broadcasting immobilization placement nutrient removal by plants
Issue Date:
Jan-1989
Abstract:
Increased soil water storage with increasing amounts of surface residue in winter wheat (Triticum aestivum. L.)-fallow cropping systems has not consistently resulted in higher grain yields in the Great Plains. Earlier results had suggested increased amounts of surface residue may increase N immobilization and limit N availability, thereby reducing potential for use of the additional stored soil water. This study was conducted to determine if N placement below the zone of organic matter or surface residue accumulation would reduce N immobilization and increase yields. The effects of N placement were evaluated by surface broadcasting and injecting below the soil surface 15N depleted NH4NO3 at 45kg ha-1 in no-till, stubble mulch, and plow fallow method systems on an Alliance silt loam (fine-silty, mixed mesic Aridic Argiustolls) in a long-term study in western Nebraska. Dry matter and grain yield, N concentration, N uptake, 15N concentration, 15N uptake, and fertilizer recovery in plant tissue were determined for fallow method and N placement during the 1985, 1986, and 1987 growing seasons. Dry matter and grain yield, N concentration, N uptake, 15N uptake, and fertilizer recovery were all significantly affected by fallow method during all 3 yr of the study, being highest in plow and lowest in no-till with stubble mulch values intermediate. Nitrogen placement however, had no effect on any of the variables in any of the tillage systems. In this environment, N immobilization does not appear to be a factor limiting use of additional stored soil water in reduced tillage systems because fertilizer recovery was equal for both placement methods in all three tillage systems.
