Corn Stand Establishment and Planter Maintenance

A 'hard' copy of this article is available by contacting the author . Ask for publication AGRY-91-01.

The importance of timely planter maintenance and adjustment simply cannot be overlooked. These relatively low-cost procedures can prevent potential yield losses as high as 20 bushels per acre by improving the uniformity of seed placement during planting. This document discusses the ins and outs of planter maintenance.

What Is Plant Spacing Variability?

Variability of plant-to-plant spacing usually consists of high percentages of crowded plants (doubles, triples, or worse); often accompanied by long skips within the row. Seeds need to be dropped uniformly within the row in order to achieve the maximum yield for any given plant population.

How important is it for producers to establish as uniform a stand of corn as they possibly can? What effect does uneven plant spacing have on grain yield? First of all, you must be able to measure this variability in order to know the size of your problem.

Measuring Plant Spacing Variability.

Plant spacing variability in a field can be determined by first measuring actual plant-to-plant spacing. Typically, I measure plant spacings in two or three locations throughout a field. Within each location, I measure all of the plant-to-plant spacings (inches between plants) that occur in 25 feet of row and repeat this for each row of the planter unit.

Within-row spacing variability can then be quantified by calculating what is called the standard deviation of the plant-to-plant spacings in the sub-samples. The standard deviation is a common statistical measure of the spread or variation of a group of individual measurements. Its units of measure are identical to whatever you are measuring.

The standard deviation can be calculated by hand, but is better suited to the use of statistical calculators or computer spreadsheets. Most spreadsheet programs, for example, can easily calculate a standard deviation value for a column of numbers.

Effect of Uneven Plant Spacing on Yield.

Yield data from our small-plot research and from replicated strip trials indicate that about 2.5 bushels per acre are lost for every 1 inch increase in the standard deviation of the plant-to-plant spacings. We've measured plant spacing variability in nearly 100 commercial fields during the past several years. Standard deviations have ranged from as low as 2 inches (pretty darn uniform) to as great as 9 inches (extremely variable). About 48% of the fields were within the 4 to 6 inch range of standard deviation.

Based on these data, it appears that the average Indiana corn grower (4- to 6-inch standard deviation) could improve grain yield anywhere from 5 to 10 bushels per acre if within-row plant spacing were improved to the best possible uniformity (which is realistically about a 2-inch standard deviation).

Causes of Plant Spacing Variability.

Plant spacing variability is typically related to misadjusted or malfunctioning planter mechanisms. With finger-pickup style planters, double or triple seed drops may occur from worn finger-pickup mechanisms, mis-adjusted finger tension, worn knockoff brushes, or from driving too fast. Aged seed conveyor belts may not deliver kernels properly to the seed chute. Mis-adjusted air pressure, leaks in the system, worn knockoff brushes, or wrong disc sizes may result in uneven seed drop with air planters.

Planter Guidelines for Preventing Uneven Seed Placement

• With plate-type planters, match the seed grade with the correct planter plate,
• Planters with finger pick-ups should be checked for wear on the back plate and brush, use a feeler gauge to check tension on the fingers, then tighten them correctly,
• Check for wear on double-disc openers and seed tubes.
• Make sure the sprocket settings on the planter transmission are correct.
• Check for worn chains, stiff chain links, and improper tire pressure.
• Lubricate all chains and grease fittings.
• Make sure seed drop tubes are clean and clear of any obstructions.
• Clean seed tube sensors if you have a planter monitor.
• Make sure coulters and disc openers are aligned properly.
• With air planters, match the air pressure to the weight of the seed being planted.

Return to The Corn Growers Guidebook , a WWW resource for corn management systems in Indiana and the eastern CornBelt.

• Return to Chapter 2. Corn Management Information .

The Chat 'n Chew Cafe.

Purdue University Agronomy Extension WWW Home Page.

Purdue Agronomy On-Line! , Purdue's Agronomy Department WWW Home Page.

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