C.W. MANSFIELD¹, P. MISLEVY² and L.C. HAMMOND³

University of Florida:
¹Plant Physiology Laboratory, Gainesville,
²Agriculture Research and Education Center, Ona, and
³Department of Soil Science, Gainesville; Florida, USA.

Abstract

In 1979 and 1980, 6 forages were compared for yield and nutritive value with and without irrigation. The perennial grasses Paspalum notatum var. saurae cv. Pensacola, Cynodon dactylon var. aridus cv. Callie, Digitaria decumbens cv. Transvala, and Cynodon aethiopicus cv. UF-5 were compared with the annual forages, Zea mays cv. Dekalb XL 395 A (corn) and Sorghum bicolor cv. Pioneer 947 (forage sorghum). Half of each grass plot was oversown with Trifolium pratense cv. Florie in the autumn and fertilised with nitrogen (N) during the summer. The other half received N throughout the year. The experiment was conducted on a spodosol soil.
Average dry matter (DM) yields of the grasses were increased from 5 to 5.5 t/ha and corn grain from 8.4 to 9.4 t/ha, with irrigation during the 150-day drier spring period. Corn produced 17 and 263% more DM during the 150-day dry period than sorghum and the perennial grasses, respectively. During the entire growing season forage sorghum yielded 37 and 109% more DM than corn and the perennial grasses, respectively.
These data indicated differences in DM production between the species tested. Irrigation during the cool dry period can significantly increase corn grain yields; however, it has little effect on seasonal perennial forage yields.