|Fangmeier, Delmar - UNIVERSITY OF AZ, TUCSON|
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 1998
Publication Date: N/A
Interpretive Summary: Field studies were conducted to determine if more frequent surface irrigations can increase cotton yields in the desert southwest. The research was partially prompted by farmers who claim that the use of high-frequency drip irrigation has dramatically improved their cotton yields and profits. Expanding upon earlier work by ARS researchers, this study demonstrated that increased frequency of surface irrigations for cotton resulted in 15-21% higher yields when compared to a less frequent surface irrigation practice. Moreover, the studies showed that high-frequency surface irrigation improved the water use efficiency for the cotton crop by 5-11%. Increasing yield per unit of applied water is particularly important to cotton growers in the arid southwest as costs for water and constraints on water availability increase.
Technical Abstract: Field studies were conducted for two years in central Arizona to evaluate the effects of surface irrigation frequency on the growth, yield and water use for cotton. Cotton was grown in level basins in 1993 and 1994 on a Mohall sandy loam under three irrigation treatments defined as low frequency irrigation for the whole season (L), high frequency irrigation for the whole season (H), and low frequency irrigation until the initiatio of rapid fruiting, high frequency during rapid fruiting, and low frequency after rapid fruiting (LHL). Treatment irrigation frequencies were governed by the percentage of allowable soil water depletion within the effective cotton root zone. The root zone water depletion targets for the low and high frequency irrigation managements were 55 and 30%, respectively. The total amount of water applied to the treatments including rainfall varied by 4% in 1993 and by 1% in 1994. However, crop evapotranspiration determined from the soil water balance was 8-9% higher for the H than the treatment and 3-5% higher for the LHL than the L treatment. Cotton growth and lint yields were maximized under the H treatment, where total plant dry mass, boll dry mass, and lint yields were 20-23%, 17-28%, and 15-21% higher for the H than L treatment, respectively. Although the LHL treatment was not as effective in increasing crop productivity as the H treatment, the LHL treatment realized an increase of 10-11%, 9-10%, and 9-11% in total plant dry mass, boll dry mass, and lint yields over the L treatment, respectively. Water use efficiency was increased in the H and LHL treatments over the L by 5-11% and 6-7%, respectively.