Abstract
ABSTRACT The increase in disputes over water use in the Brazilian Cerrado has demanded improvements in irrigation management and increase in water use productivity. In this context, deficit irrigation is an interesting management strategy, as it enables water savings without significant losses of yield. The present study aimed to evaluate the phenology and yield of a soybean cultivar subjected to different soil moisture contents. The experimental design used was randomized blocks with five treatments and four replicates. In each treatment, an irrigation strategy was applied based on the available water in the soil (AW). The T1 treatment was performed by applying from 80 to 100% AW; in T2 treatment, the allowed variation was from 60 to 80% AW; in T3 treatment, it was from 40 to 60% AW; in T4, from 20 to 40% AW; and in T5, from 0 to 20% AW. It was verified that, in winter and summer, even without the need to reduce water withdrawal, it is recommended to apply from 60 to 80% of the available water in the soil for soybean crop, without decreasing yield. In situations of water restriction, it is possible to have yield of around 55 and 70% in winter and summer, respectively, for the condition from 20 to 40% of the available water in the soil.
Highlights
With a cultivated area of approximately 37 million hectares, typically under rainfed conditions, and a national average yield (Y) of 3,330 kg ha-1 and total production of 120.9 million tons, in the 2019/2020 season, Brazil is the largest soybean producer in the world (CONAB, 2020)
Any strategy that aims to improve irrigation efficiency should prioritize the adjustment of management, and should consider improvements in the values of irrigation water use efficiency (WUEi) and water use productivity (WP) (Montoya et al, 2017; Gajić et al, 2018; Jha et al, 2018)
The total irrigation depth applied was lower in all treatments, when compared to summer
Summary
With a cultivated area of approximately 37 million hectares, typically under rainfed conditions, and a national average yield (Y) of 3,330 kg ha-1 and total production of 120.9 million tons, in the 2019/2020 season, Brazil is the largest soybean producer in the world (CONAB, 2020). Only 11% of Brazilian soybean plantations use irrigation (Silva et al, 2019), factors such as the long periods of variability in rainfall, which bring uncertainty regarding the best sowing time, as well as production, and the fall in yield (Montoya et al, 2017; Battisti & Sentelhas 2019; Wang et al, 2020), ranging from 46% to 74% (Sentelhas et al, 2015; Battisti et al, 2018), have increased the area of irrigated soybean, as in the Brazilian Cerrado This region, which concentrates about 80% of all center pivots (Althoff & Rodrigues, 2019) and holds 64% of the irrigated area in Brazil (BRASIL, 2014), has faced serious water scarcity problems in some of its main hydrographic basins. Any strategy that aims to improve irrigation efficiency should prioritize the adjustment of management, and should consider improvements in the values of irrigation water use efficiency (WUEi) and water use productivity (WP) (Montoya et al, 2017; Gajić et al, 2018; Jha et al, 2018)
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