Short-term effects of amendments on soil properties and agronomic productivity for a coastal Guyana soil
Keywords:Agriculture, soil amendments, soil properties, biochar, Guyana, South America, tropics
There is a multitude of agricultural byproducts worldwide that are not utilized productively. Converting these materials into soil amendments will not only reduce their environmental impact, but also improve soil properties, agronomic productivity, and crop yields. A field study was conducted on a clay (Typic Hydraquent) soil in Guyana to evaluate the impact of various soil amendments on maize (Zea mays L.). Three soil amendments used were: rice (Oryza sativa L.) hull biochar (RHB), poultry manure biochar (PMB), and sugarcane (Saccharum officinarum L.) filter press (FP). These amendments were applied one time at 10 Mg ha-1 and were compared to control (C) and chemical fertilizer (CF) treatments. Chemical fertilizer was also added to the RHB, PMB, and FP treatments, while the C received no further additions. Soil physical and chemical properties along with agronomic productivity and yields were measured to assess the impact of soil amendments. Soil parameters were measured at 0-10, 10-20, and 20-40 cm depths. After one growing season, no significant differences were present for several soil physical and hydrological properties (bulk density, porosity, penetration resistance, and water infiltration) measured. However, significant differences were observed for several soil chemical properties after the growing season. Soil pH increased from 4.71-4.92 in the baseline soil to 5.03-5.58 in the 0-10 cm depth, 5.46-5.61 in the 10-20 cm depth, and 5.38-5.54 in the 20-40 cm depth. Overall, electrical conductivity values were low throughout the 0-40 cm soil profile (0.18-0.56 dS m-1) and would not pose a threat of reducing crop yields. The biochar amended plots had the greatest increase in SOC concentration within the 0-10 cm depth, with RHB and PMB having a 49% and 63% increase, respectively, when compared with the control. C:N ratios for all treatment groups were optimal and ranged from 10:1-15:1 after the growing season. Significant decreases in KCl exchangeable acidity for the 0-10 cm depth were noted for PMB and FP amended soil when compared with the C, CF, and RHB treatment groups. Grain and biomass yields in the amended plots (CF, RHB, PMB, FP) were 7.6-8.8 and 2.8-3.2 times greater than the control, respectively. The harvest index for the amended plots was about 2 times greater than that of the control.