Scrutinize no-till plant stands

This fifth article in the Tough No-till Q&A series tackles evaluating no-till crop stands. Russell McLucas, Pennsylvania No-Till Alliance board member, and Del Voight, Penn State University Extension grain crop specialist, address concerns and the secrets to high-yielding stands.

McLucas, past chairman of the Pennsylvania Corn Growers Association and 30-year veteran no-tiller, farms near McConnellsburg, Pa. E-mail questions to him at russmclucas@embarqmail.com, and Voight at dgv1@psu.edu.

Key Points

• Add 20% to seed corn planting rate to reach plant population goal.

• Weeds often gain the upper hand in replant situations.

• Poor plant spacing is common in no-till corn, and very costly in yields.


Q: Do I need to make a tougher assessment of plant stands in no-till fields than in minimum-till fields?

McLucas: Yes, and be more careful when you plant the first time. To redo or not to redo; that’s the question when considering stand estimates. The single-most driving point that I consider is the time when I’m evaluating the stand.

For corn, 18,000 plants per acre on June 5 is a very different issue than 18,000 plants per acre on May 5. Based on prime planting time frame and known yield losses from untimely plantings, a 60% stand June 5 is probably best left alone. But a 60% stand on May 15 is a likely candidate for a do-over.

Look very hard at stand consistency. Is it even, or are there gaps or doubles?

Soybeans, again, are date-dependant. For instance, 125,000 plants per acre can make a very acceptable yield if the stand is consistent.

In small grains, watch closely for non-vigorous stands. I’ve seen decent emergence followed by a standstill, and then massive stand die-offs. From personal experience, paying close attention to planting equipment and soil conditions beforehand pays massive rewards in not having to redo afterward.

Voight: With only a month or so left until planting, this is a great time to review key goals in stand assessment. Here are some points to consider:

Know your goal. With small grains, 1.5 million plants per acre is the goal. If tillering is poor, nitrogen applications can boost spring tillering if assessed early. For soybeans, shoot for a final stand of 150,000 ppa. For corn, aim for 28,000 to 34,000 ppa. Those final stands should be uniform, indicating same-day germination and subsequent emergence.

Compensate for field conditions. Assuming your planter is up to achieving that goal, you’ll need to compensate seed drop for germination differences and planting conditions, pests, and weather.

With no-till, I commonly add 20% to the seed drop from the goal. For instance, if you desire a 30,000 ppa final stand, you’d drop 36,000 seeds to achieve that goal.

Calculate stand count. Once you begin to see germination, you can start determining the field population.

Start by converting the row width from inches to feet by dividing by 12 inches. Then, divide the square feet per acre (43,560) by the foot of row. This gives you linear feet. Next, multiply the number of plants you find per foot in the field by that number to get plants per acre.

Using corn, for example, 30-inch rows divided by 12 is 2.5 feet. Divide 43,560 square feet in an acre by 2.5 to get 17,424 linear feet. If you get one plant per foot, you have 17,424 plants per acre. If you get two, then you have 34,848 plants.

You can also use a plant stand calculator probably available in seed books to figure stand counts on 1/1000th of an acre. Do a simple calculation, but do this in several places to find the field’s average.

Check stand deviation.For each inch of deviation, university research suggests a 2.5- to 5-bushel-per-acre loss. This is more critical as populations are increased with traited corn.

Most corn no-tillers averaging more than 200 bushels per acre record stand deviations of less than 2. Yet an Extension survey of Pennsylvania growers showed an average deviation of 4. So there’s room for improvement.

As McLucas points out, planting and replanting times relate to yield loss as you move away from optimum planting date. This comes into play as stands are deemed inadequate and a replant is in question.

For instance, in southeastern Pennsylvania, planting corn on April 25 will produce 100% of optimum yield potential. By May 19, it slips to 90%, and by May 29, it’s 80%. That’s a 20% loss in three weeks.

So if you want to replant on, say, May 29, you will lose 20% of your yield. If you don’t replant, you’ll only lose 12%. In that case, it probably won’t pay.

Baker is a consultant for the Pennsylvania No-Till Alliance.

Don’t allow weeds to gain ground

A poor plant stand is an open invitation to weeds, according to Del Voight, Penn State Extension crop specialist. Weeds will invade anywhere light is allowed through to the soil, and they will overrun poor stands.

This is a critical issue when considering replants. Review any pesticides applied and re-crop restrictions. Also check with your dealer to determine policy for replant support.

Check with your local Cooperative Extension for more on corn and soybean replant decisions. Or see Table 4-8 in the Penn State Agronomy Guide on the Web at agguide.agronomy.psu.edu.

This article published in the March, 2010 edition of AMERICAN AGRICULTURIST.

All rights reserved. Copyright Farm Progress Cos. 2010.