Hybrid maize technology for rural development in Thailand

Maize is one of the most important crops in Thailand. From the 1950s until the 1980s, open-pollinated varieties (OPVs) were predominant in maize production. Research and development on hybrid maize at Kasetsart University was initiated in 1978, and a few years later private seed companies began their hybrid research. Kasetsart University has continuously released inbred lines (Ki 1 to Ki 45), 10 hybrids of three-way crosses, and single crosses to the public and private sectors since 1982. Hybrid seed used increased from 0.1 percent of maize planted area in 1981 to 77.5 percent in 1996, or 5.26 percent/yr. This resulted in increasing yields from 2,356 kg/ha in 1981 to 3,288 kg/ha in 1995, or 56.4 kg/ha/yr (0.55 percent/yr). In 1992, hybrids yielded, as a national average, 3,269 kg/ha which was higher than the improved OPVs (29.5 percent) and local varieties (42.9 percent). From the promotion data of the Department of Agricultural Extension in 1994, hybrids planted in advanced areas produced average yields 3,869 kg/ha higher than the improved OPVs in general areas (52.1 percent higher). From the 1992/93 crop year report, the net profits of single crosses, other types of hybrids, and OPVs were 6,445, 6,006 and 4,222 bahts/ha, respectively. In the 1980s, three-way crosses, double-crosses, and some nonconventional hybrids had high proportions in hybrid seeds used, but in this decade single-cross hybrids have more market share, especially from the mid-1990s, because of their higher yield potential and the promotion efforts of the Department of Agricultural Extenstion, Kasetsart University and private seed companies. From the 10 year (1987-96) review of the Cooperative Hybrids Yield trials showing the progress of yield improvement every year, the highest yielders produced yields higher than the OPV check (Suwan 1) in the range of 281-61.0 percent. Three-way crosses were the top yielders only the first two years but after that they were single crosses, and gave average yields of 9.0-9.5 t/ha. Even if Thai farmers can get only half the yields of on-station trials by using the single-cross hybrids, and use only half the inputs (fertilizer and other cultural practices) of on-station trials, still domestic maize production will be able to serve to stimulate rural development, and to meet needs of animal feed industries and export. Finally, hybrid maize technology, especially single crosses, allows maximum exploitation of heterosis, thus enhancing yield potential and drought tolerance. Farmers will accept the single cross technology very quickly under unpredictable environments.