Optimizing Manure Quality for Increased Food Production on Small Holder Farms in the Upper East Region of Ghana

The beneficial role of cattle manure to improving soil fertility has long been recognized. Its uses however have several drawbacks. One of such drawbacks is the nutrient content which is generally low and variable depending on the feed of the animal and manure management. This study focused on improving the quality of cattle manure for increased maize yields and consisted of five parts: 1. Assessment of the resource quality of cattle manure in seven districts of the Upper East region. 2. Composting of cattle manure. 3. Laboratory - incubation studies to determine nutrient release patterns of compost. 4. Field decomposition studies of buried compost in litter bags. 5. Assessment of the effects of compost, cowdung and NPK fertilizer on crop growth and yield. A survey was conducted in seven districts of the Upper East region using structured questionnaires to seek information on management practices likely to influence manure quality such as storage and handling. The survey revealed that nitrogen losses up to 100% were sometimes obtained by the time the manure was incorporated into the soil. An initial resource quality analysis of the manure sampled from the seven districts was conducted in the laboratory using standard protocols. The results indicated that N and P contents of the manure ranged from 0.27 to 1.14% and 0.28 to 0.76% respectively, which were all below the critical levels for net mineralization. Polyphenol levels on the other hand were lower than the critical value of 4%. Decomposition and nutrient release from the manure showed immobilization of total N during the first four weeks, suggesting the need to improve the quality by composting or by applying it in combination with mineral fertilizers. In an attempt to improve the quality of the manure, composting with Stylosanthes guinensis using the aerated pile method was carried out. Two main compost types (1:1 and 2:1 ratios of cowdung to plant material) were prepared. Total N and P contents of the composts at the end of study period ranged from 1.10 to 1.46% and 0.28 to 0.31% respectively. Mineralization studies on the resultant composts were conducted under laboratory (leaching tube method) and field (litter bag technique) conditions. Under laboratory conditions, both compost types showed net N and P immobilizations during the first two weeks of incubation. However, under field conditions, net N and P mineralization rates were observed throughout the study period for both compost types. Half life values (time required for 50% of the initial mass to decompose) of 8 and 10 days respectively were recorded for the 1:1 and 2:1 compost types. Furthermore, the 1:1 compost had a higher decomposition rate constant (k = 0.085) than the 2:1 compost (k = 0.056). In all cases, negative correlations were observed between the mass of composts remaining and nutrient released. The contribution of the composts to improving the fertility of the soil and hence crop growth was evaluated by comparing maize response to various rates of the composts with optimum mineral fertilizer combinations. The results showed that the 1:1 compost treatment at 3 t/ha, produced the highest maize grain yield (4.99 t/ha). Maize grain yields obtained from both compost types compared very well with NPK fertilizer suggesting that composting of cattle manure with Stylosanthes guinensis enhanced its quality and nutrient release potential for increased crop yield.

Source: KNUST