CO2 production trend, carbon mineralization potential and sorghum dry matter under different nitrogen sources

Soil respiration is one of the most sensitive indices which affects soil quality and soil functions. Therefore, a field experiment was conducted in a randomized complete block design with four replications in 2010 on a research farm in Shahrekord University to study the effect of integrated and solitary systems of urea fertilizer, cattle and poultry manures on soil CO2 emission, carbon mineralization potential and dry matter production of sorghum. The treatments consist of control (without fertilizer and manure), solitary application of urea, cattle manure and poultry manure (as inorganic and organic sources, respectively), and three integrated combinations of cattle manure + urea, poultry manure + urea, cattle manure + poultry manure (as 50:50). The results showed that application of poultry manure gave the highest values for the cumulative soil respiration (141.39 gm-2) and respiration rate (3.8 gm-2day-1) and the lowest at the control treatment. The greatest dry matter of sorghum (11.16 Mg ha-1) was observed in solitary application of poultry manure, but there was no significant difference in dry matter between this treatment and treatments with urea. The carbon mineralization potential was not affected by the amendments. It is concluded that poultry manure due to significantly more nutrients compared to other fertilizer sources, has led to increase in dry matter of sorghum. Additionally, poultry manure positively affects soil respiration. Also, substituting the chemical fertilizer by poultry manure can reduce environmental pollution hazard.