Synergistic Effect of Poultry Manure and Sawdust on Changes in Soil Structural Indices of a Sandy-Clay Loam Ultisol
The effect of organic matter and exchangeable cations from admixture of poultry manure and sawdust incorporated into a field soil on soil structural indices of a tropical sandy clay loam soil was carried out. The aim was to investigate the level of amelioration of the poor structural attribute of the soil by balancing the cation and/or organic matter deficiency associated with the use of either saw dust (SD) or poultry manure (PM) alone in intensively cultivated soils in the tropics. The amendments SD, PM and PM + SD were applied at the rates 0t/ha, 2t/ha, 4t/ha and 8t/ha, making twelve treatment combinations with three replicates. Soil samples were collected for laboratory analysis at 4, 8 and 12 weeks. The structural indices analysed were aggregate stability (AS), dispersion ratio (DR), clay dispersion index (CDI), clay flocculation index (CFI) and aggregated silt and clay (ASC). Data were analysed using a 3 x 3 factorial in Randomized Complete Block Design (RBCD), significant means were detected using Fischer’s Least Significant difference (F – LSD) at 5% probability level. Data were also subjected to correlation analysis using Spearman’s Rank Correlation Coefficient. Result show that the treatments were statistically significant (P = 0.05) in affecting aggregate stability relative to the control. Decreases in bulk density occurred as a result of increase in amendment applied, the trend was 8t>4t>2t for all the amendments. However, only the application of 8t/ha of poultry manure decrease bulk density significantly (p = 0.05). The soil properties studied showed increased strength in the level of correlations with time, these correlations were highest at two months of sampling and was associated with the highest level of coefficient of determination, indicating that these properties influenced each other under the amendment condition and became intrinsic factors in determining the status of each other with increase in age of the soil. Specifically, effective cation exchange capacity (ECEC), and total exchangeable base (TEB) correlated negatively with ASC and CFI, but positively with CDI and DR for all sampling times.
Keywords: Aggregate stability, dispersion ratio, clay flocculation index, cation exchange