pecan harvesting developments


Pecan Research


Department of Agricultural Engineering

Texas A&M University


THE NEED FOR MECHANICAL harvesting of pecans has become apparent during the past few years. Produce often had to pay from one-third to one-half of the value of the crop for harvesting by hand. Several million pounds of pecans remained on the ground at the close of the 1963 harvest season because hand labor was not available. An estimated 30 percent of the pecans in Texas were not harvested in 1965, even though producers paid one-half to two-thirds of the value of the crop for harvesting. This high cost of human energy for harvesting leaves little return to the producers. If this trend is not reversed, many producers will discontinue disease and insect control programs, and groves will be neglected and will deteriorate rapidly.


Rough Terrain a Problem

Since approximately 80 percent of Texas’ pecans are produced in native groves, this creates many problems for mechanical harvesting which would not be found in planted orchards. These native trees are found growing in bottomlands along creek and river banks with some of these trees actually growing in dry-stream beds. The land is frequently cut with drainage ditches and gulleys. Small sand dunes deposited by floods are found on the soil surface. The overflowing of the streams usually deposits trash, limbs and other residue which must be removed before mechanical harvesting can be successful. Even in areas where the land appears to be smooth, many small depressions create problems when efforts are made to retrieve pecans from them. It is difficult to maneuver a harvesting machine between and around the native trees because of their irregular stand and the rough terrain.


Present Research Program

The present research program for mechanization of pecan harvesting began in September 1965. Its objectives were to (a) develop equipment and procedure for mechanical harvesting of pecans; (b) develop method for preparing the ground for mechanical harvesting; (c) develop process equipment to clean the pecans for market.

Many of the native groves contained as much as 1,600 pounds of trash per acre. To reduce the cleaning load on a harvesting machine, several methods for removing trash from the ground before harvest were evaluated. It was found that 74.2 percent of this trash could be removed in a pre-harvest operation by a sweeper designed for this purpose. This sweeper utilized a conventional steel street sweeping brush with a diameter of 34 inches and bristles 12 inches long. The brush, rotating with direction of travel, swept the trash up an incline inside a metal cover or hood for 180 degrees so as to elevate the material to be deposited into a trailer connected to the rear of the brush. The trailer was dumped hydraulically when it became full.

Tests were performed using the sweeper as a harvester to determine if it was feasible to harvest pecans without cleaning equipment and to evaluate the performance of a rotating brush. The results of these tests indicated:

1. A rotating brush could be used for removing the pecans from the ground if the soil was level and had a good thick layer of grass.

2. Cleaning equipment is necessary.


Experimental Machine

An experimental machine was developed and built to evaluate different types of brushes, conveyors and cleaning methods. The machine utilized a brush for Sweeping leaves, trash and pecans up an incline into an air stream. The air stream removed most of the leaves and let the nuts fall onto a drag-type conveyor with a slotted bottom. This conveyor is perpendicular to the direction of travel of the machine and parallel to the brush. Dirt and some fine trash is lost through the slotted bottom as the conveyor takes the pecans to an elevator which elevates them to a sacking unit.


The first brush evaluated in the experimental harvester was street-sweeping type made from steel with a diameter of 34 inches. The steel brush is aggressive in removing pecans from a thick layer of grass that is 3 to 4 inches long, but picks up an excessive amount of dirt and does not remove all the pecans from depressions in the soil surface.

Rubber fingers, 10 inches long, were used as bristles for building a brush with a diameter of 33 inches. The best results were obtained when this brush was operated at a height of 12 inches which deflected 5 inches of each rubber finger backward along the surface of the ground as the brush rotated. This enabled the brush to expand into depressions and remove the pecans, and the rubber fingers will compress when passing over high spots without overloading the brush. The rubber fingers sweep up very little small trash and dirt with the pecans. Preliminary evaluation indicates good possibilities for harvesting native pecans with the rubber finger brush where recommended cultural practices are carried out.


Cultural Practices Necessary

Research to date shows that the following cultural practices will be necessary for successful mechanical harvesting of pecans in Texas:

1. The trees must be pruned so that mechanical equipment can operate under them.

2. The ground should be as level as possible.

3. The land under the trees should be free of trash, limbs, undergrowth and other obstructions which would interfere with harvesting.



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