TIME TO "DO IT"

A popular commercial on TV uses the phrase "Just do it". That slogan would be good to consider now, as we think about fertilizing alfalfa for next season's production.   

Winter is an excellent time to apply needed phosphate and potassium fertilizer on established alfalfa.   

Deciding on when to fertilize established alfalfa fields involves several factors (sound familiar!). However, aside from the considerations of available resources, weather, etc., there are only two general factors that govern effectiveness of phosphorus (P) and potassium (K) fertilizer applied to established alfalfa. These factors are reducing the fertilizer-soil tie-up that begins, especially for P, as soon as fertilizer is applied, and getting available P and K to the plant roots by the time they need it most.   

Because P and K fertilizers are usually surface applied without physical incorporation, these two factors oppose each other in terms of our field application.   

That is, to minimize fertilizer-soil tie-up, we should apply the fertilizer as close to the time the crop needs it as is possible. In order to maximize getting it to the plant roots by the time plants need it we should apply it far ahead of the time the plant roots need it to take advantage of natural processes of incorporation (soil freezing / thawing; wetting / drying).   

Mid February is a good compromise time between the extremes of applying it right after harvest and waiting until dormancy breaks.   

In the last issue of NEWS we discussed how soil test values may or may not change in relation to fertilizer P rates. Review soil tests for the past several years, if you have them, and if the soil test values (obtained from the same soil testing lab) are decreasing over time, then adjusting the rate upward slightly (20- 40 lb P/acre) may be in order.   

The soil test is still the best guide for deciding on how much P or K should be applied. Select the type of fertilizer based upon cost per lb of needed nutrients, remembering that response to any nutrient other than P or K is very unlikely, then, JUST DO IT!