Effects of different legume green manures on tropical soil microbiology after corn harvest

Vanessa Dina Cavalcante Barros,Juscélia Da Silva Ferreira,Danilo José De Barros,Felipe José Cury Fracetto,Giselle Gomes Monteiro Fracetto,Adalberto Francisco Da Silva Júnior,Mario Andrade Lira Junior

doi:10.1590/1678-4499.20200262

Vanessa Dina Cavalcante Barros, Juscélia Da Silva Ferreira + Show 5 more

Open Access

https://doi.org/10.1590/1678-4499.20200262

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Abstract

Legume green manure is a popular practice for sustainable agriculture in tropical environments. The use of grain, forage and purely green manure legumes in a subhumid tropical area in Northeast Brazil was investigated to determine the total C and N contents and estimate C-microbial biomass, soil basal respiration, microbial and metabolic quotients, before and after green manures and after the following corn. It was hypothesized that, although all legumes would increase microbial biomass and activity, there would be different effects in function of the main economic usage of the legume. The experimental design evaluated the soil before and after harvest of seven legumes: (i) purely green manures – sunn hemp (Crotalaria juncea L.) and velvet bean (Stizolobium aterrimum Piper & Tracy); (ii) forage – Campo Grande stylo (a physical mixture of 80% of Stylosanthes captata Vog. and 20% of Stylosanthes macrocephala) and calopo (Calopogonium mucunoides Dev.) and (iii) grain – common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata L.) and peanut (Arachis hypogaea L.), followed by corn crop. After corn harvest, soils had the same total C and N contents before legume seeding, but C-microbial biomass was significantly higher in soils with grain and purely green manures, which produced higher shoot and root dry mass. Soil basal respiration decreased after corn harvest for all legumes comparing to control treatments, but metabolic stress increased in soils with forage species. Despite this, microbial quotient indicated an efficiency of the microorganisms in degrading the residual organic matter of all green manures used in corn.

Highlights

Green manure is a sustainable agronomic practice based on growing a crop, usually a legume, to supply residual cover on the soil surface for subsequent crops (Diacono et al 2019)
Soil basal respiration decreased after corn harvest for all legumes comparing to control treatments, but metabolic stress increased in soils with forage species
Legumes green manure based on peanut (Arachis hypogaea L.), common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata L.) are employed in the production and trade of its grains (Degefu et al 2018; Nouralinezhad et al 2018)

Summary

Introduction

Green manure is a sustainable agronomic practice based on growing a crop, usually a legume, to supply residual cover on the soil surface for subsequent crops (Diacono et al 2019). This management has been successfully used in tropical soils due to increased organic matter incorporated and allows higher yields for corn, sugarcane and soybean, for example (Genovesi et al 2019; Oliveira et al 2018). Legume green manures effects on soil microbiology fodder production in crop rotation systems (Oliveira et al 2017; Mauad et al 2019). Legumes green manure is known to benefit soil chemical and microbiological attributes, mainly through biological nitrogen fixation and decomposition of plant biomass, respectively (Singh et al 2020)

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