Silage production and quality of pearl millet, sorghum, and corn hybrids grown from seed exposed to low doses of gamma rays

Just before planting, seeds of pearl millet, Pennisetum americanum (L.) K. Schum., (formerly P. typhoides) hybrid, “Tift 23 × li”, and corn, Zea mays L., hybrids “Coker 71”, “DeKalb 1214”, and “Pioneer 3030” were exposed to gamma ray dosages of 0, 0·15, 0·3, 0·6, 1·2, 2·4, 4·8, 9·6, and 19·2 kR. “FS26” hybrid sorghum, Sorghum bicolor (L.) Moench., seeds were exposed to gamma ray dosages of 0, 0·2, 0·4, 0·8, 1·6, 3·2, 6·4, 12·8, and 25·6 kR. In one 2-yr. experiment, pearl millet, sorghum, and Coker 71 corn gave respective dry matter yields of 12, 166, 6, 993, and 6,306 kg/ha and in vitro dry matter digestibility (IVDMD) percentages of 45·7, 52·8, and 59·9. The heaviest exposures of gamma rays generally reduced yields of all species, and lighter exposures failed to increase yield significantly. Seed irradiation did not affect the quality (IVDMD) of the forage. In a 2-yr. corn hybrid experiment, DeKalb 1214 yielded 24% more dry matter and tolerated the heavy exposures of gamma rays better than Pioneer 3030 and Coker 71. None of the lower exposures increased yield significantly.