CROP-ROTATION EFFECTS ON SWEET-POTATO YIELD AND QUALITY

As the suite of fungicides, pesticides, and fumigants available to veg etable producers continues to shrink, growers may begin to reexamine c rop rotations as an alternative method of disease, weed, and pest cont rol. Although many studies have examined field crop rotations, relativ ely few have examined a vegetable crop as a part of that rotation. In 1985 a study was initiated to evaluate the effect of various crop rota tions on sweet potato (Ipomoea batatas L.) yield and quality. Specific rotations were: (i) continuous sweet potato, (ii) sweet corn (Zea may s L. var. rugosa) and sweet potato, (iii) soybean [Glycine max (L.) Me rr.] and sweet potato, (iv) 2 yr sweet corn and one yr sweet potato, ( v) 2 yr bahiagrass (Paspalum notatum Flugge.) and 1 yr sweet potato, a nd, (vi) soybean, sweet corn and sweet potato. Two complete cycles (19 88-1990 and 1991-1993) of the rotations were analyzed. The crop rotati on producing the largest annual yield (4.70 tons/acre) and one of the largest cumulative (11.35 tons/acre) sweet potato yields was 2 yr of b ahiagrass followed by sweet potato. Continuous sweet potatoes produced the lowest annual (2.12 tons/acre) and one of the highest total marke table cumulative yields (11.39 tons/acre) during the 6 yr. In general, a rotation containing a grass (bahiagrass, sweet corn) produced highe r annual sweet potato yields than those without.