Author
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Fisher, Daniel |
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Hanks, James |
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PRINGLE, H - Mississippi State University |
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Submitted to: Irrigation Associations Exposition and Technical Conference Proceedings
Publication Type: Proceedings Publication Acceptance Date: 12/2/2009 Publication Date: 12/2/2009 Citation: Fisher, D.K., Hanks, J.E., Pringle, H.C. 2009. Comparison of Irrigation Scheduling Methods in the Humid Mid-South. Irrigation Associations Exposition and Technical Conference Proceedings. Vol. 1, pp. 1-4. Interpretive Summary: In the humid Mid-South, rainfall is often frequent during the growing season, but irrigation is increasingly being used as a supplemental source of water to meet crop-water needs. The appropriate scheduling of irrigations can result in more efficient use of water and energy resources, improved yields, and reductions in runoff and off-site pollution. A variety of irrigation scheduling methods exist, ranging from simple observation to very sophisticated models. Several different methods were tested to examine their suitability under local climate, soil, and tillage conditions, and to examine their impact on final harvest yield. Three computer-based models and a soil-sensor-based system were tested along with a non-irrigated treatment, and were used to schedule irrigations on cotton crops in three fields under two tillage conditions (conventional and minimum) on two different soil types. The four methods proved fairly simple and easy to use, and provided guidance on determining when to irrigate. It was important to measure rainfall at the field level, since rainfall can vary greatly over short distances in this region. Yields varied under each scheduling treatment in each field, but no one scheduling method was consistently better over all fields. In fields with loamy soils, yield was correlated with the amount of water applied, increasing as additional water was applied. On a clay soil, the non-irrigated treatment returned the highest yield, suggesting that no irrigation was needed and that no scheduling method was appropriate. Yields were slightly higher under minimum-tillage compared to conventional-tillage conditions. Technical Abstract: The appropriate scheduling of irrigations can result in more efficient use of water and energy resources, improved yields, and reductions in runoff and off-site pollution. A variety of irrigation scheduling methods exist, ranging from simple observation to very sophisticated models. Three computer-based models, the original Arkansas Irrigation Scheduler, an updated version of the Arkansas Irrigation Scheduler, and a spreadsheet model, all of which use weather and rainfall data to maintain a water balance and estimate soil-water levels, were tested. These were compared to a soil-sensor-based system, which measures soil-water levels directly, and to a non-irrigated treatment. The methods were used to schedule irrigations on cotton crops grown in three fields under two tillage conditions (conventional and minimum) on two different soil types. The four methods proved fairly simple and easy to use, and provided guidance on determining when to irrigate. It was important to measure rainfall at the field level, since rainfall can vary greatly over short distances in this region. Assumptions underlying the water-balance model in the Arkansas Irrigation Schedulers need to be understood, since violating them could have significant impact on the resulting soil-water deficit and irrigation schedule. Yield differences were statistically significant under each scheduling treatment in each field, but no one scheduling method was consistently better over all fields. In fields with loamy soils, yield was correlated with the amount of water applied, increasing as additional water was applied. On a clay soil, the non-irrigated treatment returned the highest yield, suggesting that no irrigation was needed and that no scheduling method was appropriate. Yields were slightly higher under minimum-tillage compared to conventional-tillage conditions. |
