Page 120 - Nutrient Management Planning Guide

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Chapter 3.4

Fertilizer Recommendations

Fertilizer recommendations are usually based on yield response curves or yield expectations for a crop based on soil moisture and growing season precipitation. Recommendations may vary considerably between labs because of different analytical methods, yield response models, yield predictions, expected precipitation and fertilizer use efficiency.

A good soil sample and an accurate soil analysis interpretation are not the only considerations for good yields and maximum profit in crop production. Even if the recommended fertilizer rate is applied, other factors may override the fertilizer effects by limiting crop yield potential. These factors include:

soil type and stored soil water at time of planting. • pest control. • irrigation water quality and management. • other agronomic and cropping system factors •

(e.g., seeding date, rate, planting system, fertilizer application method, crop rotation, variety selection, etc.).

Many of these factors are under direct control of the producer; therefore, a favourable fertilizer response is usually related to crop management. Critically examine fertilizer recommendations, yield predictions and growing season precipitation to ensure they are realistic for the area.

Figure 3.4.5 illustrates how all of these considerations are assembled into a decision-making model used to develop a fertilizer recommendation. This model is used by the AFFIRM software package. For more information, see Chapter 7.2.

tip

If a recommendation on a lab analysis does not appear reasonable, request an explanation from the testing lab, seek advice from a qualified agronomic consultant (e.g., Certified Crop Advisor), or contact AF’s Ag-Information Centre, toll-free at 310-FARM (3276).