Search

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: 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]