Water implications of selected energy crops cultivated on a field scale.

The predicted rapid increase of agricultural land areas with energy crops in the EU can cause transformation of significant amount of agricultural land, as a result, lead to serious environmental implications. One of the consequences of high biomass production by energy crops is a concomitant usage of large amounts of water. Short rotation crops (SRC) like willow and energy grasses like Miscanthus are especially thought to be deep-rooting and to have high water consumption through transpiration and interception. The aim of the article is to show the results of soil water balance simulation under permanent grass, winter wheat, Miscanthus and willow performed in a one-dimensional Wasim model, moreover to present effective water use by selected crops under studied conditions. The evaluation run in Wasim based on data from experimental stations at Osiny on sandy clay loam and at Grabow on loamy sand in eastern Poland for the period of 2003-2008 revealed, that actual evapotranspiration rates were higher for energy crops than for grass and wheat. Predicted mean annual evapotranspiration ranged from 442 mm in grass to about 500 mm in willow at Osiny and from 530 mm in winter wheat to 623 mm in willow at Grabow. Mean annual interception of energy crops generally amounted to about 16% of gross rainfall. Deficit of hydrologically effective rainfall on loamy sand ranged from 92% in the case of transformation of grass to energy crops to 94% for wheat replacement. For the assessment of crop water use per unit of biomass and per unit of energy, the water footprint concept was assumed. Willow and Miscanthus seems to have the lowest water use per ton of biomass and per potentially available energy unit by comparison with arable crops. Miscanthus has the lowest water footprint per energy unit (7.0-9.4 m(3) GJ(-1)), willow has somewhat larger footprint (11.5-13.0 m(3) GJ(-1)). The highest rates of water footprint of wheat (22.0-25.8 m(3) GJ(-1)) are the result of the lowest yields of this crop. There is a need to conduct additional investigations by other models to verify implications of energy crops on soil water balance and to understand better their impact on water resources on a small scale.