Pasture and Forage Minute: Fertilizing Cool-season Pasture, Army Cutworm Control

Army cutworm eating wheat
Army cutworm larva chewing on a blade of wheat. (CropWatch file photo)

Pasture and Forage Minute: Fertilizing Cool-season Pasture, Army Cutworm Control

Spring Turnout to Pasture

By Jerry Volesky

The time for turnout to our primary summer pastures is coming soon. A couple of important questions are what date to turnout, and which pastures should be first.

The driving factors on the amount of grass growth at a specific date varies each year depending on spring temperatures and precipitation. This spring, March and April temperatures have been above normal and there are some areas in eastern Nebraska that have some level of drought. For areas that had drought last year, or are dry this year, delaying turnout, if possible, is recommended. This will allow the grass plants to maximize growth given the current soil moisture conditions, and result in greater season-long production.

For mixed cool- and warm-season native grass pastures, it is important to allow the cool-season grasses to reach at least a 3- to 4-leaf stage. Initial grass growth in the spring comes from energy reserves stored in the roots and crowns of the grass plant. Grazing too soon could cause a depletion of those reserves and reduce production because there was not enough leaf area present to adequately begin producing energy from photosynthesis.

When grazing multiple native grass pastures in a rotation, it is beneficial to change the sequence or order of grazing for the set of pastures. This change in the time of grazing each year benefits the overall health and vigor of the grasses. For producers who have both native range and introduced grass pasture such as smooth bromegrass or crested wheatgrass, grazing the introduced grass pastures first is a great approach to use that resource and allows for a later turn-out on the native pastures. 

Does it Pay to Fertilize Cool-season Pasture?

By Shannon Sand

Does it pay to fertilize cool-season pastures? That is a question that has been recently asked. The answer is, it depends. Depending on the cool-season mixture, things like bromegrass or western wheatgrass may all have somewhat different responses to fertilizer.

According to university research on sub-irrigated grazed hay meadows, a suggested fertilizer application of 70 lbs. of N, 25 lbs. of P and 20 lbs. of S per acre resulted in an average grass increase of about three quarters of a ton per acre. So, a $150 potential hay value increase only requires $56 per acre of fertilizer investment plus application costs. Thus, this would be a 3:1 ROI ratio (return on investment).

Nebraska grazing research has shown that, in general, you get one pound of additional calf or yearling gain for every pound of nitrogen fertilizer applied, provided that the amount applied is within UNL general recommendations, which are based on the potential amount of extra grass growth expected. This is affected mostly by moisture.

Some things to look at before deciding:

  • Cost of fertilizer for your pasture.
  • Pasture production and how much it can support.
  • Expected cattle prices.
  • Your own historical margins.

Knowing these things can help producers to make an informed decision on whether fertilizing is worth it. In some parts of the state where they have received a fair amount of moisture and given the current futures market and basis, as well as the other factors previously mentioned, it might be a very effective strategy to invest in and help producers capture some additional gains. For others, it just may not be feasible for their current situation.

Scouting For Army Cutworm in Alfalfa

By Samantha Daniel

As warm weather across Nebraska continues, it is important to keep an eye on alfalfa fields for signs of army cutworm.

The army cutworm, also known as the miller moth in the adult form, is a caterpillar with a wide host range that includes alfalfa. It is 1.5 to two inches long with a greenish brown to greenish-grey body that has three stripes: two darker stripes running laterally along the sides and one lighter stripe along the back.

Because these caterpillars feed at night, feeding damage or other signs of an infestation are usually noticed first. Feeding damage from this insect consists of semi-circular areas eaten from leaf edges or circular holes in leaves. A delay in green-up or higher than average bird activity can also be signs of an infestation.

To scout for army cutworm, overturn clots of loose soil or residue near the base of the plants and count the number of larvae in one square feet of surface area. The economic or treatment threshold for army cutworm in seedling alfalfa is two or more larvae per square feet while in established alfalfa, the threshold is four larvae per square feet.

Established fields can usually better compensate for feeding damage compared to seedling fields thus the difference in the control guidelines. If the number of army cutworm in a field is above the economic threshold, an insecticide application may be considered.

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