Seventy-seven adaptive research trials were conducted, with the
participation of local farmers, on
their fields during the 1993 and 1994 wet seasons (southwest monsoon seasons) in
the warm subhumid
tropical zone on the west coast of India. The objective of the trials was to
compare the agronomic
and economic benefits of an improved management consisting of placing urea
briquettes containing
diammonium phosphate (UB–DAP) by hand (56 kg N/ha and 14 kg P/ha)
after controlled
transplanting using a modified 20×20 cm hill spacing with two other
practices: (i) the current
management system, consisting of random transplanting and two split applications
of prilled urea
(PU) and a basal application of single superphosphate (SSP) and (ii) the
farmers' traditional
management practices, involving random transplanting and broadcasting of
fertilizers. In spite of
marked variations in rainfall distribution patterns during the 1993 and 1994
seasons, the improved
management using UB–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 system. These additional yields were
obtained at a 28–36%
lower plant population density (25 hills/m2v.
35–39 hills/m2). The use of a modified 20×20 cm
spacing could reduce by up to 50% the labour normally required for the
conventional placement of
UB by hand about 1 week after transplanting using the standard 20×20 cm
spacing (8–10
workdays/ha). The estimated value: cost ratios for the improved management
ranged from 4·9 (1994)
to 8·6 (1993) and increased further when the savings in seed input were
considered. Stochastic
dominance analysis of the yield data suggests that the improved management of
UB–DAP could be
risk-free and therefore would be preferred over the other two managements by
rice farmers and policy makers.