Effectiveness Of Reduced Rates Of N On Productivity And Economic Returns Of Sorghum In Striga Infested Semi-Arid Areas Of Tanzania

ABSTRACT

Performances of three sorghum (Sorghum bicolor L. Moench) genotypes (Wahi, Hakika and Pato) and inorganic soil amendments were studied under naturally Striga asiatica [L.] Kuntze infestation for one cropping season (2015/16) in two locations, using a split plot design laid out in a randomized complete block design with four replications. A susceptible sorghum (Pato cultivar) was used as a bioassay to evaluate the effectiveness of reduced rates of N under Striga infestation. At Hombolo, 40 Kg N/ha had significantly (P< 0.05) lower emerged Striga shoots count/m2 than all other rates of N, except at 11 WAP. Yields with 30 Kg N/ha (0.64t/ha) was significantly (P< 0.05) lower than yields from all other rates of nitrogen (1.08 - 1.52t/ha). At Ngamu, fertilization played no significantly (P< 0.05) role in Striga emergence and attachment. Yields with 10 Kg N/ha (4.89t/ha) was significantly (P< 0.05) lower than yields from all other rates of nitrogen (5.2 – 6.0t/ha). Across locations, variety Hakika had significantly (P< 0.05) fewer emerged Striga shoots count/m2 compared with varieties Wahi and Pato. At Hombolo, Yields on Hakika variety (0.96t/ha) was significantly (P< 0.05) lower than the yield in all other varieties (1.21 - 1.28t/ha). At Ngamu, variety Pato gave more yields (7.21t/ha than other varieties (2.81 – 5.95t/ha). This study showed that the most effective rates of nitrogen; 40 and 60 Kg N/ha (Hombolo) and 50 Kg N/ha (Ngamu) should be promoted in semi-arid areas of Tanzania where Striga poses a serious threat. Results also showed that varieties Hakika and Wahi proved their resistance/ tolerance to Stiga asiatica compared to variety Pato. i