Studies on long term effect of INM approach on forms of sulphur under rice on a Vertisol

Abstract

Effect of INM approach on Sulphur farctions in rice grown on a Vertisol was studied under long-term fertilizer experiment during kharif 2019 at research farm of Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.). The experiment comprised of different levels or doses of NPK fertilizers alone and in combination with zinc sulphate, farmyard manure (FYM), blue green algae (BGA) and green manuring (GM) was laid out in randomized block design with four replications and ten treatments viz. Control, 50% NPK,”“100% NPK,”“150% NPK,”“100% NPK”+“ZnSO4@ 10kg”ha-1,”100% NP, “100% N,”“100% NPK + FYM” @“5t ha-1”, “50% NPK+BGA”@ “10kg ha-1” and “50% NPK + GM” @“40kg ha-1. Different S fractions were estimated in surface and sub-surface soil samples before the rice transplanting (2019). Application of 150% NPK significantly increased the sulphate sulphur (36.4 kg ha-1), water soluble sulphur (35.0 kg ha-1), organic sulphur (86 kg ha-1) and heat soluble sulphur (80 kg ha-1) as compared to other treatments. A decrease in S fractions was observed with increase in the depth of soil from 0-15 to 15-30 cm. The results of surface and sub surface soil samples (0-15 cm and 15-30 cm) collected before of rice showed that zero fertilization led to decline in the levels of all the S forms, while application of sulphur containing fertilizer (SSP and ZnSO4) and organics increased it over omission of these nutrients and control. Organic sulphur was found to be the most dominant fraction (about 90%) followed by heat soluble sulphur. Integration of inorganic fertilizers with organics proved better as compared to application of inorganic fertilizers alone. Integrated use of inorganic fertilizers in conjunction with organics increased grain and straw yields over inorganically treated plots. Highest grain and straw yields of rice were recorded in 150% NPK 6970 and 8364 (kg ha-1), respectively. The yield of rice had highest correlation with sulphate sulphur (r=0.810**) followed by water soluble (r=0.793**). The values of coefficients of correlation for sulphate S, water soluble S, heat soluble S and organic S with yield of rice were 0.810**, 0.793**, 0.737** and 0.790**, respectively. All the sulphur fractions positively correlated with each other amongst continuous application of inorganic fertilizers and organic manure.