PhD

With the objectives of identifying the most economic crop combination for the double crop wet rice fields of Kerala and to assess soil fertility changes due to rice based cropping systems and also to find out the residual effects of the summer crops on the succeeding rice crops an investigation was conducted at the R.A.R.S. Pattambi in a split – split plot design, for a period of two years. The salient findings of the investigation are as follows.
In the Cassava-rice-rice system 25 per cent saving was recorded for P and K for maximum grain yield of kharif rice than the recommended doses. A saving of 50 per cent each of P and K was recorded for the maximum straw yield than the recommended doses.
In cowpea–rice-rice system for maximum grain yield of kharif rice there was a saving of 25 per cent of P and K than recommended doses. The same trend followed for the maximum yield of strew also.
In groundnut –rice-rice system, for maximum grain yield of kharif rice there was a saving of 25 per cent of P and K than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were required.
In bhindi– rice-rice system for maximum grain yield of kharif rice there was a saving of 50 per cent of P and K than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were essential.
In rice-rice-rice system for maximum grain yield a saving of 25 per cent of P and K was recorded than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were required.
In fallow-rice-rice system for maximum grain yield full dose of recommended nutrients were essential, whereas for the production of maximum straw yield a saving of 25 per cent of P and K than the full dose was recorded.
In cassava, rice and fallow systems for the manifestation of residual effect to the rabi rice, balanced nutrients at high doses are to be applied to the preceding kharif crop where as in the cowpea, groundnut and bhindi systems, residual effects of nutrients are seen manifested to the rabi rice crop even when the kharif rice crop is applied with medium doses of nutrients.
There was a trend of slight decrease in the organic carbon content of the soil under all the cropping systems. The status of available nitrogen and potash after one and two year crop sequences also followed the above trend. Regarding the status of phosphorus in the soil, there was a slight increase after one and two year crop sequences.
Cassava system produced maximum yield in terms of energy value followed by groundnut. From the economic point of view bhindi system gave the maximum net return. Maximum dry matter production (biomass production potential) was recorded in the cassava system followed by groundnut system.
A vegetable crop like bhindi or a tuber crop like cassava seem to be more profitable than growing rice in summer season in the double crop wet rice fields of Kerala, rice being least economic.
Among the cropping systems rice-rice-rice system generates maximum employment opportunities for the farm labourers with maximum job opportunities for women labourers as well.