Mississippi County
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Wheat Spring Management
I was reviewing the January 2004 news letter and one thing about wheat seasons, they have been consistently tuff. This past fall started off dry and there were concerns about wheat emergence. Then the rains came and wheat acres went. MO and AR are way down for 2005. Wet fall, late planting, Hessian fly and once again heavy aphid feeding are not favorable conditions for a wheat crop.
Excessive rain is one factor to blame for the pale looking wheat fields. Wheat doesn’t tolerate flooded conditions for a number of reasons. The primary reason is oxygen depletion, resulting in less N uptake, which leads to less tiller development. Applying a green up fertilizer application should be considered in 2005. Remember, you have approximately a 30 day window between greenup and jointing for additional tillering. Wheat begins to grow when temperatures are 50 or above, therefore some N needs to be available for tiller development. Also, base your decision on the number of tillers (includes main shoot) present in your field. In fields with less than 60 tillers at green-up, apply at least 40 lbs of nitrogen as soon as possible to increase tillering and head size. For fields with 60-80 tillers apply a little nitrogen (20-30 lbs) and follow up with some nitrogen later. Applying nitrogen at green-up in a field with over 90 tillers can lead to a thick lush canopy which may increase the risk of disease, lodging and winter damage during late winter cold snaps. The time of greatest need for nitrogen occurs approximately 30 days after green-up (pre-jointing). Care should be taken to make sure all nitrogen is applied by Feekes growth stage 6 to maximize yields. Research shows a definite yield boost by splitting applications especially in sandy (leaching) and clay (denitrifying) soils. Past research at the MU Delta Center has shown an increase in sandy soils where considerable leaching may occur but little or no increase on well drained, nutrient holding heavier soils. Arkansas recommends split applications on both sandy and heavy wet soils to improve nitrogen efficiency.
Sulfur deficient wheat has yellow new leaves compared to N deficient yellow old leaves. Most of the Sulfur in soil is contained in soil organic matter. This sulfur is made available to plants by bacterial action. Therefore, low organic matter (usually sandy) soils of Southeast Missouri are also prone to low Sulfur conditions and Sulfur fertilizers should be part of the nutrient program. Ammonium sulfate and 28-0-0-4 are commonly available Sulfur fertilizers. Most low sulfur soils require 10 to 15 lbs./acre of Sulfur.
Injured or dead wheat, especially the main shoot could indicate Hessian fly damage. You will need to examine the injured or dead shoot at the crown or base of the plant which is at or just below the soil surface. Hessian fly is currently in the puparia stage which looks like little reddish brown “flaxseeds”. The primary ways to avoid injury from this pest is planting after the fly free period and utilizing resistant varieties. This spring the adult flies will emerge around the end of March to lay the first generation on one-to-two node wheat. Typically, temperatures and parasites keep first generation maggot numbers from significantly damaging wheat a second time. Refer to MU Guide 7180 for more information.
Determining if a crop should be kept is difficult because of the numerous factors involved in reaching your decision. However, determining the tillers per square foot is the first step in making that decision. You should make an assessment across the entire field to get an average number. Count all plants in 3 feet of an average looking row that have 3 or more leaves. Do this in at least 5 locations. Use the formula: #/square foot = {(ave. plant count X 4)/row width inches}. Remember 70-100 tillers/sq. foot prior to stem elongation (Feekes 6) is a target range. There are many factors which determine yield and this should only be used as a guide. University of Missouri's Wheat Management and University of Kentucky's Wheat Management guides are good references.
Stubby Root and Root Knot Nematodes
By the end of August, I usually start getting some calls about stunted soybeans in a sandy field. Last spring I received similar calls in corn fields. Root Knot (RKN) as well as Stubby Root Nematodes attack corn. Corn is susceptible to both of these nematodes being most sensitive to Stubby Root. Both nematodes feed in the roots blocking water and nutrients. Early planted corn, warm soil conditions, and sandy spots were where these problems emerged in 2004. Early planted corn as a result of warmer than normal soil temperatures, resulted in a larger population of nematodes to attack a young root system. Both of these nematodes under the right soil environment can have a 10-fold increase in population within 60 days. And, typically, as fast as they increase they can decrease due to over population. Therefore, obtaining an accurate count can be difficult.
RKN and stubby management in corn is difficult to say the least. Most of the time, damage will occur in sandy spots because these spots are the first to drain and first to warm up. If have experienced nematode damage in a particular field in the past and properly identifying the problem as nematodes you have a good chance the nematodes are still present. Rotation may or may not help, because these species have a wide host range including weeds.
Some management options include: rotate out of corn; maintain good weed control; avoid other stress (cold soil, low fertility, etc); use a nematicide and make sure it clearly lists corn nematodes.
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University of Missouri Extension Mississippi County mississippico@missouri.edu Updated 05/24/04 |
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