No abstract

The kinetics of NH+4 adsorption and desorption were investigated on the natural zeolite clinoptilolite to ascertain its ability to adsorb and release the important plant nutrient N in its NH+4 form at various pH values and initial NH+4 concentrations. Kinetics of NH+4 adsorption were evaluated on the samples using solutions containing 140.1, 280.2, 560.4, and 840.6 mg L−1 of NH+4‐N at pH 4, 5, 6, and 7, equilibrated for 5, 10, 15, 20, 30, 45, 60, 75, 90, and 120 min. Samples for NH+4 desorption were equilibrated with 70.1, 280.2, 560.4, and 1401 mg L−1 NH+4‐N solution at pH 4, 5, 6, and 7 for 2.5 h, and adsorbed NH+4 extracted with 2 M KCl for 5, 10, 20, 30, 45, 60, 90, 120, 150, 180, and 300 min. Equilibrium time for NH+4 adsorption ranged from 60 min for 140.1 mg L−1 initial NH+4‐N concentration at pH 4 to 120 min for 840.6 mg L−1 initial NH+4‐N concentration at pH 7. Desorption was nearly complete in 150 min for low initial NH+4 concentrations and 200 min for high initial NH+4 concentrations. Amounts of NH+4 sorbed increased with increasing pH and initial NH+4 concentrations. Models evaluated included the first‐order kinetics, modified Freundlich, parabolic diffusion, Elovich, and heterogeneous diffusion. All the models adequately described the NH+4 adsorption process, with r2 values ranging from 0.955 to 0.999. With the exception of first‐order kinetics, they also described the desorption process well, with r2 values ranging from 0.897 to 0.999, for all pH and initial NH+4 concentrations. Reaction rate coefficients (k) were calculated from the modified Freundlich model and ranged from 0.134 to 0.193 min−1 for the adsorption process, and 0.129 to 0.226 min−1 for the desorption process. The models indicated that NH+4 adsorption and desorption by the zeolite was diffusion controlled. Data from this study indicated the potential use of the tested natural zeolite as an NH+4 adsorbent and a controlled‐release NH+4 fertilizer.

. 1993. Nitrogen availability for corn in soils amended with urea' cattfe slurry, and solid anh composted manures. Can. J. Soil . This study was conducted to determine whether manu.e N availability for corn (Zea mays L.) was best estimated by a component of rhe manure N or by soil inorganic N in May or June. Liquid dairy cattle manure,-solid beef cattle manure, and composted beef cattle manure were applied in the spring of 1988, 1989 and 1990 at rates of 100, 200 unO IOO kg N ha-r. Urea was applied at rates of 50' 100 and 150 kg N ha-r for comparison. The N recovery Uy the harvested portion of the corn (grain * stover) in 1988 and 1990 averaged 49, 18, and 5% ofthe total N in urea, liquid dairy cattle manure, and solid or composted beefcatt-I. rnunu.", respectively. There was no yield response to any_N^source in 1989 because bttrigtr soit fertility. Relative nitrogenuptake by the corn grain + stov"er in-1988 and 1990 was significantly correlated with inorganic N appiiea as manure or fertilizer 1rz :0.56), but not with total N apptied 1r2 = 0.02). When-the data from all 3 years were analyzed, relative nitroqen uptake was better cbirelated with soil NH4 + NO3 in mid-May and soil NO3 in early-June (r' = 0.83 and 0.76' respectively), than with inorganiiN applied as manure or fertilizer (rz : O.20 1988 + 1990 or from all 3 years, relative N uptake was correlated with the total and inorganic N in the manures, soil NHo * NO, or NO, measured in mid-May, early June, and mid-June. A significance level of P < 0.05 was used throughout the analysis.

Ammonia emissions during composting of poultry manure can be significant, representing increased environmental pollution and decreased fertilizer value of manure. The objectives of this study were to measure NH3 volatilization losses during composting of poultry layer manure, and to evaluate the potential of different amendments to reduce NH3 losses using a laboratory composting simulator. The poultry manure was treated with various amendments which included two natural zeolites, clay, coir (mesocarp of coconut fruit), CaCl2, CaSO4, MgCl2, MgSO4, and Al2(SO4)3. The manure was composted for 49 to 56 d. Ammonia volatilized from the manure was trapped in a 0.3 M H2SO4 solution. The composts were weighed and analyzed for moisture content, total N and NH+4. The NH3 volatilization loss for the unamended manures ranged from 47 to 62% of the total manure N. A layer of 38% zeolite placed on the surface of the manure reduced NH3 losses by 44%, whereas 33% coir placed on the surface of the manure reduced NH3 losses by 49%. The 20% alum treatment reduced NH3 losses by 28%. Composting poultry manure with zeolites, coir, and alum produced composts with high NH+4 concentrations ranging from 17 to 53% of total N. The addition of 20% CaCl2 to poultry manure decreased NH3 volatilization but did not result in increased NH+4 or NO−3 concentrations. The 38% zeolite Z1 and 33% coir‐treated composts had total N concentrations of 17 and 31 g kg−1, respectively. The zeolite and coir amendments were proposed to be the most suitable for reducing NH3 losses during composting of poultry manure.

No abstract