The idea behind that title is that if crop yields drop because soil pH is too low, more land must be worked in order for farmers to harvest the necessary feed tonnage required by their livestock. Working more land than what might otherwise be necessary means bigger numbers on the dashboard hour gauge; with those increased numbers, more and more wear and tear takes its toll. Let’s review just how optimum soil pH would be beneficial.
Crop growers generally agree that fertilizer utilization is best when soil pH is optimized for the intended crop. For corn, clovers and most grasses, we get best returns on fertilizer investment by raising soil pH to 6.2. Alfalfa (less tolerant of soil acidity than most other crops) wants pH in the 6.8 – 7.0 range. When soil test results indicate a certain lime tonnage per acre for clover or corn, add one ton to that figure to get alfalfa recommendations.
Understand that one-ton recommendation is based on 100% ENV (estimated neutralizing value); with most ground limestones weighing in at 70% ENV, growers actually have to apply about 1.4 tons/acre of 70% ENV ground limestone to please alfalfa. When we undershoot the needed pH, fertilizer utilization efficiency often drops by 30% – 50%, depending on degree of undershot.
All of the big three nutrients – nitrogen (N), phosphate (P) and potash (K) – are 100% available at pH 7.0. They’re often referred to as macronutrients. When pH drops to 5.5, N and K availabilities drop to 77%. At that low pH, P is only 48% available. Land Grant Institute research has shown that at pH 5.0 – 5.2, P is only 10% available. Often, I recommend that with most crops (potatoes and blueberries excluded), don’t bother applying the big three unless pH has been dragged up into the “sixes.”
More review on the chemistry of commercial fertilizer manufacture is in order. Of the big three, I place most emphasis on N, because with commercial fertilizer, N and P are closely related. N can be applied separately from P in the commercial (non-organic) fertilizer world. But in that same world, P cannot be applied separately from N. Phosphorus must be applied as mono-ammonium phosphate or diammonium phosphate – period.
Conventional (non-organic) phosphate fertilizer production starts with mined rock phosphate being treated with sulfuric acid, a chemical reaction which yields phosphoric acid and waste slag. The phosphoric acid is then treated with ammonia, a reaction yielding mono-ammonium phosphate (MAP). When MAP is treated with more ammonia, the result is diammonium phosphate (DAP). The fertilizer analysis of MAP is 11-52-0 (N, P and K). The analysis of DAP is 18-46-0. Since ammonia is made from natural gas (CH4), along with carbon dioxide, atmospheric nitrogen and water, CH4 costs greatly influence end costs of all forms of commercial N and P fertilizers. Organic farmers often address P needs by simply using unrefined rock phosphate and/or bone meal.
Potash is somewhat independent, politically, of N and P. But in biology, N, P and K are very dependent on each other – all very critical for any life form. Politically, P and K are in their own kingdoms, mainly because their ores are mined in quite different geographic locations. Here’s why potash (83% elemental K) was center stage not too long ago, drawing both political and economic spotlights. Even before the Ukraine War started, Belarus diverted potash supplies from Lithuania to Russia. Lithuania stopped railway transport of Belarusian potash in February 2022. Washington imposed sanctions on Belarus in 2021, then blacklisted its export arm, Belarus Potash Company, as part of the punitive measures to counter Belarus’s President Lukashenko’s crackdown on his political opponents.
Almost co-incident with the COVID pandemic, the geopolitical scenario has been anything but boring. Fortunately, there are huge potash resources in North America. In Saskatchewan, Canada, K+S Potash (part of the K+S Group) is a German-based company that has been mining and processing salt for at least 125 years. With all the military and political confusion in eastern Europe, we expected continued upward price pressure on this soil nutrient, despite mineable abundance of this Canadian crop resource.
Perhaps as much as any other commodity, including energy (remember N and P price is strongly tied to methane’s), fertilizer ingredients are very susceptible to supply/demand tensions impacting the global marketplace.
American Farm Bureau data show that in 1961, U.S. farmers consumed 25% of the world’s fertilizer. In 2018, American farmers only consumed 10%. This doesn’t mean that our crop growers used less fertilizer; it means that growers elsewhere on Earth had significantly beefed up their consumption of N/P/K plant food.
With all the global uncertainty surrounding fertilizer aspects of farming, let me re-stress the need for soil testing as the cornerstone of successful crop production. Using the knowledge provided by those test results enables growers to resolve pH problems, directly improving the efficiency of herbicides and fertilizers. Usually this allows producers to lower fertilizer rates. Where most fertilizer, ag chemicals and seed costs are up 50% – 100% since 2020, ag lime cost increases remain in the single digit percentages.
This just in from Syracuse-based Mercer Milling’s monthly update: “The market quiet is over, due to freight increases. With recent issues in the Middle East, shipping lines are not allowing their vessels to go into the Red Sea, due to fear of terrorist attacks. These ships are now forced to go around the tip of Africa, adding 10 days or so to their journey. The Panama Canal has also reduced the number of its ships allowed by 38%, and lowered the weight capacity of vessels due to extremely low water levels. These two issues are causing freight rates to jump pretty dramatically.”
Once again, this all helps prove that not knowing your soil’s nutrient needs – particularly lime – is a case where ignorance is anything but bliss.
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