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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: 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]

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]