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

Abstract

Two experiments were carried out to determine the adsorption of ammonium and nitrate on litters (Exp. 1) and the volatilization of ammonia in their presence (Exp. 2). In Exp. 1, glass tubes containing 15 ml of a buffered solution enriched with NH$_4$Cl calculated as 10.59 mg.l$^{-1}$ of NH$_4^{+}$ or KNO$_3$ calculated as 50 mg.l$^{-1}$ of NO$_3^{-}$ were used. Graded amounts (0 [control], 25, 50, 100 mg) of litters (wheat straw, flax straw (Equi-lin$^{\ooalign{\hfil{\textsc{r}}\hfil\crcr\mathhexbox20D}}$), zeolite (Zeolite Stall Fresh$^{\ooalign{\hfil{\textsc{r}}\hfil\crcr\mathhexbox20D}}$), spruce sawdust and beech sawdust) were added to the tubes which were incubated for 24 h. Ammonium and nitrate concentrations, and pH, were checked on the supernatant. A preliminary experiment was carried out 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 balance 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 preliminary experiment showed that the ammonium added and adsorbed by different amounts of zeolite was completely recovered after 2 elutions. All litters, except beech sawdust, were effective in ammonium adsorption. Especially, the straws were required in very small amounts to immobilize the added ammonium or nitrate. Furthermore, with straws the pH value decreased from pH $7.50-7.60$ 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$) with straw (wheat straw, Equi-lin$^{\ooalign{\hfil{\textsc{r}}\hfil\crcr\mathhexbox20D}}$) as compared with their blank pH group. However, no significant decrease was observed with sawdust (spruce, beech) and zeolite.