Effect of Pelleting, Temperature, and Soil Type on Mineral Nitrogen Release from Poultry and Dairy Manures

Abstract

Pellets are produced from manures for more convenient and economical use. The rate of N mineralization of manures under different conditions is of agronomic importance, since it allows estimation of mineral N supply to plants as a function of time. Pelleted manure may have mineralization characteristics differing from those of its raw components due to the high temperatures and pressure involved in the pelleting process. The rate of N mineralization of raw manures and pelleted manure was studied in water and in soil incubation experiments. About 10% of total N in the manures was initially KCl‐extractable NH4. Within 1 d, 30 to 35% of total N in poultry manure and 18% in mixed 75% dairy and 25% poultry manure were mineralized in water. Mineralization kinetics of manures in soil showed an initial rapid process followed by a slow release of mineral N and could be described as two simultaneous first‐order reactions. During the first week, 34 to 44% of total N in poultry manure and 14 to 23% in 75% dairy + 25% poultry manure were mineralized in soil pellets releasing more N than ground manures. After 2 to 3 months, mineral N in soil was 34 to 50 and 27 to 44% of total N in poultry and 75% dairy manures, respectively, the pellets contributing equal or less mineral N to soil than the ground manures. Pelleting increased the relative amount of rapidly mineralizable N in the manures and created higher NH4‐N concentrations in soil, which under less favorable conditions for nitrification increased the susceptibility to loss of NH3‐N. Temperatures in the range of 14 to 35°C had little effect on the rate of mineralization but affected N loss from poultry manure pellets by delaying nitrification at 14 and 35°C compared with 25°C.

Carbon and nitrogen mineralization in soil amended with non-tabletized and tabletized poultry manure

“…Because C mineralization is theoretically related to N mineralization (Castellanos and Pratt 1981;Gale and Gilmour 1986) we also included C mineralization in our study. As far as N mineralization is concerned, our data differ from those reported by Hadas et al (1983), who noted more rapid initial N mineralization in soils amended with non-pelletized than with pelletized PM during the first week of incubation, whereas concentrations of N mineralized became similar for both manures during the rest of their study. Hadas et al (1983) suggest that pelletization reduces the quantity of readily biodegradable compounds which may be due to (1) reduction in surface area of pellets compared with untreated PM or (2) the high temperature (70°C) exposure during pelletizing compared with those observed during composting of manures (Paré et al 1998).…”

“…Concentrations of NH 4 + -N were higher in soils amended with T-PM and T-PM + NPK than other treatments during the first 30 d of incubation, and this trend persisted up to 60 d in soil amended with T-PM + NPK. Hadas et al (1983) reported that net NH 4 + -N mineralized increased in soils amended with pelletized PM rather than non-pelletized PM. They also noted that NH 4 + -N concentrations were higher during incubation with PM than with dairy manure because of the higher levels of NH 4 + -N in PM (Hadas et al 1983).…”

“…There is little information on C and N mineralization in soils amended with tabletized, pelletized or untreated manures. Hadas et al (1983) found that pelletized PM released more N than untreated PM. The pellets used in their study were produced in a commercial plant by a process that included solar drying, mixing, grinding, compression into pellets and finally adjustment to the required moisture contents, operations that may have altered the N content and quality (Hadas et al 1983).…”

“…In addition to improving soil physical and chemical properties, PM releases N, P, K and other nutrients, which usually results in higher crop yields than unfertilized soils (Bitzer and Sims 1988;Huneycutt et al 1988). However, it is more expensive to transport and broadcast manures than chemical fertilizers (Hadas et al 1983). The conversion of PM to tablets with uniform sizes is more acceptable aesthetically and tablets are easier to handle and broadcast than bulk manure.…”

“…The conversion of PM to tablets with uniform sizes is more acceptable aesthetically and tablets are easier to handle and broadcast than bulk manure. Furthermore, it is possible to incorporate minerals (Hadas et al 1983) and other plant growth-promoting substances into the tablets. There is little information on C and N mineralization in soils amended with tabletized, pelletized or untreated manures.…”