Carbon fractions in soil under no-tillage corn and cover crops in the Brazilian Cerrado

Maria Lucrécia Gerosa Ramos,Vivian Galdino Da Silva,Stefany Braz Silva,Alexsandra Duarte De Oliveira,Thais Rodrigues De Sousa,Arminda Moreira De Carvalho,Juaci Vitoria Malaquias

doi:10.1590/s1678-3921.pab2020.v55.01743

Maria Lucrécia Gerosa Ramos, Vivian Galdino Da Silva + Show 5 more

Open Access

https://doi.org/10.1590/s1678-3921.pab2020.v55.01743

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Abstract

Abstract: The objective of this work was to evaluate soil carbon fractions under cover crops cultivated after corn (Zea mays), with or without nitrogen topdressing fertilization, in a long-term experiment in the Brazilian Cerrado. The experiment was carried out in a randomized complete block design, in split-plots with three replicates. The plots were represented by the cover crops, and the subplots, by the presence or absence of N topdressing for corn. The following cover crop species were planted after the harvest of the 30F53VYHR corn hybrid: 'BRS Mandarin' pigeonpea (Cajanus cajan), sunn hemp (Crotalaria juncea), oilseed radish (Raphanus sativus), and black mucuna (Mucuna aterrima). After the cutting of the cover crops, soil samples were collected at 0.0‒0.10 and 0.10‒0.20 m soil depths. After corn harvest, samples of its residues were taken. The cover crops alter the soil chemical and physical fractions, especially fulvic acid and soil particulate organic carbon. Nitrogen topdressing for corn decreases fulvic acid, but increases the humic acid/fulvic acid ratio and particulate organic carbon in the deeper soil layer.

Highlights

Soil organic matter (SOM) is one of the most relevant soil quality indicators, especially in highly weathered Latossolos (Oxisols), in which fertility depends essentially on the SOM quantity and quality
The objective of this work was to evaluate soil carbon fractions under cover crops cultivated after corn (Zea mays), with or without nitrogen topdressing fertilization, in a long-term experiment in the Brazilian Cerrado
The following cover crop species were planted after the harvest of the 30F53VYHR corn hybrid: 'BRS Mandarin' pigeonpea (Cajanus cajan), sunn hemp (Crotalaria juncea), oilseed radish (Raphanus sativus), and black mucuna (Mucuna aterrima)

Summary

Introduction

Soil organic matter (SOM) is one of the most relevant soil quality indicators, especially in highly weathered Latossolos (Oxisols), in which fertility depends essentially on the SOM quantity and quality. This soil fraction is critical in the context of global climate change because soils represent the largest C reservoir on the Earth’s surface and contribute to the reduction of GHG emissions to the atmosphere (Chenu et al, 2019). Corn‒cover crop succession (Carvalho et al, 2015; Wittwer et al, 2017) in the Cerrado ensures a protective soil cover in the second growing season (Pissinati et al, 2018) against erosion (Anache et al, 2018). Cover crops stabilize soil aggregates (Nascimento et al, 2019) and increase the humic acid and particulate C fractions (Santos et al, 2014), which are the main components of SOM and indicators of the soil quality (Nascimento et al, 2019)

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