| Abstrakt: |
Soil‐crop management affects the soil‐N balance and, thus, has a direct bearing on soil productivity. This study determined the effects of cropping intensity (crops/time) under no‐till and grassland establishment on aboveground biomass production and the system‐N balance after 4 yr (1985–1989). The effects were examined across toposequences in the West Central Great Plains that had been tilled and frequently fallowed for >50 yr. Production systems included wheat (Triticum aestivumL.)‐fallow (WF), wheat‐corn (Zea maysL.) or sorghum (Sorghum vulgareL.)‐millet (Panicum miliaceumL.)‐fallow (WCMF), and perennial grass (CG). Intense agronomic systems (WCMF) had greater aboveground production, greater N uptake, and greater percent plant residue retention than WF. Continuous grass systems had less aboveground production and N uptake but greater percent plant residue retention than agronomic systems. Soil‐profile NO3–N was lower under WCMF systems than WF systems, but organic N showed the opposite trend implying that more intense systems are at less risk for NO3–N leaching, and have greater potential for replenishment of soil‐organic N via enhanced immobilization. Aboveground biomass production and plant residue production increased downslope, but slope position had little effect on plant‐N uptake, plant residue retention, or soil‐N dynamics. Imposing no‐till and perennial grassland systems created a N‐balance disequilibrium, but more time will be required to ascertain the trajectory of N loss or gain due to establishment of no‐till or grassland management on these soils. |
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