Chemical and biological properties of phosphorus-fertilized soil under legume and grass cover (Cerrado region, Brazil)

Marcelo Fernando Pereira Souza,Mariana Pina Da Silva,Ana Maria Rodrigues Cassiolato,Orivaldo Arf

doi:10.1590/s0100-06832013000600006

Abstract

The use of cover crops has been suggested as an effective method to maintain and/or increase the organic matter content, while maintaining and/or enhancing the soil physical, chemical and biological properties. The fertility of Cerrado soils is low and, consequently, phosphorus levels as well. Phosphorus is required at every metabolic stage of the plant, as it plays a role in the processes of protein and energy synthesis and influences the photosynthetic process. This study evaluated the influence of cover crops and phosphorus rates on soil chemical and biological properties after two consecutive years of common bean. The study analyzed an Oxisol in Selvíria (Mato Grosso do Sul, Brazil), in a randomized block, split plot design, in a total of 24 treatments with three replications. The plot treatments consisted of cover crops (millet, pigeon pea, crotalaria, velvet bean, millet + pigeon pea, millet + crotalaria, and millet + velvet bean) and one plot was left fallow. The subplots were represented by phosphorus rates applied as monoammonium phosphate (0, 60 and 90 kg ha-1 P2O5). In August 2011, the soil chemical properties were evaluated (pH, organic matter, phosphorus, potential acidity, cation exchange capacity, and base saturation) as well as biological variables (carbon of released CO2, microbial carbon, metabolic quotient and microbial quotient). After two years of cover crops in rotation with common bean, the cover crop biomass had not altered the soil chemical properties and barely influenced the microbial activity. The biomass production of millet and crotalaria (monoculture or intercropped) was highest. The biological variables were sensitive and responded to increasing phosphorus rates with increases in microbial carbon and reduction of the metabolic quotient.

Highlights

The Cerrado represents the predominant vegetation in Central Brazil, where the topography and landscape conditions are well-suited, which has led to the conversion of this biome into the main grain-producing region of the country
Phosphorus is required at every metabolic stage, as it plays a role in the protein and energy synthesis processes and in the translocation and formation of fatty acids, as well as influencing the photosynthetic process directly (Marschner, 1995)
One composite sample, composed of 20 single samples, was collected in the experimental area from the 0-0.20 m layer and analyzed according to the methods proposed by Raij et al (2001), with the following results: pH = 4.9; organic matter (OM) = 13 g dm-3, P = 12 mg dm-3; K, Ca and Mg = 1.1, 18 and 15 mmolc dm-3, respectively; potential acidity (H+Al) = 15 mmolc dm-3, and a base saturation of (BS) 70 %

Summary

Introduction

The Cerrado represents the predominant vegetation in Central Brazil, where the topography and landscape conditions are well-suited, which has led to the conversion of this biome into the main grain-producing region of the country. The replacement of native vegetation and use for pasture or grain production induces changes in the chemical and biological properties of the soil (Costa et al, 2006; Carneiro et al, 2009). Typical characteristics of these soils are low fertility, acidity and Al toxicity, and low nutrient availability, including phosphorus (P). The no-tillage management can reduce negative impacts caused by conventional systems, and maintain and/or improve soil fertility, inducing higher crop yields (Pelá et al, 2010) This system reduces soil losses by erosion, improving the soil chemical, physical and biological conditions and directly affecting fertility (Carvalho et al, 2004)

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Results