Orchard Alley Cropping the Subhumid Tropics
1. Establish contour hedgerows in an approximately 1.5 acre tropical fruit orchard in the subhumid tropics.
2. Measure hedgerow prunings fresh weight and nutrient concentrations for two NFT species at each cutting, in order to ascertain fertilizer replacement values.
3. Measure soil nutrient levels on an annual basis and crop growth on a semi-annual basis for each of six treatments and a control.
4. Measure fluctuation of soil levels on an annual basis.
5. Demonstrate the orchard alley cropping system, and present two workshops for farmers, ranchers, extension agents and agricultural consultants.
6. Determine economic costs and returns of orchard alley cropping.
This project, located on a farm in Holualoa, Hawaii, studied alley cropping for mulch production in a fruit tree orchard. In alley cropping, fast growing nitrogen-fixing trees (NFTs) are grown in contour hedgerows alternated with crops to provide an abundant source of nutrient-rich organic matter which is applied to the soil as mulch. By cycling nutrients in the agricultural system, alley cropping in an orchard setting holds promise for greatly reducing, and possibly eliminating, the need for manufactured or imported fertilizer inputs, replacing them with an on-site organic source of fertility.
Research focused primarily on the ability of the alley cropping technique to provide sufficient nutrients to tree crops, as well as the economic feasibility of the practice for orchards. The two NFT species were Acacia angustissima and Calliandra calothyrsus; the fruit tree crop was Jackfruit (Artocarpus heterophyllus).
The hedgerows were pruned for mulch four times during the project. Hedgerow prunings fresh weight and nutrient concentrations for the two NFT species were measured at each cutting, in order to ascertain fertilizer replacement values. Data show that the hedgerows produced about 300 pounds of mulch per fruit tree per year. Nutrients from this mulch source provided the nutrient equivalent to over 500 pounds of chemical fertilizer per acre per year, potentially replacing 400 pounds of urea, 25 pounds of treble super phosphate, and 120 pounds of muriate of potash. Soil analysis showed significant increases in total nitrogen and potassium as a result of the practice. Soil pH also improved, becoming more neutral. The mulch also reduced the need for weed control around the crop trees and conserved soil moisture. The health and vigor of the mulched crop trees visibly surpasses that of unmulched trees, and analysis of the data shows a trend of faster growth and larger stem diameter in the mulched trees over unmulched. The costs of this practice are roughly equivalent to using purchased mulched materials. This practice may be particularly of benefit to cash-poor Pacific Island farmers, who have better access to labor than cash.
Since the beginning of this project in August 1995, three workshops for farmers have been held at the site, as well as three field days, with a total of over 180 people having visited the project. Participants in workshops and field days were generally a mix of farmers, orchard managers, extension agents, and other agricultural professionals. One field day was targeted specifically to the interests of resource-poor growers from the Hawaiian Homelands, and displaced sugar cane workers. In addition, the practice has been shared in slide presentations for two grower groups, the Hawaii Tropical Fruit Growers Association and the Kona Outdoor Circle, with over 70 attendees. At least fourteen farmers are known to have integrated nitrogen fixing trees in their farms directly as a direct result of their participation in a workshop, field day, or evening lecture.
The two booklets produced, the Nitrogen Fixing Tree Start-Up Guide and A Guide to Orchard Alley Cropping, summarize practical recommendations for farmers who wish to plan for, install, and manage an orchard alley cropping project. Both booklets are being distributed to Hawaii and American-affiliated Pacific Island Cooperative Extension and Natural Resource Conservation Service offices. Free reproduction for educational purposes is encouraged. Booklets will also be made available in pdf format to be downloaded free of charge from the web site http://www.agroforester.com.
The costs for orchard alley cropping are approximately $2,000 per year, with over 90 percent of that cost being labor (calculated at $10/hour) to cut the hedgerows and use the mulch. Clearly this is a labor intensive practice, which demands very little capital or monetary expense if labor is not purchased.
For the purposes of comparison, commercial alfalfa hay purchased from a Hawaii distributor was used. Like the hedgerow mulch, it is generally free of weed seed, easy to apply as mulch, and has a similar nutrient composition. Using the hay for mulch would cost about $1,900 for a similar quantity of material as that produced by the hedgerows. About 80 percent of this cost is in money spent for the mulch material, and about 20 percent for labor.
The benefit-cost analysis shows that for our comparison there is a negative marginal rate of return for the alley cropping method of producing mulch of 6 percent annually, as compared to purchasing mulch.
Considering that most small farmers have limited capital to fertilize and maintain their orchards, the alley cropping method of mulch production, which relies on little outlay of capital, would be preferred. Alley cropping also gives other farm benefits including erosion control, wind shelter and farm self-sufficiency, which have not been given values in the economic analysis.
This project highlights the importance of organic matter in tropical agriculture, and in so doing stimulates the use of organic and sustainable techniques. Adoption of the orchard alley cropping practice holds great potential to reduce farmer dependence on purchased chemical fertilizers, reduce environmental pollution from chemical fertilizers and weed control, reduce erosion, and increase overall soil health, while allowing continued levels of fruit crop production. This practice produced approximately 20,000 pounds of mulch per acre per year, or about 300 pounds of mulch per crop tree. Cycling nutrients in the agricultural system mimics the production of organic matter in tropical forests, and improves soil life and crop health. The nutrients from the on-site mulch source provided the equivalent to over 500 pounds of chemical fertilizer per acre per year, equivalent to 400 pounds of urea, 25 pounds of treble super phosphate, and 120 pounds of muriate of potash.
Benefits of this system to the farmer include: an abundant on-site source of nutrient-rich organic material for use as mulch and slow-acting fertilizer; soil building through accumulation of organic matter through mulch; erosion control; reduced weed control labor; other products for the farm such as supplementary fodder and fuelwood; and an opportunity to replace expensive fertilizer imports with an on-farm source obtainable with labor.
Potential environmental benefits of this practice include: the reduction or elimination of soluble fertilizers, reducing soil and water contamination; soil conservation through the creation of erosion barriers; reduction of fossil-fuel pollution from transportation of chemical and/or organic fertilizers, particularly to the remote Pacific Islands; and potential reduction of herbicides through mulch weed control.
Reaction from Farmers and Ranchers
In general, participants in the educational events that highlighted this project seemed very receptive to the potential of this practice. Growers specializing in sustainable/organic agriculture seemed especially enthusiastic about the fertilizer replacement values. Some comments from workshop participants include:
"I planted my hedgerows right after the workshop. They took awhile to establish, but now they are 12 feet tall! I am very happy. I will be cutting them for the first time this month."
"It was valuable to learn about the potential uses for NFTs in a sustainable system and...the identification, outdoor hands-on propagation and farm tours. I learned a lot and feel motivated to begin an NFT project. Also, the handouts were very useful and concise."
This summary was prepared by the project coordinator for the 1999 reporting cycle.