Alfalfa removes high rates of potassium (K) from the soil, so MOP is commonly used as a K source to replace nutrient removal.
In addition to K, adequate soil boron (B) is needed to achieve maximum yields (Figure 1).
Granular B products can be blended with K, but application of these blends often leads to undesirable distribution.
Aspire® is a superior B delivery source that combines K with two forms of boron for both early- and late- season needs.
Additionally, application timings vary across producers (often driven by weather and logistics), so it is important to understand crop responses with different management approaches.
Crop: Alfalfa (Medicago sativa)
Locations: 6 trials (Columbus, WI; Cambridge, WI; and Deford, MI)
Data Source: Field studies conducted by independent third-party researchers.
Experimental Design: Small-plot RCBD with 4 replications.
Cropping Conditions: Trials conformed to local cropping practices and were conducted on an established stand.
Treatment (Trmnt) / Rates / Timing:
Numbered and color-coded to match bar chart. All treatments received a total of 240 lbs K₂O/ac. Trtmnts 2-5 received a total of 2 lbs B/ac. Values in ( ) represent lbs K₂O/ac or lbs B/ac
MOP (120) applied after 1st and 3rd cutting of harvest year.
MOP (120) + Granular B (1) blend applied after 1st and 3rd cutting of harvest year.
Aspire® (120/1) applied after 1st and 3rd cutting of harvest year.
Aspire® (120/1) applied fall of previous year. Aspire (120/1) applied spring of harvest year.
Aspire® (240/2) applied fall of previous year.
Application Method: Broadcast
Alfalfa yields responded positively to the addition of boron.
Aspire split-applied after 1st and 3rd cuttings of harvest year increased alfalfa yield 0.8 tons/ac over MOP and 0.5 tons/ac over the MOP+Granular B blend.
Split applications (120-Fall/120-Spring) of Aspire® and full-rate fall applications (240-Fall) yielded 0.7 ton/ac and 0.6 ton/ac over MOP, respectively.
The results suggest that while applications of Aspire® after 1st and 3rd cuttings of harvest year provide maximum yield, split application (fall/spring) or full-rate fall applications perform almost as well and demonstrate the flexible application window offered by this fertilizer technology.