Carbon and nitrogen cycling in an integrated soybean-beef cattle production system under different grazing intensities

Joice Mari Assmann,Sérgio Ely Valadão Gigante De Andrade Costa Costa,Taise Robinson Kunrath,Paulo Cesar De Faccio Carvalho,Cimélio Bayer,Ibanor Anghinoni,Alan Joseph Franzluebbers,Amanda Posselt Martins

doi:10.1590/s0100-204x2015001000013

Joice Mari Assmann, Sérgio Ely Valadão Gigante De Andrade Costa Costa + Show 6 more

Open Access

https://doi.org/10.1590/s0100-204x2015001000013

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Abstract

Abstract:The objective of this work was to evaluate the effect of grazing intensity on the decomposition of cover crop pasture, dung, and soybean residues, as well as the C and N release rates from these residues in a long-term integrated soybean-beef cattle system under no-tillage. The experiment was initiated in 2001, with soybean cultivated in summer and black oat + Italian ryegrass in winter. The treatments consisted of four sward heights (10, 20, 30, and 40 cm), plus an ungrazed area, as the control. In 2009-2011, residues from pasture, dung, and soybean stems and leaves were placed in nylon-mesh litter bags and allowed to decompose for up to 258 days. With increasing grazing intensity, residual dry matter of the pasture decreased and that of dung increased. Pasture and dung lignin concentrations and C release rates were lower with moderate grazing intensity. C and N release rates from soybean residues are not affected by grazing intensity. The moderate grazing intensity produces higher quality residues, both for pasture and dung. Total C and N release is influenced by the greater residual dry matter produced when pastures were either lightly grazed or ungrazed.

Highlights

In Brazil, one of the main food‐producing countries, studies on nutrient cycling under more complex food production systems, such as integrated crop‐livestock systems (ICLS), involving several components, are still scarce
Since no differences were observed between the two ICLS cycles, results were presented and discussed considering average values
Dung amounts increased with grazing intensity, but with low magnitude, from 0.46 Mg ha‐1 for G40 to 1.22 Mg ha‐1 for G10

Summary

Introduction

In Brazil, one of the main food‐producing countries, studies on nutrient cycling under more complex food production systems, such as integrated crop‐livestock systems (ICLS), involving several components (soil, plant, and animals), are still scarce. The importance of researches on the topic goes beyond food‐producing issues, reaching economic, social, and environmental aspects (Ryschawy et al, 2012). In this context, ICLS fit well in the modern concept of sustainable agriculture proposed by Doré et al (2011). Considering nutrient losses by the transfer of nutrients from grazing areas, through the deposition of dung and urine (Haynes & Williams, 1993), cycling of plant and animal residues becomes an important source for maintaining soil‐plant‐atmosphere equilibrium, since it contributes for nutrient supply both for pasture and cash crops (Dubeux et al, 2007)

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