Willow growth in response to nutrients and moisture on a clay landfill cap soil. II: Water use.

Water use by willow (Salix viminalis L.) was studied in lysimeters containing clay landfill cap and sandy loam soils under different watering and amendment regimes. With plentiful water and amendments, seasonal ET increased annually and was highest in the sandy loam, increasing from 360 l plant(-1) in the establishment year to almost 1200 l plant(-1) in the third year. Seasonal ET was highly correlated with leaf area duration. Amendment of Oxford clay resulted in increases in plant leaf area, dry matter production and seasonal ET. Water stress reduced seasonal ET by 10-14% in the second year and 25-41% in the third. Water use efficiency was low for the un-amended clay treatment (1.4 g kg(-1)) but was similar in the amended clay (5.0 g kg(-1)) and sandy loam (4.9 g kg(-1)). This highlights the interdependence of water use and biomass production in willow.