage (NT) and conventional tillage (CT). The parameters measured were root length (RL), root diameter (RD), root biomass (RB), seed yield and aboveground biomass. Root growth measures with minirhizotron were carried out at six soil depths for five growth stages throughout the faba bean growing season. For the calculation of RB, soil cores were collected during flowering from the same six soil depths. NT was more favorable for the development of the faba bean root system when compared with CT. This can be attributed to improved physical properties of the soil under NT, which improves the water conditions of the soil. [ABSTRACT FROM AUTHOR]

Abstract: The quantification of the below-ground N of legumes is a key to understand its effect on soil N fertility and the N economy of subsequent legume-based rotations. Significant amounts of the N fixed by legumes are incorporated into the soil as fallen leaves and stems. However, the N from roots, nodules and root exudates has rarely been quantified under field conditions, nor have the management effects been evaluated. This study measured the effects of tillage system [no-tillage (NT) and conventional tillage (CT)] on N rhizodeposition in faba bean (Vicia faba L.) and chickpea (Cicer arietinum L.) during a 3-year period (2003–2004, 2005–2006 and 2006–2007) in a Vertisol under rainfed Mediterranean conditions. Faba bean and chickpea plants were labelled in situ with 15N using stem feeding and leaf feeding, respectively. NT increased the N derived from rhizodeposition (NdfR) with respect to CT (135 vs. 68kg Nha−1 in faba bean and 115 vs. 97kg Nha−1 in chickpea). Such differences between tillage methods can be attributed to the more favourable conditions for root growth produced by NT. NdfR was significantly influenced by depth; in faba bean, the greatest amount (70%) was found in the 0–30cm layer, whereas in chickpea, 41% of the NdfR was concentrated in the 30–60cm depth. The 54% and 61% of total plant N was NdfR (in faba bean and chickpea, respectively) representing 90% of the below-ground plant N in both crops. Our results show that the N derived from rhizodeposition is an important source for N balance and is a key to soil fertility in rain-fed Mediterranean cropping systems. [ABSTRACT FROM AUTHOR]

Abstract: The determination of the technological quality of bread wheat (Triticum aestivum L.) requires a strong investment of time and money on behalf of the flour industry. For this reason, a field experiment was carried out over a 2-year period on a Vertisol under rainfed Mediterranean conditions with the objective of predicting, during the growing season, the technological quality of wheat at harvest with the use of a chlorophyll meter (Minolta SPAD 502). The SPAD meter readings were taken at the start of stem elongation and at anthesis determining the grain yield, alveogram parameters and gluten content at harvest. The chlorophyll meter readings at both growing stages were related to the grain protein content, alveogram index (W), dough extensibility (L), tenacity–extensibility ratio (P/L) and gluten content values. Dough tenacity (P) was not related to the readings. The models were validated by the full cross-validation method, showing better reliability at anthesis than stem elongation. The grain yield was correlated separately for each year, due to the influence of rain variability on the grain yield. Under rainfed Mediterranean conditions, the SPAD meter is a very useful tool in predicting the technological quality of bread wheat in advance, eliminating the need for expensive instruments and, above all, reducing the analysis time dedicated to determining the technological quality. [Copyright &y& Elsevier]

Abstract: A field experiment was conducted during a 2-year period (2001–2002 and 2002–2003) in Córdoba (Southern Spain) on a rainfed Vertisol, within the wheat-faba bean rotation framework of a long-term experiment started en 1986, to determine the effects of tillage systems [no tillage (NT) and conventional tillage (CT)], on faba bean N2 fixation. Fixation was calculated using the 15N dilution and 15N natural abundance methods using wheat as reference crop. Nitrogen derived from the atmosphere (Ndfa) percentages ranged between 70 and 96%, and N2 fixed between 39 and 144kgNha−1. The N balance was positive for all years and treatments, with a mean value of 18.3kgNha−1 and a maximum of 40kgNha−1, in terms of above-ground biomass only. No significant difference was recorded between faba bean N2 fixation values as calculated by the 15N enriched (ID) method and the 15N natural abundance (NA) method. The effect of tillage system on %Ndfa and the amount of N2 fixed was not significant, possibly due to the negligible difference in soil NO3 −–N content between the two systems. [Copyright &y& Elsevier]

Abstract: A 3-year field experiment in rainfed Vertisol was designed to study the effects of timing and splitting of N fertilizer on the efficiency of nitrogen in wheat (Triticum aestivum L.). A single rate of 150kg Nha−1 was used, different fractions being applied at sowing, tillering and stem elongation. The experiment was designed as a randomized complete block with four blocks. At the same time, a 15N experiment was conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat use of N fertilizer ranged from 14.1% when applied at sowing to 54.8% when applied as a top dressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 152kg Nha−1, representing a considerable proportion of total wheat N uptake, ranging from 83.2% when N fertilizer was applied in the fall to 49.4% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. Application of N fertilizer to wheat preferably as a top dressing, between tillering and stem elongation, is a strategy to be recommended from the standpoint both of the environment and of farmer returns. [Copyright &y& Elsevier]

Nitrogen (N) uptake is the first step in nitrate assimilation, and efficient N uptake is essential for plant growth, especially for protein biosynthesis and photosynthetic activities. In cereals, improved N uptake is closely coupled with an increase in nitrogen use efficiency (NUE) and yield improvements. Because wheat ( Triticum aestivum L.) is a leading crop worldwide, a better understanding of N uptake regulation in wheat is vital to improving NUE and developing sustainable agricultural systems. However, detailed information regarding the biological mechanisms that are responsible for the more efficient uptake of ambient N by wheat is limited. This review presents recent developments in the biological mechanisms of N uptake in wheat, including plant growth regulations, fundamental roles of root systems, interactions between N species, and genetic controls. Specifically, this paper provides a number of potential strategies that can be used to increase wheat N uptake. The information provided here may guide N fertilizer management during wheat production and further elucidate the plant regulatory mechanisms that are involved in N uptake, which can thereby increase wheat NUE. [ABSTRACT FROM AUTHOR]

Abstract: Semiarid Mediterranean climatic conditions and intensive tillage systems accelerate soil organic matter losses. Therefore, assessing agricultural practices that enhance storage of soil organic matter is needed. Stratification of soil properties with soil depth, expressed as a ratio, could indicate soil quality under different soil management. We measured soil depth stratification ratio (0–5/10–30cm and 0–5/30–50cm) of soil organic C (SOC), total N, active carbon (AC), water soluble carbon (WSC), and soil enzymatic activities [dehydrogenase activity (DHA) and β-glucosidase activity (BGA)] of a Typic Haploxerert in southern Spain. The experimental design consisted of a split–split plot design with three replications and soil properties evaluated at the end of 22 years. Tillage systems included conventional tillage (CT) and no tillage (NT). Dryland, 2-year crop rotations were wheat (Triticum aestivum L.)–fallow (WF), wheat–chickpea (Cicer arietinum L.) (WC), wheat–faba bean (Vicia faba L.) (WFb), wheat–sunflower (Helianthus annuus L.) (WS), and continuous wheat (WW). Nitrogen fertiliser rates were 0, 50 and 150kgNha−1. Stratification ratios of total N, WSC, AC, DHA, and BGA were most responsive to tillage systems; NT greater than CT. Stratification ratios of SOC, total N, WSC, AC and BGA were most responsive to crop rotation; WFb and WW greater than WF, WC, and WS. Stratification ratio of BGA was most responsive to N fertiliser rate; higher rates than no fertiliser. Stratification ratios of C and N fractions and enzymatic activities were responsive to choice of denominator used for ratio calculation. Tillage and crop rotation had more influence than N fertiliser rate in affecting stratification ratio of C and N fractions and enzymatic activities. Stratification ratio was relatively low (<2), perhaps due to the large shrinking and swelling characteristics of Vertisols. Stratification ratio of BGA was greater than of all other soil properties, suggesting that it might be a good indicator of soil quality under different soil management in Mediterranean conditions, particularly with Vertisols. This study indicated the value of stratification ratios to detect improvement in soil organic matter fractions and enzymatic activities (i.e. indicators of soil quality) with adoption of improved conservation management approaches. [Copyright &y& Elsevier]

Abstract: Studies of the impacts of the interactions of soil agricultural practices on soil quality could assist with assessment of better management to establish sustainable crop production system. The main objective was to determine the long-term effects of tillage system, crop rotation and N fertilisation on soil total N and organic C (SOC), labile fractions of organic matter (water soluble carbon, WSC, and active carbon, AC), nitrate content, and soil enzymatic activities (dehydrogenase (DHA), β-glucosidase (Glu) and alkaline phosphatase (AP)) at four different soil depths (0–5, 5–10, 10–30 and 30–50cm), in a Mediterranean dryland Vertisol in SW Spain. Tillage systems were conventional tillage (CT) and no tillage (NT). Crop rotations were wheat–sunflower (WS), wheat–chickpea (WC), wheat–faba bean (WFb), wheat–fallow (WF) and continuous wheat (WW). Nitrogen fertiliser rates were 0, 50 and 150kgNha−1. The different crop rotation systems had a great influence in soil C and N fractions and enzymatic activities. In general, the SOC, total N, WSC, and β-glucosidase contents were higher in the no tillage system than in conventional tillage system in the wheat–wheat and in the wheat–faba bean rotations at upper layer (0–5cm), while the lowest ones were obtained in the wheat–fallow rotation in both tillage systems. Carbon and N fractions, calculated by volumetric soil, showed an increase with depth in both tillage systems and in all crop rotations, which could be related to the increase of soil bulk density and soil mass with depth. The highest N fertiliser rate increased most of soil variables, especially nitrate content at deeper layers, thereby precautions should be taken with long-term N fertilisation to avoid leaching of nitrates below the tillage layer. With the exception of wheat–fallow rotation, slightly greater grain and above-ground biomass yields were obtained for wheat in NT, especially at 150kgNha−1. Combination of NT with any biannual rotation except fallow could be an adequate sustainable management in order to improve soil quality of Vertisols, under our conditions. [Copyright &y& Elsevier]

Abstract: Good root system development is essential for optimum wheat (Triticum aestivum L.) grain yield, especially under water-limiting conditions. Published information about the influence of tillage system on root dynamic and their effect on grain yield in Mediterranean rainfed Vertisols is scarce. A three-year field study was conducted on a typical Mediterranean rainfed Vertisol to determine, using a minirhizotron system, the effects of tillage system on root growth and grain yield in wheat. Tillage treatments were no-tillage (NT) and conventional tillage (CT). The parameters measured were root length (RL) and root diameter (RD) for 6 depths. Minirhizotron measurements were performed at 5 wheat growth stages. The RL was greater under NT than under CT for most growth stages and depths, this being the key to its greater grain yield (3.2 vs 3.0Mgha −1, respectively). The RD was not significantly affected by the tillage treatments, but was lower from stem elongation onward and during the dry years. The key to the development of a good wheat root system is the rainfall received during the tillering stage, regardless of soil water content at planting and rainfall before or after this growth stage. Under the rainfed Mediterranean Vertisol studied, wheat productivity is greater under NT due to better root system development. [ABSTRACT FROM AUTHOR]

Abstract: Three different experiments were designed to study the effects of N fertilizer rate, timing and splitting, and the response to combined application of N and S fertilizer on the quality of durum wheat (Triticum turgidum L.) over a 3-year period in Vertisols under rainfed Mediterranean conditions. The following parameters were analyzed: grain yield, test weight, grain protein concentration, gluten index, yellow index, ash content and vitreousness. The N rate experiment included rates of 0, 100, 150, and 200kgNha−1 carried out on 4 different sites. The experiment was designed as a randomized complete block with four blocks. For the experiment on N timing and splitting, a single rate of 150kgNha−1 was used, different fractions being applied at sowing, tillering and stem elongation, at a single site; again, experimental design was a randomized complete block with four blocks. Finally, for the experiment on the response to combined application of N and S fertilizer, a single fertilizer dose of 150kgNha−1 was applied in two forms (urea+ammonium nitrate and urea+ammonium nitrosulfate) with one leaf application at ear emergence (zero, 25kgSha−1, 25kgNha−1, 25kgSha−1 +25kgNha−1, and 50kgNha−1), also at a single site, using a split-plot design with four replications. Year-on-year variation in rainfall led to marked variations in wheat yield, grain protein concentration and quality indices. Rainfall and temperatures during grain formation and ripening (April and May) were critical for durum wheat quality. N fertilizer rate modified the behavior pattern of some quality indices as a function of climate, and had a more consistent effect on durum wheat quality than on grain yield. The highest values for grain yield were recorded at an N rate of 100kgha−1, while maximum grain protein concentration values were recorded at 200kgha−1. Increasing N rates also prompted an increase in vitreous kernel count, which was highest at 150kgNha−1. The timing and splitting of N fertilizer had no clear effect on either grain yield or quality indices. Leaf application of N at ear emergence increased only grain protein concentration, vitreous kernel count and grain ash content. Soil or leaf application of S had no effect on quality indices, with the exception of ash content, which rose with leaf application at ear emergence. The response of grain yield and grain protein concentration to fertilizer N differed from that reported for temperate climates. [Copyright &y& Elsevier]

Three different experiments were designed to study the effects of N fertilizer rate, timing and splitting, and the response to combined application of N and S fertilizer on the bread-making quality of hard red spring wheat (Triticum aestivum L.) over a 3-year period in Vertisols under rainfed Mediterranean conditions. The following parameters were analyzed: grain yield, test weight, grain protein content, gluten index and alveograph parameters (W: alveogram index; P: dough tenacity; L: dough extensibility; P/L: tenacity–extensibility ratio). The N rate experiment included rates of 0, 100, 150 and 200 kg N ha−1 applied on four different sites. The experiment was designed as a randomized complete block with four blocks. For the experiment on N timing and splitting, a single rate of 150 kg N ha−1 was used, different fractions being applied at sowing, tillering and stem elongation, at a single site; again, experimental design was a randomized complete block with four blocks. Finally, for the experiment on the response to combined application of N and S fertilizer, a single fertilizer dose of 150 kg N ha−1 was applied in two forms (urea+ammonium nitrate and urea+ammonium nitrosulfate) with one leaf application at ear emergence (zero, 25 kg S ha−1, 25 kg N ha−1, 25 kg S ha−1+25 kg N ha−1 and 50 kg N ha−1), also at a single site, using a split-plot design with four replications. Year-on-year variation in rainfall led to marked variations in wheat yield, grain protein content and bread-making quality indices. A close correlation was observed between rainfall over the September–May period and both grain yield and grain protein content (optimum values for both being recorded in the rainfall range 500–550 mm) as well as the alveogram index. A negative correlation was observed between mean maximum temperatures in May and both test weight and alveogram index (W). N fertilizer rate had a more consistent effect on bread-making quality than on grain yield. The highest values for grain yield were recorded at an N rate of 100 kg ha−1, while maximum grain protein content values were recorded at 150 kg ha−1. Application of half or one-third of total fertilizer N at stem elongation improved grain yield and grain protein content with respect to applications at sowing alone or at both sowing and tillering. Increased N rates led to a considerable increase in W values and to a reduction in the P/L ratio, thus improving dough balance, with a negative effect on the gluten index. Leaf application of N at ear emergence only affected grain protein content and the W index. Soil or leaf application of S had no effect on protein quality indices. The response of grain yield and grain protein content to fertilizer N differed from that reported for temperate climates. [Copyright &y& Elsevier]

Abstract: Roots and the nutrients that they deposit into the soil are a natural source of N for a current crop, or a subsequent crop in the case of rotations. Despite the importance of this process, there are few field studies of rhizodeposition due to methodological difficulties. A two-year field study was conducted on a typical Mediterranean rainfed Vertisol to determine the effects of the tillage system on N rhizodeposition in wheat (Triticum aestivum L.). The tillage treatments were no-tillage (NT) and conventional tillage (CT). Wheat plants were labelled in situ with 15N using a leaf feeding method. The total amount of N that was deposited by the roots in the full soil profile (0–75cm) over two years was an average of 93kgha−1. The N derived from rhizodeposition (NdfR) represented 40% of the total N content and 82% of belowground N for the wheat plant. The NdfR was higher under NT only in the first layer of the soil (0–15cm). Fifty percent of the NdfR in the soil profile was observed within the first 15cm, increasing to 74% within the first 30cm. The amount of NdfR can be important for understanding farming systems and improving their management, especially the application of fertilizers. [Copyright &y& Elsevier]

prerequisite for the calculation of the proportion of a legume's nitrogen derived from the atmosphere (%Ndfa) using the N natural abundance technique (NA) is the determination of the B value (δN value for a legume when completely dependent on N fixation for growth). With this objective, Kabuli-type chickpea seeds were inoculated with Mesorhizobium ciceri, strain ISC-6, and an indigenous strain mixture (ISM) from the Guadalquivir Valley (southern Spain); and mayor-equina-type faba bean seeds were inoculated with Rhizobium leguminosarum strain ISL-19. Both legumes were grown in perlite with an N-free nutrient solution and in a growth chamber; uninoculated plants were also grown under the same conditions. Samples of the inoculated plants were collected at full flowering and maturity, analyzing total N and N content of the nodules, root, shoot and seeds. The seeds sown and uninoculated plants at wilting were also analyzed. The uninoculated chickpea and faba bean plants showed strong N discrimination in the remobilization of reserve proteins from the cotyledons to the shoot. Only 52% of the N from the chickpea seed and 46% from the faba bean seed were translocated to the shoot. The B value for both inoculated species (−1.44‰ in chickpea and −1.33‰ in faba bean) demonstrated the existence of a significant isotopic discrimination of N in the fixation of atmospheric N. The B value did not show significant differences between full flowering and seed maturity for either species, which allowed field sampling to be performed for the calculation of %Ndfa between both growth stages. Each species presented different N discrimination for the different parts analyzed. In chickpea, strong discrimination was observed between the nodules (+3.11‰) and the rest of the plant (−1.67‰); this discrimination was less pronounced in faba bean and always with negative values between the underground parts (nodules and root, with a mean value of −0.75‰) and the shoot (−1.71‰). The B value obtained was −1.80‰ in chickpea and −1.71‰ in faba bean. However, given the importance of the amount of seed N in chickpea and faba bean, seed N contribution should be considered in the calculation of the B value using a mass balance model which considers 50% of this amount. In this case, the adjusted B values would increase to −2.05‰ and −1.89‰ in chickpea and faba bean, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural systems are important for world ecosystems. They can be managed to moderate CO2 emissions. World soils can be both a sink and source of atmospheric CO2, but it is a slow process. Data from long-term soil management experiments are needed to assess soil carbon (C) sink capacity through a complete life cycle analysis of direct and hidden C changes. Eight commonly used agricultural systems in northern Appalachia (OH, USA) were tested after 38 year to assess the magnitude of the soil C pool. Only a forest ecosystem and a no-tillage corn (Zea mays L.) crop plus manure increased soil organic carbon (SOC) by 37.3 and 33.3MgCha−1, respectively; meanwhile monoculture corn and/or no-tillage practices maintained the SOC level over the period. Thus, most of north Appalachian agriculture, with current practices, does not contribute to C sequestration. Improved agricultural practices for no-tillage continuous corn should include cultivars with higher residue production (above- and belowground) and slower decomposition rates in order to increase SOC sequestration. [Copyright &y& Elsevier]

Little research has examined the influence of tillage system on root growth in wheat grown on rainfed Vertisols. A 3-year field study (2003, 2004 and 2005) was carried out on a typical Vertisol (southern Spain), to determine the effects of tillage system on root growth in spring wheat ( Triticum aestivum L) grown in continuous rotation with faba bean ( Vicia faba L), within the framework of the long-term “Malagón” experiment started in 1986. Tillage treatments were no-tillage (NT) and conventional tillage (CT), and the experiment was designed as a randomized complete block with three replications. The following parameters were measured: above-ground biomass, grain yield, root length density (RLD), root biomass (RB) and root N content. In the topmost 10 cm of soil, higher values were found under CT than under NT for RLD in the rainiest year (20.2 km m−3 vs. 9.6 km m−3 respectively) and for RB (512 kg ha−1 vs. 261 kg ha−1 respectively) in all study years. In deeper layers, no difference was recorded between the two tillage systems. Greater wheat root development in the upper soil layer under CT may reflect the greater soil penetration resistance found in the topmost 10 cm under NT. Root separation using a sieve with a 0.5 mm mesh screen led to a marked underestimation of RLD and RB, with values up to three times higher when using a 0.2 mm mesh screen. Mean wheat root N content in the topmost 30 cm of soil accounted for over 80% of total root N content. The highest grain yield was observed under NT, since this system provided greater water storage in the soil profile in the mostly dry study years. [ABSTRACT FROM AUTHOR]