Abstract
ABSTRACT The use of gypsum to improve the root environment in tropical soils in the southeastern and central-western regions of Brazil is a widespread practice with well-established recommendation criteria. However, only recently gypsum began to be used on subtropical soils in South of Brazil, so available knowledge of its effect on crop yield is incipient and mainly for soils under no-till (NT) systems. Avaiable studies span a wide range of responses, from a substantial increase to a slight reduction in crop yield. Also, the specific conditions leading to a favorable effect of gypsum application on crop yield are yet to be accurately identified. The primary objectives of this study were to examine previously reported results to assess the likelihood of a crop response to gypsum and to develop useful recommendation criteria for gypsum application to subtropical soils under NT in Brazil. For this purpose, we examined the results of a total of 73 growing seasons, reported in 20 different scientific publications that assessed grain yield as a function of gypsum rates. Four different scenarios were examined, by the occurrence or not of high subsurface acidity (viz., Al saturation >20 % and/or exchangeable Ca 3 cmolc dm-3) failed to increase crop yield, irrespective of the soil water status. Under these conditions, high gypsum rates (6-15 Mg ha−1) may even reduce grain yield, possibly by inducing K and Mg deficiency. On the other hand, applying gypsum to soils with high subsurface acidity increased yield by 16 % in corn (87 % of cases) and by 19 % in winter cereals (83 % of cases), whether or not the soil was water-deficient. By contrast, soybean yield was only increased by gypsum applied in the simultaneous presence of high soil subsurface acidity and water deficiency (average increase 27 %, 100 % of cases).
Highlights
Soils under no-tillage (NT) in Brazil have expanded exponentially since the early 1990s, covering an area of more than 32 million hectares by 2012 (Febrapdp, 2012)
Soil critical levels used for the recommendation of gypsum in tropical soils are not the same observed in subtropical soils under no-till system, and it may be different for legumes and grasses crops
For grasses grown on subtropical Oxisol under no-till soils, the use of 10 % Al saturation and/or 3.0 cmolc dm-3 exchangeable Ca in the soil subsurface layer (0.20-0.40 m) is more suitable than the current recommendation (Al saturation of 20 % and/or 0.5 cmolc dm-3 Ca) for tropical soils
Summary
Soils under no-tillage (NT) in Brazil have expanded exponentially since the early 1990s, covering an area of more than 32 million hectares by 2012 (Febrapdp, 2012). High soil acidity in the subsurface layer may restrict root growth and decrease water and nutrient uptake, thereby leading to low crop yields (Sousa et al, 2007; Dalla Nora and Amado, 2013; Zandoná et al, 2015). Under these conditions, gypsum has been widely used in recent years to improve the soil subsurface environment and deepen rooting in NT soils. Depends on the particular soil type, crop, fertilizer rate, and rainfall regime (Zoca and Penn, 2017)
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