Changing the qualitative composition of humus of podzolized chernozem after a prolonged use of fertilizers in the field crop rotation
Trus O.M., Candidate of Agricultural Science, Lecturer of Department of Agricultural Chemistry and Soil Science, Uman National University of Horticulture, Ukraine
Issue № 92. Part 1
631.417.2 + 631.445.4:631.8:631.582
The main agronomic assessment of the humus soil state is the nature of its qualitative and quantitative changes. Therefore, the purpose of the study is to determine changes in the humus state of podzolized chernozem under the influence of the long application of different doses of fertilizers and fertilizer systems in the field crop rotation (since 1964). The total content and supply of humus and the humus composition are determined in soil samples.
According to the results of the conducted research, it is found that the application of high doses of fertilizers in different fertilizer systems provides humus content in the soil of the field crop rotation (a layer of 0–20 cm) at the level of 3.35–3.62 % indicating its low content in the soil. With depth on the soil profile the humus content decreases in all studied variants.
Depending on the variant of the experiment, the humus supply in the soil layer of 0–20 cm of the field crop rotation amounts to 70.8–89.9 t/ha which is considered low according to the accepted gradation. Humus supply ranges from 301.9 t/ha to 396.8 t/ha in the meter layer of podzolized chernozem, so it can be attributed to the third class of natural fertility potential.
There is an increase in average annual changes in humus supply in the soil compared with the initial level in most variants of the experiment. Thus, an increase in the average annual humus supply in the soil layer of 0–20 cm is carried out in the variant with the introduction of N135P135K135 (0.02 t/ha). Applying organic fertilizers they increase in variants with high doses of manure (manure of 13.5 tons and manure of 18 tons) – 0.04 t/ha and 0.08 t/ha, respectively. Combined use of organic and mineral fertilizers contributes to the largest annual increase in the humus supply in the soil variant introducing 13.5 tons of manure + N68P101K54 – 0.17 t/ha.
Depending on doses of fertilizers, the amount of humic acids in the soil layer of 0–40 cm increases from 28.7 % to 37.4 % in the carbon content of the total humus indicating a high degree of humification of organic matter. An increase in the amount of fulvic acids is noted by 10–44 % compared with the check variant which leads to the reduction of the ratio Сha: Сfa. However, the humus type in all experimental variants remains humatic. The proportion of insoluble residue decreases in comparison with the check variant and substantially depends on the dose of fertilizers.