 Greetings, I'm Chris Augustine, Director of the Dickinson Research Extension Center. You might know me from my past experiences as a soil health specialist up at the North Central Research Extension Center in Minot. Now down in Dickinson, I will be continuing my soil outreach as well as soil research for the citizens of North Dakota. So one of the things that we're doing a lot of work on is pH. So pH is regarded by many as a master variable and that's because it controls a lot of chemical processes in the soil. When pHs are too high or too acidic, a lot of minerals may be plant available or plant unavailable. One of the classic examples is phosphorus. When you have pHs greater than 7.5, phosphorus can be tied up with calcium. When the pH is less than 5.5, the phosphorus can be tied up with aluminum and then it also influences biological processes as well as the chemical weathering of different minerals in the soil. So pH is really important with how we manage and grow crops on our soils. So what pH really is, is that's the activity of the hydrogen ion and we measure that or determine that by measuring the concentration of the hydrogen ion. And so hydrogen causes acidity but then we have hydroxyl which causes alkalinity. So hydrogen is H+, hydroxyl is OH- you put the two together and you get water H2O. So we look at water as the neutral substance. So when you have more hydrogen ions than you have hydroxyl ions, the system is acidic. And when you have more hydroxyl ions than hydrogen ions, that is then alkaline. And so we define this as a negative log of hydrogen. So as acidity increases, the pH actually goes down because it's a negative scale. Because it's a log base scale, when we change a unit of pH from 6 to 5, that would be a concentration increase of hydrogen by 10 times. But if we go from 6 to 4, all of a sudden that's a difference of 100 times more hydrogen in that more acidic environment. So with pH, that's alkalinity and acidity. The causes of pH are the minerals in our soil. Dakota areas that are typically acidic, they might have volcanic or granitic parent materials in North Dakota. We have a lot of carbonates and that's limestone. And the limestone has a tendency to actually cause alkalinity because it can neutralize acidifying effects of plants. One of the causes of acidity is nitrogen fertilizers. So regardless if you put urea on your soil or an hydrosammonia, manure, 115020, any sort of nitrogen fertilizer, at some point the bacteria in the soil want to convert that into nitrate and we call this process nitrification. So as the nitrogen makes these stair steps from that fertilizer to the nitrate, hydrogen is released. And so over time we can acidify our soils with this release of hydrogen from our nitrogen fertilizers. We can amend our acidic soils by adding a lime in amendment. And it's important to know what amendment you're putting down. I think there's a misconception out there that it's the calcium that neutralizes the hydrogen when in fact they both have plus charges so they would actually repel each other and they don't really react with each other. It's the carbonate, the CO3 that's tied within the limestone that actually neutralizes the hydrogen. And so when it reacts with acidity it produces carbon dioxide as well as water. Other calcium amendments such as gypsum or maybe calcium chloride, they won't neutralize the acidity of the soil. You may have a calcium deficiency and that can help alleviate that deficiency but if you have a pH issue it'll actually exacerbate the pH. And so what happens is we have hydrogen in our cation exchange sites of the soil and if you add a calcium amendment like gypsum the calcium will dissolve in the soil solution and it will free up some sulfate which plants can need. But the calcium will also bind to that cation exchange site and release the hydrogen which will further acidify the soil. One of the issues that we're seeing with soil pH is when the pH drops below 5.5 we can see something called aluminum toxicity. We have a lot of aluminum in our soils and when you look at clays they're predominantly made out of aluminum as well as silicates. So with the aluminum when it frees up in the soil solution it's already there but it's fairly chemically inert but when you get to a pH of 5.5 it can start freeing up in that soil solution. And when it frees up in the soil solution it has the ability to split three water molecules. And what happens is the OH of the H2O binds to that aluminum so it frees up the hydrogen. So when we start getting these pHs around 5.5 and as the aluminum frees up it can have the snowball effect and acidify the soil even more. Or free aluminum may absorb to a cation exchange site and free up more hydrogen that way which would further acidify the soil. And so aluminum can create some acidity but when there's too much aluminum in the soil which the data would suggest a concentration of 25 parts per million or more you can have this aluminum toxicity effect. And what happens is phosphorus can be tied up but also when there's too much aluminum present in the soil it can stunt root growth as well as hinder germination. And so there's all these bad things going on that can reduce crop growth and we can remediate these areas by putting on some sort of liming amendment whether that's calcium carbonate or we're using beet lime on a lot of our research trials. I know a number of growers who are using waste treatment lime from a local water plant as an amendment or you can even bipelitized lime. You need that carbonate to react with that acidity and neutralize the soil. So all in all pH controls a lot of things within our soil. Controls nutrient availability as well as biological activity and many other processes within the soil. If your pH is anywhere from six to seven point three or so that's a really good pH and I wouldn't worry about that. But if your pH gets less than five point five you should really consider putting on some liming amendments and plan on applying a couple tons because the concentration of hydrogen can be really great and it would require a lot of liming material to neutralize that.