Search Results (5)

Canola cultivation at high latitudes is becoming more promising in terms of modern climate change. Sustainable crop production requires an understanding of yield-limiting factors, which need to be adjusted in agricultural management first. Therefore, our study was aimed at examining the effect of climate and soil fertility factors on the canola yield from 2012 to 2015 in northwestern Russia. Simultaneously, effectiveness of chemical fertilizer (N${}_{65}$P${}_{50}$K${}_{50}$ and N${}_{100}$P${}_{75}$K${}_{75}$) rates was tested. Studied soils had light texture, high acidity and severe sulfur deficiency. Canola yield (Y) varied from 0.81 to 1.60 t·ha${}^{-1}$ for the observed period. Applied fertilizer increased Y by around 30%, but this change was not significant. Climate effect testing with the FAO-AquaCrop simulation showed no noticeable water and heat stresses for the study period (0% to 20% reduction in potential Y). Among the tested soil properties, the content of organic carbon, available nitrogen and sulfur significantly correlated with Y (r = 0.58–0.66). Combining these factors together with soil pH in a path model explained 60% of variability in Y. Importantly, sulfur had the highest and most significant effect in this model. Thus, this soil parameter is the main yield-limiting factor in the study area, which must be the first to be adjusted in agricultural practice. Full article

The composition of soil organic carbon (SOC) is an important soil quality indicator. We investigated the effect of site-specific soil-forming factors on plant debris and SOC properties along a soil catena with Retisols and Stagnosols in a mixed coniferous–deciduous forest. We examined sites at the summit and middle slope positions with relatively well-aerated soils and sites at footslope positions with waterlogged soils. The concentrations of labile and stable pools of SOC were determined using the method of three-stage chemodestruction. The degree of litter decomposition was calculated, and ash content was determined in the folic and histic soil horizons. The results of our study showed that SOC mostly accumulated in the forest litter and histic horizons of Stagnosols at the footslope positions. The forest litter, folic, and histic horizons were dominated by labile carbon. Equal concentrations of labile and stable carbon were typical of the mineral horizons. The location of the soil in the catena affects the partition and characteristics of SOC in umbric and albic soil horizons. SOC was found to be more stable in the soils at the footslope positions compared to the soils in other locations, because of the lower decomposition of plant remains. Larger stocks of organic carbon, including labile carbon, were restricted to the footslope catena positions. Full article

Agriculture is the main contributor to nitrous oxide (N₂O) emission, but the emission intensity can be controlled by various factors, in particular, the activity of earthworms, one of the most common groups of soil invertebrates. We conducted an incubation experiment to evaluate N₂O emission in earthworm soil samples compared to non-earthworm ones with applications of high (200 kg ha⁻¹) and low (50 kg ha⁻¹) mineral N fertilizer doses. We assessed the cumulative N₂O emission, the dynamics of the soil dissolved organic carbon, and the soil microbial carbon and nitrogen content, as well as the number of nirK and nirS gene copies in bulk soil samples and in isolates from the earthworms’ gut. Our study showed a significant role of the earthworm activity in changing the intensity of N₂O emission after the application of mineral N fertilizers. The main factor leading to an increase in nitrous oxide emission in the presence of earthworms is the stimulation of free-living soil denitrifiers by the organic matter of the earthworms’ excretions, as well as the thorough mixing of plant residues and soil. Contrary to our expectations, earthworms did not increase the representation of nitrite reductase genes in soil, although the earthworm’s gut can be considered as a refugium for denitrifiers. Our results indicate a possible risk of increased N₂O emission from arable temperate soils with an increase in earthworm populations as the climate warms, even if application rates of mineral fertilizers are reduced. Full article

Agricultural soil use does not only affect the amount of soil organic matter, but also the molecular composition of humic (HAs) and fulvic acids (FAs). Changed hydrothermal conditions and composition of the incoming plant residues are reflected in the rate of humification and its products. The objective of this study was to compare the molecular composition of HAs and FAs isolated from Eutric Albic Stagnic Histic Retisol (Loamic), two Eutric Albic Retisols (Loamic)—mature and arable. Plots of mature Retisols are located at a middle taiga (Komi Republic, Russia) in a bilberry-green-moss birch-spruce forest. The plot of Retisols arable is located in the fields of the Syktyvkar state farm, which is 3.3 km northeast of mature Retisol plots. The development period is about 40 years, it is sowed with a pea-oat mixture. The results obtained indicate that soil reclamation essentially increases the proportion of aromatic components and decreases the content of carboxyl and ester groups in the humic substance (HS) structure. An increased extent of hydromorphism of Retisols leads to the enrichment of HS with aliphatic fragments. Full article

The influence of soil characteristics on the lability and bioavailability of zinc at both background and phytotoxic concentrations in Albic Retisol soil (Loamic, Ochric) was studied using various methods. Ranges of insufficient, non-phytotoxic, and phytotoxic zinc concentrations in soil solutions were established in an experiment with an aqueous barley culture. It was experimentally revealed that for a wide range of non-toxic concentrations of Zn in the soil corresponding to the indicative type of plant response, there was constancy of the concentration ratio (CR) and concentration factor (CF) migration parameters. As a result, a new method for assessing the buffer capacity of soils with respect to Zn (PBC_Zn) is proposed. The transformation processes of the chemical forms and root uptake of native (natural) zinc contained in the Albic Retisol (Loamic, Ochric) through the aqueous culture of barley were studied using a cyclic lysimetric installation and radioactive ⁶⁵Zn tracer. The distribution patterns of Zn(⁶⁵Zn) between different forms (chemical fractions) in the soil were established using the sequential fractionation scheme of BCR. The coefficients of distribution and concentration factors of natural Zn and ⁶⁵Zn, as well as accumulation and removal of the metal by plants were estimated. The values of the enrichment factor of natural (stable) Zn contained in sequentially extracted chemical fractions with the ⁶⁵Zn radioisotope were determined and the amount of the pool of labile zinc compounds in the studied soil was calculated. Full article