Integrated nutrient management for rice based cropping systems of Onattukara tract

Abstract

An investigation was carried out at the Rice Research Station, Kayamkulam to identify the most suitable rice based cropping system for the Onattukkara tract and to evolve a suitable ecologically and economically viable integrated nutrient management practice for the system. The experiment was laid out in a 4x6 factorial strip plot design and was carried for two consecutive years extending from April, 1994 to May 1996. The treatments consisted of four cropping systems (rice-rice-sesamum, rice-rice-groundnut, rice-rice-cowpea and rice-rice-bhindi) and six nutrient management levels (N1 farmers' practice, N2 - Package of practices recommendations, N3 three-fourth recommended N as chemical + one-fourth as FYM, N4 - three-fourth recommended N as chemical + one-fourth as FYM + Azospirillum, N5 - three-fourth recommended N as chemical + one-eighth as FYM + one-eighth as vermicompost and N6 - three fourth recommended N as chemical + one - eighth as FYM + one - eighth as vermicompost + Azospirillum). During the third crop season the treatments N2 to N6 was package of practices recommendations (for the respective crops) while N1 was farmers' practice itself. Among the different nutrient management levels tested, the treatment wherein one-fourth recommended N was

substituted with FYM and vermicompost along with Azospirillum recorded the maximum grain yield for first crop rice and second crop rice (irrespective of cropping system). The same treatment also supported a better straw yield by maintaining a favourable grain:straw ratio. In ricc-rice-'sesamum, the production efficiency was highp.st when one-fourth recommended nitrogen was supplied through farmyard manure and vermicompost along with Azospirillum. The BCR was maximum when the same treatment was applied without Azospirillum. In rice-rice-groundnut, rice- rice cowpea and rice-rice-bhindi, the same trend followed. Rice-rice-bhindi cropping system recorded the maximum production efficiency followed by rice-rice-groundnut during both the years, and rice-rice-sesamum recorded the minimum value. The overall mean returns was maximum with the cropping system,rice- rice-groundnut. It was followed closely by the rice-rice-bhindi cropping system. While rice-rice-cowpea recorded the meaning of economic returns during the first year, rice- rice sesamum recorded the same during the second year.

Studies on the physico-chemical properties of the soil showed that the cropping system, rice-rice-sesamum resulted in a slight increase in bulk density, water holding

capacity and water stable aggregates. The organic carbon, total nitrogen and available phosphorus content of the soil increased, while the soil pH, available nitrogen and available potassium contents decreased. The cropping system, rice-rice- groundnut resulted in an increase in bulk density, water holding capacity, water stable aggregates, organic carbon, soil pH, total nitrogen and available phosphorus and a decrease in the available nitrogen and available potassium contents. While there was an increase in the water holding capacity, water stable aggregates, organic carbon, total nitrogen, available nitrogen and available phosphorus there was a slight decrease in bulk density and soil pH in the cropping system, rice-rice- cowpea. The rice-rice-bhindi cropping system resulted in a decrease in the bulk density and soil pH and available potassium and an increase in the water holding capacity, water stable aggregates, organic carbon, total nitrogen, available nitrogen and available phosphorus. The balance sheet of nitrogen showed•a positive balance in the cropping systems rice-rice-groundnut and rice- rice-cowpea and a negative balance in the other two systems. All the cropping systems tested resulted in a negative balance for available phosphorus and a positive balance for available potassium.

The cropping system, rice-rice-groundnut was observed to be the most efficient one. followed by rice-rice-bhindi based on the productive efficiency, benefit cost ratio and soil sustainability. The marginal benefit cost ratio for the different nutrient management practices showed that the treatment comprising three fourth recommended dose of N as chemical + one-eighth as FYM + one-eighth as vermicompost (for first and second crop rice) and package of practices 1ecommendations for groundnut (third crop) was the most economic. However, for the rice-rice-bhindi cropping system, the package of practices recommendations was observed to be more economical.