Herbicide and Nonherbicide Injury Symptoms on Spring Wheat and Barley

Good seedbed preparation coupled with accurate planting are important to ensure good stand establishment. These operations are strongly connected to the environmental conditions that follow. The lack of a firm seedbed, or poorly adjusted planting equipment, can be compounded by heavy rains that can result in poor emergence, uneven stand, and weak seedlings.

Deep Planting
Wheat and barley both have elongating coleoptile-type emergence in which the coleoptile can elongate, but not the first internode. This type of emergence limits the maximum seeding depth to about 2.5 inches for tall varieties and 2 inches for semi-dwarf varieties. The most common characteristic of planting small grains too deep is uneven emergence and stand. Examination of individual plants will show an elongated subcrown internode, but the coleoptile and the subcrown internode are limited in how far they can expand. With deep plantings, the subcrown internode may elongate up to four inches, depending on the seed size and soil conditions. When cereal grains planted too deep begin to germinate, vegetative leaves may begin to emerge through the coleoptile and expand below the soil surface. Since the vegetative leaves are not adapted to penetrate soil, they often become folded and usually will die before emerging. Crop injury from deep plantings can appear similar to injury caused by herbicides in the dinitroaniline or thiocarbamate families. Deep planting also can increase crop injury from dinitroaniline and thiocarbamate herbicides. See photo 22.

Photo 22 Deep-planted small grains take longer to emerge and can result in uneven stands. Elongated internodes appear in plants on the right. Plants on left show seedling growth when planted at correct depth.

Soil Crusting Soil crusting can be caused by tilling wet soils or from standing water after heavy rains. Heavy clay soils are especially subject to soil crusting. Wheat and barley seedlings can emerge through about one quarter-inch of soil crusting without too much difficulty. Deep planting of small grains can cause even a light crust to affect wheat and barley emergence. Soil crusting can create plant malformations similar to those associated with deep plantings. Some of these symptoms are uneven stand, leafing out underground, emerged shoots bent over, shoots emerging through the side of the coleoptile, and twisted and kinked leaves. Soil crusting will affect only the plant shoot; it has no effect on the roots. Crop injury from soil crusting can appear similar to injury caused by herbicides in the dinitroaniline, thiocarbamate, and benzoic acid families. See photo 23.

Photo 23 Soil crusting can result in delayed emergence; emerged shoots that are bent over; and twisted, kinked leaves.

Soil Compaction
Soil compaction refers to the compression of the soil airspace and bulk into a smaller volume. The risk of compaction is greatest in fine-textured and low organic matter soils. Small grains growing in compacted soils tend to have smaller root systems that result in shorter plants. It is quite common to see wheel tracks made by heavy equipment that support fewer and smaller plants. The ultimate agronomic result of soil compaction is reduced top growth and yield. Crop injury from soil compaction can appear similar to injury caused by herbicides belonging to the dinitroaniline and thiocarbamate families. See photo 24.

Photo 24 Lighter colored areas in photo show the result of wheel track compaction made by postharvest tillage.

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