LYSIMETRIC AND CHEMICAL INVESTIGATIONS OF PEDOLOGICAL CHANGES

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Abstract
The study consisted of lysimeters and associated plots with shallow and deep chemical treatments. The terms shallow and deep treatments refer to application of either KHCO2 or MgCO3 at the rate of 6 me/100 g of soil in the 10–30 cm layer and 12 me/100 g of soil in the 40–60 cm layer of a Mexico silt loam profile, respectively. The chemical analyses of profile samples taken at regular intervals, extracts of soil: water mixtures, and lysimeter drainage collected periodically were made to study the chemical characteristic of the profile and the fate of the applied cations to the profile.Seven years after the initial chemical addition, 27 and 32 percent of the applied K and 75 and 48 percent of the applied Mg were recovered as exchangeable cations from the shallow and deep treated plots, respectively. The increased exchangeable and water soluble quantities of cations in the treated layers resulted in the movement and redistribution of measurable quantities of K and Mg in the profile. The effects of the chemical treatments on the exchange characteristics of the cations Na, K, Ca, and Mg were studied through the selectivity numbers.During nine years of operation of the lysimeters, the total cationic losses (which may be arranged as K-deep > K-shallow > Mg-deep > Mg-shallow > check) were related to the volume of lysimeter leachings. The chemical composition of 1:1 soil water extracts of the 70–80 cm layer of the treated plots indicated that the extracts were in equilibrium with beidellite and kaolinite. The drainage water of the lysimeters plotted in the kaolinite stability field in the mineral stability diagram. The study consisted of lysimeters and associated plots with shallow and deep chemical treatments. The terms shallow and deep treatments refer to application of either KHCO2 or MgCO3 at the rate of 6 me/100 g of soil in the 10–30 cm layer and 12 me/100 g of soil in the 40–60 cm layer of a Mexico silt loam profile, respectively. The chemical analyses of profile samples taken at regular intervals, extracts of soil: water mixtures, and lysimeter drainage collected periodically were made to study the chemical characteristic of the profile and the fate of the applied cations to the profile. Seven years after the initial chemical addition, 27 and 32 percent of the applied K and 75 and 48 percent of the applied Mg were recovered as exchangeable cations from the shallow and deep treated plots, respectively. The increased exchangeable and water soluble quantities of cations in the treated layers resulted in the movement and redistribution of measurable quantities of K and Mg in the profile. The effects of the chemical treatments on the exchange characteristics of the cations Na, K, Ca, and Mg were studied through the selectivity numbers. During nine years of operation of the lysimeters, the total cationic losses (which may be arranged as K-deep > K-shallow > Mg-deep > Mg-shallow > check) were related to the volume of lysimeter leachings. The chemical composition of 1:1 soil water extracts of the 70–80 cm layer of the treated plots indicated that the extracts were in equilibrium with beidellite and kaolinite. The drainage water of the lysimeters plotted in the kaolinite stability field in the mineral stability diagram. © Williams & Wilkins 1976. All Rights Reserved.

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