Don't Forget About pH
As fall harvest winds down, it’s a great time to take care of the most fundamental soil amendment that is critical to next year’s cropping plan success. A lot of growers miss the opportunity to get the most “bang” for their fertilizer, herbicide, and seed investment next y
ear by letting their soil PH’s slip by under the radar screen. It does little good to spend big money on nitrogen, phosphorus and potassium, while letting soil PH’s go unadjusted to proper ranges. If PH’s are low, you could be losing 50% of your fertilizer eefficiency on the dollars you are spending!! With fertilizer costs being a major part of the cost of producing a crop, that has to be taken seriously to get the highest return on input investment.
Here are some of the benefitts of adjusting PH to proper levels:
- Improving the physical, biological properties of the soil.
- Enhances the effectiveness of some herbicides.
- Supplies calcium, magnesium and other minerals to the soil.
- Better nitrogen xation by legume crops.
- Increases nutrient availability to plants.
Think about how all of this plays together... If we can’t get all of the good out of the fertilizer (N,P, K and micros) that we are putting out and spending big money on, how do we expect to get full return on our herbicide or seed investment?
So how do we go about determining whether or not we need to adjust PH? Start with a good soil test that was taken within the last 3 or 4 years. We like grid soil sampling on 2.5, 3.3 or 4.4 acre grids with 12 or more plugs taken to form the sample per grid. If your eld hasn’t been sampled in that time frame, have someone sample it this fall. Don’t guess. There can be huge variability across a eld. Keep in mind… You don’t want to add Ag Lime to an area that has a PH level above 7.0 or calcium base saturation level of 75% (This is an area a lot of folks also miss). Also, make sure that you have included on your tests the base saturation level for calcium, magnesium, potassium and hydrogen and in some area’s - soluble salts. If you don’t have those on your tests today ask for them in the future. Many testing companies don’t run them on their reports but they are available. In our opinion, this is some of the most important information on the soil test.
When looking at liming sources make sure to get a good quality sample of the lime to have it tested. There are a lot of sources of lime from Ag Lime from a quarry to water treatment plants and all things in between. When it comes to Lime… You need to know what you are spreading, so have it tested. The last thing you want to do is spread a lime source that is high in magnesium on a soil that is already high in magnesium. If you are using water treatment lime, for example, have it tested by a quality lab to determine if there are any other things in it that are harmful to the soil. Another critical reason we need to test the lime is to make sure we know what the ECCE or CCE values are to make a proper recommendation of how much lime to spread on the low testing area’s in your fields.
Once you have your soil test and a good lime source test, you are able to make a proper recommendation, if needed, to specially adjust PH on all acres within your fields. Most crops like corn, soybeans, wheat and alfalfa like to be in a general PH range of 6.4 to 6.8. Anything below that range needs to be adjusted to optimize nutrient uptake, plant growth, as well as other chemical processes that happen within the soil prole throughout the year. If you are unsure with what you are dealing with, seek help! There are a lot of folks with good software programs that write variable rate prescriptions to take care of low testing spots within a eld. For years, some growers took the approach of spreading 2 tons of Ag Lime every so many years whether they needed it or not, while others didn’t worry about spreading anything. We have seen all kinds of scenarios over the years, from fields that have extremely low PH values from no lime application, to excessively high PH values by over-applying because it was the way Dad or Grandpa did it for the last 50 years.
In closing, PH is the most important soil amendment. It is basic and fundamental to row crop production in so many ways, but is at times the most ignored by a lot of producers. It needs to be monitored and watched with care, because if it’s too high it’s a problem… and if it’s too low it’s a huge problem! If resources are limited, we would rather see a grower spend money to adjust PH than spend it on P and K for a year. We constantly see growers spend $20 to $30 per acre on “snake-oil” or “spoof-juice” that promises a 10 or 15 bushel gain in corn or 5 bushel gain in soybeans. Most of the time these programs disappoint, and the grower would have been much better o paying closer attention to the foundational fertility properties on all the acres within each field.