Seasonal droughts are normal in the southern Great Plains. Droughts occurring during the fall and winter can be especially disruptive of a usually predictable supply of forage wheat. The two most common effects of drought are decreased forage availability for spring grazing and limited hay supplies. When wheat pasture fails due to drought, there are limited opportunities to recover lost forage production. The best option to offset forage losses from wheat pasture is spring-planted oat.
Producers in Oklahoma and surrounding states grow winter wheat in a continuous system, where the field is planted in the fall and harvested in late spring. Then the field is left summer fallow, when it is prone to soil erosion. A study conducted in the southern Great Plains, which includes Oklahoma, demonstrated soil losses from summer fallow fields increased 18 times when compared to fields cover cropped in summer (Sharpley & Halvorson, 1994). This huge soil loss decreased soil nitrogen by four times and phosphorus content by three times. Those nutrient losses might have contributed to wheat yield reduction in the region (Patrignani et al., 2014). These production losses are the sales pitch of conservationists, who typically follow with the arguments that cover crops also sup-press weeds and “improve soil health” with time. The latter is a generalized term used to synthesize increased soil water infiltration, holding capacity and nutrient retention. Although all those arguments are supported by several scientific works, most of them were performed in the southeastern U.S., where summer rainfall is higher and better distributed than in Oklahoma, making summer cover crops a success.
Grain sorghum is a summer crop grown throughout Oklahoma, mostly west of I-35. Sorghum fits into most Oklahoma crop rotations and provides growers with a rotational crop option considered to have a higher heat tolerance and a lower water demand than some other summer crops. For instance, grain sorghum requires a minimum of 18 inches of precipitation during the growing season, while high-yielding corn will need up to 30 inches (Assefa et al., 2010). Grain sorghum production has seen increased challenges through the latter half of the 2010s, associated with increased competition from other crops, increasing pressure from sugarcane aphids and lower commodity prices. These challenges have resulted in a decline in production acres throughout the state. However, most crops face similar production challenges and remain a viable option for growers, specifically for winter wheat growers. For sorghum to be a profitable option, growers have to look for ways to extend the value of the crop to increase the potential benefits.
Old World bluestems were introduced from Europe and Asia from 1920-1965. These grasses have been studied extensively in Oklahoma in the last 50 years, but producer interest was not widespread until recently.
For the past four years, a grazing system consisting of winter wheat and crabgrass has been managed near Stillwater. This system is commonly utilized by beef producers in Oklahoma who choose to focus their efforts in beef production with little or no interest in grain production. It is particularly ideal for soils where grain production is limited by highly irregular or low water storage capacity, which limits grain production. It is certainly not recommended for producers interested in summer crop production, as crabgrass can be aggressive and there are limited postemergence herbicides available for controlling this plant in crops that are not glyphosate tolerant. However, crabgrass can be a resilient forage species for a grazing system to take advantage of rainfall received during the summer months. This report describes what was learned in managing this system for four years.
Johnsongrass (Sorghum halepense L.) is a warm-season grass. Originally from the Mediterranean region, it was introduced to North America in the 1800s as a forage alternative. The name “Johnsongrass” refers to Colonel William Johnson, who introduced this species to his river-bottom farm in Alabama in the 1840s. Today, Johnsongrass is found in all states except Minnesota, and is considered a noxious weed in 19 states (NRCS, 2016). Johnsongrass is popularly known as “the weed we love to hate and hate to love.” We “hate to love” it because it is one of the most common weeds in 30 different crops including corn, sorghum, cotton and soybeans. It also serves as a host for several insects, disease pathogens and nematodes of corn and sorghum. On the other hand, we “love to hate” it because it is not only a valuable forage due to its high yield, palatability and quality, but also is successful in reducing soil erosion as a plant cover alternative (Warwick and Black, 1983).
Legumes may be used in much of Oklahoma as a means of extending the length of grazing season, increasing the nutritional plane of grazing livestock, and/or reducing the amount of nitrogen fertilizer required in a forage production program. Legumes in tall, fescue pastures can also offset some of the negative effects of fescue toxicity. Several forage legumes are widely adapted to and used in Oklahoma especially in the eastern half of the state. However, several legumes have a vast untapped potential for Oklahoma forage production systems. Some of the important (and potentially important) forage legumes are briefly discussed in this report.
Selecting an appropriate variety is important when establishing crabgrass pastures. Crabgrass will re-seed itself year after year; therefore, the selected variety will dictate the potential forage yield and quality for many years to come. Site-specific adaptations, growth morphology (prostate vs. upright growth types) and forage quality are all traits that must be considered when deciding which crabgrass variety to plant.