Response of sweet potato (Ipomoea Batatas Lam) to organic and inorganic fertilizers in loamy sand soil at Tumbi, Tabora, Tanzania

DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE MASTER DEGREE IN CROP SCIENCE AT SOKOINE UNIVERSITY OF AGRICULTURE, MOROGORO, TANZANIA.A field experiment was conducted during 2014/15 growing season at Tumbi, Tabora to study response of sweet potato to organic and inorganic fertilizers. The experiment was split plot laid in a Randomized Complete Block Design with four fertilizer types and different rates; 0, 50, 100, 150 (DAP), 100, 200, 300 kg ha-1 (Minjingu Mazao), 150, 250, 350 kg ha-1 (NPK) and 2.5,5.0,7.5 ton ha-1 (FYM) as main plots and three varieties (Kasinia, Simama and Ukerewe) as subplot in three replications. Data on tuber numbers, total tuber weight, marketable tubers weight, marketable tubers diameter, vine length, branch numbers and above ground dry biomass were measured while, agronomic efficiency, net revenue and Value Cost Ratio were calculated then analyzed using Genstat Statistical Software and Tukey's test for mean separation at 5% significance level. Overall yield and yield components increased with increase in fertilizer rates. Highest total tuber weight (13.21 tons ha-1) and tuber numbers (54321) were recorded with FYM (7.5 tons ha -1) while, highest marketable tubers weight of 12.47 tons ha-1 and marketable tubers diameter (8.88 cm) was recorded in Kasinia with NPK fertilizer (Yara Mila Winner) at 350 kg ha-1. NPK (350 kg ha-1) and FYM (7.5 tons ha-1) gave highest above ground dry biomass weight at 5.70 and 5.62 ton ha-1 respectively, while NPK (350 kg ha-1) recorded longest vine (235.3 cm) and number of branches (8.89) than the control. Higher agronomic efficiency of 228.46 was recorded in variety Kasinia with FYM (7.5 ton ha-1) and net revenue of TShs 5172160/- was obtained from variety Simama, which was similar to Kasinia. Kasinia and Simama were more responsive to NPK (350 kg ha-1) and FYM (7.5 tons ha-1) than Ukerewe as they gave highest yields and net revenue