Tillage and Low-Pressure Center-Pivot Irrigation Effects on Corn Yield

reduce the amount of water used, resulting in savings Low-pressure sprinkler irrigation systems have the potential to of both water and energy. save energy, but also may aggravate soiland water-management Center-pivot systems with high pressure nozzles reproblems. The objective of this research was to determine the influquire relatively large amounts of energy to develop ence of center-pivot sprinkler irrigation method in combination with 41 0to 590-kPa pressure required for proper sprinkler various tillage practices on corn (Zea mays L.) yield and yield comOperation and uniform water distribution throughout ponents. A center-pivot irrigation machine was redesigned to apply water by high-pressure-impact (HPI), low-pressure-impact (LPI), the length the system. A significant savings in energy and low-pressure-spray (LPS) nozzles. Nozzles were sized and spaced would result with lower pressure requirements (Gilley to apply three dilTerent amounts of water: 100% (full irrigation), 75 and Mielke, 1980). and 50%. Three tillage treatments were used-till-plant (T), disk Center-pivot manufacturers offer reduced-pressure (D), and till-plant with chisel after last cultivation (C)-for each systems (1 40 to 2 10 kpa) that use either low-pressuremethod and amount of water applied. The field study was conducted impact sprinklers or spray nozzles for distribution of over a Cyear period (1978 to 1981) on a Sharpsburg silty clay loam ( h e , montmorillonitic, mesic Typic Argiudolls). Yields were influthe water. There are types 'pray enced by the seasonal distribution and amount of precipitation, iravailable for use on center-pivot systems; however, rigation water applied, tillage, and the combined management inputs. these reduced-pressure systems have the disadvantage The method of water application (HPI, LPI, and LPS nozzles) did of increased water application rates or application innot significantly (P > 0.10) influence grain yield. In 1979, the chisel tensities. The high rate of water application increases tillage treatment produced significantly less grain than other treatthe potential runoffofwater applied. hi^ may restrict ments because severe root pruning limited stored water uptake during an extremely stressful period immediately following the chisel optheir use to certain topography, soil types, or tillageeration. No inherent dzerences in productivity were associated with and crop-management systems. Depending on slope low-pressure center-pivot-sprinkler irrigation, or with various conand type of soil, runoff water may cause soil erosion senation-tillage practices used in combination with reduced-presand increase soil loss. sure-sprinkler irrigation. Therefore, use of these practices can reduce There is need to develop and use tillage systems production costs without reducing yield. compatible with irrigated agriculture that maintain Additional index ~~ords: Zea mays L., Reduced tillage, Conservaplant residues on the soil surface, thus providing soil tion tillage. erosion protection (Mannering and Meyer, 1963), reducing evaporation losses (Bond and Willis, 1969; Greb T w o of the most important problems facing groundet al., 1967), increasing surface water-holding capacity water-supplied, irrigated agriculture are energy (McCalla and Army, 196 l), and increasing infiltration consumption and limited water supplies. In Nebraska, of water into soil (Mielke et al., 1984). By using reover 40% of the energy consumed by irrigated agriduced-tillage systems, fewer energy-intensive tillage culture is used in pumping water from wells (Gilley operations are used, and soil, water, and energy are and Watts, 1977). In addition, water shortages are beconserved. The purpose of this experiment was to coming commonplace, and limited water supplies are compare effects of tillage and type of sprinkler used a reality in many areas of the USA. to apply water with a center-pivot system on corn (Zea Much of the future irrigation development in the mays L.) yield. USA will occur on lands not suited to surface (furrow) irrigation methods. Sprinkler irrigation, probably in MATERIALS AND METHODS the form of center-pivot systems, will be the primary A 54-ha center-pivot system located at the Univ. of Neused in most future irrigation development. braska-Lincoln field laboratory near Mead, NE, was Center-pivot systems have the capability of applying fied to include each of the following: (i) a high-pressurecontrolled amounts of water within relatively short impact-nozzle (HPI, conventional) system, (ii) a low-presperiods of time. Therefore, operators of center-pivot sure-impact-nozzle (LPI) system, and (iii) a low-pressuresystems can utilize more of the irrigation-scheduling spray-nozzle (LPS) system. The pressure at the end of the procedures than irrigators using surface methods (Kinline for the HPI system was approximately 410 kPa, corcaid et al., 1969). Irrigation-scheduling practices can responding to a pivot pressure of about 480 k ~ a , which is typical of a conventional center pivot. The pressure at the ' Contribution from ARS-USDA, in cooperation with the Neend of the line for the LpI and LpS systems was about 140 braska Agric. EXP. Stn. Published as Paper no. 7483, Journal Series, kpa, co,,.esponding to a pivot pressure of 2 10 kpa. ~h~ nozNebraska Agric. Exp. Stn. The work upon which this publication is based was supported in zle system and pressure were automatically changed at spepart by funds provided by the U.S. Dep. of Energy, Grant no. EMcific locations in the field by electric and hydraulic apparatus 78-G-01-5125; the Office of Water Research and Technology (Project on the center-pivot machine (Gilley et al., 1983), which reNo. B-048-NEB), U.S. Dep. of the Interior, Washington, D.C., as sulted in ' '~i~-~haped'' experimental units (Fig. 1). authorized by the Water Research and Development Act of 1978; Amount of water applied during any given irrigation was LeDio~t Land Co., Omaha, NE; Valmont Industries, Valley, NE; a function of location along the pivot lateral. Sprinklers and and the Rain Bird Corp., Glendora, CA.