Crabgrass is the common name for numerous Digitaria grass species that are warm-season annuals capable of natural, consistent and prolific reseeding. It is among the highest-quality forage grasses and is essentially nontoxic, although harmful levels of nitrates can accumulate.

The consistency and persistence of crabgrass as a forage is important. The fact that crabgrass is not a perennial does not mean it cannot persist: crabgrass grown under adequate cultural practices has longevity equal to or better than that of bermudagrass, Old World bluestems, and weeping lovegrass.

It is important to keep in mind that the crabgrasses discussed are taller forage types, not lowgrowing ecotypes.

Crabgrass supposedly evolved on the African continent. Europeans discovered it and used it in Europe before they inadvertently brought it to the United States as a contaminant in fodder and food. The United States Patent Office (the forerunner of the United States Department of Agriculture) allegedly imported crabgrass in about 1849 to help provide forage for farm animals, but there is no readily available governmental record. The grass was very successful, which made it fall into disfavor because it encroached upon cultivated field crops, yards, and gardens. Thus, its merit as a forage was ignored.

Over the past thirty years, there has been an enormous change in producers' and the academic sector's perception of crabgrass: it is now considered a legitimate forage plant. Traditions are difficult to break; crabgrass still carries a stigma, but it is diminishing as education about the grass continues.

According to Dr. Ron Tyrl of Oklahoma State University, the United States has thirty-five species of Digitaria, some of which are known as crabgrass. Some taxonomists believe that none of these grasses are indigenous to the United States.

In Oklahoma there are six species of naturally occurring Digitaria that are called crabgrass. All of these species have desirable forage qualities, but only three offer consistent good volume. Digitaria ciliaris and D. sanguinalis are the major forage species and often are classified identically as D. sanguinalis by agronomists, but plant taxonomists and cytologists separate the two. Both have ecotypes that produce voluminous useful forage. There are ecotypes that are inferior because of low potential yield or a short green season. Digitaria ischaemum is the third major forage, but not as good. All three of these species can grow in conjunction.

Crabgrass is a high-quality forage for summer grazing and hay and is an excellent choice in many double-cropping systems with winter annual forages like wheat. It can be managed as a volunteer crop to mimic perennials, thereby reducing seed and other annual costs. Crabgrass can be used as a component in warm-season annual mixtures, including forage sorghum (sudangrass), pearl millet, German (foxtail) millet, cowpeas, mungbeans, soybeans, and annual lespedeza. It also works as a component in warm-season perennial forages; i.e., bermudagrass, Old World bluestem, and alfalfa. Crabgrass is a good component of double-cropped cool-season perennials like fescue, orchardgrass, smooth bromegrass, and rescuegrass such as 'Matua' and 'Stocker' bromegrass. In the management of effluent disposal, systems for confined swine, poultry, dairy, and feedlot cattle, crabgrass uses excess soil nutrients aw well. Crabgrass can be used in soil conservation practices such as pond dike and roadside revegetation and in turf management.

Crabgrass sometimes is used alone to maximize production. In the southern Wheat Belt and throughout the southeastern United States, crabgrass is used primarily as a summer component in a winter annual/crabgrass double-cropped forage regimen. The winter small grains, annual ryegrasses, and annual legumes in some combination often compose the winter component; volunteer crabgrass, the summer component. This approach to grassland farming usually involves some form of favorable moderate soil renovation (tillage) to culture both crops. Crabgrass responds to proper soil tillage by producing earlier and more plentiful forage.

Crabgrass often is paired with warm-season legumes such as annual lespedeza and alfalfa, the latter because a one-half to two-thirds stand is open enough to allow an excellent stand of crabgrass. Good rotational grazing is critical with these mixtures because cattle usually graze crabgrass first, potentially overgrazing it. Crabgrass also has been grown with southern cowpea, hay and grain soybeans, and mungbeans.

Crabgrass is cropped in mixtures with forage sorghums (sudangrasses), pearl millet, German millet (foxtail millet), and corn because it forms a more complete soil cover for erosion prevention, provides more grass in each bite cattle take, and produces better late-season forage and soil cover than the other forages. Some producers plant crabgrass seed and only enough of the other grasses' seed for a thin stand so that a crabgrass field eventually will be established.

Crabgrass grown with bermudagrass, Old World bluestem, weeping lovegrass, or bahiagrass offers midsummer forage quality impossible to achieve with the other grasses. In order for this mixture to work, there are certain cultural practices that must be met, and rainfall must be adequate; 25 inches or more yearly is acceptable. Crabgrass is most suited for cropping with bermudagrass. In the bunchgrasses, Old World bluestem, and weeping lovegrass, clumps must be spaced at least 6 to 12 inches apart to allow good crabgrass growth. Minimal tillage (soil renovation) as a supplement to or replacement for spacing is not feasible in these grasses because it permanently destroys some of the stand. Bahiagrass also must be spaced for crabgrass growth. It recovers from light spring tillage. Bermudagrass recovers from any acceptable tillage in this syndrome. Thin the bahia- or bermudagrass to one-half to two-thirds of a full-cover stand. The more soil disturbance in spring, the more the subsequent crabgrass production.

Phosphorous, potassium, and lime must be provided for forage mixtures to be successful. Actual nitrogen at 30 to 50 pounds per acre should be applied on mixtures grown in areas with annual rainfall at 25 inches or fewer (approximately the western third of Oklahoma). In the central region of Oklahoma, which receives 25 to 30 inches of rain annually, fertilization rates for the mixture tend to be 50 to 75 pounds of nitrogen per acre. In regions with over 30 inches of rainfall, nitrogen rates can be 50 to 100 pounds or more per acre. From central Oklahoma eastward, higher rates of nitrogen can be used with or without irrigation.

Crabgrass can be used as a conservation grass for fast revegetation of a critical area.

Cool-season perennials, i.e., fescue, orchardgrass, and rescuegrass, can be used in a crabgrass mixture or double-cropping syndrome. The mixtures are best when the cool-season grass stand is sparse and perhaps low in vigor and on loam to sandy soils. There must be a space of at least 6 to 12 inches between the cool-season grass clumps where the crabgrass can establish and produce. Some fescues, and especially excellent stands, are allelopathic (toxic) to crabgrass. Orchardgrass tends to mix better with crabgrass than fescue, as does thin smooth bromegrass. The perennial or annual and perennial rescuegrasses (bromegrass) such as 'Matua' and 'Stocker' allow excellent summer crabgrass production in the stand. To encourage crabgrass growth, thinning of the cool-season component often is needed as the summer nears.

The Noble Foundation at Ardmore, Oklahoma, developed and released a variety of crabgrass named Red River. It was approved as a certifiable variety through the Oklahoma Crop Improvement Association. 'Red River' derived its name from its one-parent plant that came from the upland soils north of the Red River in southern Oklahoma. Other selections studied included plants from various regions of Oklahoma and Missouri. Since 'Red River' was released it has been compared to selections from Oklahoma, Louisiana, Delaware, New Mexico, New Zealand, and Russia, and has retained its place as the best selection.

'Red River' crabgrass has consistently high production. Production from plants of the same species but different ecotypes ranged from about 1,000 pounds per acre per year to over 12,000 pounds per year from 'Red River'.

'Red River' crabgrass has other desirable characteristics: it remains green for a full season instead of dying one to three months before the fall frost, is an excellent stoloniferous grass with prolific seed production, forms sod with a medium stem and leaf size, provides excellent grazing and hay, and has no serious disease or insect problems.

Cultural practices are as important as the variety. Good management of a good variety results in higher production.