Manage forages as a crop, not filler

There is no other crop with such a wide range of management as forages.
Some farmers apply high rates of fertilizer to push for maximum yields. Others treat forages as the “poor sibling” in the rotation, making do on whatever fertility is left over from the other crops.
There is no doubt the quickest way to improve the profitability of any farm is to manage forages as a crop, rather than as a filler.
By far, the most economical source of nitrogen for forages is the legume portion of the stand. If the stand includes more than 50 percent of any legume, there is no advantage to adding nitrogen fertilizer.
In pure grass stands, the opposite is true. A vigorous stand of forage grass will respond to large amounts of nitrogen. The limiting factors become the amount of rainfall and the risk of high nitrates in the forage, rather than the yield response.
The management of mixed stands of grass and legume is trickier. These stands will respond to nitrogen fertilizer, but applying nitrogen will allow the grasses to out-compete the legumes in the stand, which will lead to greater requirements for nitrogen the next year.
The choice to apply nitrogen will depend on the long-term plans for the stand. If the field is going to be rotated to another crop within a year or two, it will be beneficial to fertilize for the higher immediate yield.
On the other hand, if the goal is to maintain the stand as a long-term pasture, it might be better to sacrifice some yield in the short-term to concentrate on rejuvenating the legume portion of the stand.
Phosphorus is critical to the vigour and longevity of a forage stand. The ideal time to apply phosphorus is in a band below the seed at planting, at a rate high enough to supply the entire life of the stand.
Very few fields receive this treatment, so top-dressing is required unless the soil test is high.
Phosphorus top-dressing can be done at any time of year, and generally is combined with applications of potash.
If alfalfa is the queen of the forages, then potash is the royal consort. Legumes respond to ample supplies of potassium.
This cannot be applied in the seeding band, because of the danger of seed burn, but can be applied pre-plant or top-dress.
Field trials by the University of Guelph to compare different application timings found no difference in yield response between spring, between-cut, or fall applications, or between single or split applications.
The main consideration is to apply the potash according to soil test recommendations.
The one caution with high potash rates is that high levels of potassium in the forage fed to dry cows can result in increased risk of milk fever. Keeping one field specifically for dry cow hay can get around this.
High yields of high-protein forage are going to remove large amounts of sulfur from the soil. Despite this, the only areas that have shown a response to sulfur are sandy soils in Northwestern Ontario.
This can be attributed to the sulfur that is still supplied in acid rain, and to the deep roots of alfalfa that can recover sulfate that has leached below the rooting zone of most other crops.
At present, we do not recommend sulfur application in forages.
Forage crops generally are non-responsive to micronutrients in Ontario, with one exception. Alfalfa has a high demand for boron, and there are circumstances where boron application is justified.
Boron deficiency is most common on sandy or gravelly soils during dry weather. It shows up as stunted alfalfa plants with red, yellow, or purple leaves at the top of the plant.
Boron deficiency is much more prevalent in central Ontario than west of the Niagara Escarpment or east of the Frontenac axis.
Where boron is required, the optimum application time is just after first cut, blended in with the phosphorus and potash fertilizer.

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