Page 252 - Nutrient Management Planning Guide

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Chapter 7.2

Expected Crop Price

Expected crop prices (dollars per tonne, bushel, ton or pound) are essential for AFFIRM’s economics-based fertility recommendations (Figure 7.2.6).

Figure 7.2.6 AFFIRM Crop Price Calculator

Field Recommendations

AFFIRM produces fertilizer recommendations for individual fields based on the crop selected, soil test information, previous crop history, soil zone, irrigation management and spring soil moisture (Figure 7.2.7). Fertilizer recommendations for N, P

2

O

5

, K

2

O, and S are presented for dry, medium and wet moisture conditions.

Nitrogen recommendations are linked to the crop yield response and economic analysis. AFFIRM uses soil zone precipitation probabilities, spring soil moisture levels, soil test nitrogen and fertilizer nitrogen to calculate crop yield response. The crop yield response data in combination with crop prices, fertilizer nitrogen costs and investment ratio is used for the economic analysis to determine the optimum nitrogen fertilizer rate. The investment ratio (IR) is the ratio of the value of the expected yield increase from an additional 4.5 kg of fertilizer relative to the cost of the additional 4.5 kg of N fertilizer:

IR = Value of yield increase from additional 4.5 kg of N fertilizer ($) ÷ Cost of additional 4.5 kg of N fertilizer ($)

An IR greater than 1 indicates a profit is made (i.e., the additional yield produced from the extra fertilizer applied was enough to cover the extra fertilizer cost). An IR less than 1 indicates a loss, even though you may increase yield (i.e., marginal cost of fertilizer is more than marginal value of crop yield increase).

The user can change crop prices, fertilizer nitrogen costs, spring soil moisture conditions and IRs to test various cropping scenarios on fertilizer requirements. The economic analysis is presented in both tabular and graph formats.

AFFIRM provides alert messages to help with the interpretation of soil information. The messages will also help determine the impact on crop production and fertilizer management.