Once again we seem to be in a period of transition. We have discussed the problem of to much rain and cool. With last week’s hot dry winds, I have now observed moisture stressed corn across much of the area. Much of this can be attributed to shallow root development and those roots should be rapidly moving down into the soil profile following the moisture. Now is the time to have this dry period, not two weeks from now. We are entering the most critical time period in determining the yield potential of corn. Soybeans have begun to bloom and will also be entering a period of rapid dry matter accumulation. I have observed many cultivators rolling through fields the last week. I realize that this operation is necessary in some fields as a last attempt to control weeds, but it should only be used when necessary. Cultivation destroys crop roots near the soil surface and in some cases may damage roots deeper in the profile in the rows of tire traffic. Energy is required to rebuild the root system; this takes energy away from above ground growth (yield). Parts of the area (Ida, Sac and Calhoun counties) received beneficial rainfall over the weekend; other areas across the region are in need of rain now. We need to be scouting for 1^st generation Bean Leaf Beetle within the next week.

Corn development is approaching tassel in the earliest planted corn (1400 DD50's). As mentioned last week, the number of rows of kernels per ear has already been established, but the determination of the number of kernels per row will not be complete until about one week from silking or about V17. The earliest planted corn is now in the most critical period (to avoid moisture stress) in determining corn yield, typically two weeks pre and two weeks post tassel. Water stress during this period can have major impacts on final yield. Corn at the V12 stage may take up 0.24 inches of water per day and corn at early tassel may take up to 0.28 inches of water per day. From now on we need 1 ¾ inches of rain per week to maintain current soil moisture status. Ideally we should to go into tassel with a full soil profile (for those with irrigation potential, this should be your goal!), then the crop can work with the given rainfall and pull off of soil reserves to fill the grain. If the soil profile is depleted (or partially depleted as it is in some areas) then moisture stress may occur unless we receive the required amount of rainfall per week. Once the tassel emerges, root mass is at its greatest and in some cases may decline during ear development. By V18 the corn plant has taken up the vast majority of required nutrients, approximately 74%, 67% and 84% of the total Nitrogen, Phosphorus, and Potassium respectively.

Soybean Development is moving into reproductive stages across most the area (referred to as R1, beginning flower). You should notice the first flowers on the 3^rd to 6^th node of the main stem. Flowering will progress up and down the main stem from there.

The first thing to do is determine the week soybeans emerged, then refer to the accumulated GDD table and match dates. Begin sampling fields 1 week after peak emergence. If the sample is below threshold, scout again the next week. If the sample is still below threshold, scout 1 more week. If 1st generation beetles are above threshold, scout again mid August to confirm beetles are present, then spray.