Editor’s note: The following article was written by Phil Kaatz and Kurt Steinke, Michigan State University Extension crops educators.

As the 2011 growing season gets into full swing, many hay producers will be considering how much fertilizer they should apply to their established alfalfa and clover fields following a long winter season. Due to volatility of fertilizer prices, one of the growing concerns MSU Extension specialists and educators have is decreased fertilizer usage and impacts on yield. Producers need to reconsider their bottom line before determining fertilizer applications.

High fertilizer prices

According to statistics from Michigan NASS, costs of K2O and P have increased 29 percent and 19 percent, respectively, during the past five years.

Table 1.
What’s the real cost of fertilizing alfalfa?
Source: MI NASS

Fertilizer impact on yield

The primary nutrients required for high tonnage alfalfa yields are potassium (K) and  phosphorus (P), followed by boron (B) and sulfur (S ). Without maintenance nutrient applications, nutrient removal from harvested alfalfa hay will decrease soil fertility levels.

Table 2.
What’s the real cost of fertilizing alfalfa?
Source: MSU Extension Bulletin E2904, Nutrient Recommendations for Field Crops in Michigan

Research presented at the 2011 MSU Forage Technology Conference indicated that sub-optimum soil fertility  may result in inadequate plant tissue K during the third cutting . Another study presented at the conference indicated that if crop removal exceeds application, soil test K (ppm) levels decreased over time at all soil depths as deep as 36 inches in a corn-corn, corn-soybean, and corn-alfalfa rotation. Subsoil P appeared to be unaffected.

To reduce luxury potassium uptake and increase efficiency, MSU recommendations are for potassium fertilizers to be applied after first cutting. When replacing potassium due to crop removal, topdress K2O after the first and third or fourth cutting. Producers should be cautious about adding K2O to sandy or sandy-loam soils that readily leach by applying fertilizer during the growing season or before plant dormancy and soil freezing.

The bottom line

Return on investment should always be one of the driving factors when analyzing your cropping system. It’s wise to know your cost of production that includes the seeding year costs. Read MSU’s crop production budget factsheet to see a good example of an alfalfa budget.

Table 3.
What’s the real cost of fertilizing alfalfa?
K20 = $592/ton & P205 =$714/ton FOB distributor
Applied at crop removal rates Assumptions: Alfalfa = $150/ton;
*Maximum amount of 0-0-60 is 500 lbs/year. Source: Illinois Production Cost Report, USDA AMS
** Other costs are based on 5.5 tons DM/year, MSU Extension Crop & Livestock Enterprise Budgets

Don’t guess, soil test

One of the primary recommendations for successful yields is to base your fertilizer applications according to current soil test results. This practice will not only prevent unnecessary fertilizer applications when fertility levels are sufficient, but also aid in maintaining field productivity. To maximize profit, producers should analyze the cost of fertilizer applications against projected income from each ton of dry hay to determine the value of high yields.