Over the years I have often talked about the importance of correcting soil pH problems to maximize crop yields. Some people may be wondering where I am getting my information when I talk about this. A lot of research done over the years has very emphatically backed this concept. A study that Ken Kelley, Crops and Soils Research Agronomist at the K-State Ag Research Center in Parsons, did several years ago verifies the affect that different pH levels has on grain sorghum, soybeans and wheat yields here in southeast Kansas.
Ken’s work was done over a period of four years and compared crop production at five different pH levels including 5.3, 5.6, 6.3, 6.7, 7.2. Crops included in this project were grain sorghum, full season soybeans, double crop soybeans and wheat. Corn is not included but results would most likely be similar to grain sorghum. It is generally accepted that the a pH level of 6.8 is ideal for most crops grown here in Kansas. A pH of 7.0 is considered neutral with any pH below that being acid while any pH above that is considered alkaline. A soil with a pH of 5.3 would be considered very acidic from a crop production standpoint.
To make this simple I will list the yields from each pH level for each crop in consecutive order from the lowest pH level to the highest. The first yield corresponds with a pH of 5.3 and so on. Refer to the list of pH levels above to determine which pH level each yield represents. The average yields for grain sorghum over four years at the pH levels listed above were 83.8, 89.9, 96.3, 99.3 and 99 bushels per acre. The average yields over four years of testing for full season soybeans were 28.2, 30.3, 33.6, 34.2, and 35 bushels pear acre. The average yield over three years of double crop soybeans were 17.6, 20.3, 22, 23.3 and 22.3 bushels per acre. The average yield for wheat over three years were 45.4, 46.1, 47.3, 49.1 and 48.2.
As you can see, there was definitely a response by all crops to the varying pH levels. It is obvious that the best overall response from lime was on double-crop soybeans where there was a 27% response from the lowest to the highest average yield or 4.7 bushels. Full season beans were next with a positive response from the lowest to the highest yield of 24% or 6.8 bushels. Grain sorghum was next with a difference from the lowest to the highest of 18% or 15.5 bushels. Wheat gave the least response with a difference from the lowest to the highest yield of 6% or 2.8 bushels per acre.
So this study makes it clear that liming is important. However, it is also clear in cases where the pH is only slightly lower than it should be that the response may not pay off in the short run. However, maintaining a favorable pH over time is probably the best way to go. I say this because the total cost of liming over a period of years by a regular maintenance application of lime based on a soil test probably won’t cost any more than liming at long intervals. These long intervals will allow the pH to go down to levels that are seriously restricting crop yield whereas regular maintenance applications based off of a soil test will keep crop yield loss due to pH problems at a minimum. Therefore total grain produced by maintaining the pH at the ideal level will be higher meaning that long term profitability will be higher as well.
PITTSBURG —
