Changes In Soil Physical Properties Research Articles

Response of maize yield to changes in soil organic matter in a Swedish long‐term experiment

AbstractAgricultural practices that lead to soil carbon sequestration may be a win–win strategy for mitigating global warming and improving soil fertility and resource use efficiency. The mechanisms through which soil organic carbon (SOC) concentration affects crop yields are numerous but difficult to separate. The objective of this study was to disentangle these processes and estimate to what extent the yield response to SOC is mainly driven by changes in physical or biochemical properties and processes. This was achieved by analysing the response of yields in continuous maize to SOC concentrations during 20 years (2000–2019), which had evolved in 14 experimental treatments in a Swedish long‐term field experiment at Ultuna since 1956, ranging from 0.94% to 3.65% in the topsoil (0–20 cm). Average maize yields during this period varied between 1.9 and 8.4 Mg dry mass per hectare in the different treatments. The treatments comprise applications of different mineral nitrogen (N) fertilizers and organic amendments and combinations thereof. Our analysis showed that maize yield in the treatments that were not severely limited by nitrogen supply or soil acidity increased by 16% for each percentage unit increase in SOC. We applied the widely used concept of critical N concentration in plant biomass to diagnose the N status in maize in the different treatments (N nutrition index [NNI]) and parameterized a response function between yield and pH (RpH). Dry soil bulk density (BD) was used as a proxy for soil physical properties. These three variables NNI, RpH and BD explained 95% of the variation in maize yields among treatments. Further analysis of the relationship between BD, SOC and plant available water capacity revealed that about two thirds of the yield increases in response to SOC change could be ascribed to associated changes in soil physical properties. Our analysis suggests that the extra storage capacity of water, which increased by up to 15 mm in the topsoil for each unit percentage increase in SOC, was the main driver for the observed yield responses. We conclude that measures for increasing SOC in soils most likely are an effective adaptation strategy for reducing the risk of crop damage during dry spells, which probably are becoming more frequent in the future due to climate change, even in relatively humid climates as in Sweden.

Effects of herbivory, fire, and vegetation type on soil compaction and aggregate stability in a semi-arid savanna

AbstractVegetation type is an important component of savannas contributing to changes in soil health. In savanna landscapes, the tree-grass balance is primarily governed by water, nutrients, fire, herbivory, and their interactions. Here we investigated the long-term effect of herbivores, fire, and vegetation type, and their interactions on selected physical properties (bulk density, penetration resistance, aggregate size fractions, and mean weight diameter (MWD)) of water stable aggregates within the crest and foot-slope of 20-year-old Nkuhlu exclosures located in Kruger National Park, South Africa. Burning, herbivory, and open grassland zones had a significant main and interactive ecological impact on all the soil physical properties under investigation. The interactions between fire, herbivores, and vegetation type within the crest and foot-slope of the Nkuhlu exclosure had a significant impact on soil bulk density, with areas under tree canopies having lower bulk density than open grassland zones in all the exclosures. In all the sampling sites, both burnt and unburnt plots of the full exclosure had lower penetration resistance than the control site and partial exclosure. Moreover, unburnt plots and canopy cover increased aggregate size distribution and mean weight diameter of water stable aggregates. Since fire and herbivory are closely linked and bring about changes in soil physical properties, the understanding of the dynamics of fire, herbivory, vegetation, and their interactions can then be used to help make effective management decisions that incorporate concerns of biodiversity in savanna ecosystems.

Effects of varying tillage practices and weed control methods on the efficacy of infiltration models.

Agricultural land preparation and weed control techniques are essential farm management tools that affect the dynamics of soil water infiltration and the estimation accuracy of infiltration models. To analyse the interaction effect of tillage and weed control methods on the changes in soil physical properties and the efficacy of infiltration models, an experiment was conducted on a sandy clay loam forest ochrosol at Hodzo near Ho in Ghana. Four tillage systems (No Tillage [NT], Reduced Tillage [RT], Plough + Harrow + Ridging [PHR], and Deep Tillage + Plough + Harrow + Ridging [DPHR]) and three weed control methods (Hoeing [H], Machete [MAT] and No Weeding [NW]) were employed. The study also tested the reliability of the models (Kostiakov, Philip, and Horton) using the goodness of fit statistical criteria: Root mean squared error (RMSE), Mean absolute error (MAE), Coefficient of determination (R2), and Nash-Sutcliffe efficiency (NSE). The results show that conservation tillage systems (CsT) and conventional tillage systems (CT) with MAT weeding treatments recorded the highest moisture content across the studied soil profile, especially for NT x MAT (11.189%) which was significant (p < 0.05) in the 15-30 cm layer; the lowest were observed in the CsT and CT with H weeding interactions, especially for the DPHR x H (8.086%). Comparing the interaction effect on the soil infiltration, the highest mean infiltration rate was significant (p < 0.05) under the NT X H treatment combination whilst the lowest infiltration rate was recorded in the DPHR X H and PHR X NW treatment combinations. The efficiency of the fitting models (Kostiakov > Horton > Philip) highly prioritised the soil tillage operations and weed management under the treatments DPHR x MAT > DPHR x NW > DPHR x H > RT x MAT > PHR x NW > PHR x MAT > NT x NW > RT x MAT > PHR x H > RT x H > NT x MAT > RT x NW > NT x H in that order. The trend shows that the increase in tillage intensity and the decrease in weed management intensity induce the quality of the estimation process and vice versa. The study, therefore, identified the use of machete (MAT) with DPHR under the Kostiakov model as the efficient land management for modelling the cumulative infiltration characteristics of the sandy clay loam ochrosols of the study area.

Biochar modifies soil physical properties mostly through changes in soil structure rather than through its internal porosity

AbstractBesides its carbon sequestration potential, biochar application generally improves soil physical properties, but the magnitude of its impact and the underlying mechanisms remain debated and depend on soil type, biochar application rate, and age. The objective was therefore to determine the effect of biochar application rate and age on physical properties of agricultural soils in a temperate climate. On a silt loam and a sandy loam soils, we compared the physical properties of fresh biochar (1% and 2% w/w) or century‐old biochar (0.5%–1% w/w; 19th‐century kiln sites)‐enriched soil samples with biochar‐free soil samples. Biochar pore network characteristics were determined using helium pycnometry, mercury intrusion porosimetry, scanning electron microscopy observation, and electron dispersive X‐ray spectrometry, whereas location of biochar particles within soil structure was analyzed using optical microscopy observations. Fresh biochar application decreased bulk density by 16.8% and increased saturated water content by 16.0% and macroporosity by 78.8%. These effects were attributed to soil structure improvement rather than to biochar porosity. Soil type and biochar application rate had a limited impact. In the long‐term, biochar effects were mostly nonsignificant, which might result from its fairly low content in kiln sites and from the clogging of its internal porosity by clay particles. Biochar was thus able to improve some soil physical properties in the short‐term, but these effects could no longer be detected in the very long‐term. Further investigating the time rate of change in soil physical properties over several decades following biochar additions to soil would therefore seem particularly relevant.

Liming leads to changes in the physical properties of acidified forest soils

AbstractBackgroundForest liming is a common practice in many German forests, which aims primarily at improving soil chemical properties that have been negatively impacted by acid rain. Effects on physical functions have not yet been studied widely.AimsThe hypothesis of this study is that chemical changes after liming lead to changes in the physical properties of the humus layer and mineral soil.MethodsWe studied soil physical characteristics (water retention characteristics, air and water permeabilities, and conductivities) of limed and adjacent control plots of sandy to loamy, acidified soils under spruce and beech‐dominated stands.ResultsWe found differences between limed and control plots, especially in the humus layer and mineral top soil. Here, air capacity values (representing air‐filled macropores at −6 kPa) have experienced an increase, while available water capacities (representing the sum of dewatered mesopores between −6 and −1500 kPa) were reduced to a variable extent. These changes in pore size distributions affected gas diffusion as well as gas permeability positively. Unsaturated hydraulic conductivity was not affected. Below the top mineral soil, a tendency to a reduced macroporosity and gas permeability was observed, but no clear changes were detected.ConclusionsSmall but significant changes of soil physical properties and functions in the humus layer and top mineral soil are discussed to be an indirect effect of forest liming. Liming improves pH and nutrient availability, which in turn should have stimulated activity and abundance of soil fauna, especially earthworms. Where observed, their activity could explain the observed changes in soil physical properties. We believe that effects below the top soil might be due to mobilization and translocation of soil particles and a clogging of pores, but these depths were only studied at three plots. Compared to common liming practices, however, the investigated sites are characterized by significantly higher lime applications. The effects on practice liming areas in forestry praxis are therefore likely to be smaller than in this study.

Characteristics of soil physical properties in different soil management of oxisols and inceptisols

Oil palm (Elaeis guineensis Jacq.) is a plantation crop that has a bright future. Soil management such as land clearing, burning, use of heavy equipment and fertilisation in oil palm plantations will affect changes in soil physical properties. This study aims to assess the physical properties of soil in various treatments (planting circle, dead interplant spacings and live interplant spacings) on Oxisol and Inceptisol soil types. This research was conducted in Rancabungur and Malingping Banbten in October 2021 - May 2022. The method used in this study was multistage random sampling. Soil samples were taken from the Malingping area of Banten for the Oxisol soil type (2005 and 2009 planting years), and the Rancabungur area for the 2005 Inceptisol soil type. Comparison of soil physical properties of Oxisol of 2005 planting year with Oxisol of 2009 planting year and the ratio of Oxisol soil type of 2005 planting year and Inceptisol of 2005 planting year in various treatments did not show significant differences in soil physical properties (organic matter, content weight, field capacity moisture content, permanent wilting point, and particle density) between planting circle, dead interplant spacings and live interplant spacings. However, there were significant differences in the physical properties of soil texture between each management and permeability.

Rainfall‐runoff responses and hillslope moisture thresholds for an upland tropical catchment in Eastern Madagascar subject to long‐term slash‐and‐burn practices

AbstractSlash‐and‐burn agriculture is an important driver of tropical forest loss and typically results in a mosaic of land uses. However, there is little quantitative information about the hydrological effects of long‐term slash‐and‐burn agriculture and how such mosaics affect the rainfall‐runoff response at the catchment scale. We monitored streamflow responses at two points along a perennial stream in a 31.7 ha catchment in eastern Madagascar that was monitored previously between 1963 and 1972. Land cover in 2015 consisted of degraded grasslands, shrub and tree fallows at various stages of regrowth (64%), eucalypt stands for charcoal production (30%), and rice paddies and wetlands in the valley‐bottom (3%). For the majority (60%) of the events during the study period, the ratio between the total amount of stormflow and rainfall was &lt;3%, suggesting that for these events runoff was generated in the valley‐bottom only. Events for which an antecedent soil moisture storage plus rainfall (ASI + P) threshold was exceeded had much higher stormflow ratios (up to 50%), indicating that a certain wetness was required for the hillslopes to contribute to stormflow. Stable isotope sampling for four small to moderate events indicated that stormflow was dominated by pre‐event water. Total stormflow and annual water yield in 2015 were higher than in the 1960s, despite much lower rainfall in 2015. We attribute these differences to changes in soil physical properties caused by the repeated burning and loss of top‐soil, which has resulted in a reduction in the depth to the impeding layer. The changed runoff‐processes (less infiltration, more saturation‐excess overland flow) thus affect local water resources.

Effect of combined microbial-plant remediation on soil physical properties in mining area

In view of the problems of vegetation damage, soil water and fertilizer shortage, soil heavy metal pollution, ecosystem damage and other problems existing in the long-term mining of the coal mine area, this study uses micro-organism-plant to bioremediation the coal mine area. The changes of soil physical properties were studied through pot experiment. The results show that the combined remediation can change the physical properties of soil to a certain extent, but the effect is not significant in the short term.

Dynamic of Change in Soil Physical Properties and SoyBean Growth through The Application of Biochar on Lombok Vertisols

Vertisol is a type of soil whose mineral fraction is dominated by 2:1 type clay minerals (smectite) which have the property of swelling-shrinking periodically as the soil water content changes. However, these physical properties can be improved by the application of biochar so that it can support plant growth. The aim of this study was to evaluate the effect of biochar on changes in the physical characteristics of vertisols soils and growth performance of soybean plants. This research was conducted in Kawo Village, Pujut District, Central Lombok. This study was designed to test the application of two types of biochar, namely rice husk biochar (BS) and corn cob biochar (BJ) at several doses, namely 0, 15, 30 and 60 g/kg of vertisols soil and design using a randomized block design with 6 replications. The parameters measured were unit weight, soil density, porosity, soil tensile strength, available water capacity, aggregate stability, cole value, crack pattern and soybean growth test. The results showed that the application of biochar could improve the physical properties of vertisol soil and also has implications for improving the growth of soybean plants. Observational data showed that a dose of 60 g/kg of biochar, both rice husk and corn cob biochar, showed better changes in soil physical properties compared to biochar doses of 15 g/kg, 30 g/kg and without the addition of biochar. Besides that, the treatment of rice husk and corn cob biochar at a dose of 60 g/kg gave better vegetative growth of soybean plants.

Assessing the Short-Term Effects of No-Till on Crop Yield, Greenhouse Gas Emissions, and Soil C and N Pools in a Cover-Cropped, Biodynamic Mediterranean Vineyard

Background and Aims. No-till is considered a core practice of conservation and climate-smart agriculture. Nevertheless, recent evidence suggests that the benefits of this practice for climate change mitigation might be overestimated, particularly in the short term. Methods and Results. In a three-year field experiment, we investigated the environmental and agronomic performance of this practice by looking at changes in soil physical properties, C and N pools, as well as vine yield and grape quality. No-till increased stratification in the distribution of active soil C (POXC), further accentuating the already existing difference between top and subsoil. No-till also slightly reduced the daily efflux of CO2 from the soil during the rainy season, showing that these plots were less prone to lose C than tilled plots. Nonetheless, no-till did not increase total soil C stocks. This, together with the lack of differences in cumulative N2O emissions, resulted in similar global warming potential in till and no-till plots. Vine yield and grape quality remained unchanged in the no-till compared to the tilled plots. Conclusions. Even though no-till did not result in short-term climate change mitigation, results of this study suggest changes in the ecological processes leading to C accumulation and mineralization and that may result in future C sequestration. There were no deleterious effects of no-till on grape yield and quality. Significance of the Study. This study shows that reducing tillage intensity in vineyards is a feasible strategy from an agronomic standpoint.

The effects of combined throughfall reduction and snow removal on soil physical properties across a drainage gradient in aspen forests of northern Minnesota, USA

Climate change is projected to alter precipitation patterns across northern latitudes, with decreased snow accumulation and summer rainfall predicted. These changes may alter soil physical properties such as soil strength, which would have implications for the feasibility of forest management activities. Reductions in summer and winter precipitation were simulated using a paired-plot design with throughfall reduction and snow removal as treatments across four soil drainage classes (well, moderately well, somewhat poor, and poorly drained) at each of three locations in northern Minnesota, USA. Snow removal caused large reductions in soil temperature and significantly deeper penetration of frost that varied by drainage class, where frost depth decreased with decreasing (wetter) drainage. There was a positive relationship between air freezing index and frost depth, where the rate of frost development was much higher in the snow removal treatment compared to the control (r2 of treatment = 0.8, slope = 0.093, p < 0.001; r2 of control = 0.18, slope = 0.012, p < 0.001). Throughfall reduction had limited effects on soil water content (SWC) and inconsistent effects on soil strength; relationships between SWC and strength were positive, negative, or non-existent. Based on these findings, changes in soil physical properties with altered precipitation are likely to manifest primarily in winter. Drainage class and air freezing index may be used to predict when sufficient soil frost is present for forest management activities to occur without detrimental effects to soil functions.

Yields and heavy metal uptake of cocoyam (Xanthosoma sagittifolium) and effects on soil properties of different tillage practices and application of burnt rice husk dust in Abakaliki, south-east Nigeria

ABSTRACT Indigenous crops play a critical role in the socioeconomic growth of developing nations where there have been calls for exploitation of these staple crops. This study investigated the yield and heavy metal uptake of cocoyam and changes in soil physical properties in relation to different tillage practices and the application of burnt rice husk dust (BRHD). The experiment was arranged as a split plot in a randomised complete block design (RCBD) with six treatments and three replications. The treatments were: mound tillage (no BRHD); ridge tillage (no BRHD); mound + 10 t ha−1 BRHD; mound + 20 t ha−1 BRHD; ridge + 10 t ha−1 BRHD and ridge + 20 t ha−1 BRHD. The results showed that soil bulk density (at 45 days after planting, DAP) was lower when the tillage practices were combined with the amendment of burnt rice husk dust, while total porosity (at 45 DAP) and aggregate stability were higher. The yields of cocoyam corms were also higher for tillage practices combined with amendment with burnt rice husk dust. The concentrations of heavy metals (Cu, Fe, Pb and Zn) in the cocoyam corms were higher for plants grown in soil amended with BRHD, but the levels were still below the levels considered harmful in food crops. Burnt rice husk dust could be recommended for use as a soil amendment in the study area to improve soil properties and increase the production of cocoyam, without increasing the concentration of heavy metals in the corms to harmful levels.

Assessment and prediction of coastal saline soil improvement effects combining substrate amendments and salt barrier materials in typical region of the Yangtze River Delta

Coastal saline regions are characterized by high salinity, low permeability, organic matter deficiency, shallow groundwater depth, which limit leaching and lead to salt return. However, there remains a lack of targeted research on long-term coastal saline soil improvement by combining permeation promotion and salt return suppression. Based on a case study of the coastal saline area of Jiangsu Province, China, we used dynamic monitoring of soil water and salt transport, along with laboratory and field scale experiments to analyze the effect of combining substrate amendments and salt barrier materials on salt leaching and return. And numerical simulations were used to predicted the effects of the optimized combination improvement schemes under different climatic conditions in the future. The 2–4% (w/w) straw amended soil had a greater increase (＞90%) in desalinization ratio and a higher reduction (more than half) in desalination time due to changes in soil physical properties. The geocomposite isolated salt effectively due to the formation of capillary barrier compared with traditional straw burial. The results of field scale experiments and numerical simulations showed that geocomposite salt barrier material combined with straw substrate amendment scheme provides a cost-effective solution of soil salinization in coastal areas.

Implications of crop residue removal on soil physical properties: A review

AbstractCrop residues are often removed for livestock and biofuel production, but how such removal impacts soil physical properties has not been widely discussed. The objectives of this paper were to discuss: (a) the impacts of crop residue removal on soil physical properties, (b) factors affecting residue removal effects on soils, (c) threshold level of residue removal, (d) strategies to offset the removal negative effects, and (e) research needs. We compiled 66 studies on crop residue removal and soil physical properties published prior to 17 Aug. 2021. Residue removal may not affect bulk density and water infiltration rate but increases penetration resistance by 55% and soil temperature by 1.8 °C in spring. However, it reduces wet aggregate stability by 31%, dry aggregate stability by 44%, and water retention at –33 kPa by 24% in most studies, indicating residue removal can increase erosion risks and reduce soil water storage. Residue removal rate is the leading factor that explains changes in soil physical properties. Residue removal at rates above 50%, in general, adversely affected soil physical properties, which correlates to retaining about 4 Mg ha–1 of residue. Cover crops and manure application may partially offset adverse effects of residue removal on soil physical properties, but studies are too few to make a strong conclusion. Consistency of soil sampling depths, accurate reporting of residue removal rates, and additional data from long‐term experiments are needed. Overall, high rates of residue removal can increase erosion potential and reduce soil water but have mixed impacts on other physical properties.

Weeding Effectiveness and Changes in Soil Physical Properties Using Inter-Row Hoeing and a Robot

Weed control is one of the most important technological operations to ensure crop yield and quality in ecological sugar beet production. However, conventional mechanical weed control is labor- and time-intensive and has adverse effects on the soil and the environment. The aim of this study was to experimentally investigate the influence of conventional mechanical and robotic weed control systems on soil properties and to assess the effectiveness of these different weed control methods in ecological sugar beet production. This study examines two different weed control systems: robotic weed control (RWC) and conventional weed control (CWC). Field experimental studies were carried out with a solar-powered field robot and conventional inter-row cultivation (CWC1—first cultivation, CWC2—second cultivation) to determine the effectiveness of mechanical weed control in ecological sugar beet crops. The influence of different weed control systems on the physical properties of the soil in the contact zone between the soil and the tires of weed control machines was investigated. The results showed that the average weed control effectiveness inter-row was higher in the RWC (81%) compared to that in the CWC2 (46%). The overall weed control effectiveness of the robotic weed control in the sugar beet inter-row and intra-row was around 49%. The measurements showed that the weed control process reduced the soil moisture and temperature in all treatments tested. Experimental studies have confirmed that the weed control operation, although carried out with relatively lightweight robots, also has an impact on soil bulk density. RWC weed control resulted in an average increase of 0.16 g cm–3 in soil bulk density in the topsoil layer (0–10 cm) after weeding. Both CWC1 and RWC increased soil penetration resistance (PR). For CWC1, the average increase in topsoil PR after weed control was 20%, while for RWC, the increase was marginal, only around 1%. Automated precision weed control by self-propelled solar-powered field robots is an important solution to reduce the need for tedious and time-consuming manual weeding.

Ecological resilience of physical plant-soil feedback to chronic deer herbivory: Slow, partial, but functional recovery.

Ecological resilience to ungulate overbrowsing is an important issue in forest ecosystems. After chronic herbivory, the recovery rate of understory vegetation and its related functions can be slow even with decreasing grazing intensity; thus, detecting elasticity during alternative successional trajectories is fundamental to understanding state perturbations. In this context, we focused on physical plant-soil feedback (functional interactions between plant growth and soil physical conditions) and evaluated elasticity and recovery processes according to deer density. The effects of 40 years of chronic herbivory by sika deer (average density 14.7 individuals km-2 ) on the recovery of understory plant communities and associated changes in soil physical properties in headwater catchments were assessed. Using 8 years of catchment-wide exclusion (fenced) and reduction (only culled; average 4.3 individuals km-2 ) treatments, plot sampling was conducted in 2010 (before treatment) and 2018 (after treatment). The recovery of vegetation and soil physical properties were evaluated, and functional plant-soil relationships and spatial variability were assessed to detect recovery processes during alternative successional trajectory. Woody species increased only under the exclusion treatment and the average soil bulk density was lower than that under reduction treatments. Soil bulk density was negatively correlated with root biomass in the fenced catchment, and root biomass was positively associated with woody species richness. Reduced soil bulk density (~0.5g cm-3 ) was observed with greater root biomass and woody species richness on upper hillslopes in the deer-excluded catchment where plant coverage was minimal. Successional failure under the reduction treatment suggested slow recovery with a depressed threshold according to deer density, indicating a clockwise hysteretic response to deer density. Unlike plant coverage during the earlier period of overbrowsing, woody species root development led the recovery of functional physical plant-soil feedback; however, this was probably limited by the higher soil erosion rate in riparian areas and an under-developed herb layer. Our results highlight an alternative recovery trajectory of physical plant-soil feedback driven by an alternative plant element (woody roots) to recovery trajectory with increasing plant cover. However, riparian erosion and herb layer would still suppress recovery. Therefore, recovery might be slower at the landscape scale.

Assessing soil system changes under climate-smart agriculture via farmers' observations and conventional soil testing.

Soil degradation remains a challenge in African highlands, where land management lacks a strong context‐specific evidence base. We investigated the impacts of recently implemented soil and water conservation (SWC) practices—farmyard manure addition, incorporation of crop residues in soil and fanya juu terracing under an agroforestry system on soil health indicators in the East Usambara Mountains of Tanzania. Farmers' observations of soil changes were combined with conventional soil testing to assess the initial impacts of SWC practices relative to conventional non‐SWC practice. Majority of farmers (66%–83%) reported that combining fanya juu terracing with organic amendments led to soil colour change from red to black and an increase in crop yield. Despite the observed darkening of the soil, there was no significant increase in soil organic carbon stock and the contents of N, P, K. There were important changes in soil physical properties, including greater aggregate stability (mean weight diameter of 1.51–1.71 mm) in the SWC plots, a greater volume of transmission pores (>60 μm) and coarse storage pores (10–60 μm) in the surface soil layer (0–15 cm), and greater volume of fine storage pores (0.2–10 μm) and residual pores (0.2 μm) in the sub‐surface layer (15–30 cm) of the SWC plots compared with the conventional plots. These changes indicate that SWC rapidly enhances infiltration and retention of water within the root zone, which are important for increasing crop yields and improving the resilience of the agro‐ecosystem to environmental stress. Combining SWC with effective soil fertility management is needed for sustainable highland agriculture.

Impact of land use change on soil methane fluxes and diffusivity in Pampean plains, Argentina

Upland soils are the main methane (CH4) biological sink, and may be affected by land-use change. Changes in land uses and soil management affect soil properties that control diffusion of gases, which in combination with microbial activity, determine CH4 flux (fCH4) through the soil. Net CH4 fluxes and diffusivity -estimated by the CH4 diffusion coefficient- were measured in three common land uses typical from Pampean plains, South America (natural grassland NG; Eucalyptus globulus Labill. afforestation E; and agricultural land AL: oat, soybean and red clover in successive cultivation) during two years (March 2017–March 2019). Methane fluxes in the soil-atmosphere interface were measured using the static chamber technique, and a diffusion model was applied to estimate soil CH4 diffusivity from soil porosity. We aimed to quantify the effect of land use change (both E and AL vs. NG, the reference system) on fCH4 and gas diffusivity due to changes in the soil parameters. Soils were net sinks in the three land uses, with mean CH4 flux higher in the afforestation, intermediate in the natural grassland and lower in the agricultural land (− 10.99 ± 5.85, − 8.9 ± 5.32 and − 4.58 ± 4.19 ng CH4 m−2 s−1, respectively). CH4 fluxes varied significantly through seasons and space coinciding with variations in water-filled pore space and air-filled pore space variables (ρ > 0.7 and <−0.7 respectively; p < 0.05). Land-use change metric for methane flux ΔfCH4 was − 2.1 ± 3.7 and 4.4 ± 2.5 for NG-E and NG-AL, respectively, indicating a significant increment in net CH4 uptake when the natural grassland is afforested and a decrease when it was converted to agricultural use. This change was mainly explained by changes in soil physical properties (bulk density, soil water content, WFPS and air filled porosity). In relation to this, soil CH4 diffusion coefficient followed the same pattern as fCH4 (0.024 ± 0.011; 0.015 ± 0.007 and 0.008 ± 0.007 cm2 s−1 for E, NG and AL respectively); and allowed us to recalculate mean CH4 fluxes. Theoretical and in situ measured CH4 fluxes were similar and followed the same patterns across land uses, suggesting the possibility to determine CH4 fluxes by means of simple measures of soil properties (bulk density and soil water content) and soil CH4 gradient concentration.

Evaluation of Seasonal Effects of Tillage and Drainage Management Practices on Soil Physical Properties and Infiltration Characteristics in a Silt-Loam Soil

The impacts of tillage and drainage managements on soil infiltration characteristics need to be scrutinized for a better understanding and prediction of soil hydrological processes, such as runoff, evapotranspration and soil water storage. The objectives of this study were i) to evaluate the effects of tillage and drainage practices on soil physical properties and water infiltration, and ii) to compare prediction accuracy of estimated and optimized infiltration model characteristics for the observed and predicted quantities of infiltration process in the soil. The research site contains the Crosby-Kokomo soil series (fine, mixed, mesic, Aeric Ochraqualf and fine, mixed, mesic Typic Argiaquoll, respectively). The experiment was a two factorial completely randomized block design with two levels of tillage (chisel plow (CH) and no-till (NT)) and two levels of drainage (drained (D) and undrained (UD)) with three replicates. Soil bulk density (ρb), saturated hydraulic conductivity (Ksat), soil moisture retention curves (SMRC), soil infiltration capacity and piezometric water head in each treatment were also measured. Soil drainage flows at each drain lateral and outlet discharges were measured. The results showed that The UD treatments were always higher for Ksat values than the D treatments regardless of the tillage practices for both depths and the CH treatments always had greater Ksat values than those in the NT at both the depths regardless of drainage practices. The D treatments reduced the soil bulk density by 4.2 and 0.8 % in the surface soil and 4.61 and 6.7% for the subsurface soil in respect to no-till-UD and chisel-UD treatments. The UD treatments had higher bulk density at both of the depths than those of the D treatments regardless of tillage practices except the CH-UD treatments. The NT had higher bulk density at both depths of the soil than those of the CH treatments regardless of drainage practices. Drainage increased pore size distribution significantly higher than the UD treatments (p<0.05). The D treatments had significantly higher storage pores and effective pores (9.37%) (pores retaining water at -10kPa pressure head) than the ones in the UD treatments (8.96%) (p<0.05). The NT treatments yielded higher infiltration rates than the CH and the D treatments produced higher apparent infiltration rates and cumulative infiltration values than the UDs. The changes in soil physical properties were found to be strongly and significantly dependent on season, soil depth, and rainfall (p<0.05). The optimized infiltration models predicted larger range of infiltration rate values for each treatment than the estimated infiltration models, indicating that the optimization produced higher accuracy and validity of the predicted models in the field. To conclude, soil dry bulk density, soil saturated hydraulic conductivity, and increased macropore volumes can significantly impact soil hydrological responses to soil water infiltration, soil water storage and drainage flow under conservation tillage and drainage management practices on a seasonal basis. This impact enhances greater potential to capture water in soil for future crop use in the study site.

Anthropogenic Soil Experiment in Brazil Amazon: Changes in Soil Physical Properties by Organic Residues

ABSTRACT Archeological Dark Earths, known in the Brazilian Amazon as Terra Preta de Índio are fertile and structured soils considered as a potential model for sustainable agriculture. In order to recreate these soils a field experiment, named New Dark Earth, was set up in 2003 in the municipality of Tailândia, state of Pará, northern Brazil. The treatments consisted of the application of organic residues (wastes from local industries) in a loamy sand soil: cattle bones, wood charcoal, shredded wood blades, and the control. The objective of this study was to evaluate the effect of these residues on soil physico-hydrological properties. The results showed that the residues did not significantly increase the soil organic carbon content. Only the wood charcoal resulted in some improvements in soil physico-hydrological properties, such as lower soil bulk density and higher total and microporosity, which was mainly attributed to the high porosity of this material. Consequently, it also presented more available water. For now, it was concluded that despite the three residues are widely available in the region, the use of wood charcoal seems to be the best alternative to bring improvements to the soil physical properties, mainly soil water retention. However, more studies need to be carried out.