Spatial distribution of soil water repellency in a grassland located in Lithuania

Soil water repellency (SWR) it is recognized to be very heterogeneous in time in space and depends on soil type, climate, land use, vegetation and season (Doerr et al., 2002). It prevents or reduces water infiltration, with important impacts on soil hydrology, influencing the mobilization and transport of substances into the soil profile. The reduced infiltration increases surface runoff and soil erosion. SWR reduce also the seed emergency and plant growth due the reduced amount of water in the root zone. Positive aspects of SWR are the increase of soil aggregate stability, organic carbon sequestration and reduction of water evaporation (Mataix-Solera and Doerr, 2004; Diehl, 2013). SWR depends on the soil aggregate size. In fire affected areas it was founded that SWR was more persistent in small size aggregates (Mataix-Solera and Doerr, 2004; Jordan et al., 2011). However, little information is available about SWR spatial distribution according to soil aggregate size. The aim of this work is study the spatial distribution of SWR in fine earth (<2 mm) and different aggregate sizes, 2-1 mm, 1-0.5 mm, 0.5-0.25 mm and <0.25 mm. The studied area is located near Vilnius (Lithuania) at 54 42’ N, 25 08 E, 158 masl. A plot with 400 m2 (20 x 20 m with 5 m space between sampling points) and 25 soil samples were collected in the top soil (0-5 cm) and taken to the laboratory. Previously to SWR assessment, the samples were air dried. The persistence of SWR was analysed according to the Water Drop Penetration Method, which involves placing three drops of distilled water onto the soil surface and registering the time in seconds (s) required for the drop complete penetration (Wessel, 1988). Data did not respected Gaussian distribution, thus in order to meet normality requirements it was log-normal transformed. Spatial interpolations were carried out using Ordinary Kriging. The results shown that SWR was on average in fine earth 2.88 s (Coeficient of variation % (CV%)=44.62), 2-1mm 1.73 s (CV%=45.10), 1-0.5 mm 2.02 s (CV%=93.75), 0.5-0.25 mm 3.12 s (CV%=233.68) and in <0.25 mm 15.54 mm (CV%=240.74). This suggests that SWR persistence and CV% is higher in small size aggregates than in the coarser aggregate sizes. The interpolated maps showed that in fine earth SWR was higher in the western part of the studied plot and lower in the central area. In the 2-1 mm aggregate size it was higher in the southwest and lower at north and northwest area. In the 1-0.5 mm aggregate size it was lower in the central area and higher in the southwest. In the 0.5-0.25 mm aggregate size it was higher in the west part and lower in the north of the plot and. In the <0.25 mm no specific pattern was identified and the SWR was heterogeneously distributed. This suggests that the spatial distribution of SWR is very different according to the aggregate size. Future studies are needed in order to identify the causes and consequences of such dynamic. Acknowledgements The authors appreciated the support of the project “Litfire”, Fire effects in Lithuanian soils and ecosystems (MIP-048/2011) funded by the Lithuanian Research Counci

Long-term non-sustainable soil erosion rates and soil compaction in drip-irrigated citrus plantation in Eastern Iberian Peninsula.

Abstract Agriculture is known to commonly cause soil degradation. In the Mediterranean, soil erosion is widespread due to the millennia-old farming, and new drip-irrigated plantations on slopes, such as the citrus ones, accelerate the process of soil degradation. Until now, the published data about soil erosion in citrus orchards is based on short-term measurements. Long-term soil erosion measurements are needed to assess the sustainability of drip-irrigated citrus production and to design new strategies to control high soil erosion rates. The objective of this study is to assess long-term soil erosion rates in citrus plantations and report the changes in soil bulk density as indicators of land degradation. We applied ISUM (Improved Stock-Unearthing Method) to 67 paired trees in an inter-row of 134 m (802 m2 plot) with 4080 measurements to determine the changes in soil topography from the plantation (2007) till 2020. Soil core samples (469) were collected (0–6 cm depth) to determine the soil bulk density at the time of plantation (2007) and in 2020. The results demonstrate an increase in soil bulk density from 1.05 g cm−3 to 1.33 g cm−3. Changes in soil bulk density were higher in the center of the row as a result of compaction due to passing machinery. Soil erosion was calculated to be 180 Mg ha−1 y−1 due to a mean soil lowering of 1.5 cm yearly. The highest soil losses were found in the center of the inter-row and the lowest underneath the trees. The extreme soil erosion rates measured in new drip-irrigated citrus plantations are due to soil lowering in the center of the inter-row and in the lower inter-row position where the incision reached 80 cm in 13 years. The whole field showed a lowering of the soil topography due to extreme soil erosion and no net sedimentation within the plantation. The results show the urgent need for soil erosion control strategies to avoid soil degradation, loss of crop production, and damages to off-site infrastructures

Carbon dynamics of soil organic matter in bulk soil and aggregate fraction during secondary succession in a Mediterranean environment.

Clarifying which factors cause an increase or decrease in soil organic carbon (SOC) after agricultural abandonment requires integration of data on the temporal dynamics of the plant community and SOC. A chronosequence of abandoned vineyards was studied on a volcanic island (Pantelleria, Italy). Vegetation in the abandoned fields was initially dominated by annual and perennial herbs, then by Hyparrhenia hirta (L.) Stapf, and finally by woody communities. As a consequence, the dominant photosynthetic pathway changed from C3 to C4 and then back to C3. Conversion of a plant community dominated by one photosynthetic pathway to another changes the 13C/12C ratio of inputs to SOC. Using the time since abandonment and the shift in belowground δ13C of SOC relative to the aboveground δ13C plant community, we estimated C3-C and C4-C changes during secondary succession. SOC content (g kg− 1) increased linearly (R2 = 0.89 and 0.73 for 0–15 and 15–30 cm soil depth) with the age of abandonment, increasing from 12 g kg− 1 in cultivated vineyards to as high as 26 g kg− 1 in the last stage of the succession. δ13C increased in the bulk soil and its three aggregate fractions (&gt; 250, 250–25, and &lt; 25 μm) during succession, but the effect of soil depth and its interaction with succession age were significant only for soil aggregate fractions. Polynomial curves described the change in δ13C over the chronosequence for both depths. δ13C in the bulk soil had increased from − 28‰ to − 24‰ by 35 years after abandonment for both depths but then decreased to − 26‰ at 60 years after abandonment (corresponding with maturity of the woody plant community). Overall, the results indicate that abandoned vineyards on volcanic soil in a semi-arid environment are C sinks and that C storage in these soils is closely related to plant succession

Effect of Standard Disk Plough on Soil Translocation in Sloping Sicilian Vineyards

Tillage is the main force of soil redistribution in agricultural land use and has been seen as more critical than water erosion. This study aims to evaluate the effect of tillage with standard disk in vineyards. A representative study area with grapevines was selected, and 39 inter-rows were selected to test the effect of slope and forward speed. In each inter-row, a strip of soil was collected, and mixed with 2 kg of coloured sand used as a tracer, then replaced in the strip, and shallow soil tillage was performed by means of a standard disk plough. Three soil subsamples were collected along the slope every 0.30 m from the coloured strip and the sand tracer was separated from the soil and weighed. The results show that the mean soil translocation distance ranged from 0.73 to 1.14 m along the upslope direction, and from 0.32 to 0.84 m along the downslope direction. The net translocation was −0.33 ± 0.12 m which indicate an upslope soil movement. Mean translocation distance was not significantly affected by the considered forward speeds. These results demonstrate that tillage can reallocate soil upslope and open new insights into the use of disk plough as sustainable management in vineyards

Long-term Cropping Systems and Tillage Management Effects on Soil Organic Carbon Stock and Steady State Level of C Sequestration Rates in a Semiarid Environment

A calcareous and clayey xeric Chromic Haploxerepts of a long-term (19 years) experimental site in Sicily (Italy) with different land use management and cropping systems were sampled (0-15 cm depth) to study their effect on soil aggregate stability and associated organic carbon (SOC). The experimental site had three tillage managements (no till [NT], dual-layer [DL] and conventional tillage [CT]) and two cropping systems (durum wheat mono-cropping [W] and durum wheat/faba bean rotation [WB]). The whole site covered an area of 4440 m2 with individual plots having 370 m2. The soil was ploughed during the experiment. Samples (2 – 4 kg each) were taken before and after the experiment. The annually sequestered SOC with W was 2.75 times higher than with WB and higher SOC concentrations were measured. The NT management system was the most effective in SOC sequestration whereas with DL no C was sequestered. The differences in SOC concentrations between NT and CT were surprisingly small. Cumulative C input of all cropping and tillage systems and the annually sequestered SOC indicated that a steady state occurred at a sequestration rate of 7.4 Mg C ha-1 yr-1. Independent of the cropping systems, most of the SOC was stored in the silt and clay fraction. This fraction had a high N content which is typical for organic matter interacting strongly with minerals. Macro-aggregates (&gt; 250µm) were influenced by the treatments whereas the finest fractions were not. DL reduced the SOC in macro-aggregates while NT and CT gave rise to much higher SOC contents

Long-Term Durum Wheat-Based Cropping Systems Result in the Rapid Saturation of Soil Carbon in the Mediterranean Semi-arid Environment

Climate, soil physical-chemical characteristics, land management, and carbon (C) input from crop residues greatly affect soil organic carbon (SOC) sequestration. According to the concept of SOC saturation, the ability of SOC to increase with C input decreases as SOC increases and approaches a SOC saturation level. In a 12-year experiment, six semi-arid cropping systems characterized by different rates of C input to soil were compared for ability to sequester SOC, SOC saturation level, and the time necessary to reach the SOC saturation level. SOC stocks, soil aggregate sizes, and C inputs were measured in durum wheat monocropping with (Ws) and without (W) return of aboveground residue to the soil and in the following cropping systems without return of aboveground residue to soil: durum wheat/fallow (Wfall), durum wheat/berseem clover, durum wheat/barley/faba bean, and durum wheat/Hedysarum coronarium. The C sequestration rate and SOC content were lowest in Wfall plots but did not differ among the other cropping systems. The C sequestration rate ranged from 0.47MgC ha-1y-1 in Ws plots to 0.66MgCha-1y-1 in W plots but was negative (-0.06MgCha-1y-1) in Wfall plots. Increases in SOC were related to C input up to a SOC saturation value; over this value, further C inputs did not lead to SOC increase. Across all cropping systems, the C saturation value for the experimental soil was 57.7Mgha-1, which was reached with a cumulative C input of 15Mgha-1

Managing soil nitrate with cover crops and buffer strips in Sicilian vineyards

When soil nitrate levels are low, plants suffer nitrogen (N) deficiency but when the levels are excessive, soil nitrates can pollute surface and subsurface waters. Strategies to reduce the nitrate pollution are necessary to reach a sustainable use of resources such as soil, water and plant. Buffer strips and cover crops can contribute to the management of soil nitrates, but little is known of their effectiveness in semiarid vineyards plantations. The research was carried out in the south coast of Sicily (Italy) to evaluate nitrate trends in a vineyard managed both conventionally and using two different cover crops (Triticum durum and Vicia sativa cover crop). A 10 m-wide buffer strip was seeded with Lolium perenne at the bottom of the vineyard. Soil nitrate was measured monthly and nitrate movement was monitored by application of a 15N tracer to a narrow strip between the bottom of vineyard and the buffer and non-buffer strips. Lolium perenne biomass yield in the buffer strips and its isotopic nitrogen content were monitored. Vicia sativa cover crop management contributed with an excess of nitrogen, and the soil management determined the nitrogen content at the buffer areas. A 6 m buffer strip reduced the nitrate by 42% with and by 46% with a 9 m buffer strip. Thanks to catch crops, farmers can manage the N content and its distribution into the soil over the year, can reduced fertilizer wastage and reduce N pollution of surface and groundwater. © 2013 Author(s)