DRY MATTER DECOMPOSITION OF COVER CROPS IN A NO-TILLAGE COTTON SYSTEM

João Luís Da Silva Filho,Alexandre Cunha De Barcellos Ferreira,Ana Luíza Dias Coelho Borin

doi:10.1590/1983-21252018v31n201rc

Abstract

ABSTRACT No-tillage cotton systems require soil coverage with cover crop residue for a longer time due to the late cycle of cotton. However, decomposition rates may vary between cover crops, and the adjustment of models to describe it is critical to no-tillage cotton management. Two non-linear regression models, exponential (EM) and Michaelis-Menten (MM), were adjusted to dry matter decomposition of cover crops in a cotton no-tillage system, in Brazil. Three field trials were performed in 2012 for the cover crops Urochloa ruziziensis (brachiaria), Pennisetum glaucum (pearl millet), and Cajanus cajan (pigeon pea). Samples of cover crop were collected at 20, 50, 70, 110, 140, and 170 days after sowing upland cotton to measure dry matter decomposition. MM showed better adjustment than EM for all cover crops. The estimations of half-life parameters were different between the cover crops, suggesting that each cover crop has its own rate of decomposition. For pearl millet, brachiaria, and pigeon pea, the half-life estimation by exponential model was over the MM in 9, 12, and 12 days.

Highlights

The success of agriculture in the Brazilian “Cerrado” occurred parallel to the increased adoption of the no-tillage system
To ensure permanent soil cover for direct seeding of the cotton in that biome, some research has been conducted with cover crops (FERREIRA et al, 2010; FERREIRA et al, 2012), as the plant residues of the main crop provide little contribution to soil coverage and protection
The dynamics of plant residue decomposition depends on residue chemical composition, the amount of matter, and the soil and climate conditions (ESPÍNDOLA et al, 2006)

Summary

Introduction

The success of agriculture in the Brazilian “Cerrado” occurred parallel to the increased adoption of the no-tillage system. The cover crops Urochloa ruziziensis (brachiaria or ruzi grass ) and Pennisetum glaucum (millet) are frequently used in the Brazilian “Cerrado” (PACHECO et al, 2011), due to the high production of DM with a high C/N ratio, a feature that provides high persistence and soil protection; in addition, they adapt and are easy to plant and cultivate Other species, such as the legume Cajanus cajan (pigeon pea), with a semi-perennial habit and good tolerance to higher temperatures and water deficit typical conditions of the inter-crop period in the “Cerrado,” can produce large amounts of DM and increase nitrogen in the soil by biological fixation

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Conclusion