The present study was conducted to investigate the effects of nitrogen derived from dried or carbonized chicken manure on growth, nodulation, yield and N content of soybean. 15 N labeled chicken manure used in this study was obtained from the droppings of chicken fed on hulled rice grown under field conditions and fertilized with 15 N-labeled stable isotope ammonium sulphate and potassium nitrate fertilizers. Carbonized chicken manure was made by heat treatment in a muffle furnace in our laboratory. This study was conducted in pots filled with clay loam soil. Results from the study show that the application of carbonized chicken manure increased soybean seed yield by 23% and 43% for the 50 and 100 kg N ha −1 rates respectively. Dried chicken manure application increased soybean seed yield by 7% and 30% for the 50 and 100 kg N ha −1 rates respectively. There was no difference in the N manure yield of both manures when applied at the same rate. The percentage 15 N recovery was 17.6% and 8.9% for carbonized chicken manure, 19.2% and 10.5% for dried chicken manure at 50 and 100 kg N ha −1 rates respectively at peak flowering stage of soybean growth. We found high total nitrogen yields of soybean at the rate of 100 kg N ha −1 for both manures. There was a positive relationship between number of nodules and seed yield of soybean. Total N content also showed positive relationship with number of nodules and seed yield of soybean. We supposed that the higher P content of carbonized chicken manure is responsible for the higher seed yield and nodule growth compared to dried chicken manure.

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