Importance of Soil pH in Pastures

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With fertilizer prices the way that they are now, can you justify the cost of applying fertilizers to your pastures? It is hard to see the benefit since prices have more than doubled in the past several years. The good news is that there are some options and management decisions that producers can utilize to help maintain or increase soil nutrients in their pastures!

The most important thing to do is to take a soil sample and have it tested. Even if you have no intent to use commercial fertilizers, the results from the analysis are a great tool to use. It will give you the pH of the soil and the recommended amount of lime to apply. It will also give recommendations for other nutrients in the soil (nitrogen, phosphorous, potassium and minerals, and other nutrients). So, even if you are not going to apply fertilizer this year, it will show you how healthy or poor your soil is. If the recommendations and nutrient indexes look good, then your soils may be better than you thought, and you can get away without applying a lot of fertilizer. On the other hand, if the report calls for a high rate of nutrients, you may need to sharpen your pencil and see if it would be worth spending some money on fertilizers or finding an alternative source of nutrients. Either way, without taking a soil sample knowing how healthy or poor your soil is will be a shot in the dark.

Extension Agents are a great source to use to help interpret your soil analysis. Unhealthy soils will not provide the most growth in forages, which will lead to less yields. Again, to reiterate how important a soil test is in comparison to fertilize prices now is to know what your soils do recommend. Especially if you decide to apply fertilizer, you need to know exactly how much to put out. Underapplying nutrients will not give you the maximum yields and over-applying nutrients is throwing unneeded dollars out.

The most important numbers in the analysis are the pH and the recommended rate of lime needed. Why is this more important than the nutrient recommendations? All the numbers are important, but soil pH influences several factors that effect plant growth and nutrient utilization. pH is the alkalinity or sweetness of the soil. It affects soil bacteria, nutrient leaching, and absorption as well as soil structure.

The optimum Soil pH for forages is between 6 and 7. This optimum pH range is going to encourage the most soil bacteria. The bacteria help release nitrogen from organic matter and certain fertilizers so it can be absorbed by the plant. Soil pH is going to have a similar effect on other nutrients as well. When the pH is lower, it increased the solubility of Al (aluminum), Mn (manganese), and Fe (iron). These elements can be toxic to plants and slow to stop root growth. When soil pH gets too high or too low, it lowers the availability of nutrients for plants. This is why pH is so important in soil health. If the pH is not in that optimal range, even if you apply fertilizers and nutrients, you will likely not see the response from those applications. So, make sure that you are paying attention to the pH level and applying lime when needed.

The one economic benefit of applying lime to correct the pH is the overall price of lime. It is much cheaper per ton than fertilizer. If a soil report shows that 1 ton/acre or more is needed, then applying lime will be a better investment than applying fertilize that year. After applying lime, it takes a while to work and neutralize the soil pH. It can take up to 18 months to see a difference in the pH levels.

If you would like to receive more information on soil samples, soil health, or other ways to improve your pastures, please contact your local Extension Agent.