Abstract
The number of fruits that remain on an apple tree directly affects yield, fruit size and the quality of fruit that are harvested, which largely determines crop value. If the number of apples can be precisely managed the final crop value can be maximized. We are conducting a USA national SCRI project to develop precision crop load management strategies and machines to manage the number of fruits per tree to exactly the economic optimum. We have done physiological experiments to define the biological potential of yield and fruit size of ‘Gala’ and ‘Honeycrisp’ apple cultivars in 4 sites (West, Mid-West, North-East and South-East USA) to estimate the economic optimum number of fruits per tree. To determine the optimum fruit number per tree we employed: 1) precision pruning to remove flower buds at pink bud stage to various pre-determined flower bud loads followed by hand thinning to single fruitlets at 10mm fruit size; and 2) precision hand thinning to remove fruitlets on uniformly pruned trees to establish different crop loads at 10mm fruit size. Our results showed that the dry, high light climate of WA generally can support a higher crop load than the eastern USA growing regions. Our multi-location experiments demonstrated that leaving too many flower buds during pruning results in lower crop value than the optimum flower bud number. Optimum flower bud number in our studies of ‘Gala’ and ‘Honeycrisp’ was between 1.5 and 2.0 flower buds per final target fruit number. To simplify counting of flowers or fruitlets, we are developing computer vision systems to streamline the counting of buds, flowers and fruitlets. The information from each tree is geo-referenced and cloud-stored therefore can be communicated to human workers to guide their work in reducing crop load to the optimum level.
| Original language | English |
|---|---|
| Pages (from-to) | 219-225 |
| Number of pages | 7 |
| Journal | Acta Horticulturae |
| Volume | 1366 |
| DOIs | |
| State | Published - Apr 1 2023 |
Bibliographical note
Publisher Copyright:© 2023 International Society for Horticultural Science. All rights reserved.
Funding
In September of 2020 we began a 4-year national USA project on precision crop load management of apples that includes university researchers, extension educators and commercial company engineers that will bring digital solutions to manage crop load in apples. The project is funded by the federal US government through the USDA-NIFA Specialty Crops Research Initiative (SCRI). The project has horticultural objectives, engineering objectives and economic objectives. Among the horticultural objectives are to: 1) assess the optimum crop load for two important apple cultivars: ‘Gala’ (number one in USA production) and ‘Honeycrisp’ (number three in production) (US Apple Association, 2022) in different growing regions of the USA and 2) improve the three models used in chemical thinning (carbohydrate balance model, pollen tube growth model and the fruit growth rate model) to provide more precision and greater ease of use. The engineering objectives are to: 1) develop computer vision approaches and machines to count dormant fruit buds, flowers, and then fruitlets per tree and 2) process the information and communicate actionable information to human workers. The economic objectives are to: 1) assess the economic effects of thinning and 2) determine the economic feasibility of automated methods of assessing crop load and managing crop load. The project also seeks to extend to growers and tech companies the results of the research project to guide grower adoption of digital technology to manage crop load. This project was funded by USDA-NIFA through the SCRI project NYG-632521.
| Funders | Funder number |
|---|---|
| SCRI | NYG-632521 |
| US Department of Agriculture National Institute of Food and Agriculture, Agriculture and Food Research Initiative | |
| Government of South Australia |
Keywords
- Malus × domestica
- chemical thinning
- computer vision
- crop value
- fruit size
- pruning
ASJC Scopus subject areas
- Horticulture