29 Our Advertisers Appreciate Your Business Better Farming | January 2024 you’ll mostly see other nutrient deficiencies.” How does a lack of calcium cause other deficiency symptoms? That’s because one of the many roles calcium plays in the plant is “regulating the uptake of other nutrients. Calcium is also a messenger in the plant,” says Duggan. This means that when calcium is low, other nutrients are not being taken up, and are not moving throughout the plant properly. And you will begin to see other deficiencies. This is where soil sampling comes in handy – you need to know your starting point, before you can decide if adding calcium or other nutrients would help. There are two ways to measure how much calcium you have in your soil: Parts per million (ppm) or base saturation. Ppm is measured exactly as it is named – how many parts in a million are calcium. Base saturation is a little more complicated. To understand base saturation , you must understand cation exchange capacity (CEC). Cations are positively charged ions, like calcium (Ca2+) or magnesium (Mg2+). Cations are both floating in the soil solution and attached to soil particles. These cations can change places with each other – hence the term cation exchange. Therefore, CEC is the total amount of cations attached to negatively charged soil particles that can be exchanged with the cations dissolved in the soil water. You get your base saturation when you take the sum of all the base cations you are measuring for (in this case, calcium), divide it by the CEC value, and express it as a percentage. Duggan prefers to measure calcium through base saturation: “There is lots of debate over which is a better measure, but I find base saturation does a better job of showing how much calcium is actually available.” In most of the soils Duggan has dealt with, the calcium base saturation hovers around 30 per cent – and agronomists want to see over 65 per cent. That means that those soils need a fair amount of calcium to get that increase, and therefore, liming is usually the way to go – applying tons per acre, rather than pounds. Lime is used interchangeably as a term for any high calcium material that can be applied to soils. According to Duggan, liming can be seen through the lens of either nutrients or pH. “I define liming as applying calcium as a nutrient. Other people see it as applying lime to increase the pH.” This is because calcium plays a role in the soil itself. “Calcium keeps things in balance,” says Duggan. “It’s important for buffering, and increases soil pH.” There is another – often underrated – role that calcium can play in the crop, and that is disease suppression. One disease where this is being considered is clubroot. Dr. Stephen Strelkov, professor of Plant Pathology at the University of Alberta, is a clubroot expert. “Clubroot is a soil-borne disease of Brassica species, like canola. The pathogen, Plasmodiophora brassicae, is difficult to control because it produces a lot of resting spores that can persist in the soil for years,” explains Strelkov. “Clubroot forms large galls that interfere with nutrient and water uptake, leading to poor plant growth, low yield, and early senescence (plant death). “We are still working to distinguish the effects of calcium specifically versus increased pH, but both increased calcium and increased pH have been hypothesized to reduce clubroot,” says Strelkov. How does pH or calcium suppress clubroot? Generally, of course, a healthy plant withstands disease better than an unhealthy plant, so having adequate calcium and a closer to neutral soil pH helps ensure a healthy crop. Although the specific cause hasn’t been conclusively identified, “either the presence of calcium and/or the increase in pH can inhibit resting spore germination and reduce the formation and maturation of primary zoosporangia (resulting in a decrease in primary and secondary REVOLUTIONIZE AGRIBUSINESS WITH ADVANCED ITALIAN MACHINERY From harvesters to fruit picking machinery, discover Italian ingenuity and innovation Seize new opportunities and redefine success in agribusiness EXPLORE AGRICULTURAL INNOVATIONS TODAY machinesitalia.org BENEFITS OF CALCIUM Morgan Duggan Stephen Strelkov
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