The influence of nitrogen fertilizer on the yield and combustion quality of whole grain crops for solid fuel use

Whole grain crops can be suitable for the production of solid biofuels because they have a high biomass yield and can be harvested with a low water concentration. The concentrations of water, ash. nitrogen (N), sulphur (S), chlorine (Cl) and potassium (K) in solid biofuels should be as low as possible and calcium (Ca) concentrations high to avoid technical problems and environmentally harmful emissions during the combustion process. Since N fertilization can negatively influence the combustion quality of biomass. a conflict between yield and quality aims can arise. The aim of this study is to investigate the influence of the dosage of N fertilization on the yield and quality of the whole crop biomass of triticale, rye and wheat. In 1996 and 1997, field trials with winter triticale, winter rye and winter wheat were conducted at three locations in South-West Germany. N fertilizer doses were varied from 0 to 70 and 140 kg N ha(-1) a(-1). All N doses were applied between March and May. The whole crop biomass was harvested. The water concentrations and concentrations of ash, N, K. Cl and Ca in straw and grain were measured. A dose of 70 kg N significantly increased the yield of all cereal species, but yield increases at 140 kg N were not always significant when compared with 70 kg N. At 70 kg N the energy yields reached 137-249 GJ ha(-1), for wheat, 142-263 GJ ha(-1) for rye and 182-250 GJ ha(-1) for triticale. The water concentration of the biomass, mainly of the straw, was significantly increased by N fertilization when the harvest was performed early at comparatively high water concentrations. For all cereal species a significant increase of N concentrations. especially in the grain. was measured at increased N fertilizer levels. The K concentrations of the straw and the Ca concentrations of straw and grain of all cereal species were also increased by N fertilization. N fertilization had little or no effect on the ash and Cl concentrations, which slightly decreased with increased N fertilization. N fertilization can, therefore, be used as a tool to influence the concentrations of N and K in the biomass. When combining yield and quality aims. 70-100 kg ha(-1) a(-1) N fertilizer was the best dosage for the whole grain crops at the southwestern German locations tested here. (C) 2002 Elsevier Science B.V. All rights reserved.