Water Management

Profitable California walnut culture requires supplemental irrigation.

The California Walnut Board has long provided significant financial support, on behalf of the California walnut industry, for research that provides tools for both efficient use of our limited water resources through scientific irrigation management and improves both surface and ground water quality due to reduced pesticide use within the IPM program.

Efficient Water Use: California walnut growers now have access to crop water use data based upon evapotranspiration and historical climatology information. Those data, combined with a crop coefficient for walnuts, also developed within the California Walnut Board’s research program, are being used, along with cultural improvements that avoid runoff, such as laser levelling and tail water recovery systems, to apply precise amounts of irrigation water walnuts require for best productivity and quality. The research technology growers are implementing include: 


Fig. 6. Pressure chamber diagram and use in the field to determine tree water status.


Fig. 7. Walnut orchards being irrigated with buried drip and low volume irrigation systems.


Walnut farmers are reducing pesticide use: The California Walnut Board’s research funding commitment to IPM has developed pesticide alternatives: pheromone mating disruption of codling moth, less disease prone cultivars and resistant rootstocks, refined application technologies for blight, biological control of aphids, alternatives to fumigation, and harvest management technologies. These practices significantly reduce contamination of our water ways.

Fig. 8. Walnuts infected with walnut blight