Early Weed Identification

As spring nears, soil temperatures begin to warm up and many early spring weeds like cheatgrass, bulbous bluegrass, annual mustards, knapweeds, thistles, and leafy spurge begin to emerge.  These weeds and many others are fast growing and take advantage of warm days and early moisture. Many times they have germinated, grown, and set seed before they are even noticed, especially the annual weeds.  Rapid identification of these weeds in rangeland pastures during the seedling stages is the first step in the design of a successful weed management program.

This cheatgrass seedling has popped up out of the ground before the snow has even melted (Photo: Ashley Garrelts)

This cheatgrass seedling has popped up out of the ground before the snow has even melted. (Photo: Ashley Garrelts)

 

Why would identifying weed seedlings be key in an overall weed management plan? Spring is an excellent time to control weeds because of their small nature and to keep them from producing seed, which means there will be less of a seed bank in the soil in future years.  Each spring, plants are either beginning to grow from perennial roots or seeds. These tender, rapidly growing plants are quite susceptible to mechanical treatments and weed management is much easier, less costly, and more effective in the seedling stage than on mature plants.  Also, controlling weeds during the early growth stages allows desirable vegetation to take advantage of more available nutrient resources.  This improves overall plant community vigor and health.

Sustainable and beautiful rangelands are weed free. (Photo: Ashley Garrelts).

Sustainable and beautiful rangelands are weed free. (Photo: Ashley Garrelts).

 

When identifying broad-leaf weed seedlings, it best to first identify the shape of the cotyledons, which are first leaves that emerge from the soil.  Sometimes the cotyledons are referred to as seed leaves.   These leaves do not always persist and may not be present; however if seedlings have only reached the two leaf stage, cotyledons should exist.  There are many shapes that can be seen, including heart, oval with a narrow tip, kidney, linear, lance-shaped, oval, oblong, egg-shaped, round, and pear-shaped (obovate).

Cotyledons are the first leaves that emerge from the soil after seed germination (Photo: Wikipedia)

Cotyledons are the first leaves that emerge from the soil after seed germination. (Photo: Wikimedia CC 3.0)

 

Step 2 involves identifying whether the first two true leaves are opposite or alternate. Opposite leaves attach themselves at the same spot on the stem; alternate leaves do not and the newest leaf is typically smaller than the older leaf.  After these characteristics have been identified, looking at true leaf shape, surface texture, growth habit (annual, perennial, or biennial), and leaf edge characteristics can help further identify the weed species.  Consider contacting your local Extension Office for more information.

After the true leaves emerge, weed identification is much easier. (Photo: Ashley Garrelts)

After the true leaves emerge, weed identification is much easier. (Photo: Ashley Garrelts)

 

After the weed has been identified, one can then choose the appropriate control method.  It is recommended that to achieve maximum long-term control many “small tools” be used.  Often managers rely on one or two “large tools” such as tilling or chemical.  These practices typically only provide short-term control of weeds.  Long-term management refers to learning and adapting practices to manage weeds in the most responsive manner, using multiple appropriate techniques, such a combination of mechanical, chemical, biological, proper grazing management, and other cultural controls.

Goats provide another method of weed control (Photo: Doug Greenberg; CC 2.0)

Goats provide another method of weed control. (Photo: Doug Greenberg; CC 2.0)

 

Weeds are well adapted to colonize and compete with desired vegetation.  By using early detection and developing a weed management plan the impact of these invasive species can be mitigated.  So as spring nears and soil temperatures begin to warm up, taking some time to be on the lookout for weed emergence and applying the proper control method will help improve rangeland pastures.

Weed free salt desert shrublands create a wonderful view. (Photo: Ashley Garrelts)

Weed free salt desert shrublands create a wonderful view. (Photo: Ashley Garrelts)

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Feeding Your Grazing Livestock

The other day I drove out to a ranch to help put together some feed rations for the family’s beef cattle herd.  They had of course tested their hay and other harvested feed for nutritional content, but not their native range, on which the cattle were grazing.  Estimating the nutritional forage content of grazed feeds is difficult.  This is because grazing animals select their diet from a variety of plants and plant parts which change as seasons and other environmental factors change.

Harvested and stock piled forages are many times tested for nutritional quality (Photo: public domain)

Harvested and stock piled forages are many times tested for nutritional quality (Photo: public domain)

 

In general we can estimate the nutritional value of the plants through the growing season.  We know that the nutritional value of forages is highest when the plant is actively growing and leafy.  As the plant reaches maturity the nutritional value decreases.  This is due to changes in what are called cell solubles and cell wall material.  Cell solubles are contained within cell walls and are easily digested.  Nutrients that are considered cell solubles include: crude protein, sugars, starch, and fats.  Cell wall material are nutrients that are not easily digested and include fiber and lignin.  When feed is tested these items are included in the NDF and ADF analysis.

Leafy grass is more digestible than grass that has reached maturity. (Photo: NRCS Plant Materials Center)

Leafy grass is more digestible than grass that has reached maturity. (Photo: NRCS Plant Materials Center)

 

Plant leaves contain more cell solubles, while stems tend to have more cell wall materials.  When plants are actively growing and leafy they contain a higher amount of digestible nutrients like crude protein.  As plants mature, cell walls increase in thickness and as plants enter dormancy, in the fall and winter, nutrients are redistributed from the leaves to the roots, reducing the amount of cell solubles present within leaf cells.  Thus we can make the assumption that animals grazing during the growing season tend to obtain more nutrients from grazing than from supplemental feeding, but during the fall and winter, depending on the animals’ nutritional needs, they receive more nutrients from supplemental feeding than they do from grazing. If you are trying to rely only on grazed forage it is best you match the animals’ nutritional requirements to the forages’ nutritional availability.  Typically a grazing animal’s nutritional requirement peaks after giving birth, when she is nursing her young.  So devising a management plan so that your livestock hit that peak when the forage is actively growing and leafy would be recommended.

These horses are given hay in the winter when grazed forages cannot meet their nutritional needs. (Photo: public domain)

These horses are given hay in the winter when grazed forages cannot meet their nutritional needs. (Photo: public domain)

 

In the case of the ration balancing project at the ranch I visited, they were going to begin calving in February.  Thus their animals would reach their peak nutrition needs in February and March.  Here in Wyoming, nothing is green, leafy, or growing in February and March, and harvested feeds would be providing most if not all the nutrition that those animals needed.  Balancing a ration using just those harvested feeds and using the native upland range as a supplement would be recommended.  So the fact that the upland range was not tested for nutritional quality was not an issue as it would not come into the ration balancing exercise.  However what if those animals began calving in May?

Cattle grazing on dormant forages may need to be supplemented depending on their nutritional needs. (Photo: USDA/ARS).

Cattle grazing on dormant forages may need to be supplemented depending on their nutritional needs. (Photo: USDA/ARS).

 

If this is the case you may want to test your grazed forage for nutrient content.  To do this you can collect forage from several locations.  Watch what your animals are eating and try to take a sample of those grasses.  Mix the collected forages and fill the sample bag to send off to the laboratory.  However we do know, from both academic and applied research, that actively growing forage if available in enough quantity will generally meet the needs of grazing livestock.  By also carefully monitoring your livestock you can gauge how well a certain feed is meeting their nutritional needs.  Livestock that are losing weight are not having their nutritional needs met, while livestock that are maintaining or gaining weight are having their nutritional needs met.

Cow grazing on actively growing grass tend to obtain enough nutrients from grazing. (Photo: Ashley Garrelts)

Cow grazing on actively growing grass tend to obtain enough nutrients from grazing. (Photo: Ashley Garrelts)

 

Putting together rations for livestock grazing on native range can seem like a daunting task, however performing the task may help you understand how to better match your livestock’s nutritional needs to the forage you have available for grazing on your property or if supplemental feed may be needed.

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