Alfalfa Persistence and Yield with Irrigation
- J. S. Rice ,
- V. L. Quinsenberry and
- T. A. Nolan
Three field experiments were conducted to investigate the effects of irrigation on alfalfa (Medicago sativa L.) forage yield, distribution of yield, and stand persistence. Two of the studies were conducted near Clemson, SC on a Cecil sandy loam (clayey, kaolinitic, thermic, Typic Hapludults) with the third conducted at Blackville, SC on a Facevilie loamy sand (clayey, kaolinitic, thermic, Typic Paleudults). All irrigation was initiated when average soil-water pressure reached -20 kPa at the 20- and 40-cm depths as measured by tensiometers. The average forage yield response to irrigation across the studies in the Clemson (Piedmont) experiments was 2.6 Mg ha−1. The response varied from year to year and no irrigation ✕ cultivar interaction was detected. Stands deteriorated more rapidly with irrigation and seasonal distribution of forage production was only slightly improved. The average response to irrigation in the Blackville experiment (Coastal Plains) was also 2.6 Mg ha−1; however, the response in the second year was negative and the study was terminated because irrigated stands were depleted. An interaction with cultivar was detected in the second year as a result of negative irrigation responses for seven cultivars and a positive response for one cultivar. The positive response reflected the fact that only one cultivar had more than a 70% stand in August of the second season. Diseases did not appear to be severe enough to explain the losses. We conclude that irrigation of alfalfa in the Southeast is a marginal practice.
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