Winter Survival of Small Grains and Cover Crops at Risk

 

With the increased use of diverse cover crop species, some farmers are finding that winter injury and winter kill can become a problem. Traditionally, when we think of winter kill we assume that a very cold snap combined with factors such as wet soils and frost heaving are the culprits. This is generally true for late planted covers that have not developed an adequate root system nor carbohydrate reserves. Physical injury, cold temperatures, and desiccation combine to stress and potentially kill tender young plants. However, with the advent of a warm fall and extended growing season, sometimes we are seeing the opposite. Species with excellent growth and establishment go into winter looking great and when the snow melts large areas of foliage have "smothered" and died. In many cases, the growing points are also affected and the areas are either very slow to green up or are entirely dead.

 

Snow mold is often the main culprit. A thick lush canopy of leaves will hold moisture, prevent air circulation and sunlight from entering the canopy. This provides an ideal environment for the various diseases collectively called snow molds. Leaves in contact with the soil are often affected first. Snow cover coupled with temperatures just above freezing in the canopy will allow the disease to continue infecting upper leaves and with prolonged periods kill the crown. Snow molds primarily affect grasses, but I have also seen winter kill in crimson clover and other non-grass species.

 

 

Here in south central Pennsylvania, annual ryegrass seems to be particularly sensitive (see photo), with barley next in line. Rarely do I see this problem in wheat and rye. What’s the solution? Ryegrass is a great cover crop or spring forage and has excellent yield and nutritional factors; so, I don’t want to discourage you from growing it. One consideration is to include ryegrass as part of a mixture with other grasses and legume species. I have grown a ryegrass, triticale, and crimson clover mixture for the past four successive years here in Lancaster county with excellent results. If the forecast is for a warm Fall, you could delay planting ryegrass until the end of September or even early October here in the southeast.

 

Another option is to monitor growth and if needed take a late cutting to open up the canopy and remove excessive biomass. It’s not too late to walk your ryegrass plantings and consider this option. If the canopy is approaching 7-8 inches and is fairly thick, a cutting may be warranted.

 

Small grains such as wheat, barley, and rye should not be as susceptible until they are 10-12 inches tall. However, if soil warmth and plant growth continue into the end of November and early December even these fields can be "set up" for significant winter injury, with Barley of the most concern. In both cases the excessive growth could be harvested for forage provided the volume is sufficient or left on the field if uniformly scattered. Taking a high cutting about 4-5 inches is a consensus I have found among the local seed industry. If you have excessive biomass but cannot remove or uniformly scatter the forage, it may be better to do nothing. Another option for some growers would be to graze these fields when soil conditions permit.