IMPROVING PEANUT YIELD AND GRADE WITH SURFACE DRIP IRRIGATION IN UNDULATING FIELDS

A surface drip irrigation system was developed to irrigate peanut in two experimental fields: one with very little topographic variation on Greenville fine sandy loam soil, and one with undulating terrain containing 2.4% slope on Faceville fine sandy loam soil. Pod yield, kernel size distribution, and total sound mature kernels (TSMK) were evaluated with two peanut varieties, two planting patterns, and two drip tape lateral spacings. Test results were compared with the adjacent non-irrigated area planted with the same varieties of peanut. Soil temperature and volumetric water content were measured at different locations to monitor soil temperature and water movement from drip tapes. Maximum soil temperature in the irrigated area was substantially lower than in the non-irrigated area. For both 13 and 25 mm irrigations, about 16 h were required for water to move laterally 46 cm to reach the peak water content level. No significant difference (p < 0.05) was observed in yields between 0.9 m and 1.8 m drip tape lateral spacings. Peanut yields with drip irrigation were 1.4 times those of the non-irrigated yield. The irrigation water use efficiency from surface drip irrigation was 10 kg/ha-mm during the two growing seasons. Yields tended to slightly decrease as the land elevation decreased for both irrigated and non-irrigated zones. Compared to the non-irrigated areas, the drip-irrigated area produced a greater portion of larger kernels than smaller kernels. In the undulating area, the average TSMK was 73.7% and 64.9% for drip-irrigated and non-irrigated treatments, respectively. Average gross revenue was $2,093 per ha with drip irrigation and $1,253 per ha with no irrigation.