Exchangeable potassium reserve in a Brazilian savanna Oxisol after nine years under different cotton production systems

Alexandre Cunha De Barcellos Ferreira,Gilvan Barbosa Ferreira,Fernando Mendes Lamas,Álvaro Vilela De Resende,Ana Luiza Dias Coelho Borin

doi:10.1590/1678-992x-2020-0339

Abstract

Adequate potassium (K) fertilization is essential for agricultural production in soils of the Brazilian Savanna (Cerrado biome) due to the high demand by crops (especially cotton), likelihood of leaching losses, and the dependence on fertilizer importations. Therefore, sustainability requires improvements in the soil efficiency management. This study evaluated the influence of soil management and crop succession or rotation combinations with cotton on K dynamics and exchangeable reserves in the soil profile, and the partial balance of K after nine years of cultivation in a clayey Oxisol in the Cerrado. The soil was sampled in layers up to 100 cm depth in four cotton production systems treatments: 1) conventional soil tillage (CST) with cotton monoculture; 2) CST with annual cotton-soybean-cotton succession; 3) CST with cotton/soybean/maize rotation; and 4) no-tillage system (NTS) with cotton/soybean/maize rotation and Urochloa ruziziensis (ruzigrass) as a cover crop in the off-season after grain crops. The experiment was conducted using a randomized block design with four replications. CST with cotton monoculture favored the leaching of K surplus from fertilization. Crop rotation including ruzigrass in the NTS allowed better control of K dynamics, ensuring its circulation in the soil-plant compartments and reducing leaching. The increased organic matter (OM) in this system enlarges the storage capacity of K in the topsoil. The adoption of no-tillage crop systems integrating ruzigrass is viable to improve the efficiency of K fertilizers in cotton cultivation in highly weathered tropical soils.

Highlights

Brazil is one of the world’s major cotton producers with a cultivated area of 1.66 million ha in the 2019-2020 season and 98 % of the production from the Cerrado biome (CONAB, 2020), a Brazilian tropical savanna that encompasses around 205 million ha
This study evaluated the influence of soil management and crop succession or rotation combinations with cotton on K dynamics and exchangeable reserves in the soil profile, and the partial balance of K after nine years of cultivation in a clayey Oxisol in the Cerrado
This study evaluated the influence of soil management and crop combinations with cotton on K dynamics, exchangeable reserves in the soil and partial balance after nine years in a clayey Oxisol in the Brazilian Cerrado

Summary

Introduction

Brazil is one of the world’s major cotton producers with a cultivated area of 1.66 million ha in the 2019-2020 season and 98 % of the production from the Cerrado biome (CONAB, 2020), a Brazilian tropical savanna that encompasses around 205 million ha. The use of liming and fertilizer amendments in the last decades led soils to become one of the most relevant agricultural environments for food production worldwide (Lopes and Guilherme, 2016). To achieve high yield and fiber quality, cotton cropping in Cerrado uses large amounts of fertilizers, which increase the production cost. Cotton demands high amounts of K, since it is vital for fiber formation and quality (Yang et al, 2016). The production of 1 ton of seed cotton requires an extraction equivalent to 58 kg ha–1 of K2O from the soil, but only 30 % of that is exported by the harvested cottonseeds and fibers (Borin et al, 2019)

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Conclusion