By Randy Weisz and Ron Heiniger
When planting is done on time, the planting goal is to have 22 to 25 seedlings per square foot. This requires planting 30 to 35 high-quality seeds that have at least 90 percent germination. Table 6-1, below, gives seeds per row foot to achieve this plant density. For each week past the end of the opening wheat planting dates (Figure 6-1), increase seeding rates by 15 percent.
Wheat seed size can vary by up to 50 percent in size depending on variety, production season, degree of cleaning, and seed treatments used. Consequently, planting wheat based on bushels per acre can result in substantial over- or underseeding, which is why this practice is not recommended. Planting by bushels per acre will cost the producer either in unnecessary seed or lost yield. The best approach is to calibrate the drill to plant the correct number of seeds per foot of row (see Drill Calibration Procedures at the end of this file). Converting bushels per acre to seeds per foot of row is not a substitution for drill calibration. At best, it will result in a rough estimate of a seeding rate.
Figure 6-1. Opening planting dates for North Carolina. Increase seeding rates by 15 percent each week after the end of the opening dates for your area.
| Table 6-1. Optimal Seeding Rates | |||
Seed per Row Foot for Various Row Spacings |
|||
Row Width (inches) |
On Time |
2 Weeks Late* |
4 Weeks Late* |
4 |
12 |
16 |
19 |
6 |
18 |
23 |
29 |
7 |
20 |
26 |
32 |
8 |
22 |
29 |
35 |
*Late means “after the opening planting dates” for the areas as shown on in Figure 6-1.
Wheat size can vary by up to 50 percent in size depending on variety, production season, degree of cleaning, and seed treatments used. Consequently, planting wheat based on bushels per acre can result in substantial over- or underseeding, which is why this practice is not recommended. Planting by bushels per acre will cost the producer either in unnecessary seed or lost yield. The best approach is to calibrate the drill to plant the correct number of seeds per foot of row (see Drill Calibration Procedures at the end of this document). Converting bushels per acre to seeds per foot of row is not a substitution for drill calibration. At best, it will result in a rough estimate of a seeding rate.
Figure 2. John Deere no-till drill setting required to plant 26 wheat seed per row foot for each variety and seed treatment used in this on-farm experiment in 2001.
Here is an example. In 2001, Gene Hunter did an on-farm drill calibration experiment. He planted 15 varieties of wheat (most with and without GauchoXT seed treatment) with his John Deere no-till drill set for 7.5-inch rows. He calibrated his drill for each variety and each seed treatment to put out 26 seeds per row foot. The results are shown in Figure 6-2, above.
The drill seeding changed from 27 all the way to 45 depending on the variety and seed treatment! If P 26R61 had been drilled at the same seeding required for Roane, it would have been extremely underseeded. On average, Hunter found that if his drill was calibrated correctly for an untreated variety, and he switched to the same variety treated with GauchoXT, it would be 20 percent underseeded if he did not recalibrate. In conclusion, drill seedings required to achieve the correct wheat plant population vary widely between varieties and seed treatments. There is no substitute for correctly calibrating the drill.
Oats should be planted at 2 bushels per acre, and rye at 1 to 1.5 bushels per acre. The seeding rate should be increased by 15 percent for every 2 weeks planting is delayed.
Newer wheat varieties have semidwarf genes that reduce overall plant height. These also reduce the chances of seedling emergence if the seeds are placed too deep. Conversely, a shallow planting can result in uneven germination due to dry soil. Small grainseeds should be planted 1 to 1.5 inches deep when soil moisture levels are adequate, and slightly deeper, if moisture is deficient.
No-till planting causes special challenges related to uneven seed beds and surface residue. Seeds should still be planted 1 to 1.5 inches below the soil surface. When residue from the previous crop is unevenly distributed, achieving this uniform and correct planting depth can be difficult. Where the residue is uneven, the planting depth may be too shallow under high residue and too deep in areas of light residue. This can result in thin stands and excessive risk of winter-kill. Begin preparation for no-till small grains by evenly distributing crop residues while harvesting the previous crop.
Start with a seeding rate that is 20 percent higher than what is recommended for conventional tillage. When no-till drilling, stop periodically and make sure that the planting depth is uniform and correct. Determine seedling density after crop emergence. If there are 22 to 25 vigorous seedlings per square foot (if the planting was done on time), the no-till drilling operation was successful. If fewer seedlings are present, determine the cause of the reduced stand. If all causes other than seeding rate can be eliminated, use a higher seeding rate in the future.
Broadcast seeding, which is usually done with a lime spreader, is a quick way to plant large acreage. It requires at least 50 percent more seed per acre than drilling small grain, and it also requires disking or harrowing to give good seed-soil contact. Broadcast seeding often results in more uneven stands and lower yields than drilling.
Small grains may be planted by over-seeding in standing, unharvested crops. To follow soybeans, seed as the first leaves begin to drop.
Following cotton, seed just before defoliation. The small grain can be injured or killed if it is growing when a desiccant is used. If no desiccant is used, seed when the leaves begin to drop. The leaves will form a mulch that conserves moisture and enhances germination. The success or failure of over-seeding depends on available moisture. Wheat and rye over-seed better than oats or barley.
No matter how seed is planted, the grower must check stands shortly after emergence. Is the stand uniform? Determine the number of healthy seedlings present in a square foot. There should be 22 to 25 seedlings (or more, if planted late). If the stand is uniform and the plant density is correct, then the planting was successful.
Step 1. Choose the correct seeding rate based on the planting date map and the degree of lateness.
Step 2. Calculate the number of seeds required in 50 drill-row feet. For example, if a grower plants on time in 7-inch wide rows, an appropriate seeding rate would be 20 seeds per drill-row foot times 50 feet, which equals 1,000 seeds planted every 50 feet of row. Count 1,000 seeds of each variety, and put the seed in a graduated tube, such as a rain gauge or clean pesticide measuring tube. Mark the level of the 1,000 seeds in the tube.
Step 3. Hook a tractor to the grain drill so that the drive wheels of the drill can be raised off the ground, and the drive gears can be engaged. Jack up the drive wheel so that it clears the ground, and turn the wheel several revolutions to be certain that all working parts are turning freely. Check all drill spouts for blockages.
Step 4. Determine the number of revolutions the drive wheel must turn to travel 50 feet. This can be done in one of two ways.
Option A. Measure the distance around the drive wheel. The distance can be measured directly with a tape measure or indirectly by measuring the total distance across the tire and multiplying that distance by a factor of 3.2. For example, if the drill wheel measures 30 inches from tread to tread, then the distance around the tire should measure 96 inches (30 inches x 3.2). The number of tire revolutions per 50 feet is calculated by the following formulas:
Inches traveled in 50 ft = 50 ft x 12 inches/ft = 600 inches
and
Number of tire revolutions per 50 ft = 600 inches divided by 96 inches per revolution =
6.25 revolutions of the tire per 50 ft of travel.
Option B. Measure 50 feet in a field and count the number of revolutions the drive wheel makes in 50 feet. (Always check the number of tire revolutions per 50 feet on soil conditions similar to those that will be experienced during planting. This is especially important if the drive wheel is small and slippage may occur.)
Step 5: Calibrate the drill as follows:
a. Raise the drive wheel off the ground so it can be easily turned.
b. Put at least a quart of seed of the lot to be calibrated over each of two adjacent drill spouts.
c. Turn the drive wheel several revolutions so that seed is flowing through the drill, and stop the wheel at a convenient mark, such as when the valve stem is straight up.
d. Remove the rubber boot from the two drill spouts with seed and place a container under each spout to catch the seed. Catch the seed from each spout in a separate container.
e. Adjust the seeding rate to a setting that is expected to be close, and turn the drive wheel the appropriate number of turns for traveling a distance of 50 feet (determined in Step 4).
f. Pour the seed from one row into the precalibrated tube from Step 2. Check the second row the same way.
g. If the seeding rate is too high or too low, change the drill setting, and repeat steps e and f in this list until the appropriate number of seeds is obtained.
h. Steps d through g should be repeated on two rows on the opposite side of the drill if the drill is driven by more than one drive wheel.
i. Remove seed from the drill and put in the next variety, or seed lot, to be calibrated. Repeat the procedure.
Some materials in this chapter were adapted from Intensive Red Winter Wheat: A Management Guide. Blacksburg: Virginia Polytechnic Institute Cooperative Extension Service.
This file is a chapter from Small Grains Production Guide, 2004-05. Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the NC Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension Center.
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Last Revised Sept. 2004