The frequency, size and rate of development of cracks influence the transport of water, nutrients and gases in the soil profile and plant growth processes in Vertisols. Despite their importance, studies on characterising cracks in Vertisols of India are limited. This study attempts to evaluate the influence of different tillage practices, nutrient management and cropping systems on cracking behaviour of a Vertisol in central India. The length, depth, width, area and volume of cracks were recorded after the harvest of the wet season crops, i.e. soybean (Glycine max L.) and rice (Oryza saliva L.) from three ongoing tillage experiments with three different cropping systems, i.e. soybean-wheat (Triticum aestivum L.), soybean-linseed (Linum usitatissitmum L.) and rice-wheat. The results revealed that all the crack parameters were significantly negatively correlated with the water content of the 0-15 cm soil layer and, crack width and crack volume were significantly positively correlated with the bulk density of the 0-15 cm soil layer. Gravimetric water content and bulk density of the 0-15 cm soil layer together explained 79% variation in the crack volume. The crack volume was significantly negatively correlated (r = 0.86, P = 0.01) with the root length density of the previous soybean crop. Rice grown under puddled condition significantly enhanced different crack parameters viz., length, depth, width, surface area and volume of the cracks over nonpuddled direct seeded rice. Sub-soiling practised in soybean under the soybean-linseed system significantly reduced the width, depth, length and surface area of cracks by 12.5, 10, 5 and 12%, respectively, over conventional tillage. No tillage practised in soybean under soybean-wheat system resulted in significant increase in width, depth and volume of the cracks but decrease in length and surface area of cracks over conventional tillage and mould board tillage practice. Application of manure reduced the magnitude of different crack parameters in soybean-linseed cropping system. Thus cracking in Vertisols can be favourably managed by the selection of proper tillage practice, cropping system and organic manure amendments. (C) 2003 Elsevier Science B.V. All rights reserved.
