On-farm evaluation of shade cloth as a tool for reducing heat-related losses in tomato seed production

Research Objective 1: In 2023 and 2024, evaluate the impact of shade cloth on tomato seed yield and quality in 10 replicated trials across three Western states.

Methods and Materials for Research Objective 1: 

The on-farm shade cloth tomato seed trials will be carried out in WA, HI and AZ. These trials will be conducted on commercial tomato seed production farms by Producer-Cooperators Lockhart, Green, Steele, Carter, Corbin, and additional producers recruited for participation. The trials will take place in 2 years (2023 and 2024), for a minimum of 10 total trials across locations and years. 

Each trial will be grown as a randomized complete block design with 2 replications per site. Most trials will have two treatments per block: unshaded and shaded under 30% opacity shade cloth. At the Native Seed/SEARCH trial site, a more extensive trial will be grown with four treatments per block: unshaded, shaded with 30% opacity shade cloth, shaded with 40% opacity shade cloth, and shaded with 50% opacity shade cloth. All other methods in this trial will be identical to the other trial sites. 

A standard variety will be grown across trial locations. Based on listening sessions with tomato seed producers, tomato varieties exhibit a range of sensitivity to temperature. ‘Cherokee Purple’ was identified as a best-selling open-pollinated tomato variety that can be vulnerable to high temperatures during pollination and was selected as the standard variety. In addition to the standard variety, some trial sites will evaluate additional tomato varieties for their relative seed production under shade cloth. 

Tomato plants will be planted at 18 inches between plants in-row, with between-row spacing of 4 to 5 feet, matching standard production practices at each trial site, with a target population of approximately 11,000 plants / acre. Each plot will be 20 feet long, with a minimum of 12 plants per plot. 

Shade cloth will be installed horizontally above each plot using the methods described in Drost and Maughan (2018). The shade cloth itself and the materials for the shade cloth structures will be supplied by the project to each site to ensure uniformity.

Hourly temperature, precipitation and humidity data will be collected on site using portable weather stations. Plant data collected will include: total number and weight of fruit harvested, seed yield, 1000 seed weight, germination, and disease incidence.

Trials will be analyzed as replicated complete block design trials across all sites, using the following linear model for complete blocks: 

Y = μ + Treat + Loc + Year + Rep(Loc x Year) + Loc x Treat + Year x Treat + Year x Treat x Loc + ε 

Where μ = grand mean, Loc = location, Year = year, Rep = replication, Treat = shade cloth treatment, and ε  = error. Location and treatment are considered as fixed effects, whereas year and replication are considered random. 

Maximum and minimum daily and nightly temperature, diurnal temperature range, and counts of sequential spans of dry, wet, hot, and cold extremes will be included in alternate models as covariates and compared to the above model for model fit using Akaike Information Criterion (AIC; Sakamoto et al., 1986).

Research Objective 2: Conduct Partial Budget Analysis to report on the change in profit from using shade cloth to improve tomato seed yield in 2025.

A Partial Budget Analysis will be conducted to calculate the cost-effectiveness of using shade cloth in tomato seed production. Partial Budget Analysis is used to evaluate the changes in profits for farm enterprises (Roberts & Swinton, 1996). The costs will be based on the actual materials costs and the producer records of additional labor in installing, maintaining, and removing the shade cloth. In addition to the costs, the range of relative difference in seed yields under shade cloth across all trial sites will be used to calculate a range of changes in profit for the addition of shade cloth as a management approach.