Legume and Grass Cover Crops for Seedless Watermelon Production

Abstract

Although there is increasing interest in reducing the use of nitrogen (N) fertilizers due to the potential of unused N causing pollution of surface and groundwater, N is a major nutrient for plant growth. Our objective was to determine the potential of using winter legume cover crops to meet the N needs of seedless watermelon (Citrullus lanatus), a potential cash crop for farmers in Virginia. Fruit number, fruit weight, fruit yield, and fruit quality traits (flesh to rind ratio, water content, total soluble solids, sugar content, and pH) of seedless watermelons were evaluated in replicated experiments in Virginia at three locations during 1997-98 and two locations during 1998-99 following cover crop treatments consisting of crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa), crimson clover + rye (Secale cereale), hairy vetch + rye, and a bareground control treatment that received 100 lb/acre (112 kg·ha-1) of N. At all five locations, the bareground control treatment resulted in fewer fruit [1803 fruit/acre (4454 fruit/ha)], lower fruit weight [9.8 lb (4.5 kg)], and lower fruit yield [8.9 tons/acre (20.0 t·ha-1)] compared to the four cover crop treatments. The crimson clover + rye and hairy vetch treatments resulted in highest numberof fruit [2866 and 2657 fruit/acre (7079 and 6563 fruit/ha), respectively], whereas the highest fruit yield was obtained following hairy vetch [21.2 tons/acre (49.8 t·ha-1)], hairy vetch + rye [20.3 tons/acre (45.5 t·ha-1)], and crimson clover + rye [19.6 tons/acre (43.9 t·ha-1)]. Cover crop treatments did not affect the quality of watermelon flesh. The seedless watermelon fruit averaged 1.4 flesh: 1 rind ratio, 90% water content, 9.5% total soluble solids, 8.0% sugar, and a pH value of 5.9. These results indicated that legume cover crops, such as crimson clover and hairy vetch, can be successfully used to produce seedless watermelons, in a no-till system, without any use of N fertilizers with dryland conditions.