Proper fertility is important for maximizing yield. In very general terms, corn requires nitrogen (N) for growth, phosphorus (P) for root development and potassium (K) for strength and kernel quality. This is very general and these primary macronutrients are essential at the cellular level.  Corn also needs calcium (Ca), magnesium (Mg), sulfur (S), and micronutrients such as zinc (Zn). There are other mirconutrients that are necessary for plant growth and development, however, deficiency rarely occurs unless soil pH is out of balance   Zn is mentioned because of corn's high demand for grain development.  Uptake of nutrients is reduced when pH falls below 5.8. When in doubt a soil test will help determine levels. Corn utilizes nutrients throughout it’s life cycle so nutrients need to be available throughout the season. P and K should be applied pre-plant along with some nitrogen. However avoid putting all of the N out pre-plant. This could result in salt burn of young roots and/or early loss of N from the root zone. Corn goes through a rapid growth around V6 (6 leaf) so it is a good idea to have the second application of N out by then. Corn utilizes 2/3 (66%) of N from V6 through RT (tasseling) , it uses an additional 20% for grain formation. Research by Peter Scharf has shown that late season applications of N through silking has increased yield potential, especially when plants were showing signs of N stress. Tissue tests mid– to late-season could help determine a need for additional N to help the crop reach full yield potential. If concerned, collect leaf samples for analysis from upper leaves on plants over 12 inches. Collect ear-leaf tissue on tasseling plants in order to get an accurate assessment of plant needs. Contact your local Extension Center for assistance.

Weed control research in general shows that an herbicide program benefits from including atrazine. If in an atrazine sensitive area, however, there are good alternatives available that offer good control as well. If crabgrass and signalgrass are problems then the program should include a preemerge (PRE) grass herbicide. Research out of the Delta Center generally shows that a post emergence application is necessary for this part of Missouri, in order to have season long control. Therefore, one should not rely on a PRE program only approach. Monitor fields for weed emergence and corn height. Observe the height restrictions to avoid unnecessary stress and potential yield loss. Don’t get caught in a salvage situation. Scout fields after emergence for any potential insect feeding.

If you have irrigation, utilizing an irrigation scheduling tool would eliminate the guess work out of when to irrigate. Missouri’s Woodruff Chart, recommended by Joe Henggeler, Irrigation Specialist, is on the Irrigation website. Your local Extension Center can also help.

Has your soybean yield in a particular field dropped slightly despite it looking healthy all year? There could be a problem underground. Dr. Grover Shannon mentioned at a meeting this past week an increasing number of Race 2 Soybean Cyst Nematode (SCN) fields in Southeast Missouri. If you have been planting commercial SCN resistant varieties for several years you may have noticed that the primary resistance is Race 3 and 14. This is because almost all of the resistance comes from the PI88788 line. Over time, these suspect fields could have shifted to a different dominant species. The HG Tests that have come across my desk have been Race 5 dominant. So, with Race 2 and 5 moving in, the difficult question is what do you do.

As I stated, most of the commercial Roundup Ready varieties are Race 3 and 14 resistant. I also indicated in last months newsletter that SCN can silently rob up to 30% of your potential yield without showing symptoms. So, the first thing to do, if you suspect something, is to have a HG (Race) Test conducted by the nematology lab. They charge $50 and it takes about a month for the results. Once you have determined the dominant SCN species in your field the next difficult thing is finding a soybean variety that fits the SCN Race. Research is being done currently on incorporating broad Hartwig type resistance into soybean varieties. There are some conventional public varieties as well as private Roundup Ready varieties that could fit the description. Contact your local Extension Center for any possible sources.

Root Knot Nematode (RKN) is also a concern for some producers. It is also important to determine either through testing or positive identification of galls present on last season’s crop the presence of RKN. Resistant varieties is the best management strategy for this general feeder.

If flooding is a problem for some of your fields or parts then you may want to check out the research being conducted on flood tolerant varieties. The Extension Center has a list of those varieties identified as having some tolerance to flooded conditions.