Soil Carbon and Nitrogen Stock as Affected by Agricultural Wastes in a Typic Haplusult of Owerri, Southeastern Nigeria

We evaluated the effect of saw dust ash (SDA) and poultry droppings (PD) on soil physico-chemical properties, soil carbon and nitrogen stock and their effects on the growth and yield of okra (Abelmoshus esculentus) on a typic haplusult in Owerri, Imo State Southeastern Nigeria. The experiment was a factorial experiment consisted of saw dust ash applied at the rates of 0, 5 and 10 t/ha and poultry droppings applied at the rates of 0, 5 and 10 t/ha. The treatments were laid out in a randomized complete block design and replicated four times. Results showed that plots amended with 10 t/ha PD + 10 t/ha SDA significantly reduced soil bulk density from 1.37 – 1.07 g/cm3, increased soil total porosity from 48.4 – 59.7% and the percentage of soil weight that is water (soil gravimetric moisture content) was increased by 68.4%. There were significant improvements on soil chemical properties with plots amended with 10 t/ha PD + 10 t/ha SDA recording the highest values on soil organic carbon, soil total nitrogen and exchangeable bases. Plots amended with 10 t/ha PD + 10 t/ha SDA significantly increased soil carbon stock by 24% and soil nitrogen stock by 49.5% more than other treatments. There was significant increase in the growth of okra when compared to the un-amended soil with application of 10 t/ha PD + 10 t/ha SDA increasing the fresh okra pod yield by 78.5%. Significant positive correlation existed between SCS and organic carbon (r = 0.6128), exchangeable Mg (r= 0.5035), total nitrogen (r = 0.6167) and soil pH (r = 0.5221). SNS correlated positively with organic carbon (r = 0.5834), total nitrogen (r= 0.6101) and soil pH (r = 5150). Therefore applications of these agro-wastes are effective in improving soil properties, increasing soil carbon and nitrogen stock. From the results of the work, application of 10 t/ha PD + 10 t/ha SDA which was the treatment combination that improved soil properties and growth performances of okra than other treatments studied is hereby recommended for soil carbon and nitrogen stock improvement and okra production in the region.