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Title: COTTON IRRIGATION USING SUBSURFACE DRIP: GROWTH, CUTOUT, AND YIELD DEPEND ON AMOUNT OF WATER APPLIED.

Author
item Detar, William
item Maas, Stephan - Steve
item McLaughlin, John

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: With water becoming increasingly scarce and expensive in the arid western USA, it is important to find ways to save water. With subsurface drip irrigation, water and nutrients are spoon fed directly to the roots daily, at a rate equal to plant uptake so that there is little chance for water and nutrient loss, and a nearly constant level of moisture is maintained in the soil. This is a progress report on two years of subsurface drip irrigation of cotton on sandy soil. Six different water application rates were used in an attempt to find the optimum level. In 1997, the highest yields with the variety Acala Maxxa were obtained when the application rate (at full canopy) was 85% of the loss from a USDA Class A evaporation pan. There was no significant difference among treatments of 75%, 85% and 105% of pan evaporation; and with no real difference, the 75% treatment is preferred, since less water is used and the season is shorter. It was documented that both plant height and length of season were directly proportional to the water application rate. Plants in the 45% treatment matured 38 days earlier than those in the 125% treatment. In 1996, the highest yield for Maxxa occurred with an application equal to 65% of pan evaporation. However, in 1996 there were some unusual weather and soil factors. With the cotton variety Pima S-7, yields both years increased directly proportional to the water application rate. Two more seasons are planned to confirm these findings.

Technical Abstract: This is a progress report about an irrigation experiment started in 1996, with the objective of finding the optimum level of water application. Six different application rates of water were applied to cotton on sandy soil, using daily application through a subsurface drip irrigation system. The treatments in 1996 were 45%, 65%, 85%, 105%, 125%, and 145% of pan evaporation at full canopy; at less than full canopy, the application was a product of the above and percent canopy. The main irrigation plots were split into the two varieties Pima S-7, and Acala Maxxa. Due to problems with water-logged soil and excessive vegetative growth with the 145% treatment, it was changed to 75% in 1997. In 1997, the highest yields for the Maxxa came from the 85% treatment, but there was no significant difference among the 75%, 85% and 105% treatments. With no real difference, the 75% treatment is preferred since less water is used and the season is shorter. It was documented that both plant size and the length of the season were directly proportional to the rate of water application. Plants in the 45% treatment matured 38 days earlier than those in the 125% treatment. In 1996, the highest yield for Maxxa occurred with the 65% treatment, but there were some unusual weather and soil factors. With Pima S-7, the yields increased linearly with water application; the more water the better the yield. Two more seasons are planned to confirm these findings.