March weather critical to wheat development

COLUMBUS – Wheat is an amazing plant – it seems to survive all the impossible situations that Mother Nature and we present it.

Across Ohio, wheat planting was behind schedule last fall, with some of the crop even replanted in late October and November due to heavy rainfall. This was not a good start for the wheat crop in the western and northwestern counties.

According to Ohio State plant pathologist Pat Lipps and OSU Extension small grains specialist Jim Beuerlein, wheat in other areas looks fair to good, depending on planting date and winter conditions.

The first few weeks of March are critical to wheat survival. During this time the wheat is frequently trying to regrow, but cold injury and frost heaving significantly affect the plants’ ability to grow.

With this winter’s variable weather and the severe frost heaving in some fields, Lipps and Beuerlein suspect many fields will look a lot worse before they begin to show significant growth this spring.

Getting good start. Research results have consistently indicated wheat performs best when planted on the Hessian Fly Safe date, or within the first week afterward, especially if the seed was planted sufficiently deep (1.5 inches) so that the young plants have time to develop a good root system and at least 3 to 4 main tillers by the time it goes into winter dormancy.

Fortunately, the mild weather in November and early December provided more time for the crop to grow before it went into dormancy by late December. Most late-planted fields had plants with only one tiller in late December.

Short dormancy. The dormancy period for wheat was probably quite short this year. In early February, the researchers dug and examined plants to evaluate if they had broken dormancy and if any growth had taken place.

Although the wheat crop had not shown any growth, the plants probably broke dormancy sometime during the warm weather that occurred during the last two weeks of January. A cold period followed this January thaw, and then another warm period occurred in mid February.

The wheat crop greened up during this mid-February warm spell, indicating the plants were using their carbohydrate reserves. The wheat will again use and deplete these food reserves every time the temperatures get warm enough. The plant will make no new carbohydrates until temperatures get high enough to support photosynthesis (perhaps by late March).

In the first week of March there was another cold spell. The specialists are concerned that the wheat crop will continue to look worse until there is a long enough period to provide sufficient warmth to initiate new growth and nutrient uptake.

Getting growing again. Then, beginning of wheat regrowth after winter in Ohio has varies greatly. Over the last five years, regrowth has resumed between the last week of February to the first week in April. This “time of regrowth” is entirely dictated by the weather. With the weather conditions this year, the earlier regrowth begins, the better it will be for crops.

Variety differences. Varieties differ in their ability to make and store carbohydrates in their tissues and they differ in their response to the duration of warm weather required to break dormancy.

In general, varieties with good winter-hardiness store more carbohydrates and they are generally the latter ones to break dormancy in late winter. Also, wheat varieties developed for more southerly states may break dormancy after a short warm period, then when cold resumes, these fields turn yellow or brown.

Scout fields. Scout fields now to check for frost heaving of plants. Usually frost-heaved plants occur on higher ground, especially on soils with high clay content. These areas will look brown in comparison to plants on the lower ground.

Once the crowns are heaved out of the ground they will have difficulty reestablishing roots because the remaining roots become desiccated (dried out) during the day. Additionally, since the growing points are above the soil surface, they are vulnerable to cold injury. Frequently, frost heaved plants die or produce few weakened tillers.

Help avoid heaving by placing seed deeper during planting and by planting earlier. No-till planting frequently reduces heaving problems especially if seed are placed below, and not in, the surface residue.

Fertility. Applying nitrogen now before the plants are actively growing may only cause additional problems by stimulating succulent tissues susceptible to cold injury. Assuming 20-30 pounds of nitrogen was applied in the fall at planting, these overwintered plants do not need additional nitrogen right now, but nitrogen should be applied before stem elongation stage.

This growth stage corresponds to Feekes growth stage 5 to 6 that may occur as early as the first week of April in southern Ohio or mid April in northern Ohio. Of course, the weather will determine when these growth stages occur. There should be no need to rush out and apply nitrogen early.