Ionic adsorption of ammonium and nitrate on some animal litters and their role in ammonia volatilization. Laboratory results

Two experiments were carried out to determine the adsorption of ammonium an d nitrate on litters (Exp. 1) and the volatilization of ammonia in their pr esence (Exp. 2). In Exp. 1, glass tubes containing 15 mi of a buffered solu tion enriched with NH4Cl calculated as 10.59 mg.l(-1) of NH4+ or KNO3 calcu lated as 50 mg.l(-1) of NO3- were used. Graded amounts (0 [control], 25, 50 , 100 mg) of litters (wheat straw, nax straw (Equi-lin(R)), zeolite (Zeolit e Stall Fresh(R)), spruce sawdust and beech sawdust) were added to the tube s which were incubated for 24 h. Ammonium and nitrate concentrations, and p H, were checked on the supernatant. A preliminary experiment was carried ou t with zeolite to come to an ammonium balance. After adsorption of ammonium by graded amounts of zeolite, [0 (control), 0.25, 1, 2, 4 g], ammonium bal ance was assessed after two elutions with 1 N HCl. In Exp. 2, Woulff flasks were used and ammonia was trapped in a solution of 0.1 N HCl. The prelimin ary experiment showed that the ammonium added and adsorbed by different amo unts of zeolite was completely recovered after 2 elutions. All litters, exc ept beech sawdust, were effective in ammonium adsorption. Especially, the s traws were required in very small amounts to immobilize the added ammonium or nitrate. Furthermore, with straws the pH value decreased from pH 7.5-7.6 0 to pH 6.90, and this effect was related to the amounts of material added. For each pH group, ammonia volatilization was significantly decreased (P < 0.05) with straw (wheat straw, Equi-lino) as compared with their blank pH group. However, no significant decrease was observed with sawdust (spruce, beech) and zeolite.