Effect of water quality on the biomass production, nutritional value, and contents of secondary compounds of three genotypes of willow (Salix acmophylla Boiss.) grown for fodder

Shrub willow (Salix spp.) grow naturally in riparian landscapes and combine rapid growth with high rates of evapotranspiration. As willow irrigated with secondary treated wastewater (TWW) can be used as fodder for goats, it could be exploited in otherwise dry areas where such water is available. We examined the effect of irrigating Salix acmophylla Boiss. With secondary treated wastewater (TWW) or municipal freshwater (FW) on growth indices, secondary compounds, and nutritional value of willow fodder over two years grown in 50 L pots in natural soil under ambient conditions. We evaluated ten willow ecotypes belonging to three genotypes (GA, GB, and GC). Biomass production greatly differed among ecotypes. TWW irrigation resulted in a doubling in biomass production, compared with FW. In GA and GC shrubs, the leaf/total weight ratio was higher than in GB. The differences in crude protein (CP) and the in vitro dry matter digestibility (IVDMD) were 2 % and 3 % (in percentage points, on DM basis) higher respectively in plants irrigated with TWW over FW. Salicin and catechin contents were also greater under irrigation with TWW compared with FW. GC produced less salicinoids, in opposite to chlorogenic acid. Overall, genotype did not affect nutritional value but GC shrubs had more resprouting stems and produced more biomass. Our results suggest that willow genotype is important for biomass and secondary compound production and should be taken into account before large-scale planting. Willow crops irrigated with TWW could produce appreciable biomass and quality fodder for livestock under semi-arid and arid conditions.