Limited and Full Irrigation Comparison for Corn and Grain Sorghum
Southeast Colorado research shows limited irrigation more profitable as pumping costs increase.
The importance of limited irrigation (supplemental irrigation) has traditionally been associated with very low capacity irrigation wells. The current high fuel prices and associated pumping costs places new emphasis on limited irrigation as a replacement for full irrigation. We define limited irrigation on corn and grain sorghum as applying one in-season furrow irrigation of less than 9 A-in./A or a similar amount of water applied with a sprinkler. Applying less than 9 A-in./A as an in-season irrigation assumes that the soil water profile is full from sufficient winter moisture, or, if winter moisture is lacking, the soil water profile is filled by pre-irrigation.
Limited irrigation becomes a more profitable choice as fuel costs increase. Our research (http://www.colostate.edu/depts/prc/rc_pl_rp_pubs.html) suggests that the decision point for conversion from full irrigation to limited irrigation with our current costs, and the loan rate ($1.89/Bu) as the expected grain price, is $3.25/A-in. pumping cost for corn and $3.50/A-in. pumping cost for grain sorghum (Fig. 5). With a commodity price of $2.29/Bu for corn and grain sorghum, the decision point for conversion from full to limited irrigation increases to $5/A-in. pumping cost for both corn and grain sorghum.
An economic comparison between corn and grain sorghum under full and limited irrigation is dependent on commodity price. The current loan rate for corn and grain sorghum is equal ($1.89/Bu). Using the same commodity price for corn and grain sorghum provides grain sorghum with higher net income than corn under both limited and full irrigation. However, when corn and grain sorghum commodity prices are above the loan rate, corn frequently has a $0.30/Bu price advantage compared to grain sorghum in the local market. Corn priced $0.30/Bu higher than grain sorghum provides higher net income than grain sorghum under both full and limited irrigation.
Decreases in commodity prices give limited irrigation the income advantage over full irrigation. If the current loan rate becomes the price growers receive for their corn and grain sorghum crops next season and irrigation costs remain high, limited irrigation will continue to be more profitable than full irrigation for smaller capacity wells.
The current high cost of fuel makes pumping cost the most responsive variable driving conversion from full to limited irrigation. Nonetheless, inputs such as fertilizer and seed, which differ between full and limited irrigation regimes, favor limited irrigation when these input costs increase.
For comments e-mail Kevin.Larson@colostate.edu
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Net income and Pumping Cost for Limited and Full Irrigation Corn and Grain Sorghum |
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Corn and Grain Sorghum ($/A)
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 Pumping
Cost ($/A-in.) |
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Fig. 5. Full and limited sprinkler irrigation comparison of net income for corn and grain sorghum. Assumptions: yield: 151 Bu/A for full irrigation grain sorghum, 123 Bu/A for limited irrigation grain sorghum, 182 Bu/A for full irrigation corn, and 144 Bu/A for limited irrigation corn; grain price: $1.89/Bu and $2.29/Bu; irrigation: 17 A-in./A for full irrigation corn and grain sorghum, 8.3 A-in./A for limited irrigation grain sorghum, and 9 A-in./A for limited irrigation corn; production costs: pumping cost varies from $3 to $10/A-in., all other costs remain constant. |
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