Crop Performance Indexes Applied to Legume Used as Summer Cover Crops under Water Deficit Conditions

Verónica Berriel,Carlos H Perdomo,Santiago Signorelli,Jorge Monza

doi:10.3390/agronomy12020443

Verónica Berriel, Carlos H Perdomo + Show 2 more

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https://doi.org/10.3390/agronomy12020443

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Abstract

Summer legume cover crops (CC) such as Crotalaria juncea, Crotalaria spectabilis, Crotalaria ochroleuca, and Cajanus cajan could offer diverse advantages for the environment and productive cropping systems. A low transpiration efficiency (TE) of CC can induce soil water content to levels that present a challenge for the subsequent crop. In a 75-day growth chamber experiment, using the natural abundance of 13C, 18O, and 15N we evaluated the TE and BNF under two soil water conditions. Our results showed that the four species tested are good candidates for their use as CC because they showed good results in terms of productivity parameters, TE, and BFN. Cajanus cajan had the highest TE, a high shoot dry matter production, and accumulated more N from BFN in the shoot than C. spectabilis, C. juncea, and C. ochroleuca. ∆18O increased under moderate water deficit and showed an inversely proportional relationship with the amount of transpired water, supporting the use of this isotopic indicator as a proxy for transpiration and stomatal conductance. For the isotopic parameters no interaction between the factors water regimen and species were found. We propose the mass ratio of nitrogen fixed by the volume of transpired water and the isotopic discrimination of 13C as useful indicators of drought fixing legumes tolerance.

Highlights

The annual summer legumes Crotalaria juncea, C. spectabilis, C. ochroleuca, and Cajanus cajan, are species that are characterized by their high biomass production and ability for biological nitrogen fixation (BNF) [1,2,3]
The legume species C. juncea, C. spectabilis, C. ochroleuca, and Cajanus cajan were evaluated according to their shoot dry matter (DM) production, transpired water, Transpiration efficiency (TE), and isotopic parameters in two water regimes, moderate water deficit (50% field capacity (FC)) and well-watered (80% FC)
Figure 2. ∆13C, ∆18O, and fixed N in legumes used as cover crops (CC) during moderate water deficit (50% FC) and in the absence of water deficit (80% FC). (A)

Summary

Introduction

The annual summer legumes Crotalaria juncea, C. spectabilis, C. ochroleuca, and Cajanus cajan, are species that are characterized by their high biomass production and ability for biological nitrogen fixation (BNF) [1,2,3]. Due to these characteristics, they are commonly used as cover crops (CC) in cropping agriculture rotations in tropical and temperate zones [4,5]. Instantaneous WUE or TE can be determined by measuring the concentration of CO2 and H2O vapour, which can be applied at the leaf level and faster than gravimetric determination using lysimeters [11]; the robustness of this methodology is more limited than TE determination. The instantaneous WUE can be estimated by the relationship between the photosynthesis rate (A) and transpiration (T) and the intrinsic WUE by the relationship between A and stomatal conductance (gs) [12]

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