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ThesisItem Open Access Studies on the effect of multiple cropping on soil fertility and crop yields in wet land(Department of Agronomy, College of Agriculture, Vellayani, 1978) Sasidhar, V K; KAU; Sadanandan, NThe problem entitled "Studies on the effect of multiple cropping on soil fertility and crop yields in wet land" was conducted at the College of Agriculture, Vellayani, Trivandrum during the years 1974-76 to assess the effect of five cropping patterns, viz, rice-rice-sweet potato, rice-rice-cowpea, rice-rice-sesamum, rice-rice- groundnut and rice-rice-rice on the various physical and chemical properties of soil and yield of crops and finally to find out the most suitable and efficient cropping pattern. The study revealed that rice-rice-groundnut was the most efficient and suitable cropping pattern for the wet land. The maximum yield per hectare as well as per day was recorded by sweet potato and the minimum by sesamum. While the maximum annual yield was recorded by the cropping pattern rice-rice-sweet potato, the minimum was from the cropping pattern rice-rice-sesamum during both the years. The dry matter production per hectare per year from individual cropping patterns was maximum in rice-rice- sweet potato and minimum in rice-rice-cowpea during the first year and the corresponding rotations were rice-rice- groundnut and rice-rice-sesamum during the second year. The maximum economic returns were obtained from the cropping pattern rice-rice-groundnut during both the years. While the minimum economic returns were obtained from the cropping pattern rice-rice-cowpea during the first year it was from rice-rice-rice during the second year.. Soil fertility studies showed that cropping pattern rice-rice-sweet potato resulted in decrease in bulk density, pH and total nitrogen and increase in water stable aggregates, cation exchange capacity, organic carbon, C : N ratio, extractable phosphorus, exchangeable potash, exchangeable calcium, exchangeable, magnesium, and exchangeable hydrogen. The cropping pattern rice-rice-cowpea resulted in decrease in bulk density, pH, cation exchange capacity, organic carbon, c : 11 ratio, exchangeable calcium and exchangeable magnesium and increase in water stable aggregates, total nitrogen, extractable phosphorus, exchangeable potash and / exchangeable hydrogen. While there was decrease in bulk density, pH and total nitrogen there was increase in cation exchange capacity, organic carbon, G : N ratio, extractable phosphorus, exchangeable potash, exchangeable calcium, exchangeable magnesium and exchangeable hydrogen in the cropping pattern rice-rice-sesamum. The rice-rice-groundnut cropping pattern resulted in decrease in bulk density, pH,cation exchange capacity, organic carbon, G : W ratio and increase in,water stable aggregates, total nitrogen, extractable phosphorus, exchangeable potash, exchangeable calcium, exchangeable magnesium and exchangeable hydrogen. However, cropping pattern rice-rice-rice resulted in increase in bulk density, 0 * N ratio, exchangeable hydrogen and decrease in water stable aggregates, pH, cation exchange capacity, organic carbon, total nitrogen, extractable phosphorus, exchangeable potash, exchangeable calcium and exchangeable magnesium. While virippu rice was most efficient, in utilizing nitrogen for dry matter production, cowpea was least efficient in this regard. The groundnut crop showed maximum efficiency in the utilization of phosphorus and potash for dry matter production. While sesamum was least efficient in the case of phosphorus it was sweet potato in the case of potash. The highest and the lowest protein yields wereobtained during first and second years from the cropping /pattern rice-rice-groundnut and rice-rice-sesamum respectively