Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 1998
Publication Date: N/A
Interpretive Summary: Research data published earlier show LEPA irrigation to be more efficient than spray irrigation, but the LEPA method requires more intensive management and higher-cost application devices in comparison with the spray method. In addition, runoff losses with LEPA irrigation are generally larger than with spray irrigation so that the on-farm efficiency of the two omethods may be essentially equal. To provide a field comparison, two LEPA sprinkler methods and two spray sprinkler methods were used to irrigate corn with five irrigation amounts ranging from 100% irrigation for maximum yields to zero irrigation. Tillage, fertility and weed and insect control were similar to those used for high-yield corn production on large farms in the Southern Great Plains. Dikes (furrow dikes) were placed within the furrows between crop rows to form basins that held rainfall and the water applied by the LEPA and spray sprinkler devices. Overall, there was no advantage to using either the LEPA or the spray sprinkler methods to irrigate corn for high yields. The higher efficiency of the LEPA irrigation method was offset by other factors such as runoff from the furrow-diked plot areas. In contrast to the sprinkler methods, the corn was highly dependent on the irrigation amount for both high yields up to 235 bushels/acre and efficient water use. With the information in this manuscript, irrigators can make an informed decision when choosing between the LEPA and spray sprinkler methods.
Technical Abstract: Two LEPA (Low Energy Precision Application) sprinkler methods and two spray sprinkler methods were used to irrigate corn with five irrigation amounts ranging from 100% irrigation providing full soil water replenishment to zero irrigation. The two LEPA methods were bubblers at the 0.3-m height and double-ended socks drug in the furrows, and the two spray methods were in-canopy spray at the 0.3-m height and overhead spray about 0.3-m above the mature crop canopy. The 100% irrigation treatment received 25-mm irrigations to maintain soil water at a non-yield-limiting level based on earlier research. Neutron soil water measurements verified the adequacy of the irrigation applications. Deficit irrigation treatments received 0, 25, 50 and 75% of the 25-mm irrigations on the same date. The field study was conducted on Pullman clay loam soil at Bushland, TX during the 1994-95 crop years. Tillage, fertility and weed and insect control were typical of those used for high-yield corn production in the Southern Great Plains. The corn was planted on 0.76-m spaced beds, all furrows were diked, and sprinkler devices were spaced 1.52 m apart over alternate furrows. Grain yields and seasonal water use efficiency (WUE) both increased significantly with irrigation amount. For 100% irrigation across the four sprinkler methods, grain yields and WUE averaged 13.5 Mg/ha and 1.68 kg/m**3, respectively. Some significant differences in grain yields and WUE occurred among the sprinkler methods, but overall, grain yields and WUE with the four sprinkler methods were essentially equal. In conclusion, both the LEPA and the spray sprinkler methods efficiently irrigate corn for high grain yields in the Southern Great Plains.