The Nutrient Profile in Organic Fertilizers

Abstract

In order to manage nitrogen (N) and phosphorous (P) through organic fertilization in aquaculture ponds, it is important to understand the nutrient profile of different animal manures at various concentrations and the respective biological response. The rate of nutrient released from animal manure over time is a key factor in deciding the frequency and quantity of manure required to fertilize ponds. This study was conducted to elucidate the nutrient profile, and its efficiency in terms of primary productivity, of pig, cow, and buffalo manure, at different N:P concentrations in tank. Appropriate concentrations were maintained by using the minimum amount of inorganic fertilizer supplement. This paper also investigated the impact of lime-treated manure, a traditional practice in Vietnam, on primary production (phytoplankton abundance). The average nitrogen (N) and phosphorus (P) content was higher in pig manure (0.54% N and 0.173% P) compared to cow (0.31% N and 0.028% P) and buffalo (0.34% N and 0.013% P). The ammonia release rate increased with increase in N concentration. The average ammonia release rate (all concentrations, 1-2 ppm N) in the pig manure treatment was significantly higher than cow and buffalo manure treatments. Cow and buffalo manures were found to be similar in terms of ammonia release rate. However, soluble phosphorus level was significantly lower in buffalo manure treatments compared with cow manure. The pig manure treatment produced maximum soluble phosphorus levels in the tanks. The primary productivity obtained at various concentrations (1-2 ppm N:0.5 ppm P) did not differ significantly (P > 0.05) in cow and buffalo manure treatments. The primary productivity performance of pig manure was highest amongst the manure types tested. The 1 ppm N:0.5 ppm P concentration from pig manure yielded the maximum average (1.64 mg C/L) net primary productivity. Based on the primary productivity pattern in the tank, which had a significant correlation with nutrient release rate for all manures tested, the frequency of fertilizer application appeared to be most suitable every 8-10 days. However, increasing the frequency of manure application based on the level of nutrient available in the water will provide more control on nutrient and water quality management for pond aquaculture systems. This level of monitoring may not be practical for regional farmers.

Key Words:

• Nitrogen
• phosphorus
• organic fertilizer
• manure
• primary productivity