Assessment of physicochemical and аgrochemical indicators of the composting process

Mariana Hristova, Milena Harizanova and Irena Atanassova
Institute of Soil Science, Agrotechnologies and Plant Protection „Nikola Poushkarov“, 1080 Sofia, Bulgaria


Hristova, M., Harizanova, M. & Atanasova, I. (2021). Assessment of physicochemical and аgrochemical indicators of the composting process. Bulg. J. Agric. Sci., 27 (3), 498–504

The positive balance of soil organic matter (SOM) in arable land is the main issue of sustainable agriculture. Organic fertilization via composting is an effective method of soil productivity support. The deficit of traditional organic fertilizers creates the need to explore new sources of organic matter such as agricultural waste, sewage sludge, municipal and industrial waste.
The different types of organic materials were researched of their use as fertilizers by the method of composting with natural soils for circular economy purposes. That, on the one hand, is related to full use of resources, and on the other for a positive balance of humus in soils under conditions of intensive agriculture. The study included both environmental bioresources (biochar and compost) as well as traditionally known manure (cow and sheep mature) and sewage sludge from domestic wastewater.
The composting is done with two soil types - Alluvial-meadow soil and Smolnitza. The following phisico-chemical and agrochemical parameters were analyzed: pH in water; electrical conductivity; cation exchange capacity and base of saturation; the content and composition of the organic matter; total nitrogen; mobile forms of nitrogen, phosphorus and potassium.
The studied indicators reflect a more profound change with the addition of organic materials to Alluvial meadow soil compared with the Smolnitza soil type. This is mainly due to changes in CEC characteristics of both soil types. Changes in the content and composition of soil organic matter are highly indicative of the composting process. They are more sensitive for the  Alluvial-meadow soil, where the soil organic matter from humic-fulvic type is converted to humic type by addition of all organic materials, except the cow mature.

Keywords: biochar; manure; sludge; humic acids; E4/E6

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