Plant root morphology and soil biological indicators under primary development of various swards

Plant nutrition conditions are limited in naturally acidic soil due to harmful hydrogen and aluminium ions. More favourable conditions for plant nutrition (soil liming) will affect root qualitative and quantitative parameters and influence ecosystem stability. Four legume–grass swards were cultivated. The swards were a combination of one species of legume and two species of grasses: Trifolium pratense L., Trifolium repens L., Trifolium hybridum L., Medicago sativa L. (each of 50%) with Phleum pratense L. (35%) and Poa pratensis L. (15%). The aim of this study is to evaluate the root morphological and soil biological indicators of legume–grass swards under the first two years of development in soils with different pH levels.

Sward ecosystem development depends on the pH of the soil, sward species composition and soil biota. During the first year of sward development, soil pH had a significant influence on the morphology of root system. Sward‘s root mass and total root length was 2.4 and 2.2 times bigger in naturally acidic soil. This resulted in a change of biological parameters.

In the second year of sward development, soil pH had no significant influence on sward‘s root mass. However, under the impact of different soil pH, various sward‘s root systems were formed and the root C:N ratio had changed. It is observed that, regardless of the sward species composition and the year of development, at higher root C:N ratio soil microbial biomass was higher and CO₂ emissions were lower in swards in naturally acidic soils.

Regardless of soil pH, different types of clover–grass swards promoted organic carbon immobilization in microbial biomass and, at the same time, stabilized the sward ecosystem in the top soil layer (soil respiration in 0–10 and 10–20?cm layers was lower) more effectively than the alfalfa–grass sward.