Mineralization of nitrogen and phosphorous from commonly used animal manure in Tanzania .

A study was conducted at Sokoine University of Agriculture (SUA), Morogoro, Tanzania during 2007/08. The objective of the study was to evaluate extent of mineralization of N and P from four commonly used animal manure in Tanzania namely; poultry, pig, goat and cattle. The study involved a ten week incubation experiment and a glass house experiment in which okra was used as a test crop .The experimental design for the two experiments was split plot with manure types as the main plots and application rates as sub-plots. Results of the incubation experiment indicated that application of the four manure types significantly (p<0.01) increased N and P levels. Generally, Poultry manure resulted in highest levels of net N and P followed by pig, goat and cattle manure. The trend of N mineralization from the four manure types resembled that of P mineralization. Similar trends were observed for the attributes evaluated in the pot experiment .Okra shoot dry weight and root dry weight were highest in poultry manure amended pots and lowest in cattle manure amended pots. Poultry manure had the highest levels of N and P and narrowest ratios of C/N and C/P suggesting superior mineralization of N and P. Based on the fertilizer recommendation of N and P for maize in Southern Highlands of Tanzania (N=80kg N/ha and 20kgP/ha) and the highest application rate of 300kgN/ha used in this study, applications of 10.75tons/ha of poultry manure 12.84tons/ha of pig manure 18.47tons/ha of goat manure and 21.27tons/ha of cattle manure will meet the recommendation of 80kgN/ha. The above application rates will also provide 12.43kgP/ha, kgP/ha,11.54kgP/ha,13.76 kgP/ha and 10.97kgP/ha for poultry, pig, goat and cattle manure respectively which will not meet P recommendation. Based on the above the following are recommended: (1) Efforts should be directed towards improvement of animal manure quality in order to reduce amounts required to meet N and P recommendations. (2) Manures should be supplemented with inorganic P or other sources such as rock phosphate. (3)Training programmes should be designed for farmers and extension staff to sensitize them on manure use and management practices.