Author : Diaz, C.; Hossain, M.; Merca, S.; Mew, T.

Summary : A farmer participatory research was conducted in two sites of Central Luzon to examine the impact of best quality seeds on farm yield. For each site 30 farmer collaborators planted their own seed and IRRI supplied seed of the same variety in two subplots of a selected parcel. They followed their own management practices which was monitored by the researchers. An analysis of seed health of the farmer-used seeds showed a large portion were not fully filled and were discolored, 3 to 4 % of the seeds having mixtures with off-types, 5% of the seeds with lethal seed infection, and seeds had around 96% purity level. The results of the experiment showed that plot planted with IRRI supplied seeds had 7% higher yield than the planted with farmer-kept seeds in the site where the yield difference between the plots was 20%. A large part of the increase in yield was due to lower weed and pest pressures achieved by the use of high quality seeds. A multivariate regression analysis of the determinants of rice yield showed that weeds and pests are important biotic constraints reducing rice yield nearly 25 percent.