|Camp Jr, Carl|
Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2002
Publication Date: 6/1/2002
Citation: CAMP JR, C.R., SADLER, E.J. IRRIGATION, DEEP TILLAGE, AND NITROGEN MANAGEMENT FOR A CORN-SOYBEAN ROTATION. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2002. V. 45. P. 601-608.
Interpretive Summary: Year-in, year-out, the primary cause of yield variation is seasonal rainfall. This is particularly true in the southeastern Coastal Plain because frequent short dry periods can exhaust the low water storage capacity of the sandy soil. On some soils, the amount of water available for crop growth may be further limited by a compacted layer caused by tillage or machinery, which can restrict root growth to the shallow, sandy surface layer. Deep tillage can loosen this layer, and irrigation can overcome all limitations. The cost of these two solutions requires that their individual and combined effects be known. During 1995-1998, we tested a new, innovative site-specific center pivot by using it to apply irrigation treatments on a tillage and corn-soybean rotation experiment. The system test proved successful, with several refinements to the system hardware and operation being made during the project. As for research results, we found that irrigation increased corn yield by a modest 8-15% during good weather years, but more than doubled yield in the 1998 drought year. Similarly, irrigation increased soybean yields 25 to 31% except in a very good weather year, but yield-limiting factors other than those studied need to be examined in future research. This site-specific center pivot will enable researchers to continue to find ways to produce profitable grain yields with better stewardship of the increasingly scarce water resources.
Technical Abstract: Of the numerous factors affecting crop yield, the major factor for corn and soybean in the southeastern Coastal Plain appears to be available soil water. Both inadequate rainfall and soil compaction, which limits root exploration of stored soil water, exacerbate this problem. Potential solutions, though costly and energy intensive, include irrigation and annual deep tillage. Sometimes, doing both provides additive yield increases for corn. The objectives were 1) to prove the irrigation system and 2)to test the value of irrigation and tillage separately and when combined. A center pivot irrigation system that had been modified to allow variable-rate water and nutrient applications to 100-m**2 plots within the system was used to manage an experiment with corn-soybean rotation, irrigation, deep tillage, and N-fertilizer treatments during 1995-1998. The modified center pivot system satisfactorily applied water and N fertilizer to the treatment areas, and the control system reliability improved during this experiment. Irrigation increased corn yield all years (8-135%)and soybean yield three of four years (26-31%). Deep tillage increased yield in only two years, for corn (4-6%). For these soil and weather conditions, irrigation increased corn and soybean yields more consistently than deep tillage. The site-specific irrigation facility should provide the research infrastructure to answer many long-standing questions about irrigated cropping systems in the southeastern U. S.