Re-evaluating the effect of sulphur fertilization on yield and nutrient uptake in a groundnut-blackgram cropping sequence

Comprehensive information on the direct and residual effects of elemental sulphur fertilization on yield and nutrient uptake in sequential legume-based cropping systems, particularly the groundnut–blackgram sequence, remains limited, despite growing evidence of widespread sulphur deficiency and its critical role in crop productivity. The present study was conducted to evaluate the direct and residual effects of sulphur on yield and nutrient uptake in a groundnut-blackgram cropping sequence through a pot culture experiment at the Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University (TNAU), Coimbatore, in 2021. The experiment was laid out in a completely randomized design (CRD) with six levels of sulphur and three sulphur-oxidizing bacteria (SOB) treatments, each replicated four times. Elemental sulphur was applied at 0, 20, 30, 40, 50 and 60 kg S ha-1 and SOB was applied at three levels-no application, seed treatment and soil application. The results revealed that the application of 60 kg ha-1 sulphur as elemental sulphur combined with soil application of SOB at 2 kg ha-1 significantly enhanced seed yield, nutrient content and nutrient uptake in both crops for direct and residual effects and was on par with S at 40 kg ha-1 . The experiment investigated an alternative source of sulphur nutrition that could reduce sole reliance on gypsum as a sulphur source. A residual notable impact was observed, suggesting that additional sulphur application may be unnecessary for the succeeding crop.