CHANGES IN PHYSICOCHEMICAL PROPERTIES OF SOIL UNDER INTENSIVE CROPPING SYSTEMS

A field experiment was conducted during 1986-87 and 1987-88 with 5 cro pping systems, viz. rice (Oryza sativa L.)-wheat (Triticum aestivum L. emend. Fiori & Paol.)-greengram (Phaseolus radiatus L.), maize (Zea m ays L.)-pea (Pisum sativum L. sensu lato)-common millet (Panicum milia ceum L.), pegionpea [Cajanus cajan (L.) Millsp.]-wheat-greengram, maiz e-potato (Solanum tuberosum L.) + Indian mustard [Brassica juncea (L.) Czernj. & Cosson]-blackgram (P. mungo L.) and blackgram-Indian mustar d-maize + fodder cowpea [Vigna unguiculata (L.) Walp.], under irrigate d conditions. Physico-chemical analysis of soil after 2 years of exper imentation showed that the bulk density was reduced and infiltration r ate of the soil was increased from their initial values to the end of experiment. The organic carbon, available nitrogen, phosphorus and pot assium contents of the soil were increased from their initial content. The pH of the soil was decreased at the end of study under all the cr opping systems. The most productive system (maize-potato + Indian must ard-blackgram) removed greater amount of N, P and K (345.94, 78.43 and 387.86 kg/ha/year respectively) from soil compared with the other sys tems. The balance for N and K was negative in all the systems but high er depletion of N and K (110.94 and 267.93 kg/ha/year respectively) wa s recorded under maize-potato + Indian mustard-blackgram systems. The balance for P was positive in all the systems and higher build-up of P (101.56 kg/ha/year) in surface layer was found under maize-potato + I ndian mustard-blackgram cropping systems.