The effects of furrow irrigation with water and dairy manure slurry on yield of corn silage

The effects of furrow irrigation with water and dairy manure slurry on silage corn yields were studied in separate locations in Tennessee during four growing seasons. Two one-acre plots on graded land at the West Tennessee Experiment Station in Jackson were furrow irrigated with water, and one approximately one-acre plot on The University of Tennessee Cherokee Dairy Farm at Knoxville was furrow irrigated with a dairy manure slurry. Seasonal precipita-tion was near or above the long-term average for both locations during the growing seasons considered, and water or slurry was applied only when needed by the crop as determined by soil moisture conditions. Soil moisture measurements were made before and after all irrigations. Tensiometers were used on the lower ends of the West Tennessee plots to determine when sufficient irrigation water had been applied. Furrows on all plots were constructed by normal tillage operations. The West Tennessee plots were irrigated a total of nine times during the four years, with an average application of 3.2 inches and an average irrigation application efficiency of 76 percent. The Cherokee Dairy plot was irrigated eight times with an average application of 0.8 inches, and the average application efficiency for five of the eight irrigations was 44 percent. Corn on all plots was harvested for silage, and yields were determined in tons of green matter per acre. Yields were increased by irrigation on both West Tennessee plots in 1970 and on one plot in 1971 and 1973. The 1970 season was the only season studied in which the growing season rainfall was below the long—term mean. Very poor stands of corn in 1973 and 1974 resulted from late planting dates due to high spring rainfalls. On all years, yields were increased by irrigation with the manure slurry. The average increase was 3.7 tons of green matter per acre. Laboratory tests were performed on soil samples from four locations on the West Tennessee irrigation plots. A textural analysis was conducted, and soil moisture contents at various moisture tensions were determined. A study of the rate of water movement through the soil profile was conducted, using large diameter samples and a nuclear soil moisture meter with a depth probe. The high clay content of the soils was found to restrict downward soil moisture movement.