Keeping crops healthy
Depending upon when they were planted, crops are either emerging or starting to grow quickly. This time of year, million-dollar rains (rains around 1 inch) encourage crops to grow quickly. Soil microbes live in the water films around roots, using water to travel around and to process nutrients. After a nice rain, crops often have tremendous growth because plant available nutrients are being released. Unfortunately, either too much rain or not enough, greatly slows down plant nutrient acquisition.
Scouting corn, soybeans, and even vegetable crops; nutrient deficiencies are already starting to appear, although the signs are subtle. In corn, yellow striping on corn leaves is a sign of sulfur (S) deficiency and most soil test are showing that S is lacking. Sulfur is needed to make proteins like cysteine and methionine. Since the enforcement of the Clean Air Act (which was a free source of S), some fields may now need S fertilization. Sulfur is needed in a 10:1 nitrogen to sulfur ratio to maximize crop production. Sulfur is a part of many fertilizers, so it can easily be supplemented during the growing season.
Phosphorus (P) deficiency shows up as purple at the bottom of corn stalks and was quite noticeable in some field either this year. Some recent rains and warmer weather have lessened the purple coloring as soil microbes make P more available. Excess rain, soil compaction, and poor soil structure can make all nutrient deficiencies worse. Many of these nutrients need to be taken up in a reduced form, which often is soluble and leaches easily out of the soil profile. When soil compaction or poor soil structure exist, crop roots may not grow vigorously or even survive in saturated soils lacking oxygen.
Three other nutrients that may be lacking are Manganese (Mn), Iron Fe), and Zinc (Zn). The use of glyphosate (Roundup) tends to chelate or tie up these essential micro-nutrients. Oats can be planted as a cover crop to counter the negative effects of glyphosate. Manganese (Mn) and Iron (Fe) deficiency symptoms are often quite similar. On corn and soybeans, it shows up as yellow veins towards the leaf tip. All corn and soybeans should be a dark green to maximize photosynthesis. On strawberries, blackberries, and raspberries look for dark green veins with yellow green leaf tissue between the veins. For zinc (Zn)