ABSTRACT:A field study was carried out at National Root Crops research Institute Umudike in 2004 /2005 cropping seasons to determine the effect of the rate of nutrient mixture and time of application on crop establishment and root yield of sweet potato. The study involved the application of six rates of a mixture of poultry manure and inorganic fertilizer and four application periods on Sweet potato variety, Tis 87/0087. The results showed that application of 50% each of poultry manure and inorganic fertilizer (nutrient mixture) gave the best establishment of the crop (86.5 and 88.55% in both years) while time of application varied. In 2004, application at six weeks after planting gave higher root yield than two weeks after planting obtained in 2005 cropping season. Since there was no significant difference in root yield obtained between two and six weeks after planting for the two years and other parameters such as top yield root number were consistently higher at two weeks after planting , it is recommended that 50% each of such mixture be applied at two weeks for optimum establishment and root yield. Sweet potat.

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Field experiment was conducted in 2013 cropping season to evaluate the effect of integrating different agronomic practices for mitigating crack formation on sweet potato (Ipomoea batatas) roots. Cracks are malformations on the edible roots of sweet potato which make them look unattractive, form portals for disease and pest invasion, lead to decay and high peeling loss, and reduce marketability and acceptability. The agronomic practices evaluated included; two nutrient sources NPK 20:10:10 and 15:15:15, four different harvest periods 3, 4, 5, and 6 months after planting (MAP) on the three varieties of sweet potato namely TIS87/0087, UMUSPO/1 and CIP440293. It was carried out at the Eastern farm of National Root Crops Research Institute Umudike Abia State which lies between latitude 4 0 15 1 and 7 0 N and longitude 15 0 29 1 N and 7 0 33 1 E at an elevation of 122m above sea level. The experimental design was a split plot arrangement fitted into a randomized complete block design, main plot was nutrient source, subplot was time of harvest, and sub subplot was variety. There were thirty six treatments replicated three times. The soil was classified as sandy loam. Data were collected on number of roots with cracks, total root number, total root fresh weight, and rot incidence. Results showed that the effect of the nutrient sources was not statistically significant at (P≤0.05) on crack formation more cracks were recorded on varieties UMUSPO/1 and CIP440293 (orange-fleshed) than TIS87/0087 (white-fleshed). Time of harvest was very highly significant (P<0.001) on number of roots with cracks. From this work it can be concluded that time of harvest and variety played important roles in the formation of the cracks in the tuberous roots of sweet potato which reduce the quality of the crop. The type of fertilizer used has no effect on the crack formations, root size and number while early harvest is recommended.