Farming After a Toad Strangler
- 1997 style


(note: This is a somewhat edited version of an article written at about the same time in June,1996. Proof again it never pays to throw things away!)

The year of 1997 has now turned into another one of those where cattails could be a bigger weed problem than foxtails in some area farm fields. The recent deluge of water (3 to 8 inches) has prompted many questions and concerns regarding crop management for the rest of the growing season.

Let's start with corn. How long can it survive under water? Research indicates that soil oxygen levels are nearly depleted within 24 hours and seedling death may occur when flooded conditions last more than 72 hours, although corn has been known to survive after being flooded for periods of 7 to 8 days. Plant injury and reduced growth rates will follow flooding periods of 24 to 48 hours.

Even where corn does survive after extended periods of soil saturation, secondary problems such as decreased root growth and the increased risk of soil-borne diseases such as crazy top can decrease yields.

Nitrogen (N) loss is another concern in flooded or saturated soils. The nitrate form of N is susceptible to denitrification losses whereby soil bacteria obtain oxygen from the nitrate and the nitrogen is released to the atmosphere. Usually we would expect little loss where N is obtained from previous legume crops, manure, or recently applied fertilizer containing N in the ammonium form. The latter would include fertilizers such as anhydrous ammonia, urea, and liquid N to some degree.

The conversion of ammonium to nitrate in the soil for anhydrous ammonia begins about two weeks after application and is complete in about six weeks. This period is extended when a nitrification inhibitor like N-Serve is used. The conversion for urea is more rapid and is completed in about two to three weeks.

Both grain yields and quality will suffer where N is deficient. Producers will need to monitor fields closely. If water covered the soil surface for more than three days and obvious N deficiencies appear (yellow and stunted plants), apply 60 to 90 pounds of N per acre as soon as field conditions permit. "Spot" applications may be all that is needed in some fields. Where corn follows a previous grass crop and no N has been applied to date, sidedress the planned amount.

Anhydrous ammonia, although economical, may be difficult to apply in wet soils without significant losses because of "sealing" problems at the injection site. Some local fertilizer dealers are set-up to apply either dry urea or liquid nitrogen between corn rows. Both N sources will be equally effective for plant growth. Where deficiencies are limiting plant growth and development, N applications will have economic merit up to the point of tassel emergence.

Some producers are asking about options for fields that may need to be replanted. Short of a miracle occurring, harvesting dry grain for corn planted at this late date is out of the question. A 75 to 80 day hybrid needs about 1800 growing degree days (GDD) to reach maturity. Based on long term weather data, we can expect about 1675 GDD's from June 28 to October 11. Perhaps planting some short maturity corn for silage is still within the realm of possibility but only expect about 3.5 tons of dry matter yield. Planting sweet corn for silage is also an option but it will take longer to dry down than normal dent corn.

Another possibility includes forage sorghum. It can be good yielder but forage quality may not be up to "milk cow" standards if fed as a sole forage source. Past experience has shown that sorghums do not perform well in cool, wet conditions.

A few words about late-planted soybeans. Extension Agronomist, Dr. Ed Oplinger, has done some extensive planting date studies for the past four years. Short maturity varieties can be planted in southern Wisconsin up to about July 1. If this is done, don't figure on harvesting more than about 25 bushels per acre. This was the average yield obtained in the Wisconsin studies for the June 24 planting date.

What about hay? Some fields remain to be cut or have been cut but not harvested. These will now obviously fall into the category of woodlot management. Although it's hard to imagine, obtaining three cuttings of alfalfa off these fields before the end of August is not going to be an easy task. For this to happen, producers will need to cut on a rigid 30 to 35 schedule and hope for optimum growing and harvesting conditions. Even so, this may still push the last harvest into the first week of September. To quote the late and great Casey Stengal, "Who woulda thunk it?"