Location: Water Management Research
Project Number: 2034-13000-012-10-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jan 1, 2017
End Date: Dec 31, 2019
Determine effects of soil amendment with biochars produced from different feed stocks found in the San Joaqun Valley (SJV) of California on adsorption capacity for NH4+, NO3-, and N transformation (urea hydrolosis and nitrification) rates as well as soil-water retention. Determine effective amendment rate of biochar products and irrigation rates on crop response and N fate under field conditions.
Both laboratory and field studies will be utilized to achieve the project objectives. For objective 1, laboratory studies will be carried out to characterize biochar products (e.g., surface area, pore size, chemical composition) made from different feed stocks, determine adsorption capacity for N species (ammonium and nitrate) onto biochar and amended soil, and determine N transformation (urea hydrolysis and nitrification) kinetics affected by biochar, as well as soil-water retention functions affected by soil amendment with biochar. Six biochar products will be prepared for this study representing different feedstocks and/or pyrolysis conditions. The feed stocks will include tree pruning materials and/or those pulled out from old orchards (stone fruits, grapevine and almonds and tree nuts) as well as nutshells after processing (almonds, walnuts, pistachios) in CA. The type of biochar, soil types (varying in texture and SOM), soil water content (air-dry to saturation), and temperature (5-45 C) on N adsorption maxima and transformation rate in soil will be determined. The key parameters of biochar and important soil/environmental factors affecting N adsorption and transformation will be determined. Two prominent biochar products in N retention will be selected for field tests. For objective 2, two field experiments will be conducted to test incorporation of biochar for improving nitrogen use efficiency (NUE) and reduce N losses to the environment. Treatments will be selected among biochar amendment rate (e.g., 0, 25, and 50 t/ha) and irrigation level (e.g., 50, 75, and 100% of a reference which provides sufficient water for plant growth). Both field trials will be carried out at the San Joaquin Valley Agricultural Sciences Center where research fields are available for the project. A randomized complete block design with four replications will be used for the field trials. Two vegetable crops (e.g., onion and pepper, both popularly grown in the SJV) will be chosen for the field experiments using efficient irrigation method (e.g., drip). Urea and/or urea ammonium nitrate (UAN) will be used for fertilization. Vegetable crops were selected because of their relatively shallow root zone, so their production present more challenges in N management and they are prone to more N leaching compared to perennials. Field monitoring will include continuous water movement using sensors in soil profile, weekly sampling for N concentration in soil pore water, weekly measurements of NH3 and N2O emission rates, and biweekly measurements on plant growth and N uptake during growing season. At the end of growing season, total N loss, NUE, and soil N status change from the beginning will be determined. All data will be statistically analyzed. Effective biochar material and application rate that do not compromise crop yield with feasible costs will be determined.