Animal dung availability and their fertilizer values in a context of low soil fertility conditions for forage seed and crops production in Benin (West Africa)

Abstract

Livestock manure, feed biomass fed to animals that pass through digestive tract undigested and urine excreted from subsequent tissue metabolism, is conventionally termed as wastes. To optimize the use of animal manure for the purpose of agronomic processing or valorization, it is essential to know its availability and plant nutrients composition. The use of reference values ​​is a quick method of estimation. However, books on farm fertilizers generally offer only an average value that is not representative of the diversity of situations. The aim of this study was to (1) estimate the quantity of manures from cattle, sheep, goats, pigs and poultry, (2) determine the physico-chemical characteristics and plant nutrient contents of these droppings and (3) identify the inter-relationships between the physical characteristics (pH, EC and dry matter(DM)) and the most essential macronutrients (N, P and K). A total of 30 animal groups (herds or flocks) were survived per species and a total of 30 samples were collected over twelve months (January 1st to December 31, 2016) for DM, pH, electrical conductibility, nitrogen, phosphorous, potassium, calcium, magnesium and sodium contents for each sample. According to animal population of the country, the results of the study showed that, an amount of 1.630600 tons DM of cattle manure, 227800 tons DM of sheep dung, 136,900 tons DM of goat dung, 122,400 tons DM of pig dropping and 36,500 tons of poultry excreta are annually available in Benin. Physico-chemical and analyzes of droppings showed significant differences (P˂0.01) between mineral compositions of these dropping. Poultry manure are richer in macronutrients than other types of animal manure (N = 11.7 ± 3.9, P = 4.6 ± 2.3, K = 7.6 ± 1.3, Ca = 41.2 ± 16.7 g/kg), followed by goat and sheep manure (N = 6.0 ± 3.7, P = 4.9 ± 3.9, K = 7.3 ± 3.3, Ca = 7.7 ± 3.8 g / kg and N = 6.7 ± 2.3, P = 4.4 ± 1.5, K = 7.3 ± 3.6, Ca = 7.7 ± 2.6 g / kg, respectively). Mean macronutrient compositions of swine dropping were: (N = 4.5 ± 2.0, P = 1.4 ± 0.8, K = 2.9 ± 0.8, Ca = 1.8 ± 0.9 g / kg). The animal manure that showed the lowest levels of these three macronutrients were those of cattle (N = 3.0 ± 0.6, P = 0.6 ± 0.1, K = 4.1 ± y, Ca = 6.4 ± 3.1 g/kg). Correlations between physico-chemical properties (pH, EC, DM) and nutrient concentration showed that dry matter (DM) and electrical conductivity (EC) could be used to estimate nutrient (nitrogen, phosphorus and potassium) concentrations. The results vary widely depending on the source and type of dejection but they are a good basis for choosing rational and optimal soil fertilization for crop and forage productions.