Subsurface Irrigation and Fertilization of Field Corn

Trickle irrigation is a rapidly developing technology with high potential for water and energy conservation. Surface placement of emitter lines is typical of current installations. The lines interfere with cultural operations leading to costly annual replacement and limiting its use to high value crops. The objective of this experiment was to determine if deeply placed emitter lines could be used to effectively deliver water and anhydrous ammonia (AA) to the sub-tillage root zone of field corn (Zea mays L.) in the presence of several broadcast N, P, K treatments. Field corn was grown on Matapeake silt loam (fine silty, mixed mesic Typic Hapludult) and subsurface irrigated during the period 1973 to 1979. Emitter lines were placed 90 cm apart at a depth of 36 cm. Irrigation treatments included no irrigation, subsurface irrigation (SSI), and SSI plus AA. Broadcast N, P, K was applied annually at 0, ½, 1, 2, and 3 time rates with the 1 time rate equal to 112,25, and 94 kg/ha of N, P, K, respectively. Annual treatments with N, P, K were made from 1965 to 1973 but following 1973 P and K treatments were discontinued although N applications were repeated annually through 1979. Anhydrous ammonia applied through the SSI system increased N use efficiency when compared to broadcast ammonium nitrate. When AA was injected through the SSI system no benefit was derived from broadcast-N applications. Phosphorus and K availability, as measured by ear leaf analysis, was increased when AA was injected through SSI. The application of AA through SSI depressed soil pH but the effect was localized within a 10 to 12-cm radius of the emitter lines. Corn roots concentrated in soil adjacent to emitter lines causing an increase in organic matter that appeared to stabilize emitter line flow rates. It was concluded that a properly installed SSI system can have a functional life of at least 7 years.