April's Ag Advice by April Borders As we move into the harvest season, it is a good time to start thinking about your nutrient management program. Soil testing is the best science-based means we have for evaluating the health of our soils for production of crops. A good nutrient management program should have soil testing as a top priority.
Harvest time is an excellent time to evaluate the variability in fields and plan fall soil sampling. The differences you detect in grain yield when crossing a field are a good indication of variation in soils, landscape and water availability. Making notes when in the combine can be useful in later finding those parts of the field where grain yields differences require further attention, starting with a soil analysis. Using GPS to record these areas in a field can also help with future sample collection.
You need to remember that the soil test is only as good as the sample collected. Assuring that representative samples are collected means being involved in selecting the areas to be samples. If you are not doing the sampling, it becomes critical that the person taking the samples has clear directions on where to sample each field, avoiding problem areas. These "problem areas" should be sampled separately especially if production differences were noted in these areas. Separate soil samples may provide some insight into opportunities to fine tune nutrient management and overall productivity.
When to sample is a question asked each fall, especially if you practice fall fertilization. Traditionally the recommendation has been to wait until soil temperatures drop below 5 degrees C (41 degrees F) before sampling. Because soils are still mineralizing nitrogen, producers should wait until after Sept. 15, to take deep nitrate-nitrogen soil tests (24-inch depth).
Soil samples for nitrogen, sulfur and chloride need to be taken to a depth of 24 inches since these nutrients can move readily down into the soil with water. The best way to ensure that you get an accurate fertilizer recommendation for all nutrients is to send the sample to the lab in two bags, one from the top 6 inches and the other from the next 18 inches of soil. The top 6-inch depth is tested for all nutrients and the 6 to 24-inch depth is tested only for the nitrogen and sulfur or chloride if requested. Most often the soil-testing labs will bill these "two bag" samples as one sample.
Building a successful fertilizer management plan starts with a soil test. Having a representative sample, ensuring that field variability is considered, and timing your sample to best represent the field conditions, will go a long way toward building an appropriate nutrient management plan. A soil test is your way of doing a field check-up to ensure the health of future crop production.
When growing crops, the concept of building fertile soils requires some careful nutrient bookkeeping. Profitable crop production has high yields as its foundation. High yields do not just happen by chance, but rather are the result of persistent attention to detail in planning and implementing new and improved crop and nutrient management and technology.
Make the most of a nutrient management plan. It is sound science. It is the science of soil testing, crop residue inputs, crop nutrient removal, and fertilizer application rates and timing. For more information contact the Clay County Extension Office at 677-7111.