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Crop watch

August 6, 2019
By Bob Streit - Columnist , Farm News

August is here and after the longest and frustrating first half to the growing season we will have to see how the second act, that of grain fill, turns out for our two major crops.

Just as planting progressed, most growers have three different corn crops at three stages of development. In quite a few cases three separate and different operations based on growth stages utilizing different pieces of machinery had to be done so developing an efficient schedule to get all of those was rarely possible. Then with very few days suitable for field work each of those tasks completed on time was difficult.

The second large USDA report should be out in another week. Will it target correctly and identify the many deficiencies in the corn and bean crops in the major producing states? Whether the national corn crops reaches 11, 12, 13 or 14 billion bushels is now a guess on everyone's' part. In visiting with a very knowledgeable crops person who has traveled and walked fields across the entire Cornbelt regularly I asked for his guesstimate. He mentioned a figure and it aligned with what I had been thinking. There are too many variables such as heat, moisture, disease outbreaks, and the arrival of cool weather during August and September for anyone to have a handle on the final figure.

In northwest Iowa, major windstorms tore through early on Saturday mornings the last two or three weekends. Measurable rain with winds pushed the corn down and caused greensnap in many places. The corn is always highly vulnerable during the two week long period prior to tasselling. When first walking such fields an optimist hopes the plants broken off right above the ear will form a full sized ear. In reality it seldom does.

Field observations

With much of the corn reaching or approaching the tasselling stage the crop looks better. Not being able to see all the waterholes from the road helps. The first and second planting fields are generally fully tasseled and silking. Staging the plants indicates that with a warm or warmer than normal August the black layering date will be in the second half of September and beat the normal freeze date. The June planted third of the corn crops includes corn that is still two weeks away from tasselling. This places the black layering date near Oct 15th. It may take a warm August and a delayed freeze date to make it to black layer.

We made a run up to Stacyville for Bratwurst Days on Saturday night, to Charles City and over to Decorah on Sunday. I had seen the late planted fields around Luverne, Minnesota earlier in the week. About half the fields had not tasseled yet with the latest ones needing two more weeks to reach that stage. Any nutrient deficiency could delay development an additional time.

I had mentioned that we saw in 2017 at the Arise Research Farm in southeast Illinois that applying the Calcium silicate product lowered the freeze point in the corn leaves to 22 degrees by increasing sap sugar levels. This may allow corn fields to avoid being killed by the usual two nights. The first night takes kills top leaves while second night kills the lower leaves and stalks.

Depending on GDUs from AugustSeptember the grain moisture could be wetter, especially if the husks don't open until late. Operators have been booking propane to meet larger needs, or considering storing grain in the larger, poly bags.

The soybeans seemed to add enough height that half of the 30-inch rowed beans may close the rows. More are now flowering with those flowers now open as every node. It is possible to see what percent of the broadleaf weeds survived the post-emerge herbicide applications. In cases rain falling within 30 minutes of application lowered the efficacy of the herbicides. Where big broadleaves are growing the decision on how to respond becomes difficult. PPOs that burn crop leaves typically show significant yield reductions (I've seen 12 to 15 BPA loss in yield) if sprayed after flowering has begun. Then does a person make a cultivator pass, move away from the AMS and MSO if making a second pass, or opt for other means of control. Does that mean pulling the old bean buggies out again or leasing a weed Zapper?

Soybean foliar feeding

All the yield contest winning soybean list a strong foliar feeding program when asked for which program allowed their big yields to be coaxed. These programs typically recommend several different steps to be utilized and products to be used, with planter placed nutrition often in the mix. They usually follow up with foliars beginning at R1 and sometimes making applications thrgh R4 and even later. Improving early growth to reach 12inches as early as possible, then keeping the internode length and stem height short via foliar applications of fertilizer and/or hormones saves energy that can be better utilized for pod formation and filling.

There are growers who will be applying a product called Seed Set at R1 or R3 that supplies 17 different things to the soybean plants to induce flowering, strengthen the branches, and form more seed to produce higher yields. In most situations the growers planning a high yield program begin at or even before planting to know when each step will be implemented.

Fungicide thoughts and reasoning

Many airplanes were bombing the plants in fields with fungicides over this past week in an attempt to keep their plants safe from fungal attack. Were all those applications needed or were some a reaction to a neighbor spraying his/her own fields?

In too many cases cases it may have been the latter as too few growers and crop advisors have not educated themselves with the knowledge and tools they need to accurately assess a disease infection and potential loss. There are times when fungal lesions are affecting a high percent of the leaf tissue, and published treatment thresholds have been reached. The stories about Tar Spot were scary enough to not want to wait for it to reach epidemic proportions.

In cases the salesmanship and advertising of major companies over rode the dissemination of information about the disease triangle and that plants become disease prone when levels of important micro-nutrients such as Mn, Cu, Bo and Zn are deficient.

The first step in a good disease management program should start with a residue management program the fall before.

The second step would then consist of soil testing and correcting pH deficiencies or excesses, then breaking up any hardpans to allow deeper root penetration to allow improved mineral uptake.

The third step could be tissue testing for those shortages of those elements and correcting any deficiencies with a preplant, planting time, or foliar application of those minerals.

The fourth step would then be to investigate any disease symptoms that might exist after those first three steps haven't worked, match the pictorial guide to what you are seeing, and then put the cost and reward figures together. Then if the disease is near or above the published thresholds pull the trigger to make the application once the guidelines say it makes economic sense to spray. Continue determining which factors contributed to the infection that can be improved or corrected for next year.

Soybean aphids

In 2003 when soybean aphids first became a problem in soybeans in Iowa they reached sprayable levels by July 25th. They have not reached economical thresholds in many parts of Iowa the last two to three years. If some of the aphid populations now resistant to Pyrethroids, and the future availability of Lorsban unclear, which new product should we buy or watch?

One that I learned about is 'Sefina' from BASF. It has a new mode of action and is safe to beneficial and humans. It affects the aphid's joints so they keep twitching enough so they don't spend time sticking their stylets into the leaves and sucking sap. The final question to the tech rep was cost - could row crop farmers justify its use? Other new families are in the mid-teens per acre. This one is about $6/A.

Aphid populations remain very low yet at this date. Northerly winds can change this.

Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.

 
 

 

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