Long-term soil management effects on crop yields and soil quality in a dryland Alfisol

Abstract

Along-termexperimentwasconductedwith theobjectiveofselectingtheappropriatelandmanagementtreatmentsandto identify the key indicators of soil quality for dryland semi-arid tropical Alfisols. The experiment was conducted using a strip split–split plot design on an Alfisol (Typic Haplustalf) in southern India under sorghum(Sorghumvulgare (L))-castor (Ricinus communis (L)) bean rotation. The strip constituted two tillage treatments: conventional tillage (CT) and minimum tillage (MT); main plots were three residuestreatments:sorghumstover (SS), gliricidialoppings(GL),‘no’residue(NR)andsubplotswerefour nitrogenlevels:0(N0),30 (N30), 60 (N60), and 90 kg ha 1 (N90). Soil samples were collected after the sixth and seventh year of experimentation and were analyzed for physical, chemical and biological parameters. Sustainable yield index (SYI) based on long-term yield data and soil quality index (SQI) using principal component analysis (PCA) and linear scoring functionswere calculated.Application of gliricidia loppings proved superior to sorghumstover and no residue treatments inmaintaining higher SQI values. Further, increasingNlevels also helped inmaintaining higher SQI.Among the 24 treatments, the SQI ranged from0.90 to 1.27. The highest SQIwas obtained in CTGLN90 (1.27) followed by CTGLN60 (1.19) and MTSSN90 (1.18), while the lowest was under MTNRN30 (0.90) followed by MTNRN0 (0.94), indicating relatively less aggradative effects.Theapplication of90 kg N ha 1 underminimumtillage evenwithout applying any residue (MTNRN90) proved quite effective in maintaining soil quality index as high as 1.10. The key indicators, which contributedconsiderablytowardsSQI,wereavailableN,K,S,microbialbiomass carbon(MBC)andhydraulicconductivity(HC).On average, theorderofrelativecontributionoftheseindicatorstowardsSQIwas:availableN(32%),MBC(31%),availableK(17%),HC (16%), and S (4%). Among the various treatments, CTGLN90 not only had the highest SQI, but also the most promising from the viewpoint of sustainability, maintaining higher average yield levels under sorghum–castor rotation. Fromthe viewpoint of SYI,CT approach remained superior toMT.Tomaintain the yield as well as soil quality in Alfisols, primary tillage alongwith organic residue and nitrogen application are needed.