Karin Kauer

Soil compaction effects on soil bulk density and penetration resistance and growth of spring barley (Hordeum vulgare L.)

Abstract The weight of the tractor is not the only factor affecting soil compaction. Soil-management practices, such as the use of fertilizers and pesticides, also affect soil properties through an increased number of overriding. The aim of the current study was to investigate compaction effects on soil physical properties, such as dry bulk density and penetration resistance, and the growth of spring barley (Hordeum vulgare L.) as a monoculture. The five-year experiment was conducted on the Estonian University of Life Sciences’ research field at Eerika, near Tartu in 2001–2005. The soil of the experimental site is sandy loam Stagnic Luvisol. The treatments included were no compaction, one pass, three passes, and six passes. All passes were track-by-track. Measurements of soil and plant were made in the earing phase of barley and measurements of yield in the maturity phase of barley. The compaction treatment was conducted using an MTZ-82 tractor (total weight 4.84 Mg). Neither fertilizers nor herbicides were used. 5 years after compaction distinguishable subsoil and topsoil compaction was detected. Soil deformation increases with the number of passes; in the case of six passes soil bulk density increased by 0.15 Mg m−3 and penetration resistance by 3 MPa. However, there were no significant differences in the soil bulk density and penetration resistance between treatments compacted with one and three passes. The effect of compaction on soil bulk density was higher when the soil was compacted under wet conditions. Compaction decreased the quantity of barley shoots, their phytomass, and grain yield by more than 80%. In the second year of the experiment the dry weight of above ground biomass decreased by almost three times and shoots’ density by 1.5 times, compared with the first year results. In the third year of the experiment the biomass, plant density, and grain yield of barley were stabilized and no further decreases were detected in the following two experimental years. The results from the experiment revealed that even a low weight tractor can induce subsoil compaction and a high decrease of plant productivity by repeated passes over time.

Effect of Cut Plant Residue Management and Fertilization on the Dry-Matter Yield of Swards and on Carbon Content of Soil

The goal of this research was to study the impact of cut plant residues, returned to or removed from the grassland sward, on the dry-matter yield of swards and on the organic carbon (Corg) concentration of soil. The experiment was carried out during 2004–2008. The variables of the experiment were (i) sward type: turfgrass sward (Festuca rubra rubra and Poa pratensis) and grass–clover sward (Phleum pratense, Lolium perenne, and Trifolium repens) and (ii) treatment of residues: the cut plant residues were returned (RRT) to the plots or removed (RRM) from the plots after the mowing. The fertilizer treatments were as follows: N0P0K0, N80P11K48, N160P22K96, and N400P56K240 kg ha−1 for the turfgrass sward and N0P0K0 and N80P26K50 kg ha−1 for the grass–clover sward. The Corg and Ntot concentrations in the 20-cm soil layer were measured at the beginning and at the end of the experiment at depths of 0–5 cm and 5–20 cm. Nitrogen was returned as plant residues to the grass–clover sward in treatment N0P0K0 at 190 kg ha−1 and N80P26K50 at 204 kg ha−1 and consequently the returned cut plant residues increased the yield by 31% and 22%, respectively. The amount of N returned as residues to turfgrass sward was 31–236 kg ha−1 but it had no significant influence on the sward dry-matter yield. During the 5 years of the experiment the Corg content in 0- to 5-cm soil layer of grass–clover sward in treatment RRT increased by 42.9% and in RRM by 32.0% as an average of both fertilization treatments. At the depth 5–20 cm the Corg concentration did not change in treatment RRT, but in treatment RRM with fertilization the Corg concentration decreased by 8.2%. In turfgrass soil the Corg concentration increased in RRT treatment by 21.6% and in treatment RRM by 7.2% during 5 years. In the lower soil layer the concentration of Corg decreased with removal and return of plant residues. The fertilization did not influence the changes of Corg concentration in turfgrass swards soil.

The decomposition of turfgrass clippings is fast at high air humidity and moderate temperature

Abstract In grassland areas where herbage production has no economic value, the cut grass is often left on the sward surface where its decomposition is influenced by weather conditions. Although the influence of temperature and humidity on decomposition has been investigated under controlled lab conditions, experimentation has generally been under ideal moisture conditions that have not tested the combinations of climatic limitations that might occur in the field. The decomposition of mown turfgrass clippings deposited at different times of vegetation period was studied in situ using nylon bags during the first 8 weeks after deposition to investigate the effect of weather conditions (the air temperature, relative humidity, precipitation) on decomposition. Decomposition is the highest in the case of high air humidity and temperature of 10°C. Limiting factors for decomposition at temperatures above 10°C is the air humidity and below 10°C the air temperature. The general tendency was that the rate of decomposition increased with increasing air temperature up to 10°C, but with further increases of air temperature the decomposition rate slowed down. Relative air humidity had a variable impact (at the beginning of the decomposition process (weeks 1–2) the influence was negative, during weeks 3–8 of the decomposition process the effect was positive), and hence had no generalized relationship with decomposition over the studied decomposition period (weeks 1–8). The most significant influence of weather conditions on the decomposition rate was recorded directly after cutting. If the cutting was done during hot weather conditions, the material was drying fast and therefore decomposed slowly. Our results indicate that for fast decomposition of clippings it is important to maintain the freshness of material. Lower decomposition rates occurred during conditions of hot and dry weather, and also cooler (temperature near to 0°C) weather, and can be compensated as soon as favourable weather arrives.

Formation of the chemical composition of Histosols and histic soils in the forest lands of Estonia

The formation and vertical distribution of the chemical properties of fen (group I, five research areas) and transitional bog (group II, eight research areas) Histosols, and situated depressions of mineral landscape Histic Gleysols (group III, six research areas) and Histic Podzols (group IV, seven research areas) soil covers were studied. As a benchmark in the comparative analysis of Histosols, we used the 20 cm epipedon peat layers of eutrophic moderately acid (I) and mesotrophic very strongly acid (II) types. The thickness of histic soil epipedon peat varied from 10 to 30 cm and was classified as slightly acid peaty mull (IIIa) or strongly acid peaty moder (IIIb), and as very strongly acid peaty mor (IV). In forming the epipedon of the forest floor, aqua regia (mixture of hydrochloridic and nitric acids, 3:1)-extractable Fe, Cr, Al, Pb and Ni accumulated to a great extent (accumulation coefficient>2.5), and S, Na and Hg accumulated to a medium extent (accumulation coefficient 1.2–2.0); the amounts of Zn, K and Mn decreased to a great extent (accumulation coefficient<0.5), and those of Mg and P to a medium extent (accumulation coefficient 0.6–0.8); levels of Ca, Cu and Cd remained practically unchanged. Comparison of Histosol subsoil and substratum peats with a Histosol epipedon demonstrates considerable accumulation of Mn, Pb, Cd, Zn, Hg and Na in the thin (20 cm) superficial peat layer of mires.

Do green manures as winter cover crops impact the weediness and crop yield in an organic crop rotation

Abstract The effects of different winter cover crops and their combination with composted cattle manure on weeds and crop yields were investigated within a five-field crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) in three organic cropping systems. The control system (Org 0) followed the rotation. In organic systems Org I and Org II the winter cover crops were used as follows: ryegrass (Lolium perenne L. in 2011/2012) and a mixture of winter oilseed-rape (Brassica napus ssp. oleifera var. biennis) and winter rye (Secale cereale L.) in 2012/2013 before pea; winter oilseed rape before potato and winter rye before barley. In Org II system composted cattle manure was also applied. In comparison with the control system, the winter cover crops, depending on plant species used, reduced the biomass and density of the weeds. In both years winter rye was a better suppressor of weeds than the other winter cover crops. Cover crops increased the yield of potato in rotation crops. When used together with composted cattle manure the cover crops caused significant yield increase in cereals.

Winter cover crop effects on soil structural stability and microbiological activity in organic farming

Abstract In a field experiment based on a five-year crop rotation (pea, potato, barley undersown with red clover, red clover and winter wheat), several soil parameters, porosity, number and biomass of earthworms, total nitrogen, organic carbon, percentage of water stable aggregates and enzymatic activity, were studied during 2013 and 2014, the first and second year, respectively, since the first rotation concluded. This rotation was managed under three organic farming systems: Organic 0 (control), Organic I (with winter cover crops lately incorporated into the soil as green manure) and Organic II (with the same cover crops plus a yearly amendment of 40 t ha−1 of cattle manure). Crop rotation had a yearly positive effect on the soil bulk density, and enhanced the percentage of air filled pores; nonetheless, despite the leguminous crops in the rotation, all the systems presented a yearly decrease in total nitrogen in 2014. Cover crops along with manure only had a significant effect on enzymatic activity; however no significant effect was found in soil organic carbon content, soil particle aggregability or number and biomass of earthworms. This was connected with the intensive tillage carried out in the systems, the weather conditions and the characteristics of the organic amendments. However according to other studies these results could be transient and further long-term investigations will be needed.

Erosion-affected soils in the Estonian landscape: Humus status, patterns and classification

In Estonia, areas threatened by erosion are mainly situated in the south-east, where erosion-affected soils (EAS) account for 6–37% of the total area. The main tasks of this research were: (i) To characterize the humus status of EAS by their subdivisions, (ii) to define the humus status forming peculiarities of EASs, and (iii) to analyse the distribution and association of EASs with uneroded soils. To characterize the humus status of EAS epipedon thickness (cm), humus concentration (g kg−1) and humus pool (Mg ha−1) were used. For the determination of humus status parameters via sampling points, the transect method was used. The humus status of EAS varied widely (average humus concentration varies from 12–45 g kg−1 and humus pools from 39–191 Mg ha−1). The mean humus pools in eroded (n = 174), transitional (n = 224) and deluvial/colluvial (n = 159) soils are accordingly 51 ± 18 (mean ± SD), 90 ± 23 and 138 ± 67 Mg ha−1, respectively. The mean decrease in humus pools of eroded (E) soils on arable lands is 32–53 Mg ha−1, but the mean increase in deluvial (D) soils is 14–76 Mg ha−1. The greatest humus pool relocation coefficients D/E (2.8–3.3) are characteristic of the soils of hilly end moraine areas.