Stand Establishment of Winter Wheat in Oklahoma: A Survey
Authors: Stockton Roger D. , Krenzer Eugene G. , Solie John , Payton Mark E. 
Published: September 2023

Timely and adequate stand establishment of winter wheat (Triticum aestivum L.) is critical in the southern Great Plains, where wheat is frequently grazed by livestock in the winter followed by grain harvest. Poor stands reduce forage yield potential. Percentage of viable wheat seed planted that produced seedlings was determined by surveying wheat fields during the 1992 and 1993 planting seasons. Causes of poor emergence were identified. Data collected included: cultivation practices prior to planting, type of planting equipment, depth of planting, and seeding rate. Seed samples for germination tests, seed size determinations, and planter calibrations were collected at each location. Actual stand counts and seeding depth measurements were made about 2 wk after planting. Average emergence rate was 57% of viable seed planted in both years. Inaccurate planting depth and variation in planting depth within a field were identified as major causes of poor emergence. Other causes for poor emergence were placing seed in dry soil and use of small seed. Oklahoma wheat fields have too few wheat plants for the number of viable seed planted. Limiting cultivation depth prior to seeding, using depth gauges on individual row openers, and not planting seed weighing less than 7 oz/1000 seed can help improve wheat stands.

Research Question

Timely establishment is the first step toward optimum winter wheat production. This is especially critical in the southern Great Plains when wheat is used for winter livestock forage and grain production in the same crop year. If the desired stand is not achieved on the first planting, it may be 2 to 6 wk before adequate soil moisture is present to replant. Poor stands or late planting reduce wheat forage production. The objectives of this research were to determine how efficient wheat producers were in converting viable seed planted into emerged plants and to identify causes of poor efficiency when it occurred.

Literature Summary

Many factors interact in wheat stand establishment, but they may be broadly classified as soil factors, equipment factors, and seed factors. The soil conditions that favor good stands are uniform tilth and texture, good moisture, and sufficient firmness to allow uniform seed placement and limit evaporation. There are many equipment options and combinations that allow individual tailoring of planters to specific conditions. Seed factors that favor good stands are clean, uniform‐sized seed with excellent germination and vigor of a cultivar with coleoptile length sufficient for the planting conditions.

Study Description

One hundred seven Oklahoma wheat fields were randomly selected for survey during the 1992 and 1993 planting seasons. Producer responses were recorded for all pertinent cultural practices. Seed was collected from three seed‐drop tubes as the producer planted a 100‐ft distance for planter calibration. Seed samples were analyzed for germination and seed size. A second visit was made to each field 10 to 20 d after planting for stand counts, effective planting depth determinations, visual appraisal, and investigation of problems in poor stands.

Applied Questions

How efficient were wheat producers in converting viable seed planted into emerged plants?

Actual established stands were 57% of the viable seed planted in 1992 and 1993, even though weather conditions were noticeably different in the 2 yr. Stands in individual fields ranged from less than 30% to better than 80% (Fig. 1). Most producers expected more than 77% of their viable seed to emerge. Germination was less than 85% on only seven of 107 samples. Therefore, stand establishment was clearly not hindered by poor germination in most fields.

Stand establishment results showing the percentage of 107 fields surveyed contained in each percent emergence category. Percent emergence is percentage of viable seed.

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Did producers obtain their desired seeding depth?

Inaccurate setting of planting depth was a major factor in stand establishment. The effective planting depth was acceptably close to the desired planting depth as reported by the producer in only 21% of fields. Effective planting depth is defined as the distance from the soil surface to the seed at the time that stand counts were made. This may not be actual planting depth if rain had washed soil over the row between planting and the time of stand counts.

How much variation in planting depth occurred?

More than 90% of the fields had more variation in seeding depth than expected (0.24 in.). Variation in planting depth refers to how much difference in planting depth from seed to seed occurred within a field. Effective planting depths ranged from 0.5 to 2.5 in. within 1 yd of row in many locations. Depth gauges on individual row openers reduced variation of planting depth by 13%. By mounting depth gauges immediately beside the opener rather than trailing it, variation was reduced by 64%.

Another result of poor depth control was finding ungerminated seed and seed too deep to emerge in the same field. Ungerminated seeds in the top 0.5 in. of soil and seeds germinated by post‐planting rainfall, but not emerged by date of stand count, were observed in 47% of fields (10 or more observations per yard of row). Ten or more yellow, accordian‐leaf plants per yard of row were observed under the soil surface in 23% of fields. These plants resulted from seed placed deeper than their coleoptile lengths and would not emerge.

How did seed size affect stands?

Seed size was a contributing factor in poor stands (Fig 2). Seed lots smaller than 0.7 oz/1000 seed had a 25% reduction in stand compared with larger seed.

Emergence as affected by average seed size of the seed lot used to plant the 107 fields surveyed.

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Recommendation

Producers have to limit cultivation depth and frequency prior to planting. Seeding depth is more consistent if the seedbed is firm, and better germination occurs with moist soil at the seeding depth. Planter operators need to give careful attention to setting depth and overall condition and operation of the planter. Seed should weigh at least 7 oz/1000. Depth gauges mounted behind the seed opener reduce variation in seeding depth and, when mounted directly on the opener, are even more effective.