Quadratic response assessment of gypsum and elemental sulphur on the yield and S use efficiency for soybean

Abstract

As sulphur is the most vital nutrient for the growth and yield of soybean, determining its optimum source and dose becomes very critical. Experiment was conducted at the Agricultural Research Farm, Faculty of Agriculture (Wadura), SKUAST-Kashmir, India to assess the effects of different sources of sulphur at varying levels on the performance of soybean during the Kharif seasons of 2021 and 2022. Two sulphur sources (gypsum and elemental sulphur) were evaluated at five levels (0, 30, 45, 60, and 75 kg sulphur per hectare) using factorial randomized block design with three replicates. The quadratic response function was estimated for each source's optimum sulphur level. The findings showed that gypsum application consistently led to superior growth performance compared to elemental sulphur and higher seed yield of 18.53 and 18.71 q ha-1 and stover yield of 23.60 and 26.82 q ha-1 in the years 2021 and 2022 respectively. However, a significant difference was not observed between the two sources regarding AE, PE, and ANR. In the sulphur levels studied, employing 60 kg sulphur ha-1 demonstrated the most favourable outcomes for growth parameters followed by 75 kg sulphur ha-1. However, with 60 kg sulphur ha-1 an increase of 4.17 and 2.75% for seed yield was shown, 3.97 and 3.08% for stover yield, and 2.62 and 2.19% for biological yield over 75 kg sulphur ha-1 in 2021 and 2022, respectively. Gypsum application resulted in higher S uptake than elemental sulphur in grain and stover highlighting its effectiveness as a sulphur source. S uptake in grain and stover increases with increasing sulphur levels, with the highest uptake observed at 60 kg S ha-1 being coequal to 75 kg S ha-1. The quadratic response, therefore, concluded that for achieving the best performance of Soybean, the sulphur application should be optimized at 60 kg ha-1. The need to assess and analyze the use of S @ 60 kg ha-1 using gypsum is critical in future as sulphur deficiency is becoming very common in Indian soils.