As water scarcity becomes of greater concern in arid and semi-arid regions due to altered weather patterns, greater and more accurate knowledge regarding evapotranspiration of crops produced in these areas is of increased significance to better manage limited water resources. This study aimed at determining the actual evapotranspiration (ETa) and crop coefficients (Ka) in California date palms. The residual of energy balance method using a combination of surface renewal and eddy covariance techniques was applied to measure ETa in six commercial mature date palm orchards (8–22 years old) over one year. The experimental orchards represent various soil types and conditions, irrigation management practices, canopy characteristics, and the most common date cultivars in the region. The results demonstrated considerable variability in date palm consumptive water use, both spatially and temporally. The cumulative ETa (CETa) across the six sites ranged from 1299 to 1501 mm with a mean daily ETa of 7.2 mm day−1 in June–July and 1.0 mm day−1 in December at the site with the highest crop water consumption. The mean monthly Ka values varied between 0.63 (December) and 0.90 (June) in the non-salt-affected, sandy loam soil date palms with an average density of 120 plants ha−1 and an average canopy cover and tree height of more than 80% and 11.0 m, respectively. However, the values ranged from 0.62 to 0.75 in a silty clay loam saline-sodic date palm orchard with 55% canopy cover, density of 148 plants ha−1, and 7.3 m tree height. Inverse relationships were derived between the CETa and soil salinity (ECe) in the crop root zone; and between the mean annual Ka and ECe. This information addresses the immediate needs of date growers for irrigation management in the region and enables them to more efficiently utilize water and to achieve full economic gains in a sustainable manner, especially as water resources become less available or more expensive.

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Chemical defoliation is a necessary pre‐harvest practice in cotton (Gossypium hirsutum L.) production in California, and all harvest aid efforts require proper timing to preserve cotton lint yield and quality. Generally, cotton growers are advised to begin defoliation as early as possible, but not so early that they cause yield and quality loss. In order to have confidence in this final pre‐harvest step, growers monitor the growth stage of their crop by counting the number of nodes above cracked boll (NACB). In California, it is common practice to apply the first defoliant treatment at 4 NACB, which corresponds with the US Cotton Belt's recommended timing, which is when 60% of the harvestable bolls are open (9,20). It can be beneficial to have an early defoliant application because often it leads to an earlier harvest. This early harvest allows cotton growers to conduct their harvest prior to the onset of adverse late‐season fog or rains that can occur in California's San Joaquin Valley and make harvests more difficult. The objective of this research on San Joaquin Valley Acala cotton was to compare the impact of different rates of Ginstar (thidiazuron/diuron) or Ginstar plus Finish (ethephon/cyclanilide) on defoliation, yield, and fiber quality of cotton when defoliant applications were initiated at the earlier 6 NACB timing, which corresponds to 40% open boll versus the common 4 NACB timing. Starting the defoliation process with an Acala cultivar at 6 NACB instead of at 4 NACB did not significantly affect yield or cotton HVI (high volume instrument) fiber quality characteristics. Earlier defoliation could be of significant benefit in years when later‐maturing crops or worsening harvest‐season weather necessitate the initiation of an earlier harvest.

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