I had a leaching column study without plants to characterize soils. KCl was added as K fertilizers along with urea and rock phosphate. in the leachate could find more NH4+ compared to ammonium sulphate added fertilizer mixture. why is that ?
If the soil is acidic, the soluble salt KCl increases the total ionic strength, displaces Al into solution, and so decreases pH. To respond the question about ammonium, K can displace exchangeable ammonium and that presumably is the source of the 'extra' ammonium.
First hand information says, use of MOP on long term basis has displayed potentially adverse effects on soil fertility in perennial fruits , especially when used in fertigation compared to other K-sources. In your soils , presumably an acidic Alfisol, it seems unlikely...especially using MOP will influence soil pH on the basis of such a short term application ..
Dear Mahesh,
Potassium fertilizer (KCl) has little or no effect on soil pH. And high concentration of chloride has been found to inhibit nitrification in soil (Ref: Darrah et al./Plant and Soil 97:37-45/ 1987).
Hope you find this information useful in your study.
I agree with Dr. Kundu. The MOP is the K salt of hydrochloric or muriatic acid. The salt is thus referred to as muriate of potash. It contains 50-52% K or 60-63% K2O and 45-47% Cl. Due to high concentration of chloride it may inhibit growth of nitrifying bacteria (both nitrosomonas and nitrobacter) with continuous application and ultimately nitrification.
I agree with all above appreciated responses, KCl has no significant effect on soil pH and actually there is a negative relation between high concentration of chloride and growth of nitrifying bacteria. in your leachate the more NH4+ may due to urea Hydrolysis resulted in Ammonium Carbonate (NH4)2CO3 and thus NH4 but the ammonium could be fixed by soil charge( clay& organic fraction) so your results depend on your soil texture and the amount of water used these may increase the NH4 in your leachate.
If the soil is acidic, the soluble salt KCl increases the total ionic strength, displaces Al into solution, and so decreases pH. To respond the question about ammonium, K can displace exchangeable ammonium and that presumably is the source of the 'extra' ammonium.
Yes ,that could be a strong possibility as suggested by Paul. Another possibility could be the microbial load of the soil, that could also limit the further conversion of ammonium into nitrite and/or nitrates..
Interesting question. Generally pH is not much affected by MOP application, but Cl ions do create problems for plants particularly tobacco, tea, woody fruit and forest trees most probably through promoting hydrolysis of certain entities the plants. Drs. Paul Milham and Dilip Kumar Kundu rightly pointed out NH4+ replaced by applied K while the decreased NH4+ hydrolysis due to ill-functioning of soil microbes as said by Dr. Anoop Kumar Srivastava seems valid reason of elevated NH4+ leaching. But do not forget the pore-bypass in pots.
. Under normal circumstances showing near neutral pH values , KCl would not alter the pH much. How ever an acidic soil may show decreased pH values as there are ample amounts of H+ ions adsorbed that comes into the soil solution as a result of exchange with K. Hence addition of K can acidify an acidic soil further.
Besides, Al adsorbed to soil colloids may be replaced by K by increasing the Al concentration in the soil solution, which are vulnerable to hydrolysis to introduce Hydrogen Ions to the solution acidifying the soil further.
Increase of ammonium in the leachate indicates also the desorption of already present exchangeable ammonium ions by added K. Of course, the added urea may got converted to ammonium as well in a quick succession.
Yes, I already did an experiment with acidic soil and KCl. And I found a slight decrease in the pH of the soil.
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