Here’s hoping everyone is having a wonderful Thanksgiving weekend. Last week Alicia Boor, Barton County Extension ANR agent, wrote a column regarding soil testing and soil pH. This column discussed different tasks good producers perform during the winter. One of these was soil sampling reviewing the 2013 yield results and making adjustments for 2014. Some problems can be corrected quickly and immediately with good results, others require long-term planning, time, and patience. The soil environment provides a classic example of the latter, particularly soil pH. Besides the direct effects of soil pH on crop growth, disease pressure, and herbicide efficacy; soil pH is critical in determining the availability of essential plant nutrients and toxins like aluminum.
• While there are areas of soils with basic pH (pH > 7) in our area, most are not high enough for producers to be terribly concerned about. Even if the soil pH was high enough and contained significant amounts of calcium carbonate resulting in iron and phosphorus deficiencies, it isn’t typically economically feasible or practical to lower the pH to near neutral. Producers have other options in terms of crop and variety selection to address the issue. Over a very, very long time (without irrigation containing high levels of base cations) using nitrogen fertilizers will slowly decrease soil pH. However, lowering the pH for the home gardener in a small area, while pricey, is practical. But even there the acidifying materials (there are several available) take months to a year to exhibit the desired lowering of soil pH.
• While soils north of the river tend towards neutral to basic pH levels, soils south of the river, the coarser (sandier) soils tend towards the acid level. This is the result of several factors including what the soil formed from and its lack of buffering capacity. The ideal soil pH for nutrient availability of our common crops is in the range of 6.2 – 7.5. Many of the sandier soils after decades of nitrogen fertilization are often under 5.5 and a few even under 5 which is 100 times more acid than a pH of 7. Unlike dealing with high pH, raising soil pH is practical for producers and while not cheap is economically feasible, especially when amortized over the length of the benefits (five to seven years). The application of one of several forms of lime neutralizes acidity and raises the pH to acceptable levels. However, common limestone (it’s essentially rock) takes time to work, especially under dry soil conditions. It is best to allow upwards of a year for the lime to achieve the desired effect on soil pH.
The above two points are where reviewing the cropping history and yields of individual fields over time is important. Soil pH changes happen gradually over an extended period of time and cropping problems may have to become extreme before really being noticed unless detailed records are kept and examined.