Levels Of Soil Compaction Research Articles

Compaction by a forest machine affects soil quality and Quercus robur L. seedling performance in an experimental field

In recent decades, the use of heavy machinery in forest management has significantly increased, causing the compaction of forest soils and potentially affecting seedling survival and establishment. We thus investigated the effects of soil compaction on soil physical parameters, microarthropod biodiversity, soil respiration, as well as growth and physiology of Pedunculated Oak (Quercus robur) seedlings in an experimental field in central Italy (coarse loamy soil). Two levels of soil compaction were simulated, i.e. 10 tractor passes vs. 25 tractor passes. The larger number of tractor passes increased soil bulk density (+27%) and penetration resistance (+46%), while porosity declined (−11%). Compaction decreased the qualitative biodiversity of soil microarthropods (−13%), the number of growth flushes (−22%) and of leaves (−22%), shoot biomass (−26%), the shoot/root ratio (−10%), the main root length (−24%) and the longest first-order later root length in the top 10cm of soil (−31%). The decreased growth of seedlings in the soil compaction treatment was accompanied by lower photosynthetic rate (−34%) and leaf nitrogen content (−27%). We concluded that limited access and acquisition of nutrients and water due to the shorter length of main root likely played a key role for growth and physiological responses to soil compaction in Q. robur seedlings.

Soil compaction and its effects on soil microbial communities inCapsicumgrowing soil

Soil compaction is a serious problem confronting horticultural production systems globally and occurs more readily in tropical systems as a consequence of wet-dry climatic oscillations in these regions. Soil compaction alters soil microbial structure and function as a result of the limitation of air permeability and oxygen availability, which has implications for soil nutrition and soil-borne disease. This study investigates the influence of compaction on soil microbial functional diversity and activity in the presence and absence of capsicum plant roots, and with the addition of compost or changes to irrigation regimes, both of which are management strategies traditionally designed to reduce compaction in the paddock. Experimental treatments of four levels of soil compaction were established, with or without capsicum seedlings planted into the compacted media. A further experimental set-up, with two water treatments (optimal or low) and compost additions in factorial combination with compaction was also established. The findings revealed that microbial functional diversity and activity was higher in uncompacted bare (unplanted) soil compared to soil with the presence of capsicum plant roots. Further, there were lower levels of activity at higher soil compaction levels, and lower functional diversity. The results suggest that compaction is a significant driver of soil microbial health in sub-tropical horticultural systems, particularly when soil moisture and soil carbon is low, and that careful ongoing management of compaction will be required.

Lactuca sativa growth in compacted and non-compacted semi-arid alkaline soil under phosphate fertilizer treatment and cadmium contamination

Soil compaction is known to drastically modify soil properties and hence to affect both plant growth and metal distribution in the soil. Phosphate amendment is generally used to improve plant production but unfortunately it also gives rise to higher metal contamination in soils and plants. In this work, we aimed to study the effects of soil density, phosphate fertilization and cadmium contamination on the growth of Lactuca sativa. In particular, the migration of cadmium in the soil columns, its accumulation and translocation in lettuce were also examined. Lactuca sativa was selected as a model plant because it is widely cultivated in alkaline clay soils of eastern Mediterranean countries. Two levels of soil compaction (1.2 and 1.4gcm−3), two rates of P amendment (0 and 109mg Pkg−1), and two levels of Cd contamination (0 and 84mg Cdkg−1) were used in 24 model columns with a factorial randomized block experimental design. Soil compaction increased considerably both leaf area and dry weight of roots and shoots, whereas both chlorophyll content and NRA decreased. For the two soil bulk densities, the phosphate fertilizer improved lettuce growth characterized by plant height, dry matter, leaf number and NRA, whereas Cd contamination altered those parameters and increased the chlorophyll content. In soils contaminated with cadmium, the combination of compaction and phosphate fertilization resulted in a significant decrease in Cd migration along the soil columns. Cd uptake by plants increased in Cd treated soils; its accumulation was found to be more important than in plants grown in P-Cd treated soil where Cd uptake was clearly reduced in shoots and roots.

Changes in physical properties of sandy soil after long-term compost treatment

Abstract Studying the long-term effect of composted sewage sludge application on chemical, physical and biological properties of soil, an experiment was established in 2003 at the Research Institute of Nyíregyháza in Hungary. The applied compost was prepared from sewage sludge (40%), straw (25%), bentonite (5%) and rhyolite (30%). The compost was ploughed into the 0-25 cm soil layer every 3rd year in the following amounts: 0, 9, 18 and 27 Mg ha−1 of dry matter. As expected, the compost application improved the structure of sandy soil, which is related with an increase in the organic matter content of soil. The infiltration into soil was improved significantly, reducing the water erosion under simulated high intensity rainfall. The soil compaction level was reduced in the first year after compost re-treatment. In accordance with the decrease in bulk density, the air permeability of soil increased tendentially. However, in the second year the positive effects of compost application were observed only in the plots treated with the highest compost dose because of quick degradation of the organic matter. According to the results, the sewage sludge compost seems to be an effective soil improving material for acidic sandy soils, but the beneficial effect of application lasts only for two years.

Impact of soil compaction stress combined with drought or waterlogging on physiological and biochemical markers in two maize hybrids

In field conditions plants undergo combinations of stresses like soil compaction combined with soil drought or flooding. In maize there exists an intraspecific variation in responses to environmental stresses, e.g. drought, flooding and soil compaction. In this study seedlings of two maize hybrids (sensitive and resistant to soil compaction) were grown under low, moderate and high soil compaction levels and drought or flooding. Water potential, electrolyte leakage, chlorophyll a content, gas exchange, ABA and antioxidant activity were measured. In seedlings exposed to different soil compaction levels differences between soil, leaf and root water potentials were observed at noon and later in the day. Significant differences between hybrids grown in low and severe soil compactions and exposed to drought or flooding were noticed in membrane injury, leaf water potential, chlorophyll a content and gas exchange parameters. Statistically significant differences between hybrids were observed in ABA content in the stem under severe and in the root under low soil compaction and exposed to drought and flooding, and in antioxidant activity in leaf under severe soil compaction and under low soil compaction with drought or flooding stresses. Further studies on physiological responses of genotypes contrasting in tolerance to different stresses would help us explore stress tolerance mechanisms.

Water stress and soil compaction impacts on clover growth and nutrient concentration

Soil compaction and insufficient water supply generally decrease crop performance. The effects of varying compaction and water availability levels on the growth of Berseem or Egyptian clover ( Trifolium alexandrimum L.), water use efficiency and nutrient concentration were investigated under greenhouse conditions. Treatments consisted of three soil compaction levels (bulk density of 1.2, 1.4 and 1.6 Mg m -3 ), and four water availability treatments (40%, 60%, 80% and 100% of soil field capacity) in a factorial combination. Soil compaction had a significant effect on water use efficiency with the highest (0.32 g l -1 ) at bulk density of 1.4 Mg m -3 and the lowest at the other bulk densities. Soil compaction had no significant effects on leaf area, shoot, root and total dry masses. Water stress resulted in lower leaf area (from 231 to 153 mm 2 pot -1 ), and the stem lengths were 7.6 cm and 4.3 cm for 80% and 60% of field capacity, respectively. Likewise, the highest (0.47 g pot -1 ) and lowest (0.33 g pot -1 ) total dry masses were observed at 80% and 60% field capacities. Water use efficiencies were 0.32 and 0.20 g l -1 for 100% and 60% field capacities, respectively. The accumulation of N, P and K per unit length of roots increased with soil compaction. As the water supply increased, the root and shoot dry weight and water use efficiency increased. Treatment of 100% field capacity resulted in the highest accumulation of N, P and K. Results indicated that the treatment of 80% field capacity and bulk density of 1.4 Mg m -3 provided the best conditions for clover performance, among the applied treatments. This study suggests that sufficient water supply can moderate the adverse effects of soil compaction on clover performance.

Effects of irrigation, soil compaction and fertilization treatments on physiological – vegetative characteristics and root development of soybean

The present study was conducted to investigate the effects of different soil compaction levels (non-compacted control, low compaction, high compaction), irrigation management practices (conventional furrow and alternate furrow) and nitrogenous fertilizer levels (60, 90, 120 kg ha<sup>–1</sup>) on vegetative characteristics (dry biomass production, plant height, number of branch and number of pod per plant, height of the first pod, leaf area index, stem diameter), physiological characteristics (leaf relative water content, leaf chlorophyll content and leaf temperature) and root development through 0 -80 cm soil profile of soybean grown in Harran Plain of Turkey. Experiments were conducted in Sanliurfa Province of Turkey in split-split plots experimental design with 3 replications during the years of 2006 and 2007. Irrigation program was created by using KanSched simulation model. The amount of applied irrigation water in conventional and alternate furrow systems in 2006 and 2007 were measured as 435.61 and 291.59 mm, and 429.51 and 271.72 mm, respectively. While the highest yield (947.8 kg ha<sup>–1</sup>) was observed in control treatment of the year 2006, conventional furrow system had the highest yield (2099.3 kg ha<sup>–1</sup>) in the year 2007. Soil compaction, irrigation and nitrogenous fertilization in general had significant effects on entire vegetative characteristics investigated in the present study. Increasing compaction levels yielded decreasing plant height, stem diameter and leaf area indexes. Biomass production increased with increasing nitrogen doses. Results indicated that negative impacts of soil compaction in agricultural fields due to traffic and various other reasons could be eliminated with proper irrigation and fertilization implementations.

Rootcells® improve the establishment of Corylus colurna L. in a compacted car park substrate

Trees growing in an urban environment often experience very poor rooting environments that have a detrimental effect on the trees’ longevity and the benefits that the trees can provide. This study compares the condition of trees planted with RootCells® with trees planted without provision of any additional rooting volume, in a car park with a varying level of soil compaction across the site. Twelve Turkish hazels (Corylus colurna L.) were planted in compacted hard-core, half of which were supplied with RootCells® that increased the volume of these planting pits by approximately 34%. After 5 growing seasons, 2 trees had died (one control and one treatment tree) and we measured a selection of growth and health indicators in the remaining 10 trees, to assess the effect of the RootCells®. Mean stem girth at 1.5 m was 15.4% greater for the treatment group, and mean twig density was 18.3% greater for the canopies of the treatment trees. For a range of other tests, the trees growing with the RootCells® performed marginally better than the control group. However, chlorophyll fluorescence readings gave a contrary reading, which indicates that this method may not always be a reliable means of assessing successful tree establishment.

Zbijenost tala vinograda razlicite starosti u Panonskoj Hrvatskoj. I dio. Utjecaj ga�enja mehanizacijom i gospodarenja tlom na zbijenost pojedinih horizonata

Soil compaction is one of the most important problems in agricultural production. Tillage system with frequent machinery traffic due protection, agrotechnic operation and harvesting has effect on different soil compaction levels in the vineyards. The aim of this study was to determine and compare the soil resistance, soil bulk density and soil moisture within and between rows in the seven-year and thirty-year vineyard due to tillage and compacting by machinery traffic. Results show statistically lower soil resistance to a depth of 40 cm in tilled interrow position in all vineyards as a direct effect of tillage. The values of bulk density in both vineyards are lowest in row position which is convenient for root growth. Increased values of bulk density that can restrict root development are recorded in interrows position in all vineyards. The moisture content of all vineyards increases with depth. Greater deviation in compaction between seven-year and thirty-year vineyard is not recorded. The research results indicate that the soil management is more important factor than the number of machinery passes. Soil resistance values does not give a complete information about compaction because of all the factors it is most depend on current soil moisture.

Interactions between soil physicochemistry and belowground biomass production in a freshwater tidal marsh

The success of tidal freshwater wetland restoration is typically gauged by the re-establishment of characteristics found in reference marshes. Although plant species composition may resemble reference marshes within a few years after the initiation of restoration, return of soil physicochemical properties may take much longer. We investigated soil characteristics in a post-levee breach freshwater tidal marsh restoration site (Liberty Island, California), and the impacts of soil compaction on the survival and growth of emergent macrophytes. In a field study, we examined soil physicochemical properties throughout 50-cm deep soil cores collected from locations at Liberty Island that differed in location and stage of vegetation colonization. In a controlled mesocosm study, we subjected three species that are commonly implemented in restoration plantings (Schoenoplectus acutus, S. californicus, and Typha latifolia) to two levels of soil compaction (control and high soil bulk density) to determine the influence of soil compaction on soil physicochemical properties and macrophyte response. Belowground biomass increased and soil bulk density decreased with time since vegetation colonization. The controlled study showed that both Schoenoplectus species exhibited greater survival than T. latifolia. The species explored are capable of ameliorating compacted soil conditions over time; this ability can facilitate the re-establishment of wetland structure and function at restoration sites.

SWEET SORGHUM PERFORMANCE AFFECTED BY SOIL COMPACTION AND SOWING TIME AS A SECOND CROP IN THE BRAZILIAN CERRADO

ABSTRACT Increasing attention has recently been given to sweet sorghum as a renewable raw material for ethanol production, mainly because its cultivation can be fully mechanized. However, the intensive use of agricultural machinery causes soil structural degradation, especially when performed under inadequate conditions of soil moisture. The aims of this study were to evaluate the physical quality of aLatossolo Vermelho Distroférrico (Oxisol) under compaction and its components on sweet sorghum yield forsecond cropsowing in the Brazilian Cerrado (Brazilian tropical savanna). The experiment was conducted in a randomized block design, in a split plot arrangement, with four replications. Five levels of soil compaction were tested from the passing of a tractor at the following traffic intensities: 0 (absence of additional compaction), 1, 2, 7, and 15 passes over the same spot. The subplots consisted of three different sowing times of sweet sorghum during the off-season of 2013 (20/01, 17/02, and 16/03). Soil physical quality was measured through the least limiting water range (LLWR) and soil water limitation; crop yield and technological parameters were also measured. Monitoring of soil water contents indicated a reduction in the frequency of water content in the soil within the limits of the LLWR (Fwithin) as agricultural traffic increased (T0 = T1 = T2>T7>T15), and crop yield is directly associated with soil water content. The crop sown in January had higher industrial quality; however, there was stalk yield reduction when bulk density was greater than 1.26 Mg m-3, with a maximum yield of 50 Mg ha-1 in this sowing time. Cultivation of sweet sorghum as a second crop is a promising alternative, but care should be taken in cultivation under conditions of pronounced climatic risks, due to low stalk yield.

Soil physical quality on tillage and cropping systems after two decades in the subtropical region of Brazil

Sustainability of crop production systems depends on the preservation of soil physical quality over time. This study aimed to determine long-term effects of soil tillage and cropping systems on physical attributes and hydraulic properties of an Oxisol in Southern Brazil, emphasising management practices to preserve or improve the soil structure quality under no-tillage system. The experiment was conducted in randomized block design, using a 5×2 factorial arrangement (tillage×cropping systems), with four replications. The five tillage systems consisted of conventional tillage (CT); minimum tillage, chiselled soil every year (MTC1); minimum tillage, chiselled soil every three years (MTC3); continuous no-tillage for 11 years (NT11); and continuous no-tillage for 24 years (NT24). The two cropping systems consisted of annual crop sequence with wheat in the winter and soybean in the summer, designated as crop succession (CS); and a 4-year crop rotation (CR) with white lupine-maize—black oat-soybean—wheat-soybean—wheat-soybean in winter–summer, respectively. Undisturbed soil cores were collected from 0–0.10; 0.10–0.20 and 0.20–0.30 m of soil depth, to determine the soil bulk density (BD), total porosity, macroporosity, microporosity, pore size distribution and classes, soil water retention curve, infiltration rate and field-saturated hydraulic conductivity. There was no interaction between tillage and cropping systems, and no effects of cropping systems on soil physical and hydraulic properties. Regardless the cropping system, chiselling effects on soil physical properties persisted for less than 22 months, and were restricted to below 0.20m soil depth. The CT resulted in soil pulverization at 0–0.10 m depth, leading to lower BD and higher macroporosity compared to the other soil tillage systems. At layers below 0.10m, CT increased the BD and reduced the macroporosity to critical levels for crop growth. Continuous use of no-tillage improved soil physical quality mainly at deeper layers, and provided higher plant available water retention in the soil at matric potentials ranging from −10 to −200kPa in relation to CT and MTC1. The adoption of NT improves soil physical quality and plant available water over time, and periodic soil chiselling aiming to disrupt compacted layers should be avoided because of its effects on reducing soil compaction level are short-lived.

Relationship of soil physical quality parameters and maize yield in a Brazilian Oxisol

In Brazilian agriculture, maize (Tea mays L.) is prominent because of its magnitude of grain production. However, soil compaction changes negatively the soil physical attributes, limiting the crop growth. This study aimed to evaluate physical attributes of a clayey Oxisol (Rhodic Hapludox) under no-tillage, and the relationships between these attributes with maize yield in the Midwest region of Brazil. Besides this, indicators of soil physical quality when subjected to levels of compaction were determined. A randomized complete block design was applied with five replicates. Treatments were induced levels of compaction: a reference condition that reflects 8 yr of no-tillage (NT); no-tillage with additional compaction by tractor traffic in one (NT-1), two (NT-2), four (NT-4), and six passes (NT-6). There was significant correlation (P < 0.01) between all physical attributes of the studied soil. Maize yield was positively correlated to macroporosity (r = 0.41*), and negatively to penetration resistance (r = -0.42*), geometric mean diameter (r = -0.51*), and mean weighted diameter (r = -0.53*). The index of emergence speed, stem diameter, plant height, grain mass, and grain yield decreased as soil compaction increased. The physical attributes evaluated, especially the resistance to penetration and soil macroporosity, reveal the level of soil compaction and can be used as soil physical quality indicators.

Rooting behaviour of chickpea (Cicer arietinum) as affected by soil compaction levels in Vertisol of central India

Soil compaction may restrict deep root growth and adversely affect plant access to sub-soil layer. Therefore it is important to study rooting behaviour of crops to soil compaction that are imparted on it naturally or artificially. The objective of this study was to determine the effect of soil compaction levels by varying the soil bulk density (BD) on rooting parameters and to model the root growth to understand the dynamics of rooting behaviour of chickpea (Cicer arietinum L.). Compaction level treatments, i.e. BDs were (i) 1.2, (ii) 1.4, (iii) 1.5 and (iv) 1.6 Mg/m3. When BD was increased from 1.2 Mg/m3 to 1.6 Mg/m3, there was 58% and 44% reduction in plant height of JG 11 and JG 130, respectively. There was 59% and 45% reduction in root length of JG 11 and JG 130, with increase in BD from 1.2 Mg/m3 to 1.6 Mg/m3. On an average, an increase in BD by 0.1 unit resulted in 19.34 and 19.11% decrease in root main axis length of JG 11 and JG 130, respectively. There was a negative correlation between root penetration rate and soil BD (R2 = 0.88). The critical growth limiting BD for chickpea was found to be 1.89 Mg/m3 in our study. The logistic growth model was fitted well with the observed dataset obtained from study with R2 of 0.98** (P &lt; 0.01). In this study, the chickpea variety JG 130 proved to be better than JG 11 while selecting chickpea cultivars for highly compacted soils.

English

The study was conducted at the Teaching and Research Farm, Obafemi Awolowo University Ile-Ife which approximately lies on latitude 7° 28E¹N and longitude 4° 33E¹ E with an altitude of about 244 m above the sea level. Different agricultural land uses examined were: Secondary forest, planted fallow with legumes, Bush fallow (Cromolaena odoratum), Continuous cassava/cowpea plot (Manihot esculenta-Vigna unguiculata (L) Walp), Continuous maize/soybean plot (Zea mays-Glycine max), and Tree crop (Theobroma cacao). Selected soil physical properties assessed were: Aggregate stability, Bulk density, Porosity, and Gravel content. Composite soil samples were taken from each of the investigated plot. The samples were sub-sampled for aggregate stability test while the other samples were air dried, crushed and passed through 2 mm sieve for other laboratory analysis. The mean bulk density of Cassava/Cowpea plot, Maize/Soybean plot, Bush fallow plot and Secondary forest were higher and significantly different from Planted legume and Tree crop. Soil compaction and low level of organic matter were the major causes of soil degradation in continuous arable crop production that practices conventional tillage system going by history. It is suggested that a rotational system involving one year of conventional tillage following every three years of no-tillage under continuous Cassava/cowpea and Maize/soybean plots might cause less soil deterioration, hence higher grain yield. Key words: Landuse, secondary forest, compaction, porosity, farming system.

Soil compaction and surface-active arthropods in historic, agricultural, alien, and recovering vegetation

Soil compaction is a major threat to natural resources. However, little information is available on the impacts of soil compaction on arthropod diversity especially relative to different types of vegetation, land use and restoration activities. In response to this dearth of information, we studied soil compaction, as well as percentage soil moisture and mean leaf litter depth, associated with four vegetation types: natural vegetation (fynbos, the historic condition), agricultural land (vineyards), invasive alien trees, and vegetation cleared of invasive alien trees (recovering vegetation). Our study took place in the Cape Floristic Region, South Africa, a biodiversity hotspot, yet also an area of intense viticulture and heavy invasion by alien plants. We sampled soil surface-active arthropods using pitfall traps, and compared species richness and abundance in different vegetation types with various levels of soil compaction and other soil variables. Overall, vineyards had the highest soil compaction while natural fynbos and aliens had low and comparable compaction. For both arthropod species richness and abundance, the order of the four vegetation types was, from highest to lowest: natural fynbos, alien cleared sites, vineyards, and alien infested sites. Level of soil compaction negatively correlated with arthropod species richness but not with abundance. Neither soil moisture nor leaf litter depth on their own significantly affected arthropod species richness or abundance. While alien trees overall had a strong negative effect on both arthropod species richness and abundance, and much more so than vineyards, the situation is reversible, with removal of aliens being associated with rapid recovery of soil structure and of arthropod assemblages. This is an encouraging sign for restoration.

ATRIBUTOS FÍSICOS DE UM NITOSSOLO VERMELHO CULTIVADO COM TRIGO, EM SISTEMA PLANTIO DIRETO, SUBMETIDO À COMPACTAÇÃO E ESCARIFICAÇÃO - DOI: 10.13083/1414-3984/reveng.v23n1p19-28

A compactação do solo é comumente observada em solos cultivados no sistema plantio direto, podendo causar reduções na produtividade das culturas devido às limitações no crescimento radicular. O estudo objetivou avaliar a influência de níveis de compactação do solo, na produtividade de trigo cultivado em um Nitossolo Vermelho distroférrico úmbrico. O experimento foi realizado na Estação Experimental da Universidade Tecnológica Federal do Paraná (UTFPR), Campus Dois Vizinhos, PR, Brasil. Os tratamentos consistiram: sistema do plantio direto (PD), plantio direto com compactação adicional (PDA) e plantio direto com escarificação mecânica (PDE). Avaliou-se a densidade, a porosidade e a resistência do solo a penetração a cada 0,05 m até a profundidade de 0,25 m, bem como a produtividade do trigo, a massa de grãos e o peso hectolitro. Constatou-se que na camada superficial do solo ocorreram as menores densidades de solo (Ds), maior macroporosidade e porosidade total nas três situações, sendo que nas camadas inferiores a 0,05 m os tratamentos PD e PDA, superaram o valor crítico 1,30 kg dm-3 para solos muito argilosos. A compactação adicional ao sistema plantio direto afetou negativamente as propriedades físicas do solo, na sua camada superficial, acima de 0,05 m, sendo observados incrementos de densidade do solo, na resistência à penetração e redução da macroporosidade e porosidade total. A escarificação mecânica melhorou as propriedades físicas do solo até a profundidade de 0,1 m, após treze meses de intervenção, superando os demais sistemas avaliados. Entretanto, o uso do implemento subsolador, como forma de reduzir a compactação do solo, não contribuiu para o aumento da produtividade e a qualidade dos grãos de trigo.

Interspecific Differences in Tolerance to Soil Compaction, Drought and Waterlogging Stresses among Maize and Triticale Genotypes

AbstractStress susceptibility indexes (SSI) of eight maize and eight triticale genotypes for their ability to cope with soil compaction (SC) combined with drought (D) or waterlogging (W) were estimated through the determination of changes in dry matter of the shoot (S), root (R) and whole plant (S+R) grown at three levels of soil compaction (1.1, 1.3 and 1.6 g cm−3) and exposed to D or W stress for 7 or 14 days. The SSI values showed variation between and within maize and triticale genotypes, and it was possible to divide genotypes into groups of sensitive and resistant ones. The correlation coefficients (r) between stress susceptibility indexes of soil compaction (SCSI) and drought (DSI) or waterlogging (WSI) and between DSI and WSI were statistically significant. This indicates that genotypes resistant to soil compaction (SC) were resistant to drought (D) or waterlogging (W) stresses and that genotypes resistant to D were also resistant to W. Seedlings grown under the stresses showed changes in S to R ratio (S/R). Sensitive genotypes had higher S/R ratio than resistant ones. Decrease of S/R ratio depends on the duration of stresses, and it may be considered an adaptation mechanism to stress. After 7 days of recovery for D and W treatments, we observed only a partial return of growth traits to the level of control plants.

Interspecific differences in root architecture among maize and triticale genotypes grown under drought, waterlogging and soil compaction

Environmental stresses (soil compaction, drought, waterlogging) cause changes in plants’ root system structure, also affecting the growth of above-ground parts. The aim of this study was to estimate phenotypic variation among maize and triticale genotypes in root penetration ability through petrolatum-wax-layer (RPA). Also, the effect of shortage or excess of soil water on dry matter of shoots and roots and morphological changes in root system structure in sensitive and resistant maize and triticale genotypes grown in low or high soil compaction level was evaluated. To estimate RPA index, the petrolatum-wax-layer method (PWL) was used. The strength of three petrolatum-wax concentrations 60, 50 and 40 % was 0.52, 1.07 and 1.58 MPa, respectively. High coefficients of variation (CV) were observed in 0.52 and 1.07 MPa and for maize were 19.2 and 21.7 %, and for triticale, 12.5 and 18.3 %, respectively. The data indicate that the use of PWL technique is an effective screening method, and makes it possible to divide the genotypes into resistant and sensitive groups. The second part of this study investigated a multistress effect of soil compaction combined with drought or waterlogging on root and shoot growth and morphological changes in root system structure of maize and triticale genotypes differing in susceptibility to environmental stresses. Seedlings were grown for 4 weeks in root-boxes under conditions of low (LSC 1.1 g cm−3) or severe (SSC 1.6 g cm−3) soil compaction. Drought or waterlogging stresses were applied for 2 weeks from 14th to 28th day. In comparison to LSC treatment, in SSC treatment the decrease in dry matter of shoots and roots was greater for sensitive genotypes of maize and triticale (Ancora, CHD-147). Soil drought or waterlogging caused greater decrease of dry matter of shoots and roots in seedlings grown in SSC in comparison to LSC. The root penetration index (RPI) was estimated as a ratio of root dry matter in 15–40 cm root-box layer to total root dry matter. On the basis of RPI it was possible to group the genotypes according to their ability to distribute roots in soil profile. In comparison to LSC, SSC exerted a strong influence on the length of seminal and seminal adventitious roots, as well as the number and length of L- and S-type lateral roots developed on seminal and nodal roots. In both species the restriction effect of soil compaction on number and length of roots was more severe in sensitive (Ankora, CHD-147) than in resistant (Tina, CHD-247) genotypes. The restriction in roots propagation was greater in triticale than in maize. Exposure to drought or waterlogging in the case of genotypes grown in LSC and SSC treatments caused a decrease in number and length of particular components of root system structure. In both species the decrease of root number and length in plants grown under waterlogging was greater than under drought. The observed changes in root system were greater in sensitive (Ankora, CHD147) than in resistant (Tina, CHD-247) genotypes. Statistically significant correlations were found between RPA and RPI and also between these indexes and soil compaction, drought and waterlogging susceptibility indexes. This indicates that genotypes resistant to soil compaction were resistant to drought or waterlogging and also that genotypes resistant to drought were resistant to waterlogging.

Effects of tree-length timber skidding on soil compaction in the skid trail in Hyrcanian forests

Aim of study: The study was conducted to examine impact of skidding traffic, trail slope, traffic frequency, and soil depth on the soil bulk density.Area of study: This study was carried out in the Kheyrud Forest in Hyrcanian forest, Iran.Material and methods: The level of soil compaction at eight levels of traffic (1, 4, 8, 10, 15, 20, 25, and 30 passes), four levels of skid trail slopes (0, 10, -10, and -20%) and three soil depth (5, 15, 25 cm) were applied in three replicates consequently. Bulk densities were measured on the undisturbed surface (control) and within the tracks. Timbers were extracted in the tree-length logging method using rubber-tired skidder (Timberjack 450 C).Main results: About 5.2% of total area of harvesting unit were disturbed and compacted. Uphill skidding increases compaction more than downhill skidding. In the four different slopes, the highest increasing of the bulk density was occurred during the first few passes of skidder, although the bulk density continued to increase in amount and depth with the number of passes. The increases in bulk density were still important at the maximum sampling depth of 20-30 cm.Research highlights: The results indicated that slope steepness had a strong effect on the soil physical properties and soil disturbance. Designated skid trails should be used to minimize the influence on the forest soil.Key words: soil compaction; tree-length logging method; rubber-tired skidder; Hyrcanian forest.