AGRONOMIC PERFORMANCE OF UREA BRIQUETTES CONTAINING DIAMMONIUM PHOSPHATE IN RAIN-FED TRANSPLANTED RICE ON FARMERS FIELDS

Seventy-seven adaptive research trials were conducted, with the partic ipation of local farmers, on their fields during the 1993 and 1994 wet seasons (southwest monsoon seasons) in the warm subhumid tropical zon e on the west coast of India. The objective of the trials was to compa re the agronomic and economic benefits of an improved management consi sting of placing urea briquettes containing diammonium phosphate (UB-D AP) by hand (56 kg N/ha and 14 kg P/ha) after controlled transplanting using a modified 20 x 20 cm hill spacing with two other practices: (i ) the current management system, consisting of random transplanting an d two split applications of prilled urea (PU) and a basal application of single superphosphate (SSP) and (ii) the farmers' traditional manag ement practices, involving random transplanting and broadcasting of fe rtilizers. In spite of marked variations in rainfall distribution patt erns during the 1993 and 1994 seasons, the improved management using U B-DAP increased grain yields by 2.14 t/ha (89%) in 1993 and 1.23 t/ha (45%) in 1994 over traditional management practices and by 1.56 t/ha ( 52%) in 1993 and 0.83 t/ha (27%) in 1994 over the current management s ystem. These additional yields were obtained at a 28-36% lower plant p opulation density (25 hills/m(2) v. 35-39 hills/m(2)). The use of a mo dified 20 x 20 cm spacing could reduce by up to 50% the labour normall y required for the conventional placement of UB by hand about 1 week a fter transplanting using the standard 20x20 cm spacing (8-10 workdays/ ha). The estimated value:cost ratios for the improved management range d from 4.9 (1994) to 8.6 (1993) and increased further when the savings in seed input were considered. Stochastic dominance analysis of the y ield data suggests that the improved management of UB-DAP could be ris k-free and therefore would be preferred over the other two managements by rice farmers and policy makers.