EFFECTS OF FERTILIZERS ON SOIL MICROBIAL DIVERSITY, GROWTH AND YIELD OF TWO FORAGE GRASSES ( Panicum maximum and Sorghum almum)
A 6 month study was conducted in the screen house and laboratory of the Department of Crop Science, Faculty of Agriculture, University of Benin, Benin City. The objective was to ascertain the effects of fertilizers on soil microbial diversity growth and yield of two forage grasses. The experiment was set up in a Completely Randomized Design (CRD) arrangement. There were 10 factorial treatments, made up from five fertilizers (Control, Anthropogenic liquid waste (1:3 and 1:6 dilutions), NPK(15:15:15) and cattle dung) and two forage grasses (Sorghum almum and Panicum maximum) replicated three times. The parameters measured were sward height, sward regrowth, fresh and dry herbage yields. Serial dilution of the fertilized soils was carried out to enumerate the microbial populations. Generally, anthropogenic liquid waste (1:3) and NPK(15:15:15) were equal in performance and better than the other fertilizers in terms of herbage growth (sward height and sward regrowth). Anthropogenic liquid waste (1:3) produced the significantly highest fresh and dry herbage yields among the fertilizers. Furthermore anthropogenic liquid waste (1:3) favoured the highest proliferation of microbes. The favourable response of the grasses and the higher microbial population in the soils treated with Anthropogenic liquid waste implies that this fertilizer contains high quantities of readily available plant nutrients.
Soil is the habitat of an adverse array of organisms that include both micro flora and micro fauna. Soil microorganisms play an important role in soil fertility. They carry out biochemical transformations and are also important sources and sinks of mineral nutrients (Jenkison and Gadd, 1981). An understanding of microbial processes is important for the management of farming systems that rely on organic matter as source of nutrients (Smith and Paul, 1990). The soil microbial community is involved in nutrient cycling, organic matter decomposition and plays a crucial role in terrestrial carbon cycling (Schimel, 1995).The microbial community is a very reactive ecosystem with rapid growth and turnover (Panikov, 1999).
Fertilizer may directly stimulate an increase in microbial population through nutrient supply or may affect the composition of individual microbial communities in the soil (Khonje et al.,1989). The application of chemical fertilizer improves crop production while enhancing the activities of soil microbes. However, there are concerns about the severe environmental problems posed by fertilization and also about the long term sustainability of inorganic fertilization (Mueder et al., 2002),
The use of organic materials (cattle dung, poultry dung, crop residues etc) as alternative sources of fertilizer holds promise. Cattle dung has the potential benefit of improving soil structure (Reganoid et al., 1987; Pullenman et al., 2003) and enhancing soil microbial activities (Doles et al., 2001). However with the limited number of intensive livestock farms and increase in commercial cropping systems, the use of cattle dung as fertilizer has become inadequate. Furthermore, the prolonged period of curing, ability to spread weeds and high labour required for the application makes the use of cattle dung inadequate. There are other organic materials that may be used for fertilization with less logistic difficulties as those posed by cattle dung usage. Anthropogenic liquid waste or human urine contains appreciable quantities of plant nutrients especially nitrogen and other macro-nutrients in readily available forms. Although there are social hesitations among Nigerians regarding the use of human urine in agriculture, anthropogenic liquid waste has been successfully used in agriculture in Asia (Wolgast,1993)
.1.1 Justification for the Study
Due to shortage in both inorganic and organic fertilizers, coupled with indiscriminate disposal of human wastes in the environment, the recycling of anthropogenic wastes for agriculture offers a promising alternative source of fertilizer for crops. However, very little research has been conducted with anthropogenic liquid wastes as fertilizer for crops.
Tropical grasses like Panicum maximum and Sorghum almum have the ability to produce high yield and high nutrient quality when treated with fertilizer. Fertilization is one of the common practices that can increase both forage production and nutritive value (Harding, 2005). Anthropogenic liquid waste could be used to grow high quality pasture grasses to complement current emphasis on increased livestock and dairy cattle production in Nigeria. This study was conducted to evaluate the effect fertilizers (cattle dung, NPK fertilizer and anthropogenic liquid waste) on soil microbial diversity, growth and yield of Panicum maximum and Sorghum almum .