Crop Response to Gypsum Application to Subtropical Soils Under No-Till in Brazil: a Systematic Review

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 <0.5 cmol c dm-3 in the 0.20-0.40 m soil layer) and of water deficiency during the crop cycle. Based on the results, for grasses, 10 % Al saturation and/or 3 cmol c 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 cmol c dm-3 Ca) for subtropical NT soils in Brazil. Also, applying gypsum to NT soils with low subsurface acidity (Al saturation <10 %) and with an adequate Ca content (>3 cmol c 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).

Does gypsum increase crop grain yield on no‐tilled acid soils? A meta‐analysis

“…The probability of a positive response to gypsum under these conditions was 77 and 98% for the cereal crops and 88% for soybean ( Figure 9). Our results are consistent with those of Tiecher et al (2018), who showed that existing recommendations (Pauletti & Motta, 2017;Sousa & Lobato, 2004)…”

“…The number of pair observations and the total number of crop harvests (environment × year) included in each category are shown in parenthses. The critical thresholds for Al saturation in the 0.20-to 0.40-m layer for cereals were >5%, and those of soybean were >40 and >10% with and without the occurrence of water deficiency, respectively to gypsum under much less severe acid conditions Dalla Nora et al, 2017b;Tiecher et al, 2018), possibly as a result of gypsum increasing the availability of sulfate and basic cations in the subsoil and also of the potentially lower acidity tolerance and higher yield potential of current cultivars and hybrids (Dalla Nora et al, 2017b).…”

“…Based on the contribution of exchangeable Ca 2+ to the effective CEC of the subsoil, Caires and Guimarães (2018) recommended using higher gypsum rates than those typically applied to soil. However, Tiecher et al (2018) compared various methods used to identify the rates that maximized profits (95% of the maximum possible yield) and found that none exhibited adequate correlation. They concluded that a gypsum rate of 3 Mg ha −1 usually sufficed to obtain 95% of the maximum possible crop yield when subsoil thresholds for gypsum application are reached.…”

“…The effects of subsoil acidity are especially adverse in NT systems, which account for >32 Mha in Brazil and 180 Mha (12.5% of all cropland area) in the world (Kassam, Friedrich, & Derpsch, 2019). Soils under uninterrupted no-tillage typically exhibit nutrient and organic matter concentration gradients across their profile, with high values in the surface and low values in the subsoil as a result of the successive deposition of crop residues and application of fertilizers and amendments to the soil surface (Dalla Nora & Amado, 2013;Tiecher et al, 2018). In contrast, conventionally tilled soils exhibit uniform acidity and nutrient and organic matter levels as a result of the periodic mobilization of the arable layer (Bortoluzzi et al, 2014;Rheinheimer et al, 2018).…”

Crop Yield Responses to Sulfur Fertilization in Brazilian No-Till Soils: a Systematic Review

“…Grain yields for different crops, regions, and crop harvests were compared by using the equation 1 to calculate a relative yield for each crop harvest in terms of the specific treatment leading to the highest yield as reference (Tiecher et al, 2018): -S contents, which spanned 48 crop harvests for the surface soil layer (0.00-0.20 m) and 34 for the subsurface layer (0.20-0.40 m), were used to construct a calibration curve for soil available S from the initial available SO 4 2--S content for the experiment and the relative crop yields of the plots receiving no S (controls) (CQFS-RS/SC, 2016; Vieira et al, 2016). The S rate recommended to obtain 95 % of the highest relative yield, which was considered to be the maximum economic efficiency (MEE), was determined by plotting the relative yield of each S Rev Bras Cienc Solo 2019;43:e0180078 rate and the respective rate used (Tiecher et al, 2018) (Lock et al, 2017). Those results yielding P-values less than 0.05 in randomized tests were assumed to be significant.…”