Issue # 1, May 1st, 2007

• NDAWN 

• Planting Depths

• Custom Rates

NDAWN to Determine GDD for Field Crops

    The North Dakota Agricultural Weather Network (NDAWN) system can be used to determine growing degree days (GDD's) to estimate crop growth for field crops throughout the growing season.  This can be used to determine when to scout for various crop pests or for the correct growth stage for herbicide and fungicide applications.

    How are GDD determined?   GDD are calculated using the following formula.

                     Min. daily temp + Max daily temp  minus Base Temperature = Daily GDD
                                                2

    Base Temperatures vary from cool season and warm season crops.  When the temperature falls below the minimum base temperature or exceeds the maximum base temperature for the crop in question, then the minimum or maximum base temperature is used in the calculation.  The following table lists the minimum and maximum temperatures for three crops.

    It is important to be sure to use the correct base temperature for the crop.  When comparing GDD's between wheat and corn, will be totally different for the same amount of days due to the different base temperatures used.   For example, Small grains require about 180 GDD"s for germination and emergence.  While corn requires 120 GDD's for germination and emergence.  Wheat will requires 140 GDD's for each leaf whether accumulated in four days or ten days and about 2400 GDD's to reach maturity, which can range from 83 to 100 calendar days.  Corn leaf development is described be two response curves.  Emergence to leaf stage V10 (ten visible collars) takes 80 GDD's per leaf.  From V10 to the final leaf is faster and is approximately on leaf every 50 GDD's.

    The NDAWN system has other features that measures rainfall, wind speed, wind direction, solar radiation, dew point, wind chill, soil temps and relative humidity.  Us the following link for the NDAWN system. 

Planting Depth Important for Good Emergence

    Plant emergence is the first yield component for field crops.  Poor emergence will limit the amount of plants available to produce seed and also be more susceptible for weed competition due to a reduced canopy.  Each crop has a certain type of emergence. 

    Wheat & Barley:  Has an elongating coleoptile type of emergence.  The coleoptile is the soil penetrating mechanism.  The length of the coleoptile will determine how deep the plant can emerge from.  Standard height varieties can emerge from deeper planting depths than semi-dwarf varieties due to the extention of the coleoptile.  Since most of the HRSW we raise are semi-dawrf or medium height varieties, planting depths should be no deeper than 2 inches.  Once the coleoptile breaks the soil surface into the sunlight, the true leaves will emerge.  If the coleoptile is at full extension and cannot break the soil surface, the true leaves will emerge below the soil surface.  The true leaves are not capable to penetrate the soil and thus the plant will die.  This is a common occurrence in crusted soil conditions.
    Once the coleoptile breaks the soil surface and the true leave emerge, the growing point will remain below the soil surface until the plant begins to tiller.  This allows the plant to be protected from frost through the early growth stages.  The vegetative growth can be burned off but the plant can still survive.  

    Corn:  Has an elongating first internode and coleoptile type of emergence.  Both the coleoptile and first internode elongate simultaneously during seedling emergence.  Once the coleoptile breaks the surface into the sunlight, the true leaves will emerge.  The growing point will remain below the surface and still be tolerant to early season frost.  This type of emergence allows corn to be planted up to 4 inches, but with good planting moisture, 2 to 3 inches are ideal.

    Sunflower & Soybean:  Has an active hypocotyl type of emergence.  The hypocotyl begins to elongate and forms a hypocotyl arch.  This serves as the soil penetrating structure.  The cotyledons are pulled through the soil until the hypocotyl arch breaks the soil surface into the sunlight when the plant will straighten and the coleoptiles open up and the true leaves begin to emerge.  The growing point is above the soil surface at this point and is subject to early season frosts.  Planting depths for these crops is recommended no deeper than 2 inches.  Sunflowers can be planted deeper but soybeans, planting depths should be in the 1 to 1 1/2 inch range and no deeper than 2 inches.

Custom Rates

    Each spring the Extension office receives requests for the ND Agricultural Statistics Service Custom Rates bulletin.  The last printing of this publication was in 2004.  These rates no longer are current with today's fuel prices.  The next printing is the fall of 2007.  The Statistics Service will be conducting a survey this summer and will be requesting information from producers and commercial applicators.  If you are contacted, they would greatly appreciate your support to update this publication.  But for the mean time, we do not have a current price for today.  The only thing you can do is to look at how much more fuel prices are affecting operations than 2004.

Please Contact Our Office For Additional Information
E-mail: john.swenson@ndsu.edu
Go to the 2007 AgAlert Index Page