Potassium applications from 0 to 140 kg/ha at 4 locations had more influence on quality of sweet potatoes than P applications of 0 to 73.9 kg/ha as an average of years and locations. As the rate of K but not P applications increased, percent dry matter decreased. K and P applications reduced protein content and firmness of canned roots. K slightly increased the crude fiber content (dry wt basis) of the roots, whereas P applications had no affect on fiber content. K and P fertilization had no influence on carotenoid content (fresh or processed), percent splitting of canned roots, or crude fiber content (fresh weight basis). Year and location effects were noted for some of the quality variables studied. Most of the differences observed were of low magnitude, thus had little effect on the overall quality of sweet potatoes. The most outstanding effect was the reduction in dry matter content due to K applications.

‘Centennial’ sweet potatoes (Ipomoea batatas (L.) Lam.) did not respond to increasing levels of P over an 8 year period probably due to the low soil pH and relatively high native P levels. Increasing the available soil moisture to above 25% resulted in a 3.4 MT/ha increase in yield of marketable roots over that obtained with natural rainfall but increasing the available moisture had no influence on yield. The P rate had no effect on dry matter and/or carotenoid content, firmness and splitting of processed roots. Protein content as percent of dry weight was reduced with increased P rate. Increasing the available soil moisture resulted in lower dry matter, protein, and carotenoid contents but had no influence on fiber content, firmness, or splitting.

Yield, quality, and respiration studies were conducted with 23 mutations of the ‘Centennial’ sweet potato (Ipomoea batatas (L.) Lam). None of the mutant selections produced significantly higher yields than the original cultivar. Total carotenoid pigments of mutant clones ranged between 1 and 14 mg per 100 g of fresh tissue, with 10 mutants not different from the original cultivar and 13 with less pigments. Dry matter content varied from 26 to 34% in the fleshy roots with 4 selections significantly higher than the ‘Centennial’ roots. Dark skin color (rose or purple) was accompanied by orange flesh color in all samples tested. There was a large variation in respiration rates of storage roots between mutant clones and ‘Centennial’ roots.

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