Water Uptake by Cotton Roots during Fruit Filling in Relation to Irrigation Frequency
- J. W. Radin ,
- J. R. Mauney and
- P. C. Kerridge
Yield of irrigated cotton (Gossypium hirsutum L.) increases as the interval between water applications is decreased, even if the total amount of water applied is unchanged. Experiments were undertaken to compare season-long water relations of high-frequency dripirrigated cotton (I- to 2-d intervals) to cotton irrigated at approximately 2-wk intervals. The crop was grown at two locations in central Arizona on a Mohall sandy loam (fine-loamy, mixed, hyperthermic Typic Haplargid) and an Avondale clay loam (fine-loamy, mixed, hyperthermic Typic Torrifluvent) soils. In 2-yr trials at each location, irrigation frequency had inconsistent effects on midday leaf water potential (ψw) during vegetative growth. When the crop developed a heavy fruit load, however, ψw of plants on the longer cycles was much lower than that of drip-irrigated plants, even after irrigation when ample soil moisture should have been available. Plant hydraulic conductances, estimated from regressions of single-leaf transpiration rate against ψw, were high in both treatments early in the season. Hydraulic conductance decreased greatly during fruiting in plants on long irrigation cycles but less so in drip-irrigated plants. Late in the season, after fruit maturation and daring plant regrowth, conductances were again high and similar in the two treatments. The results imply that during heavy fruiting, mild water stress associated with long irrigation cycles triggers deterioration of the root system that is very slow to be reversed. High-frequency drip irrigation, by preventing cyclical stress, apparently minimized this deterioration during fruit filling.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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