The scientists used hydrolyzed fish fertilizer, inorganic nitrogen (N) source with secondary and micronutrients , inorganic nitrogen without secondary or micronutrients, and a zero nitrogen control for the study. Nitrogen was applied at: recommended rates for both squash and collards, 80% of the recommended ratesราคา, and 60% of the recommended rates. The study design included a zero nitrogen treatment used as the control. "To eliminate the rotation order effect, the cropsผักwere switched each year: yellow squash-collard in year one, and collard-yellow squash in year two," explained Ogles.