Long-term effects of lantana (Lantana spp. L.) residue additions on soil physical properties under rice–wheat cropping: I. Soil consistency, surface cracking and clod formation

Poor soil tilth is a major constraint in realizing optimum yield potential of wheat (Triticum aestivum L.) in rice (Oryza sativa L.)–wheat cropping system. The effect of long-term additions of lantana (Lantana spp. L.) biomass, a wild sage, on physical properties of a silty clay loam soil under rice–wheat cropping was studied in north-west India. Lantana was added to soil 10–15 d before puddling at 10, 20 and 30 Mg ha−1 yr−1 (fresh weight). At the end of 10th rice crop, liquid limit, plastic limit, shrinkage limit and plasticity index of soil increased significantly with lantana additions. The friability range of lantana-treated soil decreased from 8.9 to 7.8–8.2% gravimetric-moisture content, but soil became friable at relatively higher moisture content. Soil cracking changed from wide, deep cracks in hexagonal pattern to a close-spaced network of fine cracks. The cracks of sizes <5 mm increased, 10–20 mm and wider decreased, while 5–10 mm remained almost unchanged with lantana additions. The volume density of cracks decreased by 36–76% and surface area density by 19–37% compared with control. The clods of sizes <2 cm diameter increased, while 2–4 cm and 4–6 cm diameter decreased with lantana additions. The MWD of clods varied between 2.15 and 2.34 cm in lantana-treated soil as against 2.83 cm in the control. The bulk density and breaking strength of soil clods were lower in lantana-treated soil by 4–9% and 29–42% than in the control. About 23–47% less energy was required to prepare seed-bed in lantana-treated than in the control soil.