Brachiaria as a Cover Crop to Improve Phosphorus Use Efficiency in a No-till Oxisol

Moniki Campos Janegitz,Elialdo Alves De Souza,Ciro Antonio Rosolem

doi:10.1590/18069657rbcs20150128

Moniki Campos Janegitz, Elialdo Alves De Souza + Show 1 more

Open Access

https://doi.org/10.1590/18069657rbcs20150128

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Abstract

Oxidic soils are phosphorus drains in soil; hence, P availability is a limiting factor in tropical, weathered Oxidic soils. It has been shown that some brachiarias grown as cover crops may increase soil available P to subsequent crops. The objective of this study was to evaluate soil P cycling and availability, as well as the response of soybean to soluble and natural reactive phosphates as affected by ruzi grass (Urochloa ruziziensis, R. Germ. and C.M. Evrard, Crin) grown as a cover crop in a no-till system. Experimental treatments consisted of the presence or absence of ruzi grass in combination with a control (0.0 P) and soluble and reactive rock phosphate broadcast on the soil surface in the winter (80 kg ha-1 P2O5), plus three rates of P applied to soybean furrows (0, 30, and 60 kg ha-1 of P2O5) at planting, in the form of triple superphosphate. Soybean was cropped in two seasons: 2010/2011 and 2011/2012. Soil samples were taken before soybean planting (after desiccation of Brachiaria) at 0.00-0.05 and 0.05-0.10 m for soil available P. Total weight of dry matter and P accumulated in ruzi grass were determined, as well as soybean yields, P in soybean grains, and P use efficiency (PUE). The use of natural phosphate increased soil P availability. The highest yields were obtained with higher application rates of triple superphosphate in the planting furrow combined with broadcast rock phosphate. Broadcast application of Arad reactive phosphate increases and maintains soil available P, and this practice, associated with ruzi grass grown as a cover crop and the use of triple superphosphate applied to soybean furrows, results in higher use of P by soybeans.

Highlights

Oxidic soils and the climate predominant in tropical and subtropical regions are prone to the formation of high energy bonds between phosphorus and soil colloids (Schroder et al, 2011)
These soils behave as P drains and compete with plants for the nutrient, which may lead to low phosphorus use efficiency (PUE) (Syers et al, 2008)
Granulated triple superphosphate (TSP) with 41 % P2O5 was used as the soluble source, and Arad natural reactive rock phosphate (NRP) powder with 32 % total P2O5 was used as the less soluble source

Summary

Introduction

Oxidic soils and the climate predominant in tropical and subtropical regions are prone to the formation of high energy bonds between phosphorus and soil colloids (Schroder et al, 2011) As a consequence, these soils behave as P drains and compete with plants for the nutrient, which may lead to low phosphorus use efficiency (PUE) (Syers et al, 2008). Several species used as winter or spring cover crops are able to accumulate significant amounts of P. These plants can be introduced in rotation with cash crops under no-till (NT) since they may increase soil organic matter and nutrient use, decrease losses, and release nutrients for the crop as they decay (Pavinato and Rosolem, 2008; Schoninger et al, 2013)

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