Corn for Grain
Technical
Insight 14

ESTABLISHING YOUR CORN CROP SUCCESSFULLY

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Successful corn emergence is a combination of three key factors – genetics, seed quality and environment (Figure 1 click on image for closer look).

Figure 1

Seed genetics

Hybrid genetics provide the basis for tolerance to cold stress. High seed quality helps ensure that the seed will perform up to its genetic ability. DuPont Pioneer concentrates on selecting the best genetics for consistent performance across a wide range of environments including stressful conditions.

In 2009, a wide range of stress emergence conditions and soil temperatures were seen in Pioneer ‘stress emergence’ (SE) field trials. To demonstrate how stress emergence scores relate to stand establishment in the field, hybrids were grouped by ‘low SE’ – those with an SE rating of 3 or 4, and ‘high SE’ – those with an SE rating of 6 or 7.

Seventy low SE hybrids and 146 high SE hybrids were represented in the trials. Early stand counts for all hybrids within each group were averaged at each location. As stress level increased, both the low SE and high SE hybrids experienced stand loss. However, the hybrids with a SE score of 6 or 7 were able to maintain higher stands as compared to those with a low SE score (Figure 2 click on image for closer look).

Figure 2: Average stand establishment for high and low SE score hybrids in six stress emergence locations in 2009. Locations are sorted from least stressful (left) to most stressful (right) based on average early stand.

Seed quality

DuPont Pioneer Australia’s seed quality program starts in the production field and is present through every process at the Narromine plant. In fact our world class seed production procedures ensure that Pioneer has the highest quality corn seed with minimum germination rats of 90%. But is must be remembered that seed is a living product and so must be treated as such.

Environmental factors

However, even with the best genetics and highest seed quality, environmental factors can still dictate stand establishment.

Corn is a warm-season crop and does best under warm conditions. To help understand optimal corn growth, three hybrids of early, mid and late maturities were germinated in temperatures ranging from 15 to 35 °C. Growth rates of both roots and shoots were measured. All three hybrids were averaged to determine the optimal temperature for corn growth. Both shoots and roots exhibited the fastest growth rate at 30 °C and continued to grow rapidly at 35 °C, suggesting optimal seedling germination and emergence occurs at much higher soil temperatures (Figure 3 click on image for closer look ).

Figure 3: Average early root and shoot growth rates for three hybrids under four soil temperatures ranging from 15 to 35 °C.

Soil temperature remains a critical management factor to help growers minimise the risks associated with suboptimal conditions for successful germination. The timing of stress on seed is also an important factor. For instance, data suggests that planting before a cold front with rain can cause significant stand loss.

To help understand the importance of the timing of cold stress, two hybrids with SE scores of 4 (below average) and 7 (above average) were allowed to germinate in rolled towels for 0, 24, or 48 hours at 25 °C. The hybrids were then subjected to a stress of melting ice for three days and allowed to recover for 4 days at 25 °C). Hybrids were evaluated for the number of normal seedlings reported as percent germination (Figure 4 click on image for closer look).

Figure 4: Germination of two hybrids with below-average genetic potential SE and above-average genetic potential SE following imbibitional chilling induced by melting ice. Ice was applied immediately after planting (0 hours) or after 24 hours or 48 hours of pre-germination in warm conditions.

Both hybrids showed significant stand loss when the cold stress was imposed immediately (0 hours). However, the hybrid with a higher SE score had a higher percent germination than the hybrid with a low SE score. Germination rates for both hybrids were greatly improved if allowed to uptake water and germinate at warmer temperatures for at least 24 hours before the ice was added.

Data suggest that planting just before a stress event such as a cold front can cause significant stand loss. The chances of establishing a good stand are greatly improved if hybrids are allowed to germinate for at least one day in warmer, moist conditions before a cold-stress event.

One reason why temperature during imbibition is critical to corn emergence is the fact that seed imbibes most of the water needed for germination very rapidly. To illustrate the rapid timing of water uptake, seed was submerged in 10 °C water for three hours and weighed at intervals of 30, 60, 120 and 180 minutes to determine water uptake

 

Figure 5: Amount of water taken up by corn seed during the first three hours after submersion in water with a temperature of 10 °C.

The data show that seed imbibes the most water within the first 30 minutes after exposure to saturated conditions. If this early imbibition occurs at cold temperatures, it could kill the seed or result in abnormal seedlings. Growers should not only consider soil temperature at planting, but also the expected temperature when seed begins rapidly soaking up water. Seed planted in warmer, dry soils can still be injured if the dry period is followed by a cold, wet event.

Stubble residue can adversely affect plant establishment because high amounts of residue tends to hold excess water which significantly lowers soil temperature.

Temperature fluctuations can between daytime and night can also negatively impact on stand establishment. Soil temperature can vary diurnally by 6 °C in some soils.

 

Tips for successful corn establishment

    • Aim to plant into soil that is 14°C between 8 am and 9 am at seeding depth.
    • Avoid very early planting dates as this will not greatly improve harvest date but significantly increases risk of an establishment failure.
    • Monitor soil temperatures before and after irrigating.
    • Monitor water temperature when watering up on beds.
    • Pre-irrigate and plant into moisture when growing corn on the flat.
    • Minimise the time it takes to irrigate fields.
    • In very dry fields a pre-irrigation may be the best option.

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Revised: March 2017
Expires: March 2018