Phosphate fertilization and phosphorus forms in an Oxisol under no-till

Dácio Olibone,Ciro Antonio Rosolem

doi:10.1590/s0103-90162010000400014

Dácio Olibone, Ciro Antonio Rosolem

Open Access

https://doi.org/10.1590/s0103-90162010000400014

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Journal: Scientia Agricola	Publication Date: Aug 1, 2010
Citations: 47	License type: cc-by

Affiliation: Universidade Estadual Paulista (Unesp)

Abstract

Under no-till phosphorus (P) accumulates in a few centimeters of the topsoil layer. Plant residues left on the soil surface release P and organic acids, which may improve P availability and fertilizer efficiency, including both soluble (such as triple super phosphate) and less soluble sources (such as reactive natural phosphates). In this study, soybean response to P fertilizer and P forms in the top 40 cm of an Oxisol were evaluated after surface application of different phosphates in a 5-year-old no-till system. Treatments consisted of 0 or 80 kg ha-1 of total P2O5 applied on the soil surface, both as natural reactive phosphate (NRP) or triple super phosphate (TSP). In addition, 80 kg ha-1 of P2O5 were applied to subplots, in furrows below and beside the soybean (Glycine max L.) seeds, in different combinations of NRP and TSP. Soil samples were taken before and after the soybean growth, down to 0.40 m and soil phosphorus was chemically fractionated. The responses to NRP were similar to TSP, with an increase in P reserves at greater depths, even in non-available forms, such as P-occluded. After the soybean harvest, P-occluded levels were lower at the surface layer, but an increase was observed in the soluble, organic and total P down to 40 cm. An improved P distribution in soil depth, especially regarding the soluble and organic forms, resulted in higher soybean yields, even when the phosphates were applied to the soil surface.

Highlights

Under no-till (NT) surface application of phosphate fertilizers and the maintenance of plant residues on the soil surface leads to P concentration gradients across the top layers of the soil profile, with larger amounts of labile organic and inorganic forms of P close to the soil surface (Schlindwein and Anghinoni, 2000; Selles et al, 1997)
Phosphorus utilization by plants over time would not be compromised because P bioavailability could be increased as a result of increased plant root development, higher water accumulation, great mineralization of plant residues and movement in the soil by the enhanced soil fauna
Most of the no-till farmers in Brazil apply fertilizers on the soil surface to maximize machine operations and there has been a trend towards using cheaper natural reactive phosphates

Summary

Introduction

Under no-till (NT) surface application of phosphate fertilizers and the maintenance of plant residues on the soil surface leads to P concentration gradients across the top layers of the soil profile, with larger amounts of labile organic and inorganic forms of P close to the soil surface (Schlindwein and Anghinoni, 2000; Selles et al, 1997). Since no significant differences were found among treatments due to phosphate mixtures and on their interaction, results of P levels from the sub-plots were combined according to each subplot in order to be compared with the results from the first soil sampling (before soybean) i.e., three treatments with four replications for each depth.

Results

Conclusion