Resource allocation in corn production with water resource constraints

Corn (Zea mays L.) is the irrigated crop of choice for many irrigators in the Central Great Plains, but it requires significant amounts of irrigation water to produce high yields. Declining water resources in some areas have resulted in increased public scrutiny of corn irrigation practices. Some irrigators are responding by practicing deficit irrigation of corn, even though it is economically risky and sometimes complicated to successfully implement. A three-year study was initiated in the fall of 1985 on a Keith silt loam soil (Aridic Argiustoll) in northwest Kansas to determine the agronomic and economic feasibility of nine different resource-allocation management schemes for irrigated corn. Irrigation timing and amount, nitrogen fertilization, and corn seeding rate were the three allocated resources. Average corn yields ranged from 6.09 to 9.98 Mg/ha (97 to 159 bu/acre) with average irrigation amounts ranging from 100 to 380 mm (4 to 15 in.). Fully irrigated corn using the standard recommended seeding rate and full fertilization had a higher net income than did any of the other resource-allocation schemes for deficit-irrigated corn. This scheme not only maximized the mean net income but also minimized the standard deviation of net income. Assuming a corn cash market price of $0.089/kg ($2.25/bu), there was an approximately $285/ha ($700/acre) difference between the highest and lowest net incomes for the various management schemes. Management-induced variations in crop production caused a much greater shift in net income than did variations in resource costs among the management schemes, emphasizing the need for resource-allocation management schemes that produce high corn yields. If irrigation is limited, moderate amounts of water stress hardening during the corn vegetative stage with proper matching of the fertilizer and seeding rate will stretch the irrigation season. This type of management scheme increased corn yields by 20% when the water allocation was restricted to 150 mm (6 in.). Federal farm deficiency payments had a marked effect of changing the profitability status from negative to positive for seven of the nine management schemes, when the corn cash market price was $0.069/kg ($1.75/bu).