Forage Report – August 18, 2014

With recent rains, forage growth has been excellent. Making dry hay has been quite challenging in August, with lots of baleage being made. Forage inventories and quality are generally good in most parts of the province. Considerable wheat acres are being followed by seeding oats, Italian ryegrass, and alfalfa mixtures. (Forage Options Following Wheat

We are seeing more situations where there is a yield response when applying sulphur (S) to alfalfa. In some field trials the S response is quite dramatic, while in others there is little or no response. S deficiencies are more likely to occur on low organic matter soils, and soils that have not had a recent manure application. Tissue testing of alfalfa (at mid-bud to early-flower stage) is a suitable diagnostic to determine S deficiencies. Sample the top 6 inches of 30 – 40 stems and send them to a laboratory. The critical level below which alfalfa is considered S deficient is 0.25%. S deficient alfalfa plants will be spindly and light-green. A general thumb rule for S application on alfalfa is 5 lb/ac per ton of dry matter yield. The sulphur must be in the sulphate form to be taken up by the plant. Sulphate fertilizers include:

  • ammonium sulphate (21 – 0 – 0 – 24),
  • potassium sulphate (0 – 0 – 50 – 18),
  • sulphate of potash magnesia (Sul-Po-Mag or K-Mag) (0 – 0 – 22 – 20) and
  • calcium sulphate (gypsum) (0 – 0 – 0 – 17).

Sulphate-S should ideally be applied in the spring at green-up to improve plant utilization, minimize losses due to leaching, and receive a first-cut yield boost. Elemental sulphur (0-0-0-90) consists of finely ground sulphur that has been pelletized. It is much cheaper than sulphate, but must be converted by oxidation to sulphate by soil bacteria before plants can utilize it, so it it more slowly available. A single application of elemental sulphur rather than sulphate, provides a cheaper, longer term S source and reduces the need for annual applications. An application of 50 lbs/ac of S should last the life of a productive 3 year alfalfa stand. Applying elemental-S bulk blended with other fertilizer is the most cost effective method of providing long-term S, but an application of sulphate provides a more immediate yield response. (Sulphur On Alfalfa

Figure 4 - Response from potassium sulphate applied to alfalfa following 1st cut.
Figure 1 – Response from potassium sulphate applied to alfalfa following 1st cut.






elemental S applied at establishment (right)
Figure 2 – elemental S applied the fall previous to establishment (right)