Mapping the Available Water Capacity in tropical climate soils for soybean (Glycine max) cultivation in the state of Tocantins-Brazil

André De Moura Andrade,Rui Da Silva Andrade,Erich Collicchio

doi:10.4136/ambi-agua.2718

Abstract

Brazilian soybean has undergone considerable economic growth. Its production depends on the demand for some inputs. One of these inputs is the soil water supply, which can be made artificially or obtained by natural rainfall. Knowledge of available water capacity (AWC), which depends on total water availability (TWA), is poorly accessible and difficult to measure in the field. This study aimed to map the AWC of the state of Tocantins, based on pedotransfer functions (PTFs), to evaluate the water availability of the soils of the microregions of that state. We used the Arya and Paris model, aided by a computer program, Qualisolo, made by Embrapa Instrumentação. One hundred fifty-seven tropical soil samples were extracted from the Embrapa Solos portal. Preliminarily, the soil water retention curve (SWRC) was obtained and, subsequently, the TWA and AWC for this oilseed were estimated. Multiple linear regressions show the correlation between TWA and clay (CL), Silt (ST) and total sand (TS) contents. The correlation established was TWA = 3.2993 – 0.0028TS – 0.0034CL. This main conclusion reflects a fruitful AWC for decision-making by the soybean agribusiness and exposes the regional weaknesses for this crop under a rainfed regime in some regions of Tocantins. We could observe that, in terms of water availability, agribusiness is a potential threat to the environment protection area (APA) of the Ilha do Bananal/Cantão, Formoso River microregion.

Highlights

Production chains tend to adapt to the growing demands for energy resources, which inevitably implies sustainably expanding their production systems
The clay loam soils had a total water availability (TWA) of approximately 1.11 mm cm-1, with a coefficient of variation (CV) around 15.14%, while the TWA of the clay loam was around 1.53 mm cm-1 of soil, for a CV of 10.98%
The lowest averages of TWA meant higher CV values when statistically analysing 157 granulometric samples, a result measured by other authors

Summary

Introduction

Production chains tend to adapt to the growing demands for energy resources, which inevitably implies sustainably expanding their production systems. One of the criteria expected for rural expansion is the search for environmental compartments that parameterise low-risk climatic conditions and physical factors favourable to their productive performance (Santos and Martins, 2016). Among these various agribusiness segments, soybean farming stands out, an energy crop with a more significant market predominance due to the manufacture of biodiesel, cosmetics, food, fertilisers, animal nutrition, among other industrial destinations (Lemos et al, 2017). The difference between oil and protein contents, can be affected by this variation in available water, which is not currently desirable when the focus is on increasing biofuel generation (Lima et al, 2017)

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