1996 Annual Report for LS96-077
Development of Sustainable Cropping Systems for Seedless Watermelon and Fall Lettuce in Rotation with Green Manures
Summary
Objectives
The goal of the project was to develop a sustainable crop rotation system for the production of seedless watermelon and fall lettuce following selected cover crops.
Results
The cover crop treatments originally were Austrian Winter Pea, Hairy Vetch, Austrian Winter Pea and rye, and Hairy Vetch and Rye, and a non-planted control. From fall of 97 Crimson Clover replaced Austrian Winter Peas. Cover crops were planted from 96-98 at seven locations in North Carolina and Virginia at experiment stations and farmer’s fields.
The cover crop growth and biomass production were not significantly different under the treatments. The biomass production ranged from 3.2 to 4.8 tons per acre. In the spring of 1997-99, the cover crops were mowed down with a flail mower and left as a surface mulch to control weeds and soil erosion, and retain soil moisture.
Two seedless watermelon varieties were transplanted and grown in each cover crop treatment at all of the sites. The watermelon crop was established well in North Carolina sites, and Virginia sites. Seedless watermelon yields were satisfactory in Guilford, Lenoir and Rockingham counties of North Carolina. In Guilford County, watermelon yields were the highest under Hairy Vetch Treatment (14.7 ton/acre). In Rockingham County, the treatment of Austrian Winter Pea and Rye mixture yielded 29.0 ton/acre and it was the highest among all the sites. Average yield of these three sites was 17.3 ton/acre with a standard deviation of 6 ton/acre. Average number of melons in Guilford, Lenoir and Rockingham counties was 2600 per acre, average weight was 17.3 tons/acre.
A quality analysis of seedless watermelon from North Carolina sites conducted by Virginia State University revealed that the average sugar content in the watermelons from sites of Guilford and Rockingham counties was 8.17% with a standard deviation of 0.33%.
Seedless watermelon yields in Virginia ranged from 4.9 to 34.7 tons/acre. Quality analysis of Virginia melons showed meat: rind ratio 1.2 to 1.8 and it was not affected by cover crops. Also, sugar and other quality parameters were not effected by the cover crops.
Cooperating farmers of North Carolina sold all of their seedless watermelons in the local farmer’s markets. At Fletcher Crimson Clover and Rye treatment produced the highest yields (6.6 tons/acre). There was no size difference between the seedless watermelon tested. A survey was conducted by including professionals, farmers, marketeers, household individuals and others to evaluate seedless watermelons from this research and demonstration. Eighty percent of the survey participants favored the taste of seedless watermelon. Ninety-two percent of them showed their preference to buy seedless watermelons even at a higher price than seeded melons.
At the site of Guilford County, North Carolina, we monitored the nitrate leaching in watermelon plots due to cover crop mulch decomposition. The nitrate results showed that decomposition of the cover crop mulch provided enough nitrogen nutrient for the growth and development of seedless watermelon. However, there is a potential risk of nitrate leaching to deep soil or groundwater after the maturity of most of the watermelons.
Pest populations were also monitored and there were no real problems with pests and diseases. However, as the cover crop mulch decomposition progressed, weeds became a problem at the middle and late stages of the watermelon growth.
After the harvest of the watermelon there was not enough time for fall lettuce crop due to the timely planting of cover crops. Therefore, all the plots were tilled and planted with respective treatments of cover crops. Due to poor performance observed at some sites under the treatments of Austrian Winter Pea and the mixture of Austrian Winter Pea and rye, we replaced Austrian Winter Pea with Crimson Clover from the fall of 1997-99.