DOES BT CORN PREVENT ALFATOXIN?

Numerous studies by Universities in the Southeast HAVE NOT found Bt hybrids effective in eliminating alfatoxin in corn grain. In fact, Bt hybrids did not perform any better than the non-bt hybrids with respect to alfatoxin levels. Earworm damage to the ear has been associated with high levels of alfatoxin, thus it sounds logical that Bt corn would prevent alfatoxin since it controls earworms. However, there are two reasons why Bt hybrids are not effective in eliminating alfatoxin in corn grain. First, earworms must feed on the ears to ingest the Bt toxin before they die. Even a minimal amount of feeding will provide an entry site for the Aspergillis mold to colonize the damaged kernels. Second, infection may also occur through the silks. Bottom line; don’t buy Bt hybrids thinking they will prevent alfatoxin!

PLANT POPULATION AFFECTS ON CORN SILAGE YIELD AND QUALITY.

In general, increasing populations 10-20% over those recommended for grain will often maximize silage yields. However, recent research indicates higher populations may influence silage quality. At higher populations you have more stalks and less leaves. Consequently, digestibility may decrease. With this in mind, one should balance the increase in silage yield with the loss in silage quality. This may be accomplished by weighing the silage to calculate yield and sending this information along with samples to a lab for nutritional measurements. With yield and nutritional information, a qualified lab may then calculate milk yield per acre. Milk yield per acre is a useful measurement to determine the relationship of yield and quality. The grower should experiment with several plant populations and choose the population which produces the most milk per acre. Of course, standability of the particular hybrid should always be considered in this decision!

HOW LATE CAN I PLANT CORN AND STILL MAKE GOOD YIELDS?

The only logical way to approach this question is to review date of planting studies and assume this year will be somewhat similar to the average of these studies. Date of planting studies by the University of Florida show that final grain yield declines 1/2 bushel per acre per day during the first 4 weeks from when soils are warm enough to start planting. After that, the decline increases to 1 - 1.5 bushels per day.

WILL SPLITTING THE PLANTER WITH TWO DIFFERENT CORN HYBRIDS INCREASE GRAIN YIELD?

Every year I get this question. Matter of fact this is a practice we used on the family farm, however, most studies fail to find yield advantages for this practice! The main reason given for planting alternate rows of 2 different hybrids is to reduce weather related risks of poor pollination. Below are some facts to consider if one is considering this practice.

1. Yield is seldom limited by lack of pollen availability during the time when silks are receptive to pollen. Even if kernel set could be improved in mixtures, only the early hybrid in the mixture can benefit. The late hybrid can “help” the early hybrid, but there is no extended pollination period for the late hybrid. Also, chances of having unpollinated silks are greater for the later maturity hybrid since it will pollinate when hot, dry conditions are more likely.

2. If hybrid A is 6 bu/acre better than hybrid B, then planting a mixture of the two may result in a loss of 3 bu/acre on that field. Any potential yield advantage due to planting a mixture is offset by the difference in yield potential of the individual hybrids.

3. If the relative maturity of two hybrids is the same, it does not mean that they will have the same pollination dates. Careful study of days to pollination is required to select a pair of hybrids that will extend the pollination range.

4. With genetic gains of 1-2% per year, by the time the right mix of hybrids is identified, growers gain as much or more yield potential by just planting the newest and highest yielding corn hybrids.

IS THERE A YIELD ADVANTAGE FROM USING AN “IN-FURROW” STARTER VERSUS A STARTER PLACED IN A “2 x 2 BAND” (2 inches to the side and 2 inches below the seed)?

Studies conducted by the University of Tennessee showed no difference in yield with respect to placement method. One would assume this, because by the time the young corn plant spikes through the soil, the seedling roots have already reached the fertilizer in a 2 X 2 band. The “2 X 2” method is much safer than the “in-furrow”, plus you can apply enough nitrogen to last until sidedress.

HOW IS NITROGEN LOST FROM THE SOIL?

There are four major pathways in which nitrogen is lost from the soil. Listed below is a brief explanation of each:

1) Leaching loss - All plants take up nitrogen either in the ammonium (NH4+) or nitrate (NO3-) form. Most of the nitrogen absorbed by the corn plant is the (NO3-) form. Nitrate nitrogen is negatively charged and so is the soil. Two negative charges repel each other and thus leaching occurs. Eventually, the ammonium (NH4+) form will convert to the nitrate form and leach also. The amount of rainfall and texture of the soil have considerable bearing on the amount of nitrogen loss by leaching. In areas receiving considerable rain, sandy soils low in organic matter are more subject to leaching than clay soils high in organic matter.

2) Volatilization loss - There are several volatile forms of nitrogen including, ammonia (NH3) and certain oxides of nitrogen. Anhydrous ammonia (NH3) may be lost as a gas if not properly applied. Also, urea based nitrogen may be subject to loss by volatilization. Soon after application, urea is converted to ammonia (NH3), then to ammonium (NH4+). While in the ammonia (NH3) state it may be lost as gas. The speed at which this takes place depends upon the temperature and the amount of residue the urea is in contact with.

3) Denitrification loss - This occurs in warm waterlogged soils and is caused by soil organisms that live without air and get their oxygen (o) by taking it from nitrate (NO3-) nitrogen. The nitrogen is then free to go off as a gas.

4) Crop removal - When crops are harvested, considerable amounts of nitrogen are removed in the harvested portion. The amount of nitrogen removed depends upon the portion of the plant harvested.

APPLYING NITROGEN TO CORN THROUGH THE PIVOT IS A VERY EFFICIENT METHOD OF APPLICATION.

A five year study by Dr. G.J. Gascho and Dr. J.E. Hook of the University of Georgia shows this to be a very efficient way to supply nitrogen on sandy soils where leaching is a concern. Their best schedule was applying 25% of the total N as preplant and starter, about 22% at each application via the pivot at the V6, V12, V16-18 growth stages and the remainder at R1. This schedule always insured that N was available prior to optimum uptake needs. This schedule also resulted in 18 to 23 bushels per acre more corn than the conventional method of 25% at planting and 75% at V6 to V8!

AS NITROGEN PRICES SOAR, GROWERS SHOULD TAKE STEPS TO GET THE MOST OUT OF EVERY POUND APPLIED THIS YEAR.

Listed below are some steps to help maximize the efficiency and minimize the cost of applied nitrogen:

* Inject or incorporate all urea based nitrogen.
* Set nitrogen rates based upon realistic yield goals.
* Take advantage of nitrogen credits if a legume was the previous crop.
* Good weed control will increase nitrogen availability to the crop.
* Split apply your nitrogen. For dryland corn apply 1/3 at planting and the remainder at sidedress.
* For irrigated corn apply through the pivot.