LAUSR

Abstract Agricultural byproducts can be applied to soil as an amendment with strong benefits to soil properties, agronomic productivity, and crop yields. A field study was conducted on a coastal soil in Guyana to evaluate the impact of various amendments on soil properties and agronomic productivity for maize (Zea mays). An emergy analysis was also conducted for five systems under different amendment application – no amendment application (control), chemical fertilizer, rice hull biochar, poultry manure biochar, and sugarcane filter press. Mineral fertilizer was applied to each treatment except for the control. An emergy analysis of the five systems was performed to quantify overall emergy and evaluate the sustainability of maize systems receiving different soil amendments. Maize yields (Mg ha−1) were the highest amongst the amended soils (9.94 for chemical fertilizer, 9.54 for poultry manure biochar, 9.22 for rice hull biochar, 8.57 for sugarcane filter press) compared with that for the control (1.13). Emergy (E17 seJ ha−1 yr−1) for each system was as follows: 1.39 for control, 1.44 for chemical fertilizer, 2.97 for rice hull biochar, 3.33 for poultry manure biochar, and 1.49 for sugarcane filter press. Sustainability was higher for systems with more renewable and less purchased inputs. The unamended system had the highest sustainability index of the five systems (4.41). Of the amended systems, the chemical fertilizer (4.01) and sugarcane filter press (3.57) groups had higher sustainability than both the rice hull biochar (1.25) and poultry manure biochar (1.00) amended systems. It is important to reconcile high productivity with environmental quality in order to ensure a food secure future.