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ISSUE 2   May 13, 1999

WHEN IT STOPS RAINING, HOW SOON WILL IT DRY UP?

    Field drying depends on how much water is in the soil, on the soil and how fast water is removed
from soil by evaporation or through plants as transpiration. Most soils within the state have good
moisture to excess moisture. In fields that have been seeded and the water has not ponded, this is a
good thing. However, in many fields the water is ponded and many fields have not yet been seeded.
This is not a good thing.

    Getting rid of the excess water depends on the farm drainage, either man-made or natural. In some
fields, the contour of the land lets water drain away naturally. However, other fields, especially those
in the Valley are land-leveled and contoured to allow water to leave through a system of shallow ditches.
Many of these ditches are farmed through. In dry years, this is fine because crops may do better there
than in other parts of the field because of the high water table. However, this year, these areas will be
tough to seed and seeded crops may need to be reseeded. From 1993 through this year, some
producers would have been ahead to have seeded them into grass rather than try to farm them.

    Tiling is a bad word for some people, but there are those that are beginning to seriously consider this
option, even given the cost. To successfully tile, there needs to be sufficient slope to carry the water
through the tile, there needs to be an outlet for the water into a ditch, stream or river, and there must
not be any legal restrictions to draining certain land areas. If there is any interest in tiling, there are
commercial people that do this kind of work. Be sure that all factors are in place before proceeding.
This is an expensive process that often costs several hundred dollars per acre. Any mistakes are
difficult to fix.

    So when the water leaves the field, how fast does the field dry off? This depends on the amount of
solar radiation received and the wind speed, temperature and relative humidity of the air. The higher amounts
of sun, wind and temperature, the faster the field will dry. The lower the relative humidity, the faster the field
will dry. Very little drying will occur on cloudy, calm, cool, humid days, while hot, dry, windy, sunny days
will dry fields out quickly. The NDSU NDAWN system (North Dakota Agricultural Weather Network)
calculates the potential evaporation for each day from the data it receives at each reporting station. These
data are far superior to pan evaporation data that have been collected in the past. Pan data is subject to
errors from a variety of sources, including thirsty birds, dogs, splashing from wind and rainfall and placement
of pans in relation to shelter belts and buildings. The N-DAWN data are not susceptible to these problems
and are much more likely to help people estimate field drying.

    N-DAWN data are available through the Extension Network and on the internet at
www.ext.nodak.edu/weather Daily data tables provide a summary of all the data measured as calculated
at each station including the potential evapotranspiration (PET) in inches. The daily potential
evapotranspiration data provides an estimate of the maximum amount of water that will evaporate
from wet surfaces each day.

    The PET is defined as the amount of water used or consumed by an actively growing crop that
completely covers the soil surface when water is readily available. There are several different
calculation methods available, but the one used in NDAWN has been found to work well in the
windy Great Plains. This method using daily solar radiation, air temperature, wind speed, and relative
humidity data measured at each station location.

    During the spring PET typically ranges from 0.10 to 0.30 inches per day. However, on recent cool
rainy days PET amounts were near zero. For a day or two following plentiful rain, evaporation from a
ponded water surface or the soil surface is about equal to the transpiration from an established crop
with a complete canopy. However, under good drying conditions, evaporation from soil quickly
decreases as surface soil dries. This occurs because water must first migrate to the soil surface before
it can evaporate, but a plant’s root system extracts water from a volume of soil making it readily
available for a much longer time period. Ponded water may also be infiltrating the soil as well as
slowly draining away or evaporating.

    PET data is most useful in estimating how long it will take to dry out a pond. It is not quite as useful
in estimating how long the soil in a field will take to dry out. A loam textured soil contains about one
and one-quarter inches of plant available water per foot of soil. However, when these soils dry, they
tend to wick moisture up towards the surface, so what might initially appear to take a day to dry may
take longer depending on whether moisture is wicking up from below. If fields dry rapidly at the surface,
a crust may form, preventing significant wicking action to draw moisture to the surface. Drying proceeds
much more slowly and relies heavily on infiltration downwards. Another consideration is the seepy nature
of water movement below the soil surface in landscapes. Often the bottom or slope of a hillside may be
especially wet because of lateral movement of water within the landscape that is directed to these
locations. Even when fields are "dry", producers should be wary of these spots. Many tractors have been
stuck in seeps within "dry fields".

    Getting back into the field may take some time. Sun, wind, low humidity, and warm temperatures are
needed to see the dust blow again behind the seeders.

Dave Franzen and John Enz
NDSU Extension Soil Specialist
NDSU Climatologist

 

WHERE IS MY ANHYDROUS?

    With all the water lately, many producers are concerned about the fate of their recently applied
anhydrous ammonia. As long as the ammonia is ammonia, there is little risk of loss. The fertilizer applied
during the busy weeks of April are still intact. It is the nitrate that is in the soil that can move with water
or can be denitrified (transformed to nitrogen gases) when under water. Ammonia doesn’t move with
water and it is not lost as vapor when it is under water.

    The nitrogen to be somewhat concerned about is the fertilizer applied in the fall, especially those fields
that were applied in September. If crops come up yellow, especially in areas where water has ponded
or in coarse textured soils, some supplemental N application might have to be made. Plant analysis or soil
sampling can help to determine if N is short in these areas.

 

FINE TUNING THE SULFUR RECOMMENDATION FOR CANOLA

    In 1997 NDSU Extension Circular SF-1122, the statement is made that a blend of elemental sulfur
and ammonium sulfate might be preferable to ammonium sulfate alone because of sulfate leaching
concerns. However, recent work since this publication was released from Dr. Ed Deibert’s work in
North Dakota and Dr. Cynthia Grant’s work in Manitoba have not supported the use of a blend.
A straight ammonium sulfate application was superior to elemental sulfur in these studies. If a blend is
used, it is advisable to apply the full rate of sulfur as ammonium sulfate, then add additional sulfur
beyond the normal recommendation as elemental. Do not subtract from the sulfur rate as ammonium
sulfate in order to apply elemental.

    If sulfur is needed and sulfur was not applied prior to seeding, sulfur may be applied up to bolting
in an available sulfate form, such as ammonium sulfate or ammonium thiosulfate. Young canola plants
cannot tolerate the levels of liquid fertilizer needed to supply them with sulfur without suffering serious
burn and stand loss. If applying liquid fertilizers, wait until at least the 5-leaf stage before application.
The leaves on canola do not contain a sufficient waxy layer to withstand liquid fertilizer before this stage.
The sulfur fertilizer will need a rain to move it into the rooting zone before the application is effective.
Little sulfur will enter the plant through the leaves.

 

SPRING TILLAGE AFTER THE RAINS

    As the spring seeding season stretches on, producers will be anxious to reenter the fields. Many
of these fields will be wet under a crust, and tillage conducted too early may result in very cloddy
seedbeds. Rains following a too early tillage may mellow these areas out, but if the weather turns dry
the crop may never develop to its potential. Producers should try to wait until soil conditions are fit for
planting. Tillage should be as shallow as possible to work the driest possible part of the soil. Unfortunately,
it is hard to imagine fields without significant compaction after seeding is completed. There is always
a tough decision to made when weighing timely planting against resulting soil conditions and compaction.

Dr. Dave Franzen
NDSU Extension Soil Specialist

 

SPRING APPLICATION OF NITROGEN IN BEETS IS RISKY BUSINESS

    Nitrogen is the most important element of those supplied to sugarbeet in fertilizers, because few soils
contain sufficient as nitrate or ammonium, to provide for maximum plant growth. Nitrogen improves the
color, size, and vigor of the leaf canopy. This led to a widespread over-use of nitrogen, which decreases
both sugar percentage and juice quality. As such, it is imperative that the correct amount of nitrogen is
provided to the sugarbeet crop in a timely manner to increase yield of high quality sugarbeets.

    Sugarbeet growers normally apply fertilizer nitrogen to their sugarbeet crop in fall. Growers who
plant sugarbeet in sandy soils, soils with high water table, or soils that will pond are advised not to apply
nitrogen in the fall. In addition, wet falls or late harvests result in some growers applying nitrogen in the
spring to provide the sugarbeet crop nitrogen requirements.

    Spring application of nitrogen pose some risks to sugarbeet stand establishment. Application rates of
100 pounds per acre of actual nitrogen immediately followed by planting sugarbeet can result in reduced
seedling emergence.

    Certain practices and conditions increase the risk of stand loss. High fertilizer nitrogen application rates,
shallow fertilizer incorporation, coarse-textured soils that are calcareous at the surface, dry soil conditions,
and soils low in organic matter increases the possibility for stand loss.

    Broadcasting 75 pounds or less of fertilizer nitrogen that is then incorporated should not affect plant
stand. Management practices that reduce risks include delaying seeding after applying anhydrous
application, applying anhydrous at 5-6" deep (or a minimum of 2" from the seed), using narrow spacings
between shanks on equipment, and planting about 10% more seed to compensate for any possible stand
loss from anhydrous or urea.

    Growers who need to apply high nitrogen applications at spring should consider a split application to
ensure high sugarbeet plant populations. If more than 75 pounds per acre of actual nitrogen is required,
apply 60-75 pounds before or at planting and the balance by the four-leaf stage of the crop. The fertilizer
should be incorporated with a cultivator, rotary hoe, or harrow.

Mohamed Khan
Extension Sugarbeet Specialist
mkhan@ndsuext.nodak.edu


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