Poultry Litter and Inorganic Fertilization: Effects on Biomass Yield, Metal and Nutrient Concentration of Three Mixed-Season Perennial Forages

Abstract

Poultry litter and fertilizers are normally added as soil amendments. The effects of poultry litter and inorganic fertilizers on three mixed-season perennial forages were studied for two years in the field to understand growth dynamics, metals, and nutrient uptake. The primary objective was to investigate the heavy metal and nutrient concentrations, biomass yield and forage potential of a cool-season forage, stinging nettle (Urtica dioica L.), relative to warm-season forages, bermudagrass (Cynodon dactylon (L.) Pers.) and switchgrass (Panicum virgatum L.). Forage cuttings and soil samples were analyzed for heavy metals and nutrients using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Total biomass yield was higher by 66% and 50% in switchgrass and bermudagrass, respectively, compared with stinging nettle for the first year. While the warm-season forages yielded more biomass over the cool-season forage, metal concentrations were significantly higher for all elements in the cool-season forage. Stinging nettle showed greater macro-nutrient uptake with 103.20 kg ha−1, 0.87 kg ha−1, 27.49 kg ha−1 and 32.08 kg ha−1 for Ca, Fe, Mg, and P, except for K with 223.51 kg ha−1 compared with 267.29 kg ha−1 and 283.96 kg ha−1 for switchgrass and bermudagrass, respectively. Heavy metals were also higher in stinging nettle but were within the allowable limits for forages, indicating its potential as a resource for forages and nutrient cycling, particularly when double-cropped with warm-season forages.