Soil water and crop yield spatial variability induced by irrigation nonuniformity.
1992
Or D. | Hanks R.J.
Experimental evaluation of different irrigation management practices under similar conditions of soil variability often requires several plots having similar soil variability. These types of field plots are difficult to find or not available for experimental use. This study examined crop yield and soil water variability resulting from nonuniform irrigation applications as a surrogate for soil variability within an otherwise homogeneous field. The study conducted at Logan, UT, in 1989 on a Millville silt loam soil (coarse-silty, carbonatic, mesic Typic Haploxeroll) used a drip irrigation system with spatially variable application rates. The mean dripper application rate was 5.6 L/h with a standard deviation of 3.18 L/h and a spatial-correlation range of 5.3 m. Corn (Zea mays L.) was grown in 0.75-m-wide rows at a plant density of 8.9 plants/m2 in 30 by 15 m plots. Irrigation-scheduling treatments were (i) a predetermined calendar schedule (NPT), and (ii) optimized for the nonaniformity of the irrigation system (OPT). There were three replicates. Soil water, crop height, and crop-yield variability exhibited spatial structures similar to the applied-irrigation variability, but crop-yield variability (mean CV of 0.227) was less than the irrigation variability (CV of 0.57). Crop yield was highly correlated to the dripper flow rate and was 13% higher on the OPT than on the NPT schedule. Nonuniform irrigation can be used to induce a desired spatial pattern of available soil water. Irrigation scheduling methods should consider soil variability and irrigation uniformity.
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