Project grain fill

By John Brien, AgriGold

Grain fill is a critical part of a corn plant’s life, but is often overlooked because it is kind of slow, boring and uneventful to watch. What is actually occurring soon after pollination is utterly amazing considering an acre of corn has to “build” over 11,200 pounds of dry matter to equal 200 bushel of grain yield. Therefore grain fill is anything but boring and is vital for high yields.

Grain fill is the period of corn growth and development between pollination and black layering (or physiological maturity). During grain fill the corn plant is using their leaves to capture sunlight to drive photosynthesis that in turn produces the sugars the plant needs to build yield. The corn plant also uses its roots to acquire moisture and nutrients to build the dry matter. Therefore the more sunlight a corn plant can intercept and the more nutrients and water it can aquire, equates to more optimal grain fill and therefore higher yield potential.

What conditions lead to optimal grain fill? Optimal grain fill begins with having a long window of opportunity. The typical grain fill period for a corn crop is 45 to 60 days. If a grower is able to keep their corn fields in grain fill mode for 60+ days, the chance for high yields increase exponentially. The overall conditions growers should seek for optimal grain fill begin with mild daytime and night time temperatures. Temperatures in the mid 70s during the day and mid 60s at night are ideal. The closer to 90 degrees during the daytime the sooner the corn plant will shut down and shorten its grain fill window. Likewise nighttime temperatures over 70 degrees never allows the corn plant to rest and keeps the engine running and speeds the corn plant right through grain fill.

Another component to an optimal grain fill window is maintaining a healthy upper canopy in the corn plant. The goal is to keep the upper third of the corn plant green and healthy as long as possible. A grower can keep the upper canopy healthy by limiting the amount of leaf diseases the corn plant has on its upper leaves and by reducing stress caused by nutrient deficiency, tillage layers, compaction layers and/or sidewall compaction caused by the corn planter that often leads to premature death as witnessed by the corn plant dying from the top down.

The third factor in extending the grain filling period is ensuring the corn crop is not starved for any nutrients, especially nitrogen after pollination. Corn plants that have adequate nutrients will be able to fully capitalize on the captured sunlight used for photosynthesis. Also nutrient deficiency causes the corn plant to cannibalize itself to ensure the ear has everything it needs and can therefore lead to root rots that lead to premature death and a shorter grain fill window.

The final component to a long grain fill period is adequate moisture. Water is the driving medium of all portions of grain fill. Without water, the corn plant is unable to acquire nutrients via the soil and cannot perform most metabolic reactions in the corn plant that are responsible for growth and grain fill. Rainfall is unpredictable and most growers have no control over when, where and how much they will receive. Therefore to help the corn plant not to shorten its grain fill period during short periods of dryness, growers need to concentrate on establishing a deep and robust root system that will help “weather proof” their corn fields. Deep roots and ample soil oxygen can help reduce stress during grain fill and allow the corn plant to maximize yields under all conditions.

Grain fill is complicated and involves many different factors. Some of the factors are out of a growers hands, such as temperatures and rainfall events, but the job of a corn grower is to evaluate the factors they can impact, such as keeping the canopy green and growing along with establishing a deep, robust root system, and then put a plan of attack together to help lengthen grain fill as long as possible to maximize their corn yields.

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