B value and isotopic fractionation in N2 fixation by chickpea (Cicer arietinum L.) and faba bean (Vicia faba L.)

Abstract

A prerequisite for the calculation of the proportion of a legume's nitrogen derived from the atmosphere (%Ndfa) using the 15 N natural abundance technique (NA) is the determination of the B value (δ 15 N value for a legume when completely dependent on N 2 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 15 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 15 N discrimination in the remobilization of reserve proteins from the cotyledons to the shoot. Only 52% of the 15 N from the chickpea seed and 46% from the faba bean seed were translocated to the shoot. The B whole plant 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 2 . The B shoot 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 15 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 shoot 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 15 N contribution should be considered in the calculation of the B shoot value using Plant Soil (2010) 337:425-434 a mass balance model which considers 50% of this amount. In this case, the adjusted B shoot values would increase to −2.05‰ and −1.89‰ in chickpea and faba bean, respectively.

Potential Nitrogen Source from Field Bean for Rainfed Mediterranean Cropping Systems

“…Our estimates of recoverable root contribution to the total plant N are in a similar range to those reported by López‐Bellido et al (2011a) for faba bean and Mayer et al (2003) and López‐Bellido et al (2010), who obtained values <9% in faba bean, chickpea, and pea. These figures are much lower than the potential contribution of roots and nodules to the total plant N reported by Unkovich and Pate (2000), which was as high as 40% for Vicia faba grown in a glasshouse in the absence of combined N. Khan et al (2002) compared 15 N shoot labeling, 15 N‐labeled soil isotope dilution, and physical recovery of nodulated root methods for quantifying the contribution of belowground N to the total plant N. Values of belowground N represented 39% of total plant N for faba bean, 53% for chickpea, and 20% for mungbean [ Vigna radiata (L.) R. Wilczek] when estimates were based on 15 N shoot labeling, while values ranged from 4 to 13% when only physical recovery of roots was considered.…”

“…The proportion of 15 N in the field bean varied among plant parts, with significantly less isotopic excess in grain and straw than roots. A similar pattern was observed in chickpea but not in faba bean using the natural abundance method (López‐Bellido et al, 2010), while Unkovich and Pate (2000) identified little evidence of this pattern for other annual legumes. Rather than being influenced by the N 2 fixation assessment methodology that took into account the different 15 N concentrations among plant components of the non‐fixing reference species (Sulas et al, 2009), we interpreted the changes in 15 N enrichment among plant parts in terms of the isotopic discrimination that might occur during plant metabolism and translocation (Carranca et al, 1999).…”

“…Field bean is also utilized in Mediterranean cereal intercropping systems (Benincasa et al, 2012). When used in rotation, the potential N contribution of field bean to the subsequent crop is dependent on its specific use and the corresponding N harvest indices (Carranca et al, 1999), with the estimates influenced by the N and fixed N partitioning between grain and straw, as observed by Turpin et al (2002) in faba bean, by Carranca et al (1999) and Habtegebrial and Singh (2006) in pea, and by López‐Bellido et al (2010) in chickpea ( Cicer arietinum L.). For example, grain legumes may provide only a small contribution to soil N when used in rotation with a cereal if most of the fixed N is removed due to large N translocation from vegetative tissues to the grain during seed ripening (Herdina and Silsbury, 1990).…”

The origins of agriculture in Iberia: a computational model

“…We classified landscape cells based on their suitability for cereal agriculture, using a combination of terrain and climate parameters 1 1 (Bevan, Conolly 2004;López Bellido 1991). We focused on wheat, because it has the most stringent climatic requirements of the different species of early Eurasian cereals.…”

Possibility of Introducing Winter Legumes, Hairy Vetch and Faba Bean, as Green Manures to Turmeric Cropping in Temperate Region

“…The crop residues of such winter grain legumes should also be used as an organic matter. Several studies have shown the N 2 fixation of faba bean (López-Bellido et al, 2010;López-Bellido et al, 2011) and its potential contribution to the sustainability of cropping systems, including wheat (Tosti and Guiducci, 2010;Melero et al, 2011; and melon (Stagnari and Pisante, 2010). According to Köpke and Nemecek (2010) and Jensen et al (2010), this crop species has an important role in sustainable farming practice, particularly, in nutrient supply.…”