Gypsum as a source of calcium has again come to the fore as a quick way to improve soil structure.
Supplement calcium deficiencies, but above all improve the ability to harvest on clay soils. That is the place that plaster has acquired in arable farming. The calcium source quickly releases air again without structure. But does not solve any underlying problems, experts stress. The trade magazine Akkerwijzer delved a little deeper into the white panacea.
As if it had snowed. That’s how it seems when the plaster spreaders have done their job. Since the worm problem in the Flevopolder, gypsum as a source of calcium has come to the fore again, as a quick way to improve the ability to dig up the soil. Still, the use of plaster is far from new. Shortly after the war, and after the 1953 flood disaster in the Southwest, plaster of Paris was driven in large quantities over the clay soils. In order to expel the salt from the soil.
The large, positively charged calcium ions settle between the negatively charged clay plates. As a result, they are pressed apart and at the same time stably connected to each other. This contributes to a loose structure. Other positively charged elements, including sodium, but also potassium and magnesium, are pressed out of the clay-humus complex. Since sodium is the weakest bound, it is released easily and washes out. Get rid of salt.
Plaster is popular over the clay because it works quickly and does not affect the pH. Young sea clay naturally contains enough lime, in the form of shells, and the pH is often correct. But over time, the amount of easily soluble lime decreases and less calcium becomes available. Calcium is also lost through leaching and absorption by the crop. The occupancy of calcium in the clay-humus complex can therefore drop below 90 percent. That is a percentage that is seen on clay soils as an optimal occupation for a good soil structure.
Read the full background article in the trade magazine Akkerwijzer that subscribers received on Friday 19 February. Request a free trial number here