The fates of nitrogen-15 (15N)-labeled biogas slurry (BS) and chemical fertilizer (CF) applied to soil with low fertility cropped with rice were investigated. The 15N dilution method was used to estimate N uptake and recovery
potted soil was labeled with 1.0 atom % excess [ 15N] ammonium chloride ([15N]NH4Cl). Certain select soil characteristics were also measured in soil amended with the slurry to explain N losses. The values of the % N derived by fertilizer application to the plant exhibited significant differences among different plant parts. N uptake from the CF applied to rice grain, straw and the roots was significantly (p&lt
0.05) higher than that from BS, but the highest proportion of N uptake by rice was from the soil. At harvest, an average of 6.2 and 13.2% of applied N remained in the soil treated with the CF and BS, respectively. Fertilizer use efficiency calculated by the 15N dilution method tended to be higher for CF than BS. A significant amount of N fertilizer (average: 30%) was apparently lost from the soil-plant system by ammonia (NH3) volatilization. Following BS application, the pH increased by 1 to 1.2 units in the top 5 cm of the soil, resulting in high NH3 volatilization in the first 2 days of the experiment. The NH3 volatilization accounted for the decrease in soil ammonium-N (NH4 +-N) content. © 2008 Academic Journals Inc.