Effect of irrigation and nitrogen fertilization on biomass yield and efficiency of energy use in crop production of Miscanthus

The perennial C-4 grass Miscanthus has been proposed as a biomass energy cr op in Europe. Effects of crop age, irrigation and nitrogen fertilization on biomass and energy yields and N content of Miscanthus were investigated an d the energy costs of production determined. After an establishment period of 1 year, cultivation of Miscanthus resulted in a dry matter production of over 37 t ha(-1) year(-1) over a period of 4 years. Irrigation and nitroge n level greatly affected Miscanthus biomass yield. In absence of N fertiliz ation, irrigation did not modify biomass yield and the effect of irrigation increased with the increase in N level. The average N response ranged from 37 to 50 kg biomass kg(-1) N applied. Because the calorific value of Misca nthus biomass (16.5 MJ kg(-1)) was not affected by irrigation and N fertili zation, energy production depended exclusively on biomass yield. Maximum en ergy yield was 564 GJ ha(-1) year(-1). Without N supply and irrigation, ene rgy yield was 291 GJ h(-1). Net energy yield, calculated as the difference between energy output and input, but without inclusion of drying costs, was 543 GJ ha(-1) with N fertilization and irrigation and 284 GJ ha(-1) withou t; the ratios of energy output to input in crop production were 22 and 47, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.