1.1.2 fflKHiGanunga, Rosan P. (1997). Performance of Tithonia diversifolia (Hemsley) A. Gray as an organic source of nitrogen and phosphorus on the growth and yield of maize (Zea mays L.) in Dedza, Lilongwe and Mzimba districts of Malawi. (Supervisor: Dr. O. A. Yerokun).
Soil degradation and continuous cropping without the addition of external inputs have resulted in declining soil fertility and consequently smallholder maize yields in Malawi. As inorganic

fertilizers are becoming increasingly unaffordable due to rising prices, alternative sources for soil fertility improvement have to be evaluated. A study was conducted during the 1996/97 season in Dedza, Lilongwe and Mzimba districts of Malawi to assess the effect of Tithonia diversifolia on nutrient uptake and yield of maize compared to inorganic fertilizer. The following treatments were evaluated in a Randomized Complete Block Design experiment with three replicates; (1) control — no fertilizer and no Tithonia, (2) 40kg P2O5 /ha + 92 kg N/ha (standard recommendation), (3) Tithonia at 1.5t/ha (44.1 kg N + 3.75 kg P), (4) Tithonia at 3.0 t/ha (88.2 kg N + 7.5 kg P), (5) Tithonia at 4.5t/ha (132.3 kg N + 11.25 kg P), (6) Tithonia at 1.5t/ha (44.1 kg N + 3.75 kg P) + 13.5kg P from TSP, (7) Tithonia at 3.0t/ha (88.2 kg N + 7.5 kg P) + 9.7kg P from TSP, (8) Tithonia at 4.5t/ha (132.3 kg N + 11.25 kg P) + 5.95kg P from TSP. Laboratory incubation studies were also conducted to compare the rates of mineralization between Tithonia and other green manure crops. The treatments which received the application of Tithonia leaves at 1.5t/ha produced maize grain yield increases of 39% (2,692 kg/ha), 122% (4,360 kg/ha) and 162% (7,690 kg/ha) over the control (1,914, 1,965 and 2,940 kg/ha) at Bembeke, Chitedze and Champhira, respectively. Similarly, mean maize yields from the application of Tithonia diversifolia biomass at 1.5t/ha (2,607 kg/ha) were not significantly different from the inorganic

fertilizer treatment (2,734 kg/ha). Supplementation of TSP to Tithonia did not result in significant maize yield increases. With Tithonia biomass alone, maize yields ranged from 2,607 to 3,731 kg/ha, while with TSP supplementation, yields ranged from 2,640 to 3,665 kg/ha). The application of Tithonia leaves at 1.5 t/ha raised soil phosphorus status by 8%, 74% and 12% while soil nitrogen was improved by 22%, 6% and 11% at Bembeke, Chitedze and Champhira, respectively. With the application of DAP and urea at 92:18 N:P, nitrogen status was improved by 5, 10 and 44% while phosphorus was improved by 22, 47 and 68%, respectively at Bembeke, Chitedze and Champhira. From the average of the 3 sites, the treatments which received the application of Tithonia leaves only at 3.0 and 4.5t/ha resulted in the significantly highest nitrogen uptake of 20.3 and 22.2 kg/ha while with supplemental TSP, N uptake was 22.0 and 21.5 kg/ha, respectively. The application of Tithonia only at 3.0 and 4.5t/ha resulted in a P uptake of 4.4kg P/ha. With TSP supplementation the same treatments resulted in P uptake of 5.1 and 4.9 kg P/ha. The inorganic fertilizer treatment gave an uptake of 20.0 and 4.1 kg/ha of nitrogen and phosphorus respectively. Highest ammonium and nitrate concentrations were observed at 14 days after the onset of incubation while phosphorus concentrations were highest at 28 days. Nitrate concentration was highest in the soil which was mixed with Mucuna (20.4 mg NOs kg/ha). Tithonia leaves (10.1 mg NH4+ kg/ha). The soil mixed with Tithonia leaves also had the highest phosphorus concentration (11.0 mg kg/ha).