Date of this Version
2011 ASABE Annual International Meeting, Sponsored by ASABE Gault House Louisville, Kentucky August 7 – 10, 2011
With limited water resources, it becomes more critical to know how much and when to irrigate. The objective of this study was to determine the effect of the amount and timing of irrigation on corn (Zea mays L.) yield using subsurface drip irrigation (SDI). A field study was conducted at North Platte, Nebraska in 2007 - 2009, using two SDI systems. The study was replicated eight times on the older SDI system (SDI1) and four times on the newer SDI system (SDI2). On SDI1, there were nine treatments to impose different irrigation regimes, ranging from dryland to fully irrigated. Five of the nine treatments allowed for various degrees of water stress, but only after tasseling and silking. On SDI2, there were eight treatments that were very similar to those on SDI1.
In 2007, on SDI1, mean corn yield ranged from 7.8 Mg ha-1 with a season total of 57 mm of irrigation water to 11.1 Mg ha-1 for the fully irrigated treatment (253 mm of irrigation water). On SDI2, yield increased from 8.9 Mg ha-1 with 41 mm to 11.5 Mg ha-1 with 264 mm (fully irrigated). The least-irrigated treatment (158 mm) of the four treatments allowing water stress only after tasseling and silking, had a mean yield of 10.9 Mg ha-1, only 0.6 Mg ha-1 less than the fully irrigated treatment (264 mm), even though soil water content fell well below 0.20 m3 m-3 (50% depletion of soil available water) in the second part of August and in September for the former treatment (158 mm).
In 2008, yields were suppressed across the irrigation treatments. Amount or timing of irrigation did not have much effect on yields, except for the dryland treatment where yield was substantially less than for the other treatments. In 2009, yields ranged from 12.6 to 13.5 Mg ha-1 - there were no significant differences in yield among the irrigation treatments. There may have been several reasons for this. First, there was more in-season precipitation in 2009 than in 2007 and 2008, requiring less irrigation water. Second, the cooler weather in 2009, with a lower atmospheric evaporative demand, also contributed to the lower irrigation requirements. Third, much of the irrigation water was applied after mid-August, after the most water-stress sensitive stages of tasseling, silking, and pollination. After mid-August, the soil in the low-irrigation treatments dried out well below 50% depletion without causing yield losses. Finally, the lower atmospheric demand in 2009 may have been another reason why soil water contents well below 50% depletion did not cause any yield losses.
Seasonal evapotranspiration (ET) stayed below 600 mm in all three years for all irrigation treatments, which is rather low. Limited evaporation may have kept ET low. Evaporation was likely limited because of the soil surface staying dry when irrigating with these SDI systems, and because of the no-till practices that were used with a nearly 100% cover of corn residue covering the soil surface all the time.