| Willow biomass crops have potential as a source of renewable energy. To achieve this To achieve this potential, genetic materials and cultural systems should be developed that maximize biomass potential, genetic materials and cultural systems should be developed that maximize biomass yields at the lowest possible cost of production. High yields equate with high nutrient demands and fertilization costs. The utilization of organic residuals such as sludge and manures can supply nutrients, particularly N and P, reduce production costs and provide a safe disposal for the residuals. This study, conducted in three experiments, examined the effects of organic residuals' application on (1) willow clone SVI biomass production and (2) soil nitrogen dynamics.;In the greenhouse experiment, stem biomass production increased by an average of 90% with the application of 250 m3/ha of sewage sludge, composted sewage sludge, lime-stabilized sewage sludge or composted poultry manure, The incorporation of organic residuals at planting time produced more biomass than the application as top-dressing after coppicing. Gross amounts of N released by decomposition, seven months after residuals application, ranged from 75 to 550 kg N/ha. Ammonium-N leaching was insignificant. Actively growing plants limited NO3-N leaching to 4 kg N/ha while 140 kg N/ha were leached in pots with no plant growth.;In the field experiment, top-dressing of 2503/ha of composted poultry manure and lime-stabilized sludge increased stem biomass production by an average of 33%. Stem biomass production was similar between organically amended plots and plots fertilized with 300 kg N/ha of slow-release fertilizer, with an average annual growth rate of 11.6 o.d.t/ha over a three-year period. Net mineral N contributed to soil by organic residuals averaged 100 and 170 kg/ha for composted poultry manure and lime-stabilized sludge, respectively.;The growth-chamber experiment showed that temperature significantly affects N mineralization from sewage sludge and composted poultry manure. Nitrogen mineralization was the highest around 20--250°C, with approximately 3% of total N mineralized after 31 days of incubation. There were discrepancies between estimated amounts of N calculated from the incubation-derived mineralization rates and the actual amounts of N observed in the field and greenhouse experiments, attributed to differences of conditions between controlled and non-controlled environments, and the variability of the resin data. |
