May 2007

Manitoba Fertilizer Recommendation Guidelines Based on Soil Tests

This section contains tables of fertilizer recommendations for most Manitoba field crops based on soil tests. These recommendations are based on field research conducted in Manitoba and have been approved for use in Manitoba by the Manitoba Soil Fertility Advisory Committee. Following are some brief points in using the attached recommendation tables:

1. Recommendations are based on soil analysis performed according to the soil analysis section entitled “Proper Soil Analysis Techniques”.

2. Soil analysis results may be reported by soil test laboratories as lb/ac or ppm. Values in ppm can be converted to lb/ac by multiplying by a factor of 2 for each 6” increment of depth for the sample (e.g. multiply by 2 for 6” samples and by 6 for 18” samples). Ratings for soil test levels are given as very low (VL), low (L), medium (M), high (H), very high (VH and VH+).

3. Soil nitrate-nitrogen values used in these recommendations are based on fall soil sampling. Manitoba research has shown that 8 lb/ac nitrate-N may mineralize between late fall sampling and spring seeding. If samples are taken in the spring, deduct 8 lb/ac from the analytical values before using the tables.

4. Nitrogen rates are based on a spring broadcast application for all but row crops, where rates are based on a spring band application. Relative efficiency of nitrogen varies by method and time of application, so rates should be adjusted according to Table 8 in this guide.

Adjust nitrogen recommendations from tables according to method and time of application according to this formula.

Rate of N to Apply = (Rate from chart) X (Relative Value of Spring Broadcast)/ (Relative Value of Method Used)

5. Nitrogen recommendations for some cereals, canola, flax, corn and sunflowers are based on TARGET YIELDS. The TARGET YIELD is the yield that a crop might be expected to produce based upon the amount of spring soil moisture and expected growing season precipitation based on the grower’s experience. The TARGET YIELD FERTILIZER RECOMMENDATIONS indicate the fertilizer rate required to meet that yield expectation. Target yield recommendations are not intended as yield predictions; nor do they imply guaranteed yield attainment. Achieving such target yields depend upon good management and cooperation of uncontrollable factors such as weather.

More information on setting target yields can be found in the section entitled, “Agronomically, Economically and Environmentally Sensible Target Yields” in the Appendix.

6. Nitrogen recommendations for cereals are further refined based upon soil moisture supply. Moisture supply is dependent upon seasonal precipitation and soil properties such as texture and drainage which affect moisture retention. Based on these criteria, soils within the province have been assigned a moisture category of MOIST or DRY. Soils of the MOIST category have a high water holding capacity or are in the cooler areas which may experience periodic dry conditions. Examples are the clay soils of the Red River Valley and the Grey Wooded soils.

Soils of the DRY category are intermediate in water holding capacity and experience dry weather conditions.

The IDEAL moisture category would occur under irrigation or when yield is not limited by lack of rainfall.

A full listing of Manitoba soils and their moisture category are available from your MAFRI office.

7. No nitrogen is recommended for production of perennial legumes and most annual pulse crops (the exception is dry beans). All legumes should be properly inoculated at seeding to ensure nitrogen fixation.

8. In dry years, deep-rooted crop such as sunflowers will extract nitrogen below the 24” sampling depth. Consider sampling at the 2-4 foot depth for this crop.

9. High nitrogen rates are recommended for cereals and flax with high target yields and low soil N. Severe lodging may occur, so growers should temper rates based on their experiences.

10. Several of the phosphorus and potassium recommendations are based upon specific placement techniques. Crops vary in their tolerance of seed placed fertilizer and this influences recommendations (Tables 7 and 12).

• The crop to be grown is feed barley and the projected yield is 85 bu/ac. The land is located on clay soils and is classified as a “moist” moisture category. 
• Nitrogen fertilizer will be spring banded and phosphorus and potassium will be seed placed.
• From Appendix Table 4, 75 lb N/ac are required “if spring broadcast”. Use Table 8 to determine rate of spring banded N = 75 x 100/120 = 63 lb N/ac
• From Appendix Table 17 and 15 ppm soil P, one determines that 15 lb P₂O₅/ac is required.
• From Appendix Table 18 and 240 ppm soil K, one determines that no K₂O is required.
• From Appendix Table 19 and 20 lb/ac soil sulphate-S, one determines that 15 lb S/ac is required.

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