Why should every landowner have some knowledge of soil testing?
Soil Testing is often misunderstood by both crop producers and landowners. I will attempt to clarify some things about soil tests. I would like readers to understand that soil tests have their limitations, however, they are still one of our most valuable tools in assessing soil fertility status and even more, understanding differences in how soils may compare.
First, as the saying goes the soil test is only as good as the sample taken. Most soil samplers do a good job taking samples and recognize the importance of consistency in sample depth. Sampling areas are much smaller than what used to be sampled so sample variability is reduced. The time of year the soil sample is taken, the crop grown previous to soil sampling and how mellow the soil is can also be factors in sample variability from one sampling period to another.
Soil sampling needs history
A history of soil samples from a field is much more valuable than a single soil sample. Be certain that you are keeping records which include soil tests from each field. Histories of soil samples reveal trends in fertility levels and pH, which could signal that some actions need to be taken. Using the same laboratory helps assure consistency in data. If different laboratories have been used, visit with the labs or your crop advisor to understand what differences in procedures or analyses are being used.
It is well to understand that most soil tests are indices of availability and do not reflect “actual” pounds of available nutrients. In other words, the numbers indicate whether the nutrient level in the soil should be adequate for crop demand or not. Think of it as a dipstick for oil in your engine. Some automobiles require 5 quarts of oil to be adequate on the dipstick. Others require 7 quarts. The dipstick level is simply telling you if you have an adequate level. It doesn’t actually tell you how many quarts of oil you have.
Does soil testing tell me how productive my soil are?
Soil tests will not necessarily indicate that one soil is more productive than another. There are many other factors that affect productivity besides fertility. One of the main factors that affect soil productivity is air and water management. There are some factors on the soil test that can be indicators of poor soil and water management, but are not the only factors.
Soil and crop management can also affect nutrient availability and uptake. Even though the soil test reveals adequate levels, sidewall compaction caused at planting or a compacted soil from tillage or heavy equipment will limit root growth and reduce nutrient availability. Chemical damage to root systems can also limit nutrient uptake.
Understand, though, that soil tests are still our best tool in developing crop nutrient plans and assessing our soils. Your doctor wouldn’t diagnose your ailments without first running some tests. The same should be true when we are making recommendations for our crops.
In the next blog, I will detail some of the soil chemistry that is reflective of more productive soils.
This post was written by Bob Hecht. Bob was an agronomist for Midwest Laboratories, Inc for 21 years before becoming a partner in Soil Solutions in 2001. Advising agricultural producers to make them most profitable has been the cornerstone of their business. Helping farmers with cropping decisions, understanding soil fertility, air and water management, and the benefits of soil amendments such as gypsum and lime are key components to a producers profitability. You can learn more at www.soilsolutions.net