With the exception of this year, the past few years have been incredibly stressful on our perennial forages. I have visited many bermuda hayfields and pastures that have been under extreme drought for successive seasons. Not only has drought plagued these fields, but late spring freezes and major weed problems have also been a concern. As a result of these adverse conditions, forage stands have thinned considerably. Some bermudagrass fields have gone from a solid stand to less than a 50 percent stand "just in the last year or so."

This problem is broadly called "bermudagrass decline." The reason this term is so broad is because this problem is often linked to several causes. Often several factors will occur at the same time, so it is quite difficult to pinpoint the actual problem. Let's discuss a few possible causes of bermudagrass decline.

Low Potassium Fertility

At the top of the list are low Potassium (K) levels. A deficiency of K will result in poor stress tolerance, reduced winterhardiness, decreased disease resistance, and diminished rhizome and stolon production. To determine if K deficiency is causing the problem, take a representative soil sample from the affected areas and another from areas nearby that are unaffected or less affected. Submit these samples for soil testing and compare the results. It is also highly recommended that plant tissue samples (clippings from the top 6 inches of 3-4-week-old growth) also be collected from the affected and unaffected areas.

Low Soil pH

Low soil pH is very high on the list for reasons for bermudagrass decline. This accounts for at least 75 percent of the causes of bermudagrass decline. Low soil pH causes a problem in several ways. First, toxic levels of soluble Al can occur in soils where the pH has dropped too low. This effectively burns back the fine root hairs and prevents root growth. Low soil pH also reduces the availability of many of the other nutrients, such P, K, Mg, Ca, and others. In effect, low soil pH starves the plant of water and other nutrients. As you might imagine when low soil pH is coupled with low K, the rate of bermudagrass decline is even more rapid.

Soil Compaction

With the frequent use of heavy machinery in hayfields, excessive animal foot traffic, and our soil types that are low in organic matter, many times we are dealing with soil compaction. Many times, fields that have not been limed are suffering from soil compaction. Lime has a positive effect on soil tilth, aeration, and drainage. We have seen that aeration has produced mixed results. Sometimes fields that have been aerated will allow weeds to germinate in gap areas.

Drought

Last, but not least, is our old friend dry weather. Drought stress is extremely hard on any plant, including bermudagrass. However, bermudagrass is quite drought tolerant. By itself, drought will not kill bermudagrass. When combined with other stressors, especially K and pH stress, drought can be the "last nail in the coffin."

These are not the only causes of bermuda problems. However, these are the main culprits. If you notice your field deteriorating in quality and quantity, think about a few of the reasons I have listed!

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