Project Overview
Fruit thinning is a practice that – if executed well – allows plants to allocate their energy and resources into producing larger, higher-quality fruits, prioritizing quality over quantity. This practice is most commonly implemented in tree fruits (i.e., apple, pear, peach, plum, apricot), but its utility for a particular crop species depends on several factors, including (1) tradeoffs between reproductive and vegetative growth, (2) plant resource use efficiency, (3) sugar accumulation and transport, and more.
When implementing fruit thinning, growers need to make educated predictions about how much they think the quality of their fruit will improve, relative to any anticipated yield (quantity) reductions. Fruit thinning has been trialed in tomato production systems, with observed benefits to tomato fruit quality without significant yield reductions. For organic growers vying for a competitive ‘leg-up’ in tomato quality, fruit thinning could be an incredibly useful tool for producing higher-quality tomatoes with fewer inputs.
In this study, researchers in Colorado set out to understand how tomato fruit thinning might work in organic, high-tunnel production systems. In these intensified systems, fruit thinning could be appropriate to help growers address multiple production goals and produce balanced tomato plants. The experiments in this study evaluated multiple levels of fruit thinning in both heirloom and hybrid tomato cultivars.
Farmer Takeaways
- Tomato yield was not significantly affected by cluster thinning, regardless of cultivar.
- Cluster thinning to three fruits remaining resulted in a roughly 30% increase in individual fruit weight for the two hybrid tomato cultivars, but did not impact individual fruit weight for the heirloom cultivar. None of the cultivars differed in fruit weight under the more moderate thinning treatment (to six fruits remaining).
- Fruit thinning did not affect soluble solid content, and effects on marketable and non-marketable yield were inconsistent.
Project Objectives and Approach
Evaluate the effects of fruit cluster thinning on tomato yield and quality in an intensified organic production system
- Researchers in Colorado established randomized trials in certified-organic high tunnels. Tomatoes were transplanted into rototilled beds covered with weed barrier, trained onto a trellis system, and drip irrigated.
- Tomato plants from each cultivar (see below) were assigned to a fruit thinning treatment. Fruit thinning treatments included: (1) control (no fruit thinning), (2) thinning until six tomatoes remain per cluster, or (3) thinning until three tomatoes remain per cluster. **Non-thinned tomato plants generally had about 10 fruit per cluster.
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- To thin the clusters, researchers cut the rachis when fruitlets were roughly 0.5” in diameter, removing the furthest fruitlets from the main stem and leaving the closest. Thinning was performed throughout the duration of the experiment, when individual clusters reached the appropriate size.
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- Tomato fruit were harvested at commercial ripeness. At harvest, researchers recorded each plant’s total yield, weight per fruit, and marketable and non-marketable yield fractions. At approximate peak harvest, researchers collected tomato juice samples to analyze soluble solid content.
Understand how tomato cultivars respond differently to cluster thinning in an intensified organic production system
- Tomato cultivar treatments included: (1) ‘Cherokee Purple’ (heirloom), (2) ‘Jet Star’ (hybrid), and (3) ‘Lola’ (hybrid). All three cultivars are indeterminate tomatoes suitable for continuous harvest in a high-tunnel system.
- Tomato plants from each cultivar were assigned to a fruit thinning treatment (see above), and data was collected at harvest on tomato plant performance (total yield, weight per fruit, and marketable/non-marketable yield) to assess cultivar-specific responses to different thinning practices.
Key Findings
Tomato fruit thinning in organic high tunnels increased individual fruit weight for hybrid tomatoes, but had few other impacts on yield or quality
- In the two hybrid tomato cultivars (‘Jet Star’ and ‘Lola’), the more aggressive thinning treatment (to three fruits remaining) resulted in a ~30% increase in individual fruit weight compared to the less aggressive thinning treatment and control (no thinning). These findings suggest that aggressive thinning may be an effective strategy for increasing fruit weight/quality in organic hybrid tomatoes.
- Across all thinning treatments and cultivars, cluster thinning did not significantly affect overall yield. This result differed from previous research, emphasizing the importance of such studies and reiterating the need for further research on fruit thinning in organic tomato production.
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- The more aggressive fruit thinning treatment somewhat increased non-marketable yield in the ‘Lola’ hybrid cultivar, but had no effect on non-marketable yields for the other two cultivars. Researchers did not observe a statistical difference in marketable yields between thinning treatments for any of the cultivars, including ‘Lola’.
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- Other quality factors, including total soluble solids, were largely unaffected by thinning treatment and cultivar.
Resources
Mitchell, B. A., Uchanski, M. E., & Elliott, A. (2019). Fruit Cluster Pruning of Tomato in an Organic High-Tunnel System.
Read MoreLocation
ColoradoCollaborators
Mark Uchanski, Colorado State University
Adriane Elliott, Colorado State University
Region
Plains
Topic
Crop Nutrient Management, Cropping Systems, Post-Harvest Quality and Safety
Category
Vegetables/Fruits
Year Published
2019
