The Importance of Spacing and Density

Evaluating plant spacing is one of the best techniques for identifying potential equipment problems and therefore ways to improve next season’s crop. Getting into fields while plants are still young makes this task much easier.

Calculating the standard deviation is the best way to check consistency of spacing. Measure the distance between 30 consecutive plants. Repeat this process four times at randomly selected points. The standard deviation is a common statistical measure that most spreadsheet programs will calculate.

According to agronomy experts, for every one-inch increase in the standard deviation above a threshold of two inches, the yield-loss potential for corn is about 2 ½ bushels an acre.

Some problems that may be observed while measuring standard deviation are missing plants, irregular spacing, and two-plant hills. Each problem indicates planter malfunction and can lead to a loss of yield.

Experts speculate that doubles or triples could weaken a crop’s ability to handle stress, and these close neighbors compete for water and nutrients. Skips affect yield slightly more than doubles, and have the most detrimental effect in fields where population is at or slightly below the optimum.

Double-dropped, irregularly-spaced, and skipped seeds are often the result of the planter being operated at a speed that is higher than recommended in the owner’s manual. Typically, the speed for planting should be limited to 4 ½ to 5 miles per hour.

Worn seed meter components, poorly lubricated chains and fittings, and mismatch of seed size to planter plate or disc size can also cause the uneven plant density that negatively affects yields.

Variation in Emergence Equals Trouble for Yields

Even more important than plant spacing to achieve high yields is uniform emergence. A growth stage difference of two leaves or more between adjacent plants will almost always result in the smaller (younger) of the plants being barren or producing nubbins. Ideally, emergence of all plants will occur in a 24-hour period.

Coulter blade selection has an enormous impact on emergence and root development. The proper coulter blade will ensure ideal seed-to-soil contact and fracture soil crusts directly around the seedling for excellent closure. Through coulter tillage techniques, the capacity of the soil to hold moisture is
improved, aiding germination and uniform emergence.

Check rows for excessive and large residue in seed trenches. When properly used, residue managers eliminate planter bounce and hairpinning, two factors that can contribute to problems with seed placement and seed-to-soil contact.

Seeds planted too deep or shallow due to poor planter adjustment will also contribute to emergence problems. If scouting reveals seeds that have swelled but not sprouted, they may have been planted too shallow. Nodal roots developing above ground also point to shallow planting. These roots are exposed to more environmental conditions and have a higher probability of encountering disease and nutrientdeficiency.

Seeds that emerge and are leafing out underground could be the result of too deep a placement. No emergence could also be the result if seeds are planted too deep. As a rule of thumb, corn should be planted about 2 inches deep. This depth will need to be adjusted depending on soil moisture.

If scouting reveals evidence of poor seed-trench closing, poorly adjusted or selected closing wheels could be to blame. If the seed trench is not closed properly, all previous efforts to improve yield are jeopardized. There are a wide variety of closing products currently available on the market to prevent
such misfortune. Spiked-closing wheels and drag chains are two popular choices.

Effective closing wheels gently firm the soil around the seed, leaving loose soil above the seed for ideal seed-to-soil contact, eliminating soil crusting and air pockets, and promoting fast even emergence. Improperly adjusted closing wheels could cause sidewall compaction and uneven stands. Adjust the spring pressure on the closing wheels according to soil type and moisture. Correctly adjusted springpressure eliminates air pockets in the seed furrow and covers the seed without creating compaction on top of the seed.

older leaves may be caused by a shortage of mobile nutrients such as nitrogen, potassium, and magnesium. In younger leaves, it may indicate a deficiency of an immobile nutrient such as sulfur or iron. Stunting may be the only indication of a lack of phosphorous.

If you notice deficiencies during scouting, your plants may have already compromised yield potential. Side dressing additional nutrients may be an option to boost yields before harvest, but consider the addition of a starter fertilizer when planting next year to ensure your crops never go hungry.

Choosing the correct placement and minimizing disturbance when placing starter fertilizer is critical, but if correctly placed, the benefits will be apparent in larger, healthy, deep green plants. A pass through the field before or during planting with precision fertilizer injection equipment puts fertilizer in the optimum place for seeds and young roots to access needed nutrients. Roots continue to encounter nutrients during critical growth stages, making starter fertilizer a good investment in many situations.

Scouting Now Sets the Stage for 2011

A scouting expedition to check seed density and spacing along with uniform emergence has endless benefits. The trip can reveal problems that can be corrected with relatively inexpensive adjustments to equipment and processes, or a change to the nutrient management plan. Awareness and commitment to improvement will result in higher yields from future crops.