Growth, Nitrogen Uptake, and Nutritional Value of a Diverse Panel of Shrub Willow (Salix spp.) Genotypes in Response to Nitrogen Fertilization

Abstract

Riparian buffers are a practical strategy to reduce N runoff. Shrub willows (Salix spp.) are a well-suited natural means to manage water quality due to dense aboveground biomass growth, diffuse root systems at a shallow depth, and low water- and nutrient-use efficiencies that will maximize uptake. Perennial forage crops in the margins of agricultural lands could provide biomass for fodder. The response of fifty genotypes to a single N level of fertilizer under standard conditions at a very high nutrient loading level (500 ppm N, delivered weekly) was compared with water-only controls. Irrigation with excess N caused greater aboveground growth measured as biomass, stem length, and diameter, as well as morphological properties that varied significantly by genotype, indicating a potential for selection in a breeding program. SPAD was a reliable indicator of the effect of fertilizer on foliar crude protein and showed different effects of fertilizer on N uptake and nutritional value among genotypes. We identified genotypes that display high N uptake and good relative feed value. This intentional design for environmental benefits could have a dual purpose should this potentially nutrient-dense biomass by used as fodder for small ruminants.