Growing interest in American Kinsey-Albrecht soil analysis RE SEARCH of potassium and sodium in the soil. You can only proceed to step 2 when step 1, the calcium/magnesium ratio, is in order. Clay soils often have a calcium/ magnesium ratio of 80/10. The pH (water) is then higher than 7 and there’s no hydrogen present. The exchange with potassium is then difficult in that type of soil. You’ll first have to lower the level of calcium in the soil in order to create space for potassium. This is done by leaching with anions (negatively-charged elements) such as phosphates, sulphates and nitrates. These take cations such as calcium and magnesium with them. In this case, we recommend sprinkling potassium and/or kieserite. The sulphate from these fertilisers binds to calcium and/or magnesium and is flushed out, creating space for potassium’, says Van Gurp. Also ensure sufficient organic material ‘If you’ve completed steps 1 and 2, you’ll see the ideal pH (water) value of 6.3. At this value, the occupancy rate of hydrogen is exactly 10 percent. Yes, this is a slightly acidic soil, but that’s what it should be. A soil always needs some form of acidification, because that’s the way to make micronutrients available to a plant. Close to the roots of the potato plant, the rhizosphere, the acidity is even lower. There the pH (water) is 4.5 to 5.0. That’s because the plant creates it itself. It’s an ideal pH for the bacteria that make minerals available for absorption by the plant roots. Sometimes potato growers apply sulphuric ammonia to their crop. This can get very close to the plant roots. But it disrupts the pH around the roots, and the biology, the interaction between soil life and the plant, no longer works, ‘explains the soil and fertilisation specialist. ‘There are still three more steps necessary to achieve optimal availability of macro and micro nutrients in the soil. Step 3 in this process is the correction of the amount of sulphur and phosphate in the soil because in combination with steps 1 and 2, this creates ideal conditions for the availability of trace elements for plants such as the potato. Step 4 involves the correction of the micronutrients, which The soil properties per EC category lead to much more accurate advice and recommendations based on the actual soil fertility per square metre. Potato World 2020 • number 2 29 Pagina 28

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