ABSTRACT
Newer, higher yielding Upland and Pima cultivars are generally shorter and earlier maturing with Pima approaching Upland cultivars in these traits. Since only limited information is available on desired plant water relations for the currently grown 'Pima S-6', a two-year field study was conducted in the San Joaquin Valley (SJV) to establish water stress-temporal plant responses, determine critical soil water content and plant water stress levels for irrigation scheduling, and define economical water management alternatives. As with Upland cultivars, Pima expansive-vegetative growth was most sensitive to water stress with reduced growth observed as midday IYT(L) declined below -1.2 MPa. Young boll abscission was initiated at -2 MPa and reduced boll growth was observed as IYT(L) declined below -2.3 MPa. These values are slightly lower than those generally reported for Upland cultivars and appear to be associated with a higher flow resistance in Pima. Though differences exist in such Pima - Acala Upland comparisons, critical plant water stress levels previously established for Acala cultivars also resulted in highest yields for Pima.
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