Fertilization rate (pounds N/acre, x-axis) vs. forage accumulation (ton/acre, y-axis). The fitted line increases from 0 lb N/ac to the agronomic optimum, where it levels off.

Figure 5. Forage accumulation of crabgrass as a function of nitrogen rate from chemical fertilizer and broiler litter. Black line shows the fitted line to the dataset. Dotted red line shows the agronomic optimum nitrogen rate (177 pounds/acre).