Vegetable production in an era of water limitations

Vegetable growers in the Salinas Valley of California are facing constraints related to irrigation water availability and environmental water quality protection.  Reliance on well water for irrigation has resulted in seawater intrusion in the northern Valley; throughout the Valley growers are under regulatory pressure to reduce surface runoff and leaching to minimize off-field movement of sediment, pesticides and nutrients.  To combat seawater intrusion a municipal wastewater recycling project was developed which now provides approximately 60% of the irrigation volume used on approximately 5,000 ha of prime coastal vegetable land.  In the 10 years this project has operated extensive water and soil testing has proven that recycled water presents no hazard to either long-term soil health or microbial safety of the produce grown.  The widespread adoption of drip irrigation in the last 5 years has provided vegetable growers a degree of control unattainable with sprinkler irrigation, which had long been the standard practice in the Valley.  Drip irrigation virtually eliminates field runoff, and the high distribution uniformity possible with drip can limit in-season leaching and concurrent nitrate loss to groundwater.  While an overall reduction of water application has been achieved with drip, individual growers differ widely in their understanding of efficient drip management practices, and an aggressive program of grower education is underway to maximize the benefits of this technology to the industry as a whole.