Fig. 3: Trends in changes in grain yield with N and P rates and the agronomic efficiencies of N (AEN) and P (AEP) with the N to P ratios in livestock manure, manure + NPK fertilizer and the recommended synthetic NP(K) fertilizer.

a, b present the variations in grain yield with N and P application rates, respectively. c, d present the variations in AEN and AEP with N application rates, respectively. The smooth trend lines represent polynomial fit to the data. All trends were generated assuming quadratic response as it fits data better than linear functions. The figures were created using MS Excel.