Influence of Rice Husk Biomass and Its Biochar on Some Enzymatic Activities in a Calcareous Sandy Soil

The present study was conducted to investigate the effects of rice husk biomass (RH) and its biochar (RHBC) on some chemical properties and enzymatic activities involved in carbon and phosphorus cycling of a calcareous sandy soil (control, U) after two (M2), four (M4), eight (M8), and twelve (M12) months incubation. For this purpose, a factorial experiment with a randomized complete block design and four replications and two treatments (RH and RHBC) was performed. Three levels of organic amendments (L1= 1.25%, L2= 2.5% and L3= 5%) were added to the soil. The results showed that the amount of soil organic carbon (SOC) was significantly (p < 0.001) affected by the types of organic amendments, their application rate and incubation time. The highest and the lowest values of SOC were observed in RHBCL3M2 and RHL1M12 treatments with 96.3% and 73.2% increase as compared to the control treatment, respectively. The trend of changes in SOC and TN was similar and decreased with incubation time. The highest and the lowest activity of β-glucosidase were corresponded to the treatments of RHL3M12 (1.6 μgPNP.gr-1h-1) and RHBCL1M2 (0.6 μgPNP.gr-1h-1), respectively. The RHBCL3M8 and RHL1M2 treatments exhibited the highest (590.6 mg Glu.g-13h-1) and the lowest (109.6 mg Glu.g-13h-1) invertase enzyme activity, respectively. So that, the highest enzyme activity was observed in 8th month of incubation. The highest activity of alkaline and acid phosphatases activities were found in RHL3M12 treatment which were 78.1% and 81.7% higher than that in control treatment, respectively. In general, the addition of good quality biochars to the soil could be a very good source for compensation of soil organic carbon deficiency and thereby improving chemical and biochemical properties and soil health, because of its higher carbon content than its biomass. Therefore, based on the effects of rice biomass and its biochar on the increasing of SOC content as well as enzymatic activities, these organic amendments are suggested to improve the quality of sandy soils.