Why is that spot in the field so yellow? Why are the plants in this area green and growing and others looking like they are suffering from disease or other problems? Why do my plants start to grow so slowly, my neighbors grew much faster than mine and we planted the same day? How many times have you asked yourself these or similar questions?
Diagnosing problem areas in fields can be challenging but it is part of any agronomist’s job. Sometimes we determine the exact cause of the problem and other times we may have a list of potential problems. One of the most frustrating problems to solve occurs when a grower asks us in the winter about a problem they had the previous summer and wants to know the problem. NOW is the time to look at problem fields and determine what is occurring in the field.
When I visit a problem field, I begin by looking at the overall appearance of the field. It doesn’t matter if the grower is growing tobacco, corn, soybeans, cotton, peanuts or other crops. I observe which areas are different in the field. Are some areas or spots yellow while the majority of the field is green, or is most of the field yellow with a few spots of green? I look for any patterns that may be visible. If a farmer is applying starter fertilizer and some lines clog, there will be a definite row pattern.
A more common occurrence is for some spots in the field to be yellow. If that is the case, is there a difference in color of the soil? Sandy or clay areas in fields are often problems waiting for the correct weather to show themselves. This spring has been one of those years. Many fields have yellow spots, especially in sandy areas of the field. As soon as you enter an area of the field where the soil is darker, the plants are green. Yellow sandy spots in fields may be caused by a deficiency of Nitrogen, Sulfur, Magnesium, Manganese or other nutrients. The only way to determine which nutrient(s) are deficient is to pull a “Problem Area Soil Sample”. To do this, we pull a sample from the yellow area of the field and a separate sample from the green area. We label these samples “Bad” and “Good” and submit them to the lab for analysis. The lab not only analyzes each sample, but they look for differences that may explain the problem. Many fields this spring have shown problems that have been associated with either a low or a high pH in the problem areas. Without “Problem Area Soil Samples”, many of these problems would not be diagnosed. With these diagnostic samples, farmers are told which areas of the field to treat with which nutrient or lime.
Pulling these site-specific soil samples must be done while the symptoms are showing up in the field. If you wait until the fall, you may not remember where the problems were. Check your fields and see if you have any “problem areas”. If so, ask your local Extension Agent to assist you with determining what problems you have. Don’t wait and ask us this winter about the problem. With proper diagnosis and proper treatments, your crops will look better, yield better and your neighbors will not be wondering what is going on in your fields.
source: ncsu.edu