Nitrogen Management and Interseeding Effects on Irrigated Corn and Sorghum and on Soil Strength 1

摘要: A 15-yr experiment on Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) investigated N management effects corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] grown side by side, under identical furrow-irrigated conditions. Included were comparisons of anhydrous ammonia (AA) solution (UAN) as sources, planting time (UAN-PL) vs. summer sidedressing (UAN-SD) application the N, rates 90,180, 270 kg ha-'. Additionally, interseeding rye (Secale cereale into high plots alfalfa (Medicago sativa check was accomplished at ridging for furrow irrigation. The objectives to evaluate long term varied two carriers interseedings yields utilization, relative these treatments soil strength. Grain more productive crop conditions low availability while responded higher rates, becoming economic with approaching 10 Mg ha-l when plentiful. Yield increases averaged 5% greater UAN-SD over UAN-PL, AA slightly effective than both crops. Interseeded green manures provided average yield 880 585 ha-@, respectively, explainable in part improved economy. No significant differences penetrometer or vane shear tests found between soils from plots, although there a tendency toward lower soil-strength values carriers, plots. RTILIZER has contributed increasE ing crops U.S. world past 30 years, any other single factor. At same become foremost input relation cost energy requirement advanced agricultural production systems. national growth its use current approximate 11 million tons annual consumption, far exceeding inputs prior Chemical Age agriculture, added further dimensions excessive groundwater pollution nitrate (5,7,14,25). Accordingly, it is best interests farmer, fertilizer dealer, manufacturer that be used most efficient way possible minimizing costs production, conserving energy, preserving environmental integrity. Many short-term studies have demonstrated need adjusting rate obtainable, even importantly, amount residual mineral rooting zone soil's nitrification capacity (1 0,16,17,22). Imgation, where practiced, recognized primary vehicle carrying NO; groundwater, therewith necessitating integration water practices