From Penn State Extension Agronomy Guide, Crop & Soil Management: Corn
Basic Fertility Management
Lime, phosphate (P2O5), potash (K2O), and magnesium (Mg) requirements are best determined by soil testing. Soil test recommendations take into account the yield goal or the crop yield potential for the soil type, the fertility level of the specific soil, and projected crop nutrient removal. Nitrogen (N) fertilizer recommendations are based on the yield potential of the crop and the contribution of previous legume crops. On manured fields, sidedress nitrogen requirements also can be estimated using the presidedress nitrogen soil test. For a more detailed discussion of basic soil fertility management, see Section 1.2, “Soil Fertility Management.”
Adjusting RecommendationsTo determine the amount of commercial fertilizer required to produce a corn crop:
- Determine total nutrient requirements from soil test recommendations or, in lieu of a soil test, from Table 1.2-5.
- Adjust the recommendations for manure applications using Tables 1.2-13, 1.2-14, and 1.2-15. (See Table 1.4-2 for an example.)
- If you did not check the appropriate previous legume crop on your soil test questionnaire, adjust the nitrogen recommendations using Table 1.2-8. (For an example, see Table 1.4-3.)
- Determine the amount of N-P2O5-K2O to be applied as row (starter) fertilizer and subtract this amount from the adjusted recommendation to determine broadcast or plowdown requirement. (For examples, see Tables 1.4-2 and 1.4-3.)