Abstract: The aim of this study is to assess soil quality in Mediterranean forests of Central Italy, from evergreen to deciduous, with different types of management (coppice vs. high forest vs. secondary old growth) and compaction impacts (machinery vs. recreational). Soil quality was evaluated studying soil microarthropod communities and applying a biological index (QBS-ar) based on the concept that the higher is the soil quality, the higher will be the number of microarthropod groups well adapted to the soil habitat. Our results confirm that hardwood soils are characterised by the highest biodiversity level among terrestrial communities and by a well-structured and mature microarthropod community, which is typical of stable ecosystems (QBS value, >200). While silvicultural practices and forest composition do not seem to influence QBS-ar values or microarthropod community structure, the index is very efficient in detecting soil impacts (soil compaction due to logging activities). Several taxa (Protura, Diplura, Coleoptera adults, Pauropoda, Diplopoda, Symphyla, Chilopoda, Diptera larvae and Opiliones) react negatively to soil compaction and degradation (QBS value, <150). In particular, Protura, Diplura, Symphyla and Pauropoda, are taxonomic groups linked to undisturbed soil. This index could also be a useful tool in monitoring soil biodiversity in protected areas and in urban forestry to prevent the negative effects of trampling. QBS-ar is a candidate index for biomonitoring of soil microarthropod biodiversity across the landscape to provide guidance for the sustainable management of renewable resource and nature conservation.

Abstract: This paper presents artificial neural network (ANN) prediction models for estimating the compaction parameters of both coarse- and fine-grained soils. A total number of 200 soil mixtures were prepared and compacted at standard Proctor energy. The compaction parameters were predicted by means of ANN models using different input data sets. The ANN prediction models were developed to find out which of the index properties correlate well with compaction parameters. In this respect, the transition fine content ratio (TFR) was defined as a new input parameter in addition to traditional soil index parameters (i.e. liquid limit, plastic limit, passing No. 4 sieve and passing No. 200 sieve). Highly nonlinear nature of the compaction data dictated development of two separate ANN models for maximum dry unit weight (γdmax) and optimum water content (ωopt). It was found that generalization capability and prediction accuracy of ANN models could be further enhanced by sub-clustered data division techniques.

Abstract: Published in Agron. J. 105:1658–1664 (2013) doi:10.2134/agronj2013.0089 Available freely online through the author-supported open access option. Copyright © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. T value of using cover crops includes reduced soil erosion, gains in soil organic matter, capture of unused fertilizer N, decreased soil compaction, and suppression of diseases and weeds when compared with bare soil or winter fallow (Snapp et al., 2005; Tonitto et al., 2006; Cherr et al., 2006). Before industrial manufacturing of inorganic fertilizers, the most common reason for using a legume cover crop was to enhance soil fertility, especially N (Dinnes et al., 2002). Many studies have attributed the benefit of a legume cover crop before corn to an increase in soil N levels following legume incorporation (Hesterman et al., 1986; Blevins et al., 1990; Torbert et al., 1996; Vyn et al., 1999; Sanchez et al., 2001); however, other non-N rotational benefits have been identified as well (McVay et al., 1989; Raimbault and Vyn, 1991; Corak et al., 1991). In total, the direct contribution of N from legume N2 fixation coupled with factors such as improved soil physical, chemical, and biological properties may synergistically produce the overall “rotational effect” (Gaudin et al., 2013); however, legume cover crops are generally managed as a N source (Tonitto et al., 2006; Liebman et al., 2012). Red clover, when frost-seeded into winter wheat (Triticum aestivum L.), has been shown to fix and accumulate large amounts of N in the aboveground biomass and has been evaluated as a green manure prior to corn production (Hesterman et al., 1992; Tiffin and Hesterman, 1998; Schipanski and Drinkwater, 2011; Gaudin et al., 2013). Due to the low C/N ratio of red clover tissues, N turnover is generally faster than for nonleguminous cover crops (Varco et al., 1989; Wagger, 1989); however, environmental and management factors can markedly influence decomposition dynamics, and it is difficult to accurately predict the amount of N that will become available, or when it will become available, to a subsequent crop (Crews and Peoples, 2005; McSwiney et al., 2010; Ruffo and Bollero, 2003). Snapp et al. (2005) determined that uncertainty regarding N mineralization and availability was one of the chief barriers to adoption of legume cover crops among surveyed Michigan farmers. Determining the N credit value of a cover crop is critical for calculating the N fertilizer application rate that maximizes profit and protects the environment (Andraski and Bundy, 2002; Stute and Posner, 1995; Vyn et al., 1999). Knowledge is limited, however, concerning longer term, decadal interactions of producing cover crops within a given cropping system. Long-term field crop experiments greatly improve our understanding of historical management effects on soil properties, including slow processes such as soil organic matter accumulation (Sanchez et al., 2004; Robertson et al., 2008). During the first decade of a row crop experiment in southwest Michigan, the presence of cover crops in a corn–soybean [Glycine max (L.) Merr.]–wheat rotation supported soil C increases of 10 to 40 g C m–2 annually (Robertson et al., 2000). Similarly, diversification with cover crops in a 14-yr organic corn–soybean–wheat rotation experiment in Pennsylvania enhanced soil C by 42 g C m–2 annually (Drinkwater et al., 1998). Although these studies demonstrate gains in soil C and improved soil fertility, the timing of nutrient release, particularly with regard to soil N supply, has been shown to be one of the primary yield-limiting factors for cash crop production in organic farming systems (Cavigelli et al., 2008). Soil fertility amendments (i.e., fertilizers, composted dairy manure, and green manures) are generally applied to enhance the growth and yield of the cash crop. Although rarely studied, it can be inferred that practices improving soil nutrient and organic matter status will, in turn, enhance cover crop performance. We hypothesized that agricultural systems that have ABSTRACT Corn (Zea mays L.) production systems can benefit from introducing a leguminous winter cover crop into the rotation, especially with regard to increased N availability (i.e., legume N credit); however, it is not known if the full agronomic benefit is realized in the first year of cover crop introduction or if the benefit is cumulative with time. The objective of this study was to determine the apparent red clover (Trifolium pratense L.) N credit to corn in a conventional system where red clover was introduced for the first time compared with three agricultural systems that had a 14-yr history of using cover crops. The apparent red clover N credit was calculated by the difference in unfertilized corn N accumulation between cover and no-cover split-split plots. These data suggest that corn growers can realize the full benefits of a red clover cover crop in the first year of introduction.

Abstract: This paper provides a new methodology for determining soil water content and density under different compaction energies. A new calibration equation was introduced making use of the voltage drop associated with the first passage of the electromagnetic wave through the soil specimen, the final voltage level after wave propagation ceases, and dry density normalized by the density of water. The new calibration equation allows for the direct calculation of dry density. Values of dry density are then used in the normalized apparent dielectric constant equation to determine the water content. Results of numerous laboratory tests on a wide variety of soils (including coarse-grained soils) showed that the proposed method accommodates different levels of compaction energy. The method also was validated with different field tests at sites commonly used in geotechnical earthwork construction, using soil-specific model coefficients determined from laboratory compaction tests. The results of this study indicat...

Abstract: Abstract The field experiment was carried out on a smoothstalked meadow-grass to analyse the effect of tractor traffic on herbage production and root morphology. The multiple passes of tractor changed physical properties of soil. Increase in bulk density and penetration resistance of soil under smooth-stalked meadow-grass was recorded up to the depth of 30 cm. The tractor traffic resulted in changes in smooth-stalked meadow-grass yields. During the second and the third harvest it was found that wheel traffic decreased plant yields. For the first harvest the opposite effect in herbage production was noticed. The tractor traffic significantly changed the root morphometric properties in the upper, 0-5 cm, soil layer. Intensive tractor traffic (four and six passes) significantly increased the root length in diameter range of 0.1-0.5 mm. There were no differences in both mean root diameter and specific root length what indicated that traffic treatment applied did not change the root diameter. The results indicate that smooth-stalked meadow-grass could be recommended for compacted soils when intensive traffic is present.

Abstract: The quality of constructed pavement foundation layers was studied with rapid and near-continuous soil stiffness measurements as alternatives to traditional nuclear gauge moisture-density measurements. Sixteen sections of stabilized pavement foundations covering 4.8 mi, with ground conditions ranging from soft to very stiff, were studied. Measurements from falling weight deflectometer, light weight deflectometer, dynamic cone penetrometer, and roller-integrated compaction monitoring systems were used to assess soil stiffness. Statistical analyses of the results were reported in the form of coefficient of variation and empirical correlations between measurements. Results of soil stiffness were compared with two independent groups of nuclear moisture-density measurements to demonstrate some of the shortcomings of traditional nucleargauge testing for quality assessment. The findings from this paper show the value in using soil stiffness measurements to characterize ground variations. Cost data are also report...

Abstract: A long-term field experiment with rice-wheat cropping was started in the wet season of 1988 with four levels of lantana (Lantana camara L.) (0, 10, 20, and 30 Mg ha−1 on fresh weight basis) and three tillage practices (No puddling, puddling, and soil compaction). From wet season of 1997, however, three tillage practices were replaced with three levels of nitrogen (N) and potassium (K) to rice (33, 66, and 100% of recommended) and 66% of recommended N, phosphorus (P), and K to wheat. Phosphorus was totally omitted for the rice crop. The recommended N and K for rice was 90 and 40 kg ha−1, whereas the recommendations for N, P, and K for wheat were 120, 90 and 30 kg ha−1. Organic amendments are known to improve soil productivity under rice-wheat cropping by improving physical conditions and nutrient status of the soil, but their availability is restricted. There is a need to identify locally available and cost-effective organic materials that have minimal alternate uses as fodder and fuel. We evaluated Lantan...

Abstract: Visitor’s access to understorey vegetation in park forest stands results in the impoverishment of plant species composition and a reduction in habitat quality. The phenomenon of biotic homogenisation is typical in urban landscapes, but it can proceed differently depending on the scale, a detail that has not been observed in previous studies. This research was carried out in seven Warsaw parks (both public and restricted access). Thirty-four forested areas were randomly selected, some subjected to strong visitors’ pressure and some within restricted access areas, free of such impacts. The latter category included woodlands growing in old forest and secondary habitats. Public access to the study areas contributed to the disappearance of some forest species and their replacement by cosmopolitan non-forest species, leading to loss of floristic biodiversity in areas of high ecological importance at the city scale. Some human-induced factors, including soil compaction and changes in soil pH, moisture and capillary volume, were found to cause habitat changes that favoured native non-forest plants. Despite changes in species composition, the taxonomic similarity of understorey vegetation in both categories—public access and restricted access—was comparable. In a distance gradient of measurements taken around selected individual trees, there was found to be significant variation (in light, soil pH and compaction) affecting the quality and quantity of understorey vegetation (including rare species). In conclusion, the protection of rare forest species could be achieved by limiting access to forested areas, particularly in old forest fragments, and we highly recommend its consideration in the proposal of future park restoration plans.

Abstract: White clover can reduce fertilizer-N requirements, improve sward nutritive value and increase environmental sustainability of grazed grasslands. Results of previous experiments in glasshouse conditions and on mown plots have suggested that white clover may be more susceptible than perennial ryegrass to treading damage on wet soils. However, this phenomenon has not been investigated under actual grazing conditions. This experiment examined the effects of treading on clover content, herbage production and soil properties within three clover-based grazing systems on a wet soil in Ireland for 1 year. Treading resulted in soil compaction, as evidenced by increased soil bulk density (P < 0·001) and reductions in the proportion of large (air-filled) soil pores (P < 0·001). Treading reduced annual herbage production of both grass and white clover by similar amounts 0·59 and 0·45 t ha−1 respectively (P < 0·001). Treading reduced the sward clover content in June (P < 0·01) but had no effect on annual clover content, clover stolon mass or clover content at the end of the experiment. Therefore, there was little evidence that white clover is more susceptible to treading damage than perennial ryegrass under grazing conditions on wet soils.

Abstract: Global land use and ongoing climate change highlight the importance of ecological restoration as an emerging discipline and underscore the need for successful revegetation techniques. To link mechanistic drivers of seedling establishment with techniques to increase revegetation success, we undertook field-based experiments in degraded peri-urban woodlands in Mediterranean southwestern Australia using two iconic tree species. Over the course of an entire growing season, our objectives were to: (1) characterise soil moisture profiles in relation to site preparation techniques (ripping and created ashbeds) and (2) determine whether early seedling establishment can be increased through site preparation techniques (ripping and ashbeds), plant treatments (various fertilisers and biochar) and early planting during the wet season. Ripping significantly reduced soil compaction and was associated with a significant soil moisture stratification; moisture penetrated to greater depths in soils that were ripped or treated with ashbeds. Particular site preparation techniques (ripping) and early planting significantly increased early establishment, health and growth of tree seedlings. Fertilisation effects varied by species with generally neutral effects on seedlings. Finally, seedlings planted in ripped soils had significantly longer, deeper root systems accessing portions of the soil profile with higher summer moisture. Techniques such as ripping, even in deep sandy soils, reduce soil compaction and alter moisture availability within the soil profile, promoting deeper root growth and thus increasing revegetation success in these degraded Mediterranean ecosystems. Linkage of revegetation outcomes with plant response and physical soil properties associated with particular treatments provides critical knowledge for both restoration scientists and land managers.

Abstract: Feral pigs (Sus scrofa) occupy many different habitats worldwide. Their rooting foraging behaviour poses a serious threat to biodiversity as the resulting soil disturbance alters ecosystem structure and function. Understanding what characteristics are important in selecting rooting locations can be used to predict the impact of pigs on ecosystems. We investigated patch selection for rooting by feral pigs at two spatial scales: (1) habitat variables at a site level, and (2) dependency between observations in a spatial context. Seasonal influences on the modelled environmental variables were also examined. We applied a generalised linear modelling approach and model-averaging to explain the relative importance of variables, as measured by the standardised parameter estimates and unconditional variance. Soil texture, rock cover, soil compaction and sand texture were important explanatory variables in the presence of pig rooting. Soil compaction and distance to roads had a negative influence. The highest ranking model included seven explanatory variables with a 41 % chance that this is the Kullback–Leibler best model. Six of the 128 candidate models were in the 95 % confidence set indicating low model uncertainty. Although no differences in pig rootings were detected between seasons, most rooting (65.7 %) occurred during the dry season with soil and sand texture having the strongest effect. This study highlights how pig control programmes can focus limited resources on either the strategic positioning of control devices (e.g., traps and baits) to either reduce the number of pigs or help prioritise habitats of high conservation value for protection (e.g., exclusion fencing).

Abstract: The improvement of degraded pastures is important for increasing pasture herbage mass and animal production in southern Chile. While research has normally focused on how animal treading affects soil compaction, no major work has yet been done to define the impact of pasture improvement managements on soil physical functions, particularly when the initial situation is a degraded pasture. Thus, the aim of this study is to define the short-term effects of different pasture improvement managements on the physical quality and related processes of a volcanic ash soil. Four treatments were defined: two tilled, fertilized and seeded plots (T1 and T2), one non-tilled and non-fertilized plot (T3) and one non-tilled and fertilized plot (T4), all of which were compared to the initial situation of a highly degraded pasture (IS). Undisturbed soil samples were collected (1-10 cm) and the volumetric water content and temperature was continuously monitored at the 10 cm depth. The short-term effects of pasture improvement managements on soil physical quality and related processes differed in relation to the treatment method. As compared to the non-tilled plots, the aggregate destruction after tillage induced an increase in the water holding capacity, but a decrease in the air capacity and pore-continuity values due to grazing. The physical quality assessed by the S-Index reflected a good soil structural quality (S > 0.035). The tilled plots presented a higher S-Index as compared to the non-tilled plots, which is related to a slightly lower mechanical strength and larger water holding capacity. The latter also increased due to tillage and was positively correlated to pasture yields during the first intensive soil drying. Soil temperature differences between treatments were assessed and can be related to the higher water contents in the tilled plots and the presence of broad-leaf species in the non-tilled pastures. Finally, in order to properly understand how the implementation of pasture improvement managements affects the soil physical quality and related processes, long-term studies are required.

Abstract: The structure change caused by soil compaction is a limiting factor to growth and development of plants. The objective of this study was to evaluate the physical parameters of an Eutrophic Oxisol in Jaboticabal, SP. Aggregate stability, hydraulic conductivity and "S" index were evaluated in a completely randomized split-plot (four levels of compaction and two depth), with four replications and an area of native forest (NF) as control. The compaction treatments consisted of C0 = 0, C1 = 2, C2= 4 and C3 = 6 tractor passed of 11 Mg. It was observed that NF had high rates compared to GMD (geometric mean diameter) and WMD (weighted mean diameter) with larger and more stable aggregates compared to other treatments. The "S" value of 0,036 and a reduction in the most compacted levels to 0,026 were obtained, since the compaction reduced the value of "S", which reached its limiting value (< 0,035) despite the oxidic mineralogy of the analyzed soil.

Abstract: The scope of the study as presented in this paper is to re-examine the prediction of resilient modulus (M R) by the classical California Bearing Ratio (CBR) approach, specifically for compacted saprolitic subgrade soils. Through the extensive experiments carried out for this research, a more precise model yielded to estimate M R based on CBR values and the relative degrees of soil compaction. Likewise, comments are also made critically for the suitability of using the well-known models which were developed during the past decades. In addition to the core results, this study has produced a number of other important findings: (1) the influence of soil compaction densities on CBR and M R is relatively significant when soil is relatively dry, whereas saturation ratio becomes a dominant factor while the soil is in wetter condition; (2) when the saturation ratio becomes dominant, the soil material could rarely reach a CBR of 5% or above, which was often regarded as competent materials by many design standards; ...

Abstract: This paper presents the relationship between the Atterberg limits and soil compaction parameters obtained by the correlation- regression analysis. The relations between the liquid limit wl, plastic limit wp, maximum dry density dmax and optimum moisture content wopt are obtained on the basis of the results of laboratory tests measured on a large number of samples of clay core earthfill dams Rovni, Selova, Prvonek and Barje. The regression and correlation analysis were obtained empirical equations and diagrams. Based on the obtained, the value of the optimum moisture content and maximum dry density of knowing the Atterberg limits of plasticity can be estimated.

Abstract: When constructing earthen embankments, it is essential that the soil be placed and spread in uniform lifts prior to compaction. To ensure that the resulting soil lifts are evenly compacted, typical compaction specification approaches place restrictions on the thickness that is acceptable for each soil lift. In current practice, it can be extremely difficult for a field inspector to verify that lift thickness requirements are being met when soil is being placed and spread over a large area, without the use of frequent surveying (which adds both costs and delays to earthwork projects). Recent advances in compaction control include the development of continuous compaction control (CCC) and intelligent compaction (IC) systems, which provide real-time monitoring and feedback about the operation and performance of soil compaction. Typically, CCC and IC compaction equipment is outfitted with a real-time kinematic global positioning system (RTK-GPS) that monitors and records the position of the compacter as the soil lift is being compacted. This paper suggests that geotechnical engineers use field RTK-GPS measurements that are made by CCC or IC equipment to monitor and control the thickness of compacted soil lifts. Data collected from a full-scale field study is used to illustrate the practical issues with using GPS measurements for field monitoring of lift thickness during construction of a roadway embankment, such as varying roller position from lift-to-lift and the measurement uncertainty associated with RTK-GPS measurement data. The use of both simple and sophisticated spatial analysis techniques are explored for interpolating measured field elevation data onto a uniform grid for lift thickness assessment. The resulting methodology that is presented can be utilized to build spatial maps of compacted soil lift thickness, a process that can be used to great benefit by field engineers who are trying to ensure the quality of compacted soil lifts.

Abstract: Regolith is the term we give parent material that h as been weathered. The regolith consists of weather ed bedrock near the surface including the soil layer. In the Iranian soil layer we will find: decayed par ent materials, decaying plant material, decaying animal matter (manure) along with vegetation. Results of the present study show us that methods stimulating natu ral fertility in Iran includes composting-adds humu s layer, drip irrigation-balances illuviation and elu viation in arid regions, crop rotation/ intercroppi ng-reflects natural diversity and limits gleization, add lime-r educes gleization, non-cultivation techniques-reduc es hard pan (calcification) caused by compaction and reduce pesticide use-keeps decomposers alive in humus layer.

Abstract: A two-year research work was performed under greenhouse conditions to evaluate: 1) the effects of soil compaction on corn growth, and 2) if using different species of mycorrhizal fungi under non-sterilized and sterilized conditions can alleviate the stress of soil compaction on corn growth. After sieving the field soil and sterilizing half of it using an autoclave, it was compacted in 2-kg pots. The soil was then planted with corn seeds and inoculated with different species of AM species including Glomus etunicatum, G. mosseae, and G. intraradices. While high levels of soil compaction decreased corn growth, AM inoculation significantly enhanced root and shoot growth and hence plant growth under compaction and G. etunicatum was the most efficient one. These results are important complementary to the previously little documented results regarding the effects of AM fungi on corn growth under compaction stress and are of agricultural and ecological significance.

Abstract: Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improvement using rapid impact compaction (RIC). The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh, Malaysia. In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10 m. Groundwater is approximately 0.5 m below the ground surface. Evaluation of improvement was based on the results of pre- and post-improvement cone penetration test (CPT). Interpretation software has been used to infer soil properties. Load test was conducted to estimate soil settlement. It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%, the friction angle of soil is increased by an average of 3°, and the soil settlement is reduced by 50%. The technique succeeds in improving soil properties to approximately 5.0 m in depth depending on soil uniformity with depth.

Abstract: Commercial willow planting is mostly performed by machines, using long rods which are automatically pressed in the soil and cut. This procedure exerts a large mechanical impact on the cuttings, and may lead to damage, especially when planted in compacted soils. We studied cuttings and early growth performance of willow (in terms of produced shoot biomass, shoot height, leaf area, and number of shoots per cutting) after machine planting, in comparison to manually prepared and planted cuttings. To isolate the effect of mechanical planting from the effects of field variation after planting, we dug out cuttings from five different clones directly after machine planting in well prepared and compacted soil respectively and grew them under controlled conditions, together with a manually prepared control. We found that undamaged cuttings had a better growth performance than visibly damaged cuttings. Planting by machine on compacted soil resulted in a relatively large number of cuttings landing on the soil surface, instead of being planted vertically in the soil. Soil compaction and machine planting interacted with cutting dimensions, the poorer performance of thinner cuttings being more pronounced in compacted soil. To obtain a faster and more even establishment of willows, we recommend thorough soil cultivation prior to planting, further development of planting machines to minimize damage to cuttings at planting, and the use of cuttings with a diameter of at least 10–11 mm.

Abstract: Evaluating the accuracy of Decision Support System for Agrotechnology Transfer (DSSAT) and ProPlanta fertilizer advisory system for maize crop (Zea mays L.) using the 2010 and 2011 database, it was concluded that simulations led to large inaccuracies in small plot sizes (0.25 ha). However the differences between simulated and measured yields related to a research field (15.3 ha) were relatively good. The 10-year databases have also been taken into consideration. The aim of the research was to adapt the different crop system models to site-specific precision technologies by taking the soil physical parameters electrical conductivity, cone index and tillage draught force into account.

Abstract: A soil compaction reduction system and method determine a path through the field for a mobile machine or control a soil compaction characteristic of the mobile machine based upon a varying soil compaction characteristic of the mobile machine as the mobile machine traverses the field and based upon a soil compaction constraint.

Abstract: It is essential to know the levels of pressure applied to the soil by different weed managements to adapt the management of coffee plantations in a sustainable manner. The objectives of this study were: a) to generate load-bearing capacity models of a Red-Yellow Latosol (Oxisol) submitted to different weed managements and b) to determine which weed management resulted in higher compression. The study was conducted at the Experimental Farm of EPAMIG, located near the community Farias, in Lavras-MG (latitude 21° 14' 43" S and longitude 44° 59' 59" W and altitude of 919 m). The soil is a Red-Yellow Latosol (LVA) cultivated with coffee plantation using Topazio MG 1190 coffee variety, since 2006. We evaluated five weed managements, three being through mechanical control (harrow (GD), mowing (RC) and brush (TC)) and two by chemical control (post-emergence herbicide (HPos) and pre emergence herbicide (HPre)). To obtain the load-bearing capacity models, 10 undisturbed soil samples were randomly collected in the 0-3, 10-13 and 25-28 cm layers between the rows. The load-bearing capacity models which indicated a higher compaction were: in the 0-3 cm layer, TC and GD; in the 10-13 cm layer, HPre, HPos and RC and in the 25-28 cm layer, GD. The load-bearing capacity models that indicated greater susceptibility to compaction were: in the 0-3 cm layer, HPos; in the 10-13 cm layer, GD and TC and in the 25-28 cm layer, HPre.

Abstract: Physical properties of soil, such as compaction, have immense effects on the physico-morphological characters of plants, namely on the roots. For this reason per se, roots are immersed in a soil matrix with distinct conditions that may affect their anatomy, structure and function. Soil’s physical characteristics, such as texture and compaction force, are some of the main factors affecting root growth and development. This study investigates how soil compaction, soil moisture and type of soil can modify the regular growth of Zea mays L., and thus reveal the changes influencing plant’s physiology and growth. This experiment focuses on simulating two magnitudes of compaction (1.25 and 1.45 g cm -3 ), two irrigation rates in two soil types, and assessing their effects on Z. mays . Despite intrinsic differences in the physico-chemical properties of the two soils, soil compaction had the highest influence on the decrease of leaf area, relative growth rate, total length of roots and shoot and dry mass of stem and roots, while it showed an increase in nitrate reductase activity and total chlorophyll content of the leaves and a limited bacterial growth. Soil moisture interactively aggravated the negative effects of soil compaction. In conclusion, soil compaction shows momentous effects on root anatomy and morphology during the seedling stage, with consequences on plant physiology and growth.

Abstract: The purpose of this study was to determine the effects of soil compaction on the chemical properties of soil and herbage yield of lucerne (Medicago sativa L.). A field experiment was conducted on a silty loam Mollic Fluvisols soil in 2003-07. Four compaction treatments were applied three times annually by tractor using the following number of passes: control without experimental traffic, two passes, four passes, and six passes. This study confirmed the unfavorable effect of multiple tractor passes on lucerne dry matter production. The results showed that tractor traffic reduced the yields of lucerne, particularly during the second and third harvests in each year. Soil compaction caused by tractors changed some chemical properties of soil. Tractor passes resulted in increasing pH and EC. It also increased P and Zn content. Most of these changes were statistically significant only in the deeper 20-30 cm soil layer. This effect could be ascribed to higher soil density and lower air permeability. The upper (0-20 cm) soil layer was resistant to changes in chemical properties, probably due to the dense root system that recovers the soil after compaction and improves physical properties. The decrease in lucerne production probably was the result of mechanical damages to roots and above-ground parts of plants rather than problems in nutrient uptake. We can conclude that chemical properties, particularly N content, are not significantly important factors in reduction of lucerne production exposed to tractor traffic.