Effects of calcium lignosulphonates on urea hydrolysis and nitrification in soil
1993
XIE, R. J. | Meier, J. | FYLES, J. W. | MACKENZIE, A. F. | OʼHALLORAN, I. P. | Russell, E.
The increases in urea consumption in crop production have encouraged research activities evaluating various materials as potential urease and nitrification inhibitors. This report presents results of three experiments testing lignosulfonate (LS), a waste product of the pulp and paper industry, as a urease and nitrification inhibitor. The first experiment was for urea hydrolysis in a clay soil with or without bulk-digested (BD) or sugar-free (SF) calcium lignosulphonate (CaLS). The second experiment studied the effect of BD on jack bean urease activity in solution. The third experiment evaluated the effect of BD or SF on changes in soil NO3 content. Calculation of half-life times of urea showed that application of either BD or SF reduced urea hydrolysis in the soil at high rates, with SF being more effective than BD. The decreases in urea hydrolysis were attributed to inhibition of urease activity by LS as indicated by the solution incubation experiment. After incubation for 24 h, 80% urea remained in solutions with simultaneous additions of jack bean urease and BD, compared with 20% in solutions without BD. For incubation of the soil without urea, NO3-N contents with LS additions were 0.5 to 10.1% of that without LS, and NO4-N contents were significantly higher than NO3-N contents. Low NO3-N content after incubation of the soil with LS was attributed to immobilization by microbes, inhibition of nitrification, and possibly induced denitrification of native NO3- by sugars added with LS.
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