Respiratory response of living phase to stress as a criterion for assessment of soil condition

Abstract

The possibility of developing a scale for assessing the degree of soil degradation based on measuring the respiratory response (RR) of its living phase to the application of a natural nutrient substrate, straw, was studied. The studies were carried out in the vicinity ofNovosibirskregion. The soil was leached medium loamy medium humus chernozem. Experiment options included long-term fallow (virgin land); permanent fallow; arable soil; a lawn formed more than 20 years ago by dumping leached chernozem removed from agricultural fi an old trail on this lawn; forest (additional control). The level of anthropogenic impact was determined on the basis of empirical estimates. Topsoil samples were taken in the autumn of 2018, 2019 after harvesting spring wheat. In the laboratory experiment, dry crushed wheat straw (carbon content 40%, nitrogen content 0.54%) was added into the soil at a dose of 3 g/kg. The soil was incubated at a temperature of25 °C, humidity of 60% of the total field moisture capacity for each option. Records of СО2 production were made by the adsorption method. The duration of the experiment was 30 days. The respiratory response is the relative value of the increase in СО2 production when straw is applied (experiment) compared to the soil without additives (control), measured in percent. In the experiment, the respiratory response was inversely proportional to the level of anthropogenic impact on the soil. The indicator in the variant with the maximum anthropogenic impact (permanent fallow) was 250–300%, in the variant with the minimum impact (long-term fallow) – 0–10%. The ranking of research objects according to the criterion under study was carried out using multivariate analysis by the method of principal components. A preliminary scale is proposed for assessing the degree of soil degradation. The soil was assessed as non-degraded or slightly degraded with a respiratory response equal to 0–25%, moderately degraded – 25–50%, and highly degraded – above 50%.