Focus Groups of California Nursery Managers Identified Education Priorities for Irrigators

Introduction

California’s nursery and greenhouse industry relies heavily on irrigation, and extended droughts, such as the 2012–2016 drought, highlight the critical need for efficient water management. While soil moisture sensors could optimize irrigation, the cost of installing thousands of sensors makes this approach prohibitive for many operations. Training employees in irrigation best management practices could offer a more cost-effective solution.

Research Design

We received a grant from the California Department of Food and Agriculture to develop an irrigation training course for nursery and greenhouse employees. Prior to developing the curriculum, we conducted focus groups with nursery and greenhouse managers to identify educational priorities. Two focus groups were organized geographically:

• Northern California: 6 participants operating between Visalia and the Oregon border
• Southern California: 5 participants operating between Fresno and the Mexico border

Participants grew diverse containerized crops including ornamental plants, cut flowers, California natives, and fruit and nut trees.

Key Findings

Overwatering is a Systemic Issue

Both groups identified overwatering as widespread in the industry. Managers determined that workers need skills to recognize overwatering symptoms in plants and irrigation blocks. While plant symptoms were deemed valuable, no specific indicators were identified. Runoff from irrigation blocks was recognized as the most practical indicator of overwatering.

Essential Training Topics

Plant Physiology: Managers emphasized that workers need foundational knowledge of water uptake and transpiration to understand irrigation demand. A critical concept is understanding the need for oxygen in the rootzone and the growth problems that result from prolonged substrate saturation.

Evapotranspiration: Both groups acknowledged the importance of evapotranspiration but worried that the term itself might confuse workers. It was recommended that training should help workers understand how environmental factors (temperature, humidity, sunlight) and plant characteristics influence water needs. Workers should learn to use current weather, historical data, and past irrigation schedules to adjust watering frequency and duration.

Container Capacity: Workers need to understand how container capacity varies with substrate composition, particle size, and container dimensions. While some managers wanted to teach staff how to calculate container capacity, time constraints made this impractical during the training course.

Hydrozoning: Arranging plants by similar water requirements could significantly improve irrigation efficiency. Currently, many nurseries group diverse plants together and irrigate when the driest plants need water, resulting in overwatering of others. Barriers to hydrozoning include space limitations and lack of awareness among staff about its benefits.

Training Course Considerations

Both groups stressed that content must be simple and accessible for workers without science backgrounds. One Southern California manager suggested using simple cartoons to illustrate concepts. Operational continuity poses a challenge because it is difficult to send all irrigators to a training course simultaneously during certain times of the year.

Regional Variations

Southern California Priorities 

This group emphasized training about technology including irrigation booms, timers, and soil moisture sensors. One grower suggested using graphs of soil moisture sensor data to visually demonstrate water use patterns related to weather and plant growth stages. However, few California nurseries currently use sensors. Irrigation audits and maintenance were identified as training priorities.

Northern California Priorities 

This group recommended on-site mentoring where experienced staff train newer irrigators through weekly nursery tours, teaching observational skills for climate and plant assessment. This requires senior personnel with sufficient time, knowledge, and experience. This group also prioritized Spanish-language training with culturally appropriate terminology for key concepts.

Industry-Wide Challenges

Labor Market Constraints

The Southern California group emphasized how labor shortages affect irrigation practices. A lack of labor often leads to overwatering because workers do not have time to assess individual plant needs nor hand-water plants that require additional irrigation. This issue could potentially be addressed through improved hydrozoning.

Workforce Stability

While workforce instability affects the industry nationwide, the Southern California group included both stable and unstable operations. Operations with competitive wages generally retained employees better but still struggled to find detail-oriented candidates. Regardless of workforce stability, all operations shared similar training needs for irrigation decision-makers.

Conclusions

The focus groups revealed consistent educational priorities across California's diverse nursery operations. Overwatering, limited plant physiology knowledge, and labor challenges emerged as key topics for irrigation training. These findings informed development of a comprehensive training course delivered to help the industry adapt to current and future water scarcity while developing the workforce.

• Contact your local cooperative extension advisor if you would like training at your nursery.