Emmanuel Amoakwah abstract

Effects of Corn Cob Biochar on the Physical, Chemical and Biological Properties of a Weathered Tropical Soil

In this study, the effect of corn cob biochar on the soil physico-chemical and microbiological properties were investigated on a highly weathered tropical sandy loam. The study comprised of four treatments with four replicates established in a randomized complete block design. Biochar was applied in two batches; corn cob biochar was first incorporated at rates of 10 t ha-1 (BC-10), 20 t ha-1 (BC-20), and 20 t ha-1 + triple super phosphate (BC-20+P) to study its effects on aggregate characteristics, water retention, gas transport and pore structure characteristics. Incorporation of biochar decreased the tensile strength of the large aggregates (4–8 mm and 8–16 mm), but increased same in the smaller aggregates (1–2 mm). Soil friability and workability were significantly improved in the BC-20 and BC-20+P treatments. Soil water retention was measured within a pF range of 1 to 6.8. Application of 20 t ha-1 led to significant increase in soil water retention. The second batch had 50% of the first batch added to the respective initial biochar treatments. Thus, the total biochar application rates were 15 t ha-1 (BC-15), 30 t ha-1 (BC-30), and 30 t ha-1 + triple super phosphate (BC-30+P). Soil samples were randomly collected from 20 different spots in each treatment at 0 to 20 cm depth and the bulked soil samples from each treatment were analyzed. Biochar amendment resulted in a significant increase in the carbon lability index in the labile C pools. The carbon and nitrogen pool indices, as well as carbon and nitrogen management indices were increased with biochar amendment, especially in the BC-30 and BC-30+P treated plots. Incorporation of biochar at 30 t ha-1 had significant effects on soil microbial community composition, diversity and total PLFA. Dehydrogenase and urease enzyme activities increased with the increase of biochar application rate. In perspective, incorporation of biochar improved the soil physical, chemical and biological quality of the soil. This was manifested in the enhanced generic soil quality index calculated based on the integration of all the measured properties in the soils treated with the second batch of biochar application.