The Mango Loa Project phase two: Improving Hawaii's mango industry by incorporating high density orchard management systems

A Quick Project Recap of The Mango Loa Project , click the link for the entire playlist for more details.

The Ultra High Density Plantation (UHDP) techniques were developed in India, where they started a program to train new farmers using this orchard management system; however other areas have incorporated these practices such as Australia, Israel, South Africa, Japan, Florida, California, and Mexico.  There is no set density that makes an orchard high density or ultra high density, but the principal investigator considers anything above 300 trees per acre as ultra high density. 

The open Tatura trellis system was developed in Australia for temperate zoned fruits and began being adapted to tropical fruits in the early 2010’s.  This system consists of two posts set 20 inches apart forming an open “V” and trees are planted along each side of the trellis.

The search for an alternative orchard management system for Hawaii’s fruit growers was driven by the desire to take advantage of the popularity of mangoes and to increase our mango production to meet this rise in demand.  It was important to find a system designed for small farmers that may lack the labor force, the large expensive equipment, or land and natural resources that the larger mango orchards across the world have access to.  One of the most attractive aspects of high density orchard management systems is that it reduces the demand on labor; most work is on the ground with hand tools and can be managed by one person.  Also, these systems have shown to improve the quality and yield of the harvest for small farmers.  We will evaluate this point and a few others that were identified at the beginning of the project and the results after 5 years.

The conventional mango orchard has a tree spacing of 25 feet by 25 feet or 50 trees per acre and the mango trees are maintained at a 15 to 20 feet height.  Yields are around five tons per acre.

The uhdp field consists of 310 trees on a .7 acre field, for a density of 450 trees per acre.  The spacing is 8 feet in row by 10 feet between rows and the trees are maintained at a height of 8 to 10 feet.  The orchard is in its’ fifth year and most of the trees are full size, except for trees that needed to be replaced.

The open Tatura trellis field has 300 trees planted on a half acre for a density of 600 trees per acre.  The trellises are 240 feet long with 30 trees planted on each side of the trellis.  Each trellis has five wires that branches are secured along; the top trellis wire is set at an eight feet height and the trees are spaced eight feet apart.  The trees in this field are in its fourth year and have been in production for two years.

 Quicker time to full production 

An overview of the uhdp system; part 1 and part 2 

The time to full production using the UHDP system is 3 to 5 years where the conventional mango orchard reaches full production at 7 to 10 years.  The quicker time to production is due to the high density planting.  If you have a one acre field that is planted with 450 trees versus the conventional density of 50 trees per acre, at year three the UHDP field will have about 75% canopy coverage over the acre while the conventional field will have less than 50% coverage.  Also, at three years the UHDP trees are at or close to full size and are allowed to set fruit, while in the conventional field, the trees are still developing the structure of the canopy and fruit production is not the priority.   Looking at the potential harvest between these two systems after three years; if you average 50 mangoes per tree, the uhdp field has the potential to harvest over 20,000 pounds, where the conventional field will be harvesting around 2500 pounds.  However, when the conventional field reaches full maturity the difference in yield becomes less.  With that said, there are a lot outside variables that can affect or delay the development of the orchard.  In Hawaii, feral pigs are one of those variables.

Open Tatura trellis videos: trellis  and trellis pruning  

The open Tatura trellis system began production earlier than the uhdp field.  One reason for the quicker time to production is because the damage caused by feral pigs in the trellised field was less extensive than the uhdp field.  After two years, the bottom two to three wires were completely filled out and were allowed to carry fruit, even though the remaining two wires were still filling in the space.  So, overall the open Tatura trellis field began production earliest, but still needed more time to completely fill in the allotted space.

Increased quality and yields per acre

Many factors attribute to improved quality and increased yields; water and nutrient management, increased sunlight and airflow through the canopy, pest management, harvest and post harvest practices to name a few.  Pressurized irrigation is a requirement for the UHDP system. Having a drip or spray system is the most efficient and is necessary for the fruit to develop optimally.  The irrigation system is also used to deliver water soluble nutrients directly to the root zone, which is more economical and requires less labor than broadcasting granular fertilizers.  Increased sunlight distributed evenly throughout the canopy stimulates flowering, provides the energy needed for proper fruit maturation, and enables the development of the great colors that make mangoes so attractive.  Pruning to open up the canopy for better airflow through the orchard can reduce damage caused by powdery mildew, anthracnose, scales, mealy bugs, and other pests and diseases that can find shelter within the canopy.  Harvesting by hand at eye level allows for better selection for ripeness and avoids the incidental damage caused by the mango picker. So, ultimately it takes a highly efficient well organized orchard management system to improve the quality and yield of mango production, and the high density orchard management systems are that.   However, the opposite is also true.  If the irrigation and nutrient management is subpar, if pruning is insufficient, or if pest management is inadequate, then this system will not work and quality and yield will be depressed.  Here are a few pictures of damaged fruit.

Improves canopy observation and management

Maintaining the trees at 8 to 10 feet allows the farmer to observe and manage the canopy of the orchard in a way that conventional mango farmers are not able to do.  This is true for every aspect of the UHDP and the open Tatura trellis system from planting to harvest.

Reduced demand on labor

A major factor for adopting the Ultra High Density Plantation system as well as the open Tatura trellis system is a reduction in the demand on labor, in that one person can maintain multiple acres singlehandedly.  All work is done from the ground with hand tools and no heavy equipment is needed in the process other than a lawnmower.  Pruning is intensive, time consuming, and time sensitive.  So, while no expensive specialized equipment is needed in maintaining the UHDP orchard, it is still a lot of work hand pruning and at this point on the farm, it is a challenge for one person to get through three acres of mangoes in a timely matter.  In this trial, the open Tatura trellis system requires more work training the branches on the wire and shaping the trees into the two dimensional canopy that is desired, but once the branches are secured along the wires, the difference in time to manage the uhdp field versus the open Tatura trellis field becomes less significant.

Easier harvest and post harvest management

The most significant difference between the high density orchard systems versus the conventional orchard is in harvesting.  Picking mangoes is fast when done by hand.  The ability to hand pick allows the picker to be very selective, ensuring that the fruit is at the right maturity level.  In Hawaii, there can be as much as three different sets of fruit on the tree at the same time and the harvest spans over a three to five month period.  Harvesting by hand reduces damage caused by scratching the fruit and knocking down adjacent fruit by the pickers.  So, there is a tradeoff between the demands on labor needed to maintain the pruning of the orchard for the lessened demands on labor during the harvesting period.

The ability to protect the trees using netting

An important factor that emerged during the trial is the need to protect the crop from fruit eating birds, insects and mammals.  More farmers are beginning to incorporate netting in the orchard to protect their crops from birds.  In the last couple of decades, Hawaii has seen the population of the rose-ring parakeet explode and the tropical fruit farmers are facing the brunt of the damage caused by these birds.  As a result, farmers have been reducing the height of some of the taller fruit trees like mango, lychee, longan, and avocados in order to cover the trees with netting.

This fits right in with the high density orchard management systems.  Both the uhdp and the open Tatura trellis system with the make it easier to cover the trees in order to protect the fruit from birds. The netting being used is citrus netting that has 2mm eyelets and not only does this netting protect the fruit from birds, but the small eyelets are enough to also keep out fruit flies, which is another pest that plagues Hawaii’s fruit farmers.  An additional benefit of this netting is that it can provide a little bit of sun block for newly planted trees, giving them relief from the hot summer sun when establishing itself in the ground.  The Open Tatura trellises have the framework already built in and it is fairly easy to cover the entire trellis.  The uhdp field can also be covered with the netting sitting right on the trees or “T” frames can be erected every 50 to 60 feet with cables running along the outside keeping the netting off of the trees, therefore reducing damage that may be caused by the netting, like rubbing. 

Production

As stated earlier, the easiest way to increase production is to choose a productive variety.  There are thousands of named varieties of mangoes throughout the world, but only a small number has the characteristics needed to be profitable to the farmer.  The uhdp orchard is effective at growing mangoes, but will not make an unproductive variety productive.  The global average for mango production is 3.5 tons per acres and in the conventional mango orchard 5 tons per acre is a reasonable expectation.

Ideally one variety of mango would be planted in each block, however for this trial we wanted to test a few varieties to see different results.  In the uhdp field there are four rows of “Keitt”, three rows of “Rapoza”, and three rows of “Manzanillo” mangoes.  The open Tatura trellis field has two rows of “Keitt”, three rows of “Nom dok mai”, and five rows of “White Pirie”.  This has given us the ability to see how different varieties do in the high density setting. 

The “Keitt” is a Florida variety, is one of the most widely grown mangoes around the world, and has many good characteristics for commercial production, namely it is a late season mango, has good shelf life, it regularly bears fruit, is very consistent, and productive.  I’ve visited a conventional mango orchard that was harvesting 8 to 10 tons per acre, triple the global average. In my fields, the “Keitt” mango has been the most productive variety of mango averaging over 60 mangoes per tree.  In the high density orchard system, this would be over 16 tons per acres, a pretty significant increase over the conventional orchard. 

the “Rapoza” is a Hawaiian variety that has become the most widely grown commercial variety in the islands.  It is a moderately growing tree that produces large beautiful mangoes, is a regular bearer, and is resistant to some of the diseases that effect mango production.  This mango is really consistent and usually has two harvests a year, one large harvest in the summer and a smaller harvest in the winter.  These trees have averaged around 40 mangoes per tree.  This equates to over 10 tons per acre.   

“Manzanillo” is a seedling from a "Haden" mango that was selected in Mexico.  This variety produces large beautiful fruit with gorgeous coloring, has no fibers, and a small seed.  It is not widely planted in a commercial setting, maybe due to the large size about 2.5 pounds per fruit, but is a high quality mango.  So far, the production has been very similar to the "Rapoza", averaging about 40 mangoes per tree. 

The “Nom dok mai” is a very compact, slow growing mango tree.  is is a high quality Thai mango the is commercially grown throughout the world. This mango also has two harvest seasons, produces a beautiful yellow fruit that is very sweet, has little to no fibers, and a paper thin seed.   This variety has been a little inconsistent but when it does bear fruit, it has anywhere from 30 mangoes to 200 mangoes, so has the potential to be a prolific producer.  

The “White pirie” is a West Indies mango that came to Hawaii in the late 1800's and has been a local favorite ever since.  This tree produces a medium sized yellow fruit that is very fragrant and exceptionally sweet.  It is known to be a shy bearer and is susceptible to powdery mildew and anthracnose, two diseases that can severely reduce production.  This mango tree has been the most work to set fruit, needing multiple applications of fungicide during the flowering season.   So, far this mango tree averages about 25 fruit per tree, but is a smaller mango, so produces maybe 4 to 5 tons per acre.  This is better than the global average, but significantly less than the other varieties in this trial.  The "White Pirie" is an example of a mango that has exceptional flavor and is beloved, but would be a challenge to turn a profit.