MONOCULTURE AND ROTATION SYSTEM EFFECTS ON PRECIPITATION USE EFFICIENCY OF CORN

Development and utilization of cropping systems in rainfed areas are highly dependent on their water use efficiencies, especially in subhumid areas. The objective was to evaluate the effect of crop rotation and N fertilizer rates on precipitation use efficiency by dryland corn (Zea mays L.). Corn was grown under rainfed conditions at Mead, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in four cropping systems: (i) continuous corn, (ii) a 2-yr soybean [Glycine max (L.) Merr.]-corn rotation, (iii) a 4-yr rotation of oat [Avena sativa (L.)] + clover [80% Melilotus officinalis Lam. and 20% Trifolium pratense L.]-grain sorghum [Sorghum bicolor (L.) Moench]-soybean-corn, and (iv) a 4-yr rotation of soybean-grain sorghum-oat + clover-corn. Nitrogen fertilizer rates used for corn were 0, 90, and 180 kg N ha-1 as NH4NO3. Corn grain precipitation use efficiency was significantly affected by year, rotation, and N fertilizer rates from 1984 through 1991. Precipitation use efficiency ranged from 36 to 137 kg ha-1 cm-1 for continuous corn and from 57 to 165 kg ha-1 cm-1 for corn grown in rotation from 1984 through 1991. Precipitation use efficiency was greater in rotation (101.8 kg ha-1 cm-1) than in continuous corn (83.6 kg ha-1 cm-1). In dryland production areas, cropping systems with greater and more stable precipitation use efficiency can reduce crop failures.