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We have tried to respond to your requests to make IFC more "readable". You will find less detail than in previous issues, with fewer diagrams, numbers and chemical equations. Nevertheless, we hope that you will find the articles informative and interesting and, if you would like more details, please do not hesitate to contact us at IPI and we will do our best to supply them. You will also notice that we have decided to restart the numbering system and that this issue is therefore No. 1.
The need to explain the role of potassium in plant nutrition is as important as ever. Potash is often referred to as the "hidden" element. It is only hidden in the sense that the effect of its removal from the soil is less obvious in the short term than with some other plant nutrients and, if the soil is badly depleted, replenishment does not create an immediate crop response. In fact potassium in the soil is no more hidden than the money in a savings bank. Just as savings are "locked" away in safe keeping, most of the potassium in the soil is "locked" on to clay particles. Plants take up potassium from the soil that is in solution, rather like the cash in the pocket that is used for every day needs. Between the "savings" and the "cash" there is the small amount of potassium referred to as "exchangeable K". This is the rough equivalent of a current account at a bank. While in credit, the account can be drawn upon without penalty but, once the funds are exhausted, borrowings will be necessary for short term needs and these borrowings will incur interest charges. If the demand from crops exhausts the readily available potassium, replenishment in the form of inorganic fertilizer will go into the soil "bank" to repay what has been borrowed. It is only the excess over the borrowing that is available to nourish the crop. We hope to convince farmers not to let their potassium account run dry!