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Crop watch

By Bob Streit - Columnist | May 25, 2021

As the season progresses into late May there appears to be a big discrepancy for soil moisture levels between different sections of the state. In central Iowa and west, last week consisted of five days with rain but barely one inch of accumulated moisture. That will provide enough moisture to supply the crop’s needs given the fact that the tallest corn is still in the V1 to V2 growth stage. As the corn grows taller every grower is hoping that timely rains keep arriving to supply the corn plants as they get to the tasseling stages when .3 to .33 inches per day will be needed. Most growers think their stands look good enough to maximize yields but recognize the biggest threats this season are dry weather and heat that could place plants in moisture stress.

I had to travel down Hwy 163 through Ottumwa and Bloomfield into the Memphis, Missouri area. While we remain dry they are extremely wet with quite a few fields either loosing stands due to the waterlogging or not being able to get any spring fieldwork or planting done. Receiving 4inches-plus of rain every week with no sun is beginning to threaten their planned corn acre total. Having tight clay soils with very flat topography is getting those growers be very nervous for the next two weeks. This could be the third year in a row for very wet conditions.

On the worldwide commodity scale China continues with their corn purchasing as they seem to anticipate show supplies. The news coming in from Argentina and Brazil about the status of their 2020/2021 spring harvested crops was that the rains were erratic since planting time and in many areas the fields were replanted a total of two or three times before they had stands they could consider leaving the plants that did emerge. In recent years people familiar with those two countries have asked the questions

“Have they removed enough of the forested canopy that the weather patterns have been altered” In the U.S. enough growers are asking if any structures constructed on their or neighboring fields to steer moisture fronts or storm fronts from their fields. That remains a plausible question.

Crop status

What we are seeing in Iowa fields are corn plants that have not grown much due to the lack of heat and sunshine. Without those two things the plants are not able to make sugars. While the plants are stalled out on the cool days the root systems can be under attack from soil dwelling fungi and bacteria. The heat and sunshine that arrived over the weekend appears to have helped the small corn plants to turn green and begin adding leaf stages.

The most discussed issue in April was whether or not it was wise to begin planting. That can be a question where no one has the correct answer as the weather can turn so quickly and abruptly. The trend in the last decade for the month is to have May type weather for ten to fifteen days followed by ten to fifteen days of early March type weather. The guys who normally start very early get the heat units to gain those extra heat units, and end up fine. Those who wait a few weeks and begin before the temps drop then have to hope to not get hit with the cold-water damaged seedlings.

As to stands and if they look decent. It took a while to receive the rain needed to germinate the kernels placed in dry soils or where the ground was harder and the seeds were placed shallower. So, it took additional time for all of the seedling to emerge. It will be months before we see if the late emergers will be productive or will act as weeds. It is difficult to see if any lessons learned this spring can apply to future seasons.

One change seen with growing soybeans and attempts to increase yields has been to plant them earlier and often before the seed corn has gone into the ground. Earlier planted beans do form more podded nodes on the main stem, and if everything else goes well, can contribute to producing higher yields. But with an event of late winter returning in mid or late April or even in mid-May there is the risk of freezing temps occurring in low lying fields or spots in normal fields. This occurred in central and N Illinois and an unannounced number of acres required replanting. Thought this is in the past now anyone with beans that may have been frozen, it will take a close field inspection to determine if the plant tissue froze above or below the growing point. Such inspections should be made four to six days after the cold hit to allow recovering plants to form new growth. Fields with higher residue levels tended to suffer the most plant loss as the thick mat of residue both held in the cold while preventing winds from bringing in warmer air.

Higher yielding bean approaches

A safer approach to achieve the same end which is more pods on a plant would be to apply a cytokine forming bacteria (CPBs) to the seed or the young plants by the early V3 to V4 or even V5/R1 growth stages. This application will force the plant to devote more energy to forming more side branches rather than more upward growth. An application of Spraytec’s Impulse for beans will also cause additional side branches to form. Applying both will really have an effect and it will really be visible. The trick them to maximize yield is to keep the plant well fed through the R4 and R5 growth stages, even if the ground is dry or the stems don’t have the capacity to move enough minerals thru them to maximize grain fill.

Different companies have developed products to help increase seed size, but so far no comparative plot work has been done to determine which company has develop the best mix. We saw a mix of Seed Set and Advanced from BioDyne looked very good in 2020. Jimmy Fredricks uses a mix from Roger Smith’s company from Cape Girardeau, MO that appears to work. NutraBoost from AgriGuardian has also produce good results. To enable grower to make later seed size enlarging mixes after V3 they need to make V4 to V5/R1 applications of a product mix containing sugar and phosphorous which cause the hormonal chain reaction to shorten the internodes. Important to those shortened plants with extra branches will be foliar applied chelated calcium. Due to its normal limited movement into the plant the best product will be the PhytoBiotics Calcium glycinate at a few oz/A.

In past years we have had growers applying a three-way mix of Foliar Blend, MicroMix and Respire to fields which were waterlogged and not growing. That mix at half rates of each always provided the energy boosts the plant and associated microbes needed.

Early soybean pests

Though I have seen bean leaf beetles already in the air and on other surfaces, I have not observed any cotyledon or leaf feeding on soybean plants. The GDU tracking system that entomologists use and calculate from tells that beetle mortality was +75 to 80% in northern Iowa.

There has been seed corn maggot feeding seen in some bean fields. They seem to like the taste of the cotyledons and will chew on them. If they eat these off there is less energy available to the developing seedling.

Those planting into standing rye need to be watchful of a shift in their insect pests feeding on the small bean plants. Millipedes and slugs become the problem pests that need to be observed and managed.

While planting a new batch of purple asparagus roots we turned over lots of large grubs which must be the larvae of the Japanese beetles. The adults must have laid their eggs there were feeding on the fern type tops to the plants. Did the fall applied Beauveria bassiana control them over the rest of the lawn?

Herbicide activity

One effect of the dry soils and lack of rain after application is that the lack of moisture to disperse the herbicide through the top inch or so of soil. This seems to have happened in many fields as one can take a shovel to turn several piles of soil over and see lots of grasses and weeds in the white stage getting ready to emerge. This may require the addition of a post grass herbicide or a pass with a tined weeder. Such weeders can dislodge the seeding from the soil letting it desiccate on a warmer day. The herbicides used most commonly in corn will be one of the HPPDs such as Armeazon, Impact or Laudis. It will be important to take note of the size of the grass.

Soybean weed control

About four years ago Spraytec, a mineral based company from Maringa, Sao Paulo State, from Brazil place an engineer agronomist in Iowa to open up the market. They chose to fight the toughest battle possible, which was the one against broadleaves in soybeans. This was after farmers got hooked on the ease of a one shot at any time post application. Those growers had gotten used to adding AMS and a full short of crop oil and many of them had gotten used to looking at dead brown bean plants that looked like they had died. They surmised that by heating the mix up with the oil and AMS they were knocking off the leaves of both the crop and the weeds. This cut 2.5 to 3 weeks’ worth of growth or grain fill from the bean plants plus the herbicide AI stayed on the weed leaves which fell on the ground, never getting entry into the plant. Thus, the weed recovered and was more resistant to any second application. Growers are now using the Fulltec adjuvant and getting improved control. The new mixes containing minerals and amino acids are providing improved weed control and plant health benefits as well.

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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