Sulphur flow in soil–plant system with long‐term agricultural practices on a Vertisol

Abstract

Sulphur (S) deficiency is widespread in agricultural fields across the globe. Its flow in the soil–plant system under different management practices is too poorly understood to strategize S fertilisation with increased efficiency. Accordingly, an attempt was made to elucidate the pathways of S flow in soils and to plants under organic, inorganic, and integrated nitrogen (N) management practices using a 30‐year‐old long‐term field experiment planted with sorghum in the semi‐arid tropics. Partitioning soil S into pools, we observed that exchangeable (4.2%) and adsorbed (4.6%) pools constituted a small part of total soil S but contributed mainly to S nutrition (46% and 33%) of sorghum; it also contributed to the variability of S extractable by six commonly used extractants. Using multiple criteria, the superiority of monocalcium phosphate as an extractant for assessment of S in Vertisols was established. Among the N management practices, integrated N management performed better in supplying S in soils and to sorghum, and excelled, both in retention (35.9% of applied) and utilisation (13%) of S, curbing its losses (51.1%) from the system, over the organics (26%, 8.4%, and 65.6%, respectively) and inorganic (11.6%, 7.1%, and 81.3%, respectively) management practices. The integrated management practices with farmyard manure (FYM) excelled in improving S in soils, including economics. Out of the organics, FYM was more effective in improving S availability in soils and its nutrition of the crop over the crop residue, and green manure. Changes in organic C, and oxides and hydroxides of Fe and Al in soils are the keys governing the flows of S in the soil–plant system. A detailed pathway of the increased efficacy of S fertilisation upon conjoint application of N sources over the others was highlighted for adoption in Vertisols of semi‐arid tropics. Highlights Inter‐relationship between pools and extractants of S were elucidated. Organic C and sesquioxides played a key role in S transformation in soils. Monocalcium phosphate was the most sensitive extractant for S in soils. Sixty two percent of the applied S was lost, 28% retained and 10% utilised.

Soil degradation and mitigation in agricultural lands in the Indian Anthropocene

“…Residue burning is still widespread, and causes GHG emissions, loss of plant nutrients such as N, P, K and sulphur (S), hasadverse impacts on soil properties, and causes wastage of valuable crop residues (Samra et al, 2003). S deficiency is severe in India where plant‐available S was deficient or marginal in ~70% of soil samples analysed in major soil testing programs (Ghosh et al, 2022). About 90–140 Mt per year of crop residues are burnt in the field to clear land of straw and stubble after harvest (NAAS, 2012).…”