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

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.

Chemical composition of cover crops and soil organic matter pools in no‐tillage systems in the Cerrado

“…The extensive root system of U . ruziziensis may have favoured TOC accumulation below 10 cm (Ramos et al, 2020; Rossi et al, 2012; Santos et al, 2014), confirming the hypothesis that tropical grasses may be recommended as cover crops to improve some soil attributes, through the action of their roots, can be just as important as the production of soil cover (Rosolem et al, 2016). A deeper root system makes these cover crops more resistant to drought, which is favourable in the edaphoclimatic conditions of the Cerrado, and also contributes to deep C accumulation and the formation of soil aggregates (Loss et al, 2012; Silva et al, 2016).…”

“…In contrast, plants with higher lignin/N, such as C . cajan , are more efficient for soil protection, in the short term, because of the higher proportion of aromatic C (Carvalho et al, 2009), which favours the accumulation of POC in soils (Ramos et al, 2020).…”

“…Recalde et al, (2015) reported that the dry matter of cover plants, both in quantity and in quality, can effectively contribute to the increase in SOM with gains in C stocks over the years (Ramos et al, 2020). This is desirable for the management of soils, since SOM is linked to key processes such as the cycling and accumulation of nutrients and the stability of soil aggregates (Nascimento et al, 2019; Silva et al, 2016).…”

Dynamics of Carbon and Soil Enzyme Activities under Arabica Coffee Intercropped with Brachiaria decumbens in the Brazilian Cerrado

“…The biochemical composition of plant residues affects the dynamics of decomposition and nutrient cycling [ 14 ], microbial biomass formation [ 9 ] and soil enzymatic activity [ 15 , 16 ]. Soil management systems using cover crops can also alter the chemical and physical fractions of soil organic C [ 17 ]. The POC physical fraction consists mainly of decomposed relatively lighter plant material and is sensitive to soil management [ 17 , 18 , 19 , 20 , 21 ].…”

“…Soil management systems using cover crops can also alter the chemical and physical fractions of soil organic C [ 17 ]. The POC physical fraction consists mainly of decomposed relatively lighter plant material and is sensitive to soil management [ 17 , 18 , 19 , 20 , 21 ]. In addition to this management sensitivity, the humic fractions and chemical fractionation SOM represent a soil C reserve [ 22 ].…”