Seeder Calibration and Planting Best Practices for Wheat

KEY POINTS

• A drill that is well-maintained and calibrated to deliver an optimal seeding rate can help improve stands and increase the return on investment potential for seed and starter fertilizer costs.
• Adjusting seeding rates to accommodate factors such as variety selection, planting date, end use, seed size, soil type, and seedbed conditions can help maximize the economic yield potential of a wheat crop.
• Planting into a firm seedbed can help improve seed-to-soil contact, thus promoting even germination and emergence.

Introduction

Profitable wheat production begins with planting at the optimum time for the area, using high quality seed, starting with adequate preplant fertility, planting into a weed free seed bed, and using planting rates recommended for your geography and yield environment.¹ To help maximize yield potential, measures must be taken at and before the time of planting to select the best performing varieties, to check seeder calibration, and to make sure planting conditions are all optimum to establishing a high yielding wheat crop.

Seeder Calibration

Calibration is simply the process of confirming the rate of delivery of an input such as fertilizer, herbicide, or seed.² The crucial but often overlooked step of calibration can help control seed costs and benefit a grower’s bottom line by optimizing seeding rates to achieve the proper populations, thus reducing under- or over-seeding and helping to maximize yield potential.

Wheat kernel size can vary by as much as 50%. Therefore, the drill should be calibrated for each seed variety and seed lot that is used. The number of seeds per pound (seeds/lb) should be listed on the seed tag along with germination rates, though seed label requirements vary from state to state.³ If the seeds/lb is not listed on the seed tag, it can be determined by first counting out 1,000 seeds, weighing them on a scale capable of weighing in grams, and then doing the following calculation. First, take 453.6 and divide it by the measured weight of the seeds in grams. Second, multiply that by 1,000 (or the number of seeds counted). This is the number of seeds per pound. The mathematical formula for this calculation is.³

(453.6 ÷ weight of seeds in grams) × number of seeds weighed = number of seeds per pound

When you purchase WestBred^® Wheat varieties, work with your local WestBred^® supplier to get recommendations on the optimum seeding rate for your planting date, available water, and geography for the variety you purchased. You might consider increasing the seeding rate when planting into less-than-ideal seedbed conditions, such as no-till or cloddy fields, or when planting at a late date. Seeding rates vary by region, so it is best to consult with your local WestBred^® Seed Supplier, Technical Product Manager, or Extension service for the best seeding rate for the projected planting date, wheat variety, and end use.

Calculating Seeding Rate

There are multiple methods available to calibrate a drill. Most popular methods start by determining the desired seeding rate.

To determine your seeding rate, multiply your desired plant population by the pure live seed (PLS) for each lot. For example, let’s say you have a wheat seed lot with 90% PLS and you want a plant population of 900,000 plants per acre.

To calculate the seeding rate per acre, take 900,000 (desired plant population) and divide it by 0.90 (the percent PLS written as a decimal). In this situation, you would need a seeding rate of 1,000,000 seeds per acre to achieve your desired 900,000 plants per acre population.

900,000 plants per acre ÷ 0.9 PLS = 1,000,000 seeds per acre

If you need to calculate the number of seeds per pound, you can use the formula provided above. In this example, let’s say you counted out 1,000 seeds, weighed them on a gram scale, and got a weight of 35 grams. Divide 453.6 by 35 grams, which equals 12.96. Multiply 12.96 by 1,000, which equals 12,960 seeds per lb.

(453.6 ÷ 35 g) × 1,000 seeds = 12,960 seeds per pound

From there, you can calculate how many pounds of seed are needed per acre by dividing the number of seeds per acre by the number of seeds per pound. In this example, using the previously calculated values, this is:

1,000,000 seeds per acre ÷ 12,960 seeds per pound = 77.16 pounds of seed per acre

You can further calculate the predicted number of plants per square foot by taking the desired plant population (900,000 in this example) and dividing that by 43,560, to get 20.7 plants per square foot.

900,000 plants per acre ÷ 43,560 = 20.7 plants per square foot

A seeding rate calculator to calculate the seeding rate needed to achieve the target plant stand (plants/sq ft) is available at this link, Seeding Rate Calculator.⁴

Setting a Drill

Once the seeding rate has been determined, start by referring to the chart of the manufacturer's settings for the desired pounds per acre. This chart is often located on the drill box. Use the chart as a starting point for setting the drill to the desired seeding rate.

Drill Calibration Steps

• Use the settings on the manufacturer’s chart and then run the drill for a measured test distance in the field, such as 100 ft.
• Collect the seeds that were dispensed during the drill test run.
• Repeat the drill run and the seed collection several times, counting the number of drill runs.
• Weigh the total collected seed.
• Use the following formula to determine the seeing rate in lb of seed /acre: ²

weight of seed in grams ÷ number of drill runs ÷ row spacing in inches × 12 = seeding rate in pounds per acre

If the seeding rate calculated in the previous step does not match your desired seeding rate, adjust the drill calibration by adjusting the seed metering system accordingly. Repeat the process until your desired seeding rate is achieved.

This method can be adapted for use in the shop by measuring the number of wheel revolutions needed to travel the 100 ft testing distance. The seeds would then be collected into a bag or bucket and weighed. To calculate the number of wheel revolutions needed to travel 100 ft, use the following formula:

110 ft ÷ wheel circumference in ft = number of wheel revolutions

Note: The in-shop test uses 110 ft instead of 100 ft to compensate for wheel slippage in the field.

Once this calculation is complete, use the number of wheel rotations to complete several test runs, collect the seed, weigh the total seed collected, and use the formula for the in-field test to calculate the seeding rate in lb/acre.

Setting an Air Seeder Seeding Rate

Calibrating an Air Seeder Without a Seeder Scale

Air seeders should be calibrated by following the procedure in the operator’s manual. If your air seeder has a monitor (as most do), follow the calibration directions on the monitor. If the desired planting rate is not achieved after following those directions, adjust the seeding rate and repeat the steps according to the monitor’s directions. Here are some additional tips to make the calibration process easier:

• Make sure the correct color or type of meter roller is being used for the wheat crop to be planted.
• Many units have a catch box/bag that can be attached directly under the seed meter, which is used for calibration.
• It is important to first charge the air seeder unit to make sure the system is full of seed, and then run a meter rate verification test to verify the meter is putting out the correct rate of seed for the selected seed lot.
• When weighing the collected seed, ensure that the scale is only measuring seed weight and that the bag weight is subtracted from the weight of the seed collected.

Calibrating an Air Seeder with a Seeder Scale

Whether or not your air seeder has a seeder scale, it should still be calibrated by following the procedure in the operator’s manual. This type of calibration can be done at any time throughout the planting season, such as when planting conditions change or if seed lots are changed. If the seeding rate does not match the desired rate after calibration, adjust the calibration number up or down to change the seeding rate. Here are some additional tips for calibrating an air seeder with a seeder scale:

• Make sure the correct color or type of meter roller is being used for the wheat crop to be planted.
• It is important to first run the drill in the field for a short distance to charge the air seeder unit and make sure the system is full of seed.
• When recording the weight of seed in the drill, the drill should be at least half full of seed.
• Stop seeding after three to five acres.
• Record the number of acres seeded.
• Determine the amount of weight that was seeded.
• Divide the pounds of seed planted by the number of acres planted to determine the pounds of seed planted per acre.
• Check the seeding unit settings and observe its performance by checking how the seed is being placed in the field.

Product Selection

Evaluating and selecting wheat varieties with high yield potential for the end use, test weight, and appropriate insect and disease tolerance for your geography is the first step toward helping to maximize economic yield potential. Since each variety will have specific strengths and weaknesses, more than one product should be considered. Choosing multiple varieties of varying maturities can also help mitigate the risks associated with agronomic challenges such as insects, diseases, and weather, and can aid in harvest scheduling.

Planting Date

Like seeding rates, ideal planting dates will vary by region. Spring wheat should be planted when the average two-inch soil temperature exceeds 40 °F. Planting too early in the spring can delay germination and result in weaker, less vigorous plants.

Hessian fly-free dates should be considered when determining your planting date for winter wheat to be harvested for grain in the fall. The fly-free date is a prediction of when most Hessian fly adults (Figure 2) will no longer be alive or able to lay eggs in wheat fields.⁵ Planting after the fly-free date may also reduce the incidence of disease, such as barley yellow dwarf virus (BYDV), as the population of disease transmitting aphids declines after these dates. It is always best to consult your local WestBred^® Seed Supplier, Technical Product Manager, or Extension service for recommended planting dates in your area.

Planting Depth

A planting depth of 1 to 1.5 inches deep is recommended for most semi-dwarf wheat varieties. Taller wheat varieties with a longer coleoptile can be planed deeper, often up to 2.5 inches deep depending on growing conditions. But note that warm soil conditions can shorten the coleoptile length.

Planting into moisture will help ensure an even stand and emergence. However, if planting into dry conditions is necessary, avoid planting depths of less than one inch. Shallow planting depths in dry conditions can increase the risk of premature germination after light rains, potentially causing seeds to sprout and die from inadequate moisture below the seed. Planting depths of one to 1.5 inches help ensure that seeds receive enough rain to thoroughly wet the seedbed area in dry conditions, while encouraging proper crown root development and reducing the risk of lodging at maturity. A wheat seed will begin germination by absorbing moisture and oxygen from the soil. In favorable conditions, emergence should occur five to seven days after planting. However, in cool, excessively dry or wet soils, or where seeding depth was greater than 1.5 inches, emergence may be delayed and potentially more variable.

Proper tractor speed is also important when drilling wheat. In most cases a speed of five to six miles per hour is recommended. However, in rougher field conditions, slower speeds should be used to reduce drill bouncing and to help maintain a more uniform and proper seeding depth.

Seedbed Preparation

Wheat should always be planted into a firm seedbed to provide good seed-to-soil contact. This will help the seed to rapidly absorb soil moisture to encourage uniform germination and emergence. Seeding into a fluffy or loose seedbed is one of the leading causes of winter injury such as winterkill, root rot, and crown rot. Thick or bunched residue can also pose a threat to even stands. Residue from the previous crop should be removed or uniformly spread, particularly in no-till operations. If planting a field back to wheat following a previous wheat crop, make sure that the residue is evenly distributed, and the straw is dry. Planting into damp or tough wheat straw can lead to hair-pinning, resulting in poor seed-to-soil contact that may reduce uniform wheat emergence.

Weed Management

Weeds growing along with the wheat crop can deplete soil moisture, sunlight, and nutrients available for growth, and can harbor insects and diseases that may reduce wheat yield and quality. A healthy, vigorous wheat crop is one of the best tools for suppressing weeds. Growers should be careful to only plant certified wheat seed that is free of weed seeds.

Weed species should be accurately identified before creating a weed management plan. Depending on the herbicide selected, an application may only be appropriate during certain stages of wheat growth to avoid crop damage. When applied post-emergence on wheat, Beyond® herbicide provides broad-spectrum grass and broadleaf weed control. Always read and follow pesticide label restrictions to ensure maximum effectiveness and to reduce the chances of crop damage.

For more information about winter wheat production go to Establishing and assessing winter wheat stands. This article explores several different end uses for a wheat crop and how they affect planting date and seeding rate.

Sources:

¹Weisz, R., Cowger, C., Reisig, D., and Suchoff, D. 2024. Chapter 4: Crop Production Management – Wheat and Small Grains. In D. Suchoff and H. Moshay. North Carolina organic commodities production guide. NC State Extension Publications. https://content.ces.ncsu.edu/north-carolina-organic-commodities-production-guide/chapter-4-crop-production-management-organic-wheat-and-small-grains

² 2012. How to calibrate the seeder between seed lots. Canola Watch, Plant Establishment. Issue 11. https://www.canolacouncil.org/canola-watch/2012/05/09/how-to-calibrate-the-seeder-between-seed-lots/

³Brown, K. Calculating seeding rates. Montana State University Extension in Roosevelt County. https://www.montana.edu/extension/roosevelt/calcseedrates.html

⁴2024. Seeding rate calculator. Alberta Grains. https://www.albertagrains.com/seeding-rate-calculator

⁵Insect control. Ohio State University Extension, Agronomic Crops Network. https://agcrops.osu.edu/node/4392

Web sources verified 10/15/2024. 1710_453641