Abstract
The highly weathered, acidic tropical soils are generally less fertile because of their low pH, high exchangeable acidity, and Al, Fe, and Mn saturations. Using soil amendments to solve the aforementioned problems is essential. To this end, Calciprill and sodium silicate are worth considering because of their high neutralizing value and dissolution to suppress exchangeable acidity and Al, Fe, and Mn hydrolysis, while at the same time increasing soil pH to improve the availability of inorganic N, available P, exchangeable base cations, and Effective Cation Exchange Capacity (ECEC). An incubation study was conducted to determine the right combination of Calciprill and sodium silicate to reduce exchangeable acidity and Al and Fe hydrolysis to improve inorganic N, available P, exchangeable base cations availability, and ECEC. Bekenu series (Typic Paleudults) was incubated with a combined use of Calciprill at 80%, 90%, and 100% Ca saturations and sodium silicate at 90, 105, 120, 135, and 150 kg ha−1 for 40, 80, and 120 days, respectively. The laboratory incubation study was carried out using a Completely Randomized Design (CRD) with triplicates to determine the aforementioned treatment effects of the combined use of Calciprill and sodium silicate on soil pH, exchangeable, Al, inorganic N, available P, electrical conductivity, exchangeable cations (K, Ca, Mg, Na, Fe, and Mn), and ECEC using standard procedures. Soils with both amendments significantly increased soil inorganic N, available P, electrical conductivity, exchangeable base cations (K, Ca, Mg, and Na), and ECEC. This was because the amendments increased soil pH by suppressing exchangeable acidity. Moreover, they transformed Al, Fe, and Mn ions into insoluble compounds such as Al and Fe hydroxides and Mn oxides because of their high inherent exchangeable cations, especially Ca and Na. This suggests that the combined use of Calciprill and sodium silicate can enhance soil productivity. The most suitable combination is 7.80 g Calciprill and 9.26 g sodium silicate (C3S5) per one kilogram soil. Additionally, the findings provide fundamental information for future greenhouse and field trials to determine the effects of the suitable combination of the amendments uncovered by this present study on soil health and crop productivity.
Highlights
In the tropics, high rainfall and warm temperature cause the formation of highly weathered acidic soils because of the leaching of exchangeable base cations (Ca, Mg, K, andNa) which are replaced by soluble Al3+, Fe2+, Mn2+, and H+ on the exchange sites of the weathered soils [1,2]
This suggests that the soil was saturated with Al toxicity and this explains its low available P (1.24 ppm) because of Al fixation; it required the application of Calciprill and sodium silicate to increase its pH to a desirable range of 5.5 to 7 [19]
Combined use of Calciprill and sodium silicate on Bekenu series improves its chemical properties via increased inorganic N, available P, electrical conductivity, exchangeable base cations (K, Ca, Mg, and Na), and Exchange Capacity (ECEC). This is because the amendments increase soil pH to reduce exchangeable acidity, in addition to transforming soluble acidic cations (Al, Fe, and Mn) into insoluble and unreactive forms through neutralization and immobilization of exchangeable H+
Summary
Na) which are replaced by soluble Al3+ , Fe2+ , Mn2+ , and H+ on the exchange sites of the weathered soils [1,2] This results in acidification that can impair soil and crop productivity because of the reduced availability of macronutrients (P, K, Ca, and Mg) following the occupation of soluble Al and Fe oxides known to be detrimental to crop health, because these ions are toxic [3]. Fe, and Mn ions can fix P by reacting with HPO4 2− and H2 PO4 − to form insoluble precipitates. This chemical reaction reduces soil P availability [5]. On the other hand, when soil pH is higher than 7.3, P availability is significantly reduced because of P fixation by
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