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Optimizing Organic Fertilizer Applications under Steady-State Conditions

Department of Environmental Sciences, University of California, Riverside, CA 92521

View larger version (17K): [in a new window]   Fig. 1. Mean daily soil temperatures (15 cm) and cumulative temperature-adjusted time (TAT) for Modesto, CA (Tr = 25°C, Q10 = 2).

View larger version (32K): [in a new window]   Fig. 2. Total crop N demand, manure inorganic N, and manure-derived plant-available nitrogen (PAN) during 10-d planning periods when total fertilizer N is applied at 30% above crop needs (+ 30%). PAN is the manure inorganic N + mineralized N. Shaded areas represent potential crop N deficits and surplus N.

View larger version (25K): [in a new window]   Fig. 3. Total crop N demand, manure inorganic N, and manure-derived plant-available nitrogen (PAN) during 10-d planning periods for a deterministically optimized application schedule (DOpt). Shaded areas represent potential crop N deficits and surplus N.

View larger version (22K): [in a new window]   Fig. 4. Application schedules associated with applications 30% above crop N demand (+30%) and after deterministic (DOpt) and stochastic optimization (SOpt).

View larger version (34K): [in a new window]   Fig. 5. Total crop N demand, manure inorganic N, and manure-derived plant-available nitrogen (PAN) with 10-d summer planning periods and a single winter application after deterministic optimization (DOpt). Summer application rates are twice the manure inorganic N level. Winter application is 551 kg ha–1.

View larger version (26K): [in a new window]   Fig. 6. Monte Carlo simulation results after 10 000 trials varying net mineralization rate (k) and the heat adjustment parameter (Q10). Results illustrate probabilities for annual N surpluses along with total, maize, and triticale N deficits resulting from applications 30% above crop uptake (+30%), deterministic optimization (DOpt), and stochastic optimization (SOpt) application schedules. 1Wtr schedule surplus N, which allows only one winter application, included for comparison. Arrows indicate the presence of values beyond the figure scale.

View larger version (25K): [in a new window]   Fig. 7. Monte Carlo simulation results after 10 000 trials varying the net mineralization rate (k), the heat adjustment parameter (Q10), soil temperatures, and the manure organic N fraction (a). Results illustrate probabilities for annual N surpluses along with total, maize, and triticale N deficits resulting from applications 30% above crop uptake (+30%), and stochastic optimization (SOpt) application schedules. Arrow indicates the presence of values beyond the figure scale.

View larger version (25K): [in a new window]   Fig. 8. Expected plant-available nitrogen (PAN) patterns when mineralization rates vary by ±2/3 from a 283 d° design half-life (t1/2).