Orange Tree Yield per hectare and acre
The average healthy and mature orange tree produces approximately 200-400 oranges per season. However, a skilled and experienced farmer can reach a production of up to 400 to 600 fruits per tree, which is around 25 to 40 tons per hectare (22,400-35,840 lbs/acre) annually.
The yield may differ in high-density orchards depending on the orange cultivar and the rootstock chosen. For example, in high-density orchards with 2,500-5,000 Valencia orange trees per hectare or (1,000-2,000 trees/acre), production reaches around 60 tons/hectare (53,760 lbs/acre). With semi-dwarf rootstocks (e.g. P. trifoliata ), yield can rise even to 260 tons/hectare (232,960 lbs/acre). However, it is important to highlight that such densities and yields are not viable for many years and after some time, the production declines.
Fruits Ripening – When and how to harvest Oranges
Depending on the variety, the rootstock, the planting distance, the cultivation practices, and the environment, orange trees may start bearing fruits 2-6 years after planting. Oranges reach acceptable ripening about 6-12 or even 14 months after flowering and may be harvested within 2-3 months before they over-ripe. It is essential to complete the harvest, if possible, before the frosts start or take measures to protect the fruits from low temperatures.
This time depends on the environmental conditions and the variety cultivated. The perfect time to harvest oranges greatly depends on the variety and the region. In the US, navel oranges are often harvested from October to June, while Valencia oranges are often harvested from March to October. Florida citrus growers report that they can harvest orange fruits all year round except for the summer. You can tell that it’s time to harvest oranges when you can see a couple of mature oranges falling off the tree.
However, harvesting time is different regarding oranges intended for juice production. In this case, farmers do more than just examine/observe the exterior characteristics of the fruit to define the harvesting moment. Fruit production companies require specific characteristics such as acids, sugars, and essences to buy the fruits. Thus, producers use special portable devices to measure those parameters.
Standards and Indices for Harvesting Oranges
The most widely used ways-indices of defining the harvesting moment by monitoring the orange ripening process is the:
- Measurement of the juice content (%)
More specifically, based on FAO, the Minimum Juice Content for the different orange varieties is: Blood oranges 30% - Navels group 33% - Other varieties 35% - Varieties Mosambi, Sathgudi and Pacitan with more than one-fifth green colour 33% - Other varieties with more than one-fifth green colour 45%.
- Measurement of total soluble solids (TSS) - Brixo (expressed in sugar content in g per 100 g of juice)
- TSS/acid ratio ( the desirable ranges between 7 to 9:1)
- Color of the juice extracted (especially for the fruits for processing)
How to harvest oranges
Manual harvesting of oranges
Harvesting of oranges represents up to 35-45% of the total costs of crop cultivation. The orange fruits are traditionally harvested by hand, with a combined movement of twisting and pulling the wrist. Some growers use clippers or shears to cut the stem. This is very common when harvesting fruits with very thin crusts. Manual harvesting has been facilitated by using fiberglass ladders and platforms and using semi-dwarf rootstocks, when appropriate training and pruning practices have been applied. In some cases, farmers also use an abscission chemical agent to facilitate the detachment of the fruit from the trees. Experienced workers may be very efficient, collecting up to 40.8 kg (90 lbs) or 9.1 boxes per hour.
Mechanical harvesting of oranges
However, during the last decade, there has been a strong trend in introducing mechanical harvesting, especially in the US, due to the increased labor costs and scarcity of personnel. To minimize costs through labor-saving technology, growers use giant shakers that are attached to tractors. Many different options are available, like trunk shaking, air shaking, limb shaking, and canopy shaking mechanical harvesting systems. Each option has its pros and cons. For example, using tree shakers leads to the harvesting of the majority of fruits from the trees and an increased amount of collected foreign matter (like leaves and twinges) that needs to be removed later on (more than 250% compared to manual harvesting).
The performance of these machines depends on and is also affected by the size of the farm, the planting distances, and the tree canopy size and scheme. Their efficiency can decrease even by 15% if the detachment force of the fruit is reduced by 50–80%. The air and trunk shaker's harvesting efficiencies are around 77% and 87%, respectively.
"In under 15 minutes, the machines shake, lose 16,300 kg or 36,000 pounds of oranges from 100 trees, catch the fruit, and drop it into a large storage car. This would have taken four pickers all day long", an orange farmer reported. However, according to the New York Times, these sophisticated machines work best only on the big, regularly spaced, groomed young groves in the southwest, and some do not work at all on the smaller, older, more irregular acreage in central Florida. Machines are hard to use on Valencia orange trees because shaking them risks prematurely dislodging much of the following year's harvest.
Post-Harvest Handling of Oranges
How to Store Oranges
Oranges have, in general, good storage and self-life and can be preserved for 3 to 5 months at 11 oC (52 oF) and 2-4 oC (36-39 oF) accordingly. Prolonged storage of the fruit with relatively low relative humidity may lead to deterioration of the quality of the fruit, mainly due to transpiration loss of moisture. The peel may become thinner, brittle, and dry in such cases. For this reason, most harvested oranges are treated with a polyethylene/wax emulsion.
Market Quality Standards and Grading of Oranges
The grading and quality standards for oranges in international markets focus on key factors such as minimum quality, size, and maturity criteria. The Codex Alimentarius, the UNECE, and various national standards establish strict requirements for oranges that are sold as fresh. Minimum standards ensure oranges are whole, clean, free of decay, and have the appropriate juice content. Size is determined by equatorial diameter, with a classification scale from 0 (largest) to 13 (smallest). Maturity standards dictate coloring and juice content, which varies by variety. Classes range from “Extra” (premium, blemish-free) to Class II, which allows more defects but still maintains edible quality.
Quality standards vary slightly by region. For example, Australian guidelines are tailored to national consumer preferences for color, texture, and sweetness. Meanwhile, in Europe, regulations align with EU marketing standards, ensuring that oranges meet specific expectations for each class.
References
https://hort.purdue.edu/newcrop/morton/orange.html
https://ourworldindata.org/grapher/orange-yields?tab=chart&country=~ALB
https://agresearchmag.ars.usda.gov/1998/mar/harv/
https://www.sciencedirect.com/science/article/abs/pii/S1537511004001977
https://www.sciencedirect.com/science/article/abs/pii/B9780323993067000244?via%3Dihub
https://www.ams.usda.gov/sites/default/files/media/TXOrangeStandards.pdf
https://unece.org/fileadmin/DAM/trade/agr/meetings/ge.01/2010/INF2e_CitrusFruit.pdf
https://citrusaustralia.com.au/wp-content/uploads/ProductDescriptionLanguageOranges.pdf
Seminara, S., Bennici, S., Di Guardo, M., Caruso, M., Gentile, A., La Malfa, S., & Distefano, G. (2023). Sweet Orange: Evolution, Characterization, Varieties, and Breeding Perspectives. Agriculture, 13(2), 264. (https://www.mdpi.com/2077-0472/13/2/264)
4.) How to grow Orange Trees from seed
5.) How to grow an Orange Tree from cuttings
6.) Growing Orange Trees for Profit
7.) Orange Tree Climate & Soil Requirements
8.) Choosing Orange Tree variety
9.) Orange Tree Propagation & Pollination
11.) Orange Tree Fertilizer Requirements
12.) Orange Tree Water Requirements
14.) Orange Tree Harvest & Yields
