Comparison of the effect of sugarcane bagasse and rice straw residues on some quality characteristics of a sodic vertisols

The present study investigated and compared the effects of two types of crop residues, sugarcane bagasse (BG) and rice straw (RH), on some soil chemical properties and enzymatic activities related to the carbon and phosphorus cycle in sodic vertisols (control, C). The pot experiment was conducted in four replications using the factorial structure in complete randomized design in the greenhouse of Zanjan University in 2016. The factors of this experiment included two type of organic amendment (BG and RH), three application rates (L1=1.25%, L2=2.5% and L3=5% by weight) and four incubation times (two (M2), four (M4), eight (M8) and twelve (M12) months). Some of the most important chemical and biological properties were measured after the treatments. The results showed that values of soil organic carbon (SOC), carbon to nitrogen ratio (C:N), and available phosphorus (AP) were significantly (p< 0.001) affected by the type of organic amendments, their application rate, and incubation time. The highest and lowest SOC values were measured in the BGL3M2 and RHL1M12 treatments, respectively. Changes in SOC and total nitrogen (TN) were increasing by increasing the amount of organic amendments and decreasing by increasing incubation time. Total nitrogen in the RHL3M12 treatment increased 51.6% compared to the RHL1M12 treatment and decreased 8.5% (p<0.01) compared to the RHL3M2 treatment. AP in BGL3M12 treatment had a significant increase of 21.5% compared to BGL2M12 treatment. The highest alkaline and acid phosphatase activity was related to RHL3M12 (18.6 µg PNP g-1h-1) and BGL3M12 (7.1 µg PNP g-1h-1) treatments, respectively. RHL3M12 and BGL1M2 treatments showed the highest and lowest beta-glucosidase activity, respectively, and showed a significant difference of 87.5% and 70.3% with the control treatment. The highest and lowest levels of microbial biomass carbon (MBC) were related to RHL3M2 (71.5 mg kg-1) and BGL1M12 (28 mg kg-1) treatments, respectively.