June 1997
Growth Staging Small Grains
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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.
by Michael D. Peel, NDSU Extension Small Grains Specialist
Monitoring the developmental stage of small grain crops is crucial for applying post-emergent herbicides and monitoring for insect pests at the right time. Growth stages in small grain are based on vegetative as well as reproductive stages of the crop.
When staging a field, choose plants at random. This can be done several ways; I suggest using a baseball cap. In your mind choose a specific spot on the cap, then toss it in a spinning motion on the ground. The plant closest to the predetermined spot on your cap will then be the plant chosen for staging. The other way is to bend down and stage the plant closest to the toe of your boot. Regardless of the process it is critical that it is repeated 10 to 12 times per field and plants are not chosen in a biased manner. The average growth stage of all plants is the stage of the crop in that field.
It is critical to distinguish wild oat from wheat and barley to determine when to control the wild oat. Differences in auricles located in the collar region (that area where the leaf sheath and leaf blade join) of wheat, barley and wild oat can be used to distinguish between the three. Auricles are absent on wild oat, while barley has long clasping auricles and wheat has shorter hairy auricles.
Small grains are staged in vegetative and reproductive stages, and each are divided into several additional stages. Vegetative stages are defined by the number of leaves produced on the main stem and the number of tillers on a plant. Leaf stages are defined by the number of leaves on the main stem only. A leaf is counted as complete when it is at least one-half the length of the leaf below it. Only leaves from the main stem are counted.
Each tiller produced following the main stem is numbered and counted after it becomes visible. There are two types of tillers: those arising from the crown and those arising from the coleoptilar node. Only tillers arising from the crown are counted. When present there will only be one coleoptilar tiller and it will appear separate from the other tillers (see accompanying figure).
All tillers originating from the crown are surrounded by a small membranous structure called a prophyll. These tillers arise from the axis of main stem leaves and are sometimes called axillary tillers. The leaf sheath of leaves from the main stem surround the prophyll and thus can be distinguished.
The main stem flag leaf is the last leaf produced. Jointing begins once the flag leaf has emerged, which is the time when stem elongation begins and the growing point emerges from the soil surface.
Most herbicide applications are made in the early vegetative stages of the crop's growth. It is important that staging of the crop is done correctly to avoid injury to the crop and achieve maximum weed control.
The plant enters its reproductive stage when flowering starts. In wheat this is generally three days after heading where as in barley flowering occurs just before heading while still in late boot stage.
There are six developmental stages that occur after flowering in small grains: watery stage, milk stage, soft dough stage, hard dough stage, kernel hard stage, and harvest ripe. The names of each of these stages are sufficiently descriptive that they need not be described.
Hard dough is the stage in small grains when physiological maturity is reached, and occurs at 30 - 32 percent moisture. Once physiological maturity has been reached the crop will not assimilate additional dry matter into the kernel. When swathing wheat or barley to facilitate drying and hasten harvest, it should be done at or after the hard dough stage. Swathing before this stage will reduce yield and result in shriveled kernels.n