Phosphorus and potassium fertilization in no till southern Brazilian soils

Jairo André Schlindwein,Leandro Bortolon,Elaine Cosma Fioreli-Pereira,Clesio Gianello,Elisandra Solange Oliveira Bortolon

doi:10.4236/as.2013.412a004

Abstract

Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended system. This study aims to evaluate the increase in P and K levels in 0-10 and 0-20 cm deep samples from no-till soils using the Mehlich-1 (M1) and Mehlich-3 (M3) extractants as well as resin methods and to estimate the amount of P2O5 and K2O fertilizers necessary to increase the P and K soil levels by 1 mg·kg-1. The study was conducted in fields cultivated using a no-till system (direct planting) to grow soybeans, wheat, maize, pasture, and cover crops and fertilized with P2O5 and K2O. Soil samples were collected from the 0-10 and 0-20 cm soil layers and analyzed by the M1, M3, and resin methods. The results demonstrated that the P and K levels increased in the 0-10 and 0-20 cm layers. However, the amount of these levels increased depending on the source of phosphate fertilization and on the P and K extraction methods used. The amount of P2O5 fertilization needed to raise the P level by 1 mg·kg-1 was greater in the 0-20 cm layer than in the 0-10 cm layer, and the amount of K2O fertilization needed to raise the K level by 1 mg·kg-1 was higher in the 0-10 cm layer than in the 0-20 cm layer.

Highlights

Soybean, wheat and maize are the most commonly grown crops in the oxidized soil with low fertility of Rio Grande do Sul (RS), Brazil; their cultivation occupies an area of approximately 5 million hectares, and this amount of cultivated land has not changed greatly over the years [1]
In the most recent soil fertility survey performed by [5], after more than four decades of agricultural expansion and the use of amendments and fertilizers in RS, approximately 80% and 40% of the soil analyses conducted between 1998 and 2000 showed P and K levels below the minimum required for satisfactory yields, respectively
The P (Tables 2 and 3) and K (Table 4) levels estimated by the polynomial functions and extracted by the M1, M3, and resin methods had increased values in all of the assessments as P2O5 and K2O, respectively, were added

Summary

Introduction

Wheat and maize are the most commonly grown crops in the oxidized soil with low fertility of Rio Grande do Sul (RS), Brazil; their cultivation occupies an area of approximately 5 million hectares, and this amount of cultivated land has not changed greatly over the years [1]. The average yields for crops grown in RS are lower than the average yields in some other Brazilian regions and other countries; in 2009/10, the soybean, wheat, and maize yields were 2570, 2100, and 4860 kg·ha−1, respectively [1]. These yields are partially due to low soil fertility [2,3,4,5]. Fertilizer costs are approximately 20% of the total crop investment in RS for soybeans, wheat, and maize grown under a no-till system [9]. Fertilizer levels must be reasonable and based on calibration field studies to determine the specific nutrient amounts needed for maximizing economic efficiency, which is achieved when the soil fertility is raised to near the criti-

Objectives

Methods

Results

Conclusion