Organic Soil Amendments of Agricultural By-Products for Vegetable Production Systems in the Mississippi Delta Region
There are ways to recycle and reuse agricultural wastes so they do not go to waste. This is particularly important in the South where agricultural waste products are so abundant. In Arkansas alone, the state’s poultry and cotton industries produce billions of pounds of by-products and wastes each year. In 1993 Arkansas’ billion broiler chickens produced 2 to 2.5 pounds of litter per bird. During ginning of the state’s 1.5 million bales of cotton, 100 to 150 pounds of gin trash were produced per bale. In this project our aim has been to take advantage of the availability of these materials by putting wastes to work improving soils on small scale vegetable farms.
University researchers and farmers worked together in this SARE/ACE project to evaluate availability, agroecological impact and economic feasibility of agricultural wastes when used as soil amendments. The bulk of the research/demonstration work was carried out on small scale vegetable farms operated by African American growers in eastern Arkansas’ Mississippi Delta region. Farmers were directly involved in the planning of the research and implementation of the results. This allowed us to take research out of the controlled environment of the laboratory and agricultural research station directly to farms where people are growing crops.
Research has included work with animal manures and organic wastes from processing facilities such as cotton gins, rice mills and fisheries. Field studies began in 1992 at the Demonstration Farm of the Arkansas Land and Farm Development Corporation (ALFDC) in Monroe County, and the farms of Harvey Williams (Phillips Co.), Ben Anthony, Jr. (Lee Co.) and Jim Burton (Monroe Co.). Additional sites added in 1993 and 1994 were the farms of Randy Hardin (Jefferson Co.), Abraham Carpenter (Jefferson Co.), Arther Beam (St. Francis Co.) and Dennis Clark (Mississippi Co.).
Studies with aquaculture wastes have been performed at the University of Arkansas at Pine Bluff Agricultural Experiment Station.
Because of widespread interest by farmers on effects of poultry litter on vegetable production, much of the field work has involved evaluations with litter (manure + bedding material such as rice hulls) from broiler and turkey production. Several demonstrations were made with raw litter, but a composted pelletized form of litter was used on most of the replicated trials. Pelletized poultry litter (PPL) with NPK analysis of 4-4-4, has been evaluated with six farmer cooperators on cabbage, sweet potato, tomato, okra, basil, watermelon, broccoli, turnip and collard greens production fields. Benefits of using poultry litter have been most apparent in fields that previously had been precision leveled to improve irrigation efficiency. In these fields, topsoil has been disturbed and low pH (<6) is common. Significant crop responses also have been observed with shallow rooted plants (cabbage, collards, spinach) grown in light textured soils with low organic matter.
In several studies and demonstrations, we compared different sources of poultry manure (rates were adjusted to provide equivalent amounts of N). In replicated trials on the ALFDC farm with cabbage, no differences in yield were apparent between treatments of raw hen manure, pelletized hen manure, pelletized litter, composted litter and raw litter. Although the pelletized products are easier to store and apply, high costs of these value-added manure products precludes their use by many farmers.
Low-cost agricultural wastes most available in the Delta are rice hulls and cotton gin trash. Our replicated trials with gin trash and rice hulls included studies to determine effects of cotton gin trash (raw and composted) and cover crops on yield of cabbage, broccoli, southern peas, snap beans and cucumbers particularly with marginal soils. Significant problems with weeds and plant disease resulted in green beans following use of raw gin trash. Composting alleviated these problems and we found that composting didn’t have to require huge inputs of time by the farmer to produce an amendment that could improve productivity of the soil.
Ben Anthony routinely hauls gin trash in his pick-up truck from a local gin to his cattle pasture where cows feed on the material over the winter. By summer’s end the trash has decomposed. We applied this decomposed (composted) gin trash to damaged soil on his vegetable farm in 1994. Four tons/acre increased earliness and yield of his spring transplanted cabbage. In fall trials that year with turnips at the ALFDC farm, applications of two tons per acre of this composted gin trash + fertilizer (60 lb N/A provided with 13-13-13) resulted in significantly higher yield of greens compared to plots receiving fertilizer alone.
Additional studies with composted gin trash have included using the material as a potting media for growing watermelon and tomato transplants on the Ben Anthony Farm. Mixed in a 2:1 combination with perlite, tomato and watermelon transplants grown in composted gin trash were equivalent in plant height and color to plants grown in standard potting media; however root development was reduced compared to the standard. This resulted in significant problems pulling the plants during high speed transplanting with mechanical transplanters.
In watermelon field trials on the Clark and Anthony farms, once transplants were set, there were no differences in yield or quality in final harvests. In other work, composted gin trash was found to be a good material for production of potted ornamental plants, Swedish ivy and wandering Jew.
No significant improvements in yield of cabbage or collards have been observed with applications of raw rice hulls. The negative effects of over application of raw rice hulls were demonstrated on the ALFDC farm with spring transplanted cabbage when rates up to 10 tons/acre of raw hulls resulted in nutritional deficiencies (primarily N). This demonstration was valuable to several farmers and area Extension agents who had routinely recommended high amounts of rice hulls for garden plots.
Work with aquaculture wastes has included construction of composting units at the University of Arkansas at Pine Bluff Aquaculture Research Station. Applications of composted fish remains and spoiled feed were evaluated on the UAPB research farm in replicated trials with collards and southern peas. Hairy vetch and rye were evaluated as winter cover crops in combination with compost. Cover crops had varying effects on southern pea yield in three years of trials, but there was no significant differences in yield. Results have been variable with collards, but significant increases in yield of spring transplanted collards were observed in 1994 following application of two tons compost/acre.
Education and outreach have been an important part of our project. The ALFDC has been instrumental in these efforts sponsoring several workshops, field days and conferences including the ALFDC Annual Conference in Fargo, AR held each October. In 1994, our research was highlighted in a special sustainable agriculture section held during the conference, which included tours of research plots. Additional field days were conducted on the Ben Anthony and Abraham Carpenter farms. Project results have been presented at a number of professional and grower meetings including the 1995 Southern Sustainable Agriculture Working Group Annual Conference, and annual meetings of the Arkansas State Horticultural Society and the American Society of Horticultural Science.
In this project, we have found that benefits from applying low-cost agricultural waste products include improvements in soil productivity, making possible increases in farm profitability. The most outstanding results have been observed with crops grown on land that had been recently precision leveled and with crops with shallow root systems. An additional benefit is the contribution to solving waste disposal problems confronting the region.