Wiles Bros Fertilizer, Inc. Plattsmouth, NE (402) 298-8550

Most of the corn has is between the 5-6 leaf stage of development. It has now accumulated approximately 500 (GDD). The seminal and nodal roots have finally developed and now that corn has emerged the nodal roots will continue to further develop with every additional node of plant (on average 7-10 nodes total). The nodal root system is the major supplier of water and nutrients to the plant by V6 (6 leaf corn). This is important since the developing plant uses the kernel until about V6 for much of its nutritional requirements. Once the nodal roots develop, then the plant roots into fertility zones for additional nutrient needs. The lack of nodal root development is part of the reason why the corn had pale green/yellow color the past few weeks—along with cold weather, slow growth, wet conditions, insect feeding, etc. The corn will now grow quickly and unfurl one leaf about every 3 days or every additional 65 GDD’s.

Most weather stations across Eastern Nebraska indicate that we have acquired many heat units within the past 7-10 days. NO SECRET! Corn that was later planted due to weather delays can catch up and the old saying of “you can watch the corn grow with the right weather” is true however, much of rapid corn growth occurs at night due to increased water supply within the plant at that time. As some of the early planted corn begins to reach the V10 stage you usually see a new leaf emerge from the whorl of the plant every two to three days. An average corn plant has between 20 and 23 leaves within the whorl that developed before V6 stage and tassel development. Many ear shoots are currently visible when splitting the plant in half and as the plant soon develops into the V12 stage potential kernels and the size of the ear will be determined. This one of the reasons why many “over the top” herbicide applications reach the end of their application windows due to risks that certain active ingredients can pose to the developing ear. Many applications can continue using drop nozzles on the sprayer to keep much of the spray solution out of the whorl of the plant. The main ear shoot can now been seen and based on genetics and plant population/fertility a second ear can also be seen.

Many of the soybeans are in the unifoliate (V1) stage with the 1st trifoliate emerging and the 2nd and 3rd trifoliate visible. Bean Leaf Beetles have begun to feed with the emerging crop. Remember, that once the first trifoliate has developed, the plant can withstand up to 50-60% of vegetative feeding/tissue loss from bean leaf beetle feeding before a treatment is economically justified. This amount of feeding can have an approximate yield loss of 5%, which would pay for the cost of treatment—even with today’s market prices. I have not seen any injury severe enough to require a treatment--yet.

When corn grows quickly water is consumed at an amazing rate. Water use in corn in Eastern Nebraska on average transpires between 25-28” of water through the plants during the growing season. We now are using between 0.05”and 0.10” of moisture transpired through the plants each day. The plant roots are in the top 6-8” of the soil profile and a typical corn plant can root up to 4 feet deep. Forty percent of water absorption occurs within the top 12”, 30% in the second foot, 20% in the third foot, and 10% in the fourth foot of the soil profile. The following table demonstrates the amount of water used per day.

Soybeans on average transpire between 22-25” inches of water through the plants each year. They use 65% of total water use during the reproductive stage (flowering/podding) of development. Nitrogen-fixation (nodulation) has begun with lateral root development occurring in the top 6 inches of the soil profile. Soybean root development can reach 5 and 6 foot depths, but like corn, the largest concentration of root development and water uptake occurs within the top 2 feet of the soil profile. The following table demonstrates the amount of water used per day.

Yellow, streaked corn continues to be an issue in some areas. A very quick growth spurt can temporarily cause yellow streaks between the veins of the leaves and/or yellow the whorl. Under quick growth conditions, the plant cannot keep up with the chlorophyll production demand of the plant causing the yellowing to occur. The larger issue of yellow corn is a product of the weather conditions of the past weeks.

The uptake of plant nutrients is an energy requiring process, much of which is provided by oxygen. In situations where soil pores are filled with water and oxygen is displaced, uptake capacity of the roots is limited. Once the soil drains, and air can get back into the soil pores, and with the warm weather we are now experiencing, this should be a short term problem.

What becomes of the nitrate in these situations? Nitrate, which is the plant available form of nitrogen, and also water soluble, is subject to leaching, or denitrification in saturated conditions. How far nitrate will leach is dependent largely by how far down the water moves. One inch of rain on a dry silt loam soil will penetrate about 4-6”. Additional water can move nitrate down further and out of the root zone of small corn plants. However, in heavier soils, especially with high clay content in the subsoil, leaching is reduced due to smaller pore spaces, and less mass flow through the profile. As roots grow down, they can get to the nitrate, providing it doesn’t leach below about 4’. Remember too, that as water evaporates from the soil, water moves upward and can take nitrate with it, bringing some back to upper levels of the soil profile.

Denitrification occurs when anaerobic (require little or no oxygen) bacteria increase in activity and break down the nitrate molecule to gaseous forms of nitrogen, which in turn is lost to the atmosphere. This can occur if soils are saturated for at least two days, at temperatures above 60 degrees. Losses can be 2 lbs./acre/day or more as reported by the University of Nebraska. Another corn belt study cites losses of 4-5% per day of saturation. In this same study, saturated soils for 5-6 days cost about 10-20 bu/acre in lost corn yield. Again, as the water drains and the soil returns to field capacity (which is defined as the amount of water in the soil remaining after having been saturated, and after free drainage has stopped), the activity of the anaerobic bacteria will decline and denitrification will cease. So, unless water is “ponded” for an extended period of time, denitrification should be short lived.

Soybeans after June 10th--Corn and soybeans are unlike in what promotes them into their respective reproductive phases of development. Corn does it through the accumulation of heat units (GDU’s). Soybeans do it through day length or the amount of sunlight the plant is exposed too. So, we are past the optimal time for planting corn in order to maximize yield potential. Some areas have been wet enough to switch corn acres to soybeans. With soybeans it is common knowledge that they should be in the ground prior to Memorial day in order to achieve the greatest yield potential. Soybeans can be planted up to June 10^th with little reduction in yield potential. Some early planting soybean fields are experiencing some stand establishment reductions in light of the cold and wet conditions this May. There are some fields with stand losses upwards of 40-50% which could be candidates for replanting. Should you replant them? Should you use the same maturity on the second planting? Replant soybeans only if you have a stand loss of greater than 40% of your original seeding rate. Use the same maturity of soybean that you initially planted. A week from June 10th, replant soybeans only if you have a stand loss of greater then 50% of your original seeding and still use the same maturity of soybean that you initially planted. Once the calendar gets into the 20’s of June is the only time we would decrease the maturity of the soybean being used by ½ of a maturity point (From a Group 3 to a Group 2.5). Yield potential in soybeans is always greater with the maturity adapted for your geography. As we get further past June 10^th, you are taking a yield potential reduction no matter how you look at it. Still, you have the greatest potential with genetics developed for your growing region until the calendar reaches the 20’s of June.

Seedling Diseases---Corn and soybean diseases such damping off from Phythium and Phytophthora are and will continue to be prevalent in water-logged soils. Stand reduction has and will continue to occur in these areas. “Damping off” is a cover-all term used to describe symptomology of the disease. The rule is if damping-off occurs in warm soil (70 to 80 degrees) it is more likely to be caused by Phytophthora Root Rot (PRR). There are upwards of 45 races of Phytophthora, which greatly complicates breeding for resistance and adds confusion to growers when selecting appropriate resistant varieties. The specific gene resistance, known as Rps1 genes that is bred into many soybean varieties provides protection against several known races of PRR. The gene Rps1a provides protection against 17 races of Phytophthora; Rps1c, against 23 races; Rps1k, against 24 races. However, none of these specific genes provides protection from race 25, which is becoming more common in many areas in Eastern Nebraska.

PRR may attack soybeans at any growth stage. Seed rot and preemergence damping-off can occur in flooded or ponded soils, while postemergence damping-off and seedling stem rot cause wilting and plant death. Symptoms of older seedlings on "low-tolerance" varieties include soft, water-soaked stems with leaves yellowing and wilting — often leading to plant death. Older plants of affected low-tolerance varieties may be killed gradually. The roots turn brown and the upper leaves become yellow between the veins and leaf margins, accompanied by complete wilting of the plant. Generally, symptoms occur on isolated plants scattered across areas of a field, rather than large patches of infected plants as seen with sudden death syndrome or soybean cyst nematode damage

Damping off occuring in cool soils (50-60 degrees which we have right now) it is more likely to be caused by Phythium. Both diseases cause the root and lower stem tissue to turn brown/purple with a slimy texture, which can lead to seedling death. Phythium can also affect the integrity of the corn seed during establishment. The best line of defense is to purchase genetic packages with strong tolerances to these diseases. Although some fungicides have activity through box treatments or seed coatings against these diseases, they generally lack in the residual needed to withstand a long-term cool and wet spell, which we are currently enduring.

INSECTS-Where are we at and what to expect--Many of us fall into the treatment blizzard for numerous insect pests which invade our crops every year. This year, insects have posed a big threat in getting the crops established and growing. Scouting for insect infestations is critically important not only from the standpoint of how much potential yield is impacted, but also the economical cost involved with some of these treatments. This year is certainly no exception to this rule.

Insecticide Failures--This wet spring has produced many insect pressures in corn at levels, which have caused some producers to replant the affected areas. Even with in-furrow or broadcast insecticides or seed treatment, Eastern Nebraska has had a fairly widespread amount of black cutworm white grub and wireworm feeding. There are many reasons, which contribute to the insecticide failures, but the predominant cause this year is the cool, wet weather during the seedling establishment phase of the corn development, causing higher, viable populations of these insects. If an in-furrow insecticide was not used--there is not an alternative except to replant if the feeding continues and stands are drastically reduced OR accept the stand you have left. Given the calendar date, accepting your current stand may be your only option. Wireworm and white grub are nearing the end of there feeding cycle but can remain viable as long as the soil profile temperature is below seventy degrees. Black Cutworm feeding continues to be an issue. Given the right soil type and organic matter, ample soil moisture has the ability to also leach many treatments out of the their effective zones in the soil for insect and weed control--much of the reasoning behind in-furrow insecticide failures. Many of the soil insecticides being used have only a one to two week soil residual. During the two weeks after application, much of the corn has struggled for active growth, but insect pressures have thrived. This spring, seedling corn insects have had a wider feeding window on the developing corn plants mainly due to these weather conditions limiting active plant growth. Seedling plants are very vulnerable when less than V6 (4 leaf). After the V8 to V10 (6-8 collars) stage of development in the corn seedling insect concerns fade.

Vegetative Feeding from grasshoppers appears to be decreasing in chances of it becoming an issue this year. Last year feeding from this insect prompted many producers to make an insecticide application to decrease plant injury from their subsequent feeding. The cool wet weather has not eliminated this threat but, it has increased the mortality of the eggs, which were laid/hatched in May. Some species can lay/hatch eggs from May to June and still others can hatch eggs far into July. For this reason it is still a good idea to scout field borders, pastures, ditches and waterways for populations of hatching grasshoppers. Remember it is easier to achieve some insecticidal control of grasshoppers with most insecticides when they are in the early stages of development (nymph).