The present study aims to test and evaluate the efficiency of a new modified method of organic matter evaluation. It allows the assessment of the quality and quantity of the primary soil organic matter and the stable organic fractions separately. The new method was tested in six soil samples of different localities in the Czech Republic. This method is based on observing reaction kinetics during the oxidation of soil organic matter and measuring the cation-exchange capacity of stable organic fractions. The results were compared with classical methods, which rely on the isolation of humic substances, determination of the content of humic acids and fulvic acids and their ratio CHA:CFA, quotient E4/6, and fractionation of soil organic matter according to resistance to oxidation. It turned out that the results of the new modified method are more sensitive in comparison with the results obtained by classical procedures. The linear regression demonstrated the dependence between the amounts of soil organic matter determined by the classical method compared with the modified method. Moreover, the new modified method was found to be faster and not demanding on laboratory equipment. The new method has been improved to be easily repeatable, and some shortcomings of the previous method were eliminated. Based on our results and other recent studies, the modified method may be recommended for the practical evaluation of soil organic matter conditions.
Global deposits of concentrated phosphates, which are a necessary source for the production of phosphate fertilizers, are limited. These reserves keep getting thinner, and every day, large amounts of phosphorus end up in watercourses. In this study, we verified that modified biochar (saturated with FeCl3 solution and then neutralized with NaOH solution) can adsorb significant amounts of phosphorus from wastewater. Moreover, the agrochemical qualities of sludge water from a municipal wastewater treatment plant, struvite, phosphorus-saturated biochar, and iron(III) phosphate from a reused biochar filter were tested in this study. We determined the amount of mobile phosphorus as well as the amount of extractable phosphorus and its five fractions. It was found that modified biochar can hold one-third of the phosphorus amount contained in the commonly used agricultural fertilizer simple superphosphate (1 × 105 g of modified biochar captures up to 2.79 × 103 g of P). Moreover, plants can more easily access phosphorus biochar fractions than struvite, which is formed spontaneously during sludge management. The results of this research prove that the proposed method of recycling phosphorus from wastewater can be applied in technological practice.
A hypothesis is tested that allows study of not only the quantity but also the quality of ion exchange in soils, composts, peats, and its mixtures, which is common in natural and synthetic ion exchangers, on the basis of the ion-exchange process and its selectivity. For practical application of ion exchange in the soil not only the quantity of base cations and hydroxon ions bound by the solid soil phase is significant but also their readiness to ion exchange or ion exchange elasticity. Selectivity of ion exchange, expressed by selectivity coefficient, reflects the readiness of ion exchange while ion-exchange thermodynamics show the degree of spontaneity of the ion-exchange process. The results document that soil humus is the highest-quality ion exchanger in soil and that its quality may be assessed by the proposed method. The effort to replace humus by any synthetic ion exchangers cannot be successful: Although they have a high value of cation exchange capacity, they also show high selectivity for ions of higher valence and low ion-exchange elasticity, and their desorption of calcium and magnesium is poor.
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