Dept. of Animal Science, G.B. Pant University of Agric. and Techn., Pantnagar-263145, India.
Online published on 5 January, 2012.
Two experiments were conducted with chaffed rice straw to evaluate the effect of levels of urea, moisture and temperature on ammoniation of straw in terms of in situ DMD, total and ammonicai-N, incidence of fungus and % N-loss. In expt. 1, 3 levels of urea (30, 40 and 50 g/kg field dry straw) and 4 leveisof moisture (45, 55 65 and 75% on wet basis) were studied by storing the treated straw (TS) in plastic jars at room temperature for 5 wks. In expt. II, Held dried straw treated with 5 kg urea/100 kg and 50 % moisture was sealed in air tight polythene bags and incubated at 5, 15, 25, 35 and 45° C for different periods from 0 to 30 days. The increase in situ DMD was significantly (P<0.05) higher when the straw was treated with 40 g urea/kg straw and at 45-55% level of moisture. The incidence of fungus and % N loss at these levels was lowest. Though the total N of TS at these levels was significantly (P<0.05) lower than those treated with higher levels of urea and moisture, the TS kept well upto 12 weeks without any decrease in in situ DMD or increase in incidence of fungus, However, the total-N content of TS decreased significantly (P<0.05). The in-situ DMD at treatment temperature of 5°C was significantly (P<0.05) lower than the values at temperatures of 15°C and above which inturn did not differ significantly (P<0.05) from each other. The in situ DMD, however increased significantly (P<0.05) with increase in treatment period upto 30 d. The total-N content of TS at35°C was the lowest and it was significantly (P<0.05) lower than the values at at! other temperatures which did not differ among themselves. The hydrolysis of urea to NH3 was affected significantly by the treatment temperature. The decline in urea concentration and increase in NH3-N concentration was abrupt, nearly 2/3rd of the urea disappeared within first 3d, It is concluded that urea 40g/kg field dry straw or 50 g/kg straw DM and 50% moisture constitute the optimum conditions for ammonia (urea) treatment of chaffed rice straw. The ambient temperature may be important only when it is below 15° C and for obtaining the maximum Increase in DMD at lower temperature, longer treatment period is required.
