Saturday, 15 July 2006

N Transformations of Fresh Poultry Manure Composts.

S. Agyenim Boateng, Soil Research Institute, Academy Post Office, Kwadaso-Kumasi, Ghana

Nitrogen transformation in manure, especially when fresh manure undergoes decomposition, is of interest to farmers and researchers alike. Fresh poultry droppings from layers without feathers or any other additives were used for composting. The manure was collected 1-3 weeks after dropping from a battery cage system. The decomposition processes were manipulated in different ways by leaving the manure in the open (A), placing the manure under a shed of iron roof (S) and placing the manure under anaerobic conditions (B). Soil or wood shavings or none of these were mixed with the manure as additives and the manure heaps were composted in netted wooden boxes for 90 days. Samples of the manure under compost were taken and analyzed for temperature, pH and N contents at certain stages. Temperature changes in the course of decomposition processes indicated sharp increases of temperature to maximum levels on the third day followed by gradual decline after 7 d to 90 d. Only the B treatments (i.e. anaerobic treatments) did not show sudden rise in temperature as the others. Changes in pH followed a similar trend. Changes in N forms indicated a rise in organic nitrogen resulting in increase of total nitrogen in the first month of composting. However, the mineral nitrogen level decreased signifying N immobilization. The trend continued in the second month for A and B treatments, although the percentage decreases were lower. The anaerobic treatments, however, experienced gains of about 100% with the non-additive treatment and with the shavings additive. The soil additive had about 25% increase. In the third month, further decreases of mineral nitrogen were observed. The A treatments registered about 30% decreases while the other treatments had between 40 and 50% decreases. The organic forms of the A treatments decreased by an average of 20%, while the S treatments remained almost constant. There was an increase by the B treatments. From the changes observed, the following conclusions could be made: that addition of soil to fresh manure during composting enhances N loss, especially mineral N; that organic N content increases irrespective of presence or absence of any additive; that if fresh poultry manure is covered or placed under a shed mineral N loss may be reduced by about 25% while N loss in fresh manure when wood shavings are added may be reduced by about 40%; that N loss is equally high if fresh manure is composted over a long time - 60 d may be enough; and that composting under anaerobic conditions may increase N levels.

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