Browsing by Author "Lisuma, Jacob Bulenga"

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Identification and correction of some micronutrient constraints in a volcanic soil from Mpangala village, Makete district for optimization of maize yields.
(Sokoine University of Agriculture, 2003) Lisuma, Jacob Bulenga
A study was conducted in field and glasshouse conditions to identify and correct some micronutrient constraints in Mpangala volcanic soil for optimization of maize yields. The study involved routine soil analysis, pot experiments and a field experiment. Soil analysis revealed the level of Cu to be 0.14 mg kg*1, which was ranked as deficient; Zn was 0.86 mg kg' (marginal) and boron was 0.52 mg kg"1 (medium). In the first pot experiment, P and N were applied at constant rates of 160 mg kg'1 and 240 mg kg'1, respectively. However in one treatment a higher rate of 320 mg P kg-1 was applied in order to test whether a higher rate of P was still required in Mpangala soil. Boron was applied at rates of 0 and 2 mg-kg'1, Cu at rates of 0 and 5 mg kg'1 and Zn at rates of 0 and 10 mg kg-1. The results indicated that a combination of Cu, N and P increased yields dramatically. Moreover the treatment that received the high P rate of 320 mg kg'1 together with N, B, Cu and Zn fertilizers had significantly (p = 0.05) higher DM yield than the Cu treatment. Analyses of plant leaves showed very low concentrations of Cu followed by Zn. However, Zn did not increase DM yield significantly. It was concluded that Zn may be the next limiting nutrient after Cu. A second pot experiment was conducted to estimate the optimum rate of Cu. Nitrogen and P were applied at constant rates of 240 and 320 mg kg", respectively, and Cu at rates of 0, 5, 7.5, 10, 15 or 20 mg Cu kg'1. The experiment indicated the rate of 20 mg Cu kg'1 to be optimum in Mpangala soil. In the field experiment, significantly (p = 0.05) higher grain yield of 5.84 ton ha'1 was obtained when 2.5 kg Cu ha-1 was applied. The results in this study revealed that Cu was the most limiting micronutrient in Mpangala soil, followed by Zn. Zinc may need to be added in addition to Cu, after one harvesting cycle, in order to provide proper nutrition to the maize crop in the long run. Higher rates of N and P may still be beneficial, especially if Cu and Zn are optimized.