Conventional Tillage Management Research Articles

The impact of arable soil management on physical functions – The ratio of air capacity and air permeability or hydraulic conductivity as a document of harmful soil compaction

Soil health or soil degradation criteria are until now not well documented for a greater number of soil profiles under conventional and conservation tillage management in the literature. In order to evaluate the compaction status of more than 700 arable sites analyzed within the last 40 years, the Compaction Verification Tool (CVT) was applied according to Zink et al. (2011). Besides the ratio of air capacity (AC, at a matric potential of −6 kPa) and saturated hydraulic conductivity (Ks), the ratio of AC and air conductivity (Ka, at a matric potential of −6 kPa) was considered for evaluating the compaction status with respect to potentially harmful soil alterations. The compaction status was classified into the CVT classes I–IV, where a harmful subsoil compaction was assumed, if both values of AC and Ks or AC and Ka simultaneously exceeded (are smaller than) their defined critical value indicating limited conditions for plant growth (CVT class IV). We analyzed the compaction status of soil profiles with respect to clay content, soil type, structural stage (aggregate forms) and time span of sampling (1980–1999, 2000–2020) under conventional and conservation tillage for top- and subsoil horizons. While also some of the annually plowed topsoils under conventional tillage showed critical values of AC, Ks and Ka, the occurrence of harmful soil compaction is most dominant in the subsoil horizons (> 30 cm depth) because of a higher proportion of class IV which increased with the clay content (from < 12 % to > 12 % clay), irrespective of the applied ratio used for verification (AC/Ks or AC/Ka). Especially the highly productive Luvisols showed a high percentage of harmful compaction in the subsoil (30–41 % in CVT class IV). Soil profiles under conservation tillage management are less affected by harmful compaction. The more aggregated subsoils showed smaller proportions of class IV, which was further influenced by the clay content.

Improving Soil Health of Commercial Vegetable Home Gardens through Conservation Agriculture in Cambodia

Tillage systems are components of broad agricultural practices that affect soil properties and soil health. These changes include soil respiration, density, moisture, and pH. Conservation agriculture practices have the potential to improve soil health by reducing tillage. In agricultural production, there can be numerous approaches to achieving consistently high yields annually; however, this study specifically looked at conventional tillage and conservation agriculture systems. This study aimed to determine soil fauna biodiversity and soil health under conservation agriculture (CA) and conventional tillage (CT) management practices of vegetable production in Cambodia. Five CA and five CT plots were selected and included in this study. Fifty soil samples were collected from CA and CT plots for soil fauna measurement, and in-situ tests were made using Biofunctool© for soil health assessment. The results showed that the abundance of soil fauna and aggregation stability were greater in CA than in CT. Soil fauna biodiversity enhancement may provide better soil health for soil improvement by adapting farming management practices.

Liming remediates soil acidity and improves crop yield and profitability - a meta-analysis

Soil acidity reduces base cations required for plant growth and may result in phytotoxic concentrations of soluble aluminum. Liming acidic soils is generally promoted as an effective management practice to increase soil pH, base cation concentrations, and ameliorate toxicity caused by aluminum and manganese. Through a global literature review using data published from field experiments on liming, the objective of this paper is to understand the effects of liming on soil pH, crop yields, and economic profitability. The results show that liming positively influenced crop yields and soil pH, implying that various lime sources can increase soil pH and crop productivity. The effect sizes of liming on crop yields when lime was incorporated into soils were higher than surface application irrespective of tillage practice. Liming under no-tillage (NT) compared to conventional tillage (CT) management showed higher effect sizes for crop yields. Liming increased effect sizes for crop yields in fertilized compared with unfertilized trials. Gypsum, calcium hydroxide and calcium carbonate showed higher effect sizes when compared with Cement Klin Dust (CKD), dolomite and wood ash. The results show that liming increased yields for all crops except potatoes and oats. Liming generally increases soil pH and changes in soil pH increased with higher lime application rates and yield increases were proportional to the magnitude of increases in soil pH. The profitability of liming differed with crop type and liming rate, being more profitable at lower liming rates. Overall, this meta-analysis shows that liming decreases soil acidity and improves crop yields. Attaining maximum gains from liming agricultural crops under acidic soil conditions requires an understanding of the appropriate lime rates required for specific crops and soil types to ensure overall profitability for producers and sustainable improvement of soil health.

Effect of No-Tillage Management on Soil Organic Matter and Net Greenhouse Gas Fluxes in a Rice-Oilseed Rape Cropping System

No-tillage (NT) management is considered a leading approach for sustaining crop production and improving soil and environmental quality. Based on a long-term no-tillage experiment in a rice–oilseed rape cropping system, we examined differences in soil organic matter (SOM), soil microbial carbon (C) and nitrogen (N) content, and methane (CH4) and carbon dioxide (CO2) fluxes between NT and conventional tillage (CT) management. SOM under NT was 21.0 g kg–1, and a significant difference was detected between 2004 and 2016. SOM increased under NT and CT by averages of 0.60 and 0.32 g kg–1 year–1, respectively. Soil microbial C and N content were higher under CT than under NT. However, soil C:N ratios under NT were 17.4 and 9.7% higher than the CT, respectively, whereas soil microbial C:N ratios under NT were on average 9.47 and 9.70% higher. In addition, about 70% of CO2 net uptake and over 99% of net CH4 emissions occurred during the rice season in May–September in the rice–oilseed rape cropping system. Annual cumulative CH4 and daytime net ecosystem CO2 exchange (NEE) under NT was 1813.9 g CO2 equiv. m–2, 10.8% higher than that under CT. Our results suggest that a higher soil microbial C:N ratio and NEE (CH4 and daytime CO2) could contribute to increasing SOM/C in the surface soil under NT management.

Using olive mill waste compost with sprinkler irrigation as a strategy to achieve sustainable rice cropping under Mediterranean conditions

Traditional rice (Oryza sativa L.) cropping systems under flooding irrigation combined with conventional tillage management are under increasing threat due to a loss of soil quality and a scarcity of water resources, especially in Mediterranean environments. Hence, the development of such management strategies as no-tillage, the application of organic amendments, and water-saving methods could be vital in enhancing the sustainability of rice crops. This work tests the combination of various management systems for growing rice under Mediterranean conditions. It assesses for the first time their influence on soil properties and rice yield components. A field experiment was carried out in southern Spain over 3 years (2015–2017) with six treatments: tillage and continuous flood irrigation either without or with application of two-phase olive mill waste compost; tillage and sprinkler irrigation either without or with application of mill waste compost; direct seeding (no tillage) and sprinkler irrigation either without or with application of mill waste compost. Applying mill waste compost in combination with sprinkler-rice systems improved significantly the soils’ properties. Sprinkler-rice yield was similar to that of rice under tillage and flooding, but it used less irrigation water. In 2017, the greatest rice yield occurred under tillage and sprinkler irrigation with application of mill waste compost (8581 kg ha-1), showing the importance of soil organic matter on yields. Additionnally, flooding increased significantly weed density because it lowered herbicide efficacy, making weed control a key issue for rice yields. Thus, the novelty of this communication is showing that the application of mill waste compost combined with sprinkler irrigation may be a sustainable alternative for rice crops under Mediterranean conditions, increasing the water efficiency and reducing weed pressure, while improving different soil properties.

Non-target impacts of fungicide disturbance on phyllosphere yeasts in conventional and no-till management

Fungicides reduce fungal pathogen populations and are essential to food security. Understanding the impacts of fungicides on crop microbiomes is vital to minimizing unintended consequences while maintaining their use for plant protection. However, fungicide disturbance of plant microbiomes has received limited attention, and has not been examined in different agricultural management systems. We used amplicon sequencing of fungi and prokaryotes in maize and soybean microbiomes before and after foliar fungicide application in leaves and roots from plots under long-term no-till and conventional tillage management. We examined fungicide disturbance and resilience, which revealed consistent non-target effects and greater resiliency under no-till management. Fungicides lowered pathogen abundance in maize and soybean and decreased the abundance of Tremellomycetes yeasts, especially Bulleribasidiaceae, including core microbiome members. Fungicide application reduced network complexity in the soybean phyllosphere, which revealed altered co-occurrence patterns between yeast species of Bulleribasidiaceae, and Sphingomonas and Hymenobacter in fungicide treated plots. Results indicate that foliar fungicides lower pathogen and non-target fungal abundance and may impact prokaryotes indirectly. Treatment effects were confined to the phyllosphere and did not impact belowground microbial communities. Overall, these results demonstrate the resilience of no-till management to fungicide disturbance, a potential novel ecosystem service provided by no-till agriculture.

Soil health assessment after 40 years of conservation and conventional tillage management in Southeastern Coastal Plain soils

AbstractConservation tillage (CST) and cover crops are important components of soil health management. In the present study, we applied two independent soil health assessment approaches to evaluate the impacts of 40‐yr CST and additional 4‐yr cover cropping on a range of soil health indicators and the overall soil health in typical southeastern Coastal Plain soils. Soils were collected at 0–15 cm and analyzed for physical, chemical, and biological indicators. The Soil Management Assessment Framework (SMAF) and Cornell's Comprehensive Assessment of Soil Health (CASH) were used to calculate soil health indices. When compared to conventional tillage, 40‐yr CST increased active carbon (C) from 301 to 420 mg kg–1 and organic nitrogen (N) mineralization potentials from 0.78 to 0.91 mg kg–1 d–1, but it reduced soil electrical conductivity from 133 to 101 μs cm–1. No difference in soil aggregate stability, total C, extractable phosphorous and potassium, microbial biomass C, respiration, and glucosidase activities were observed between the two tillage treatments. Cover cropping had no impacts on any measured variables, except that it increased soil total N. Regardless of tillage and cover cropping, both the SMAF and CASH scoring functions suggested no changes in overall soil health. Soil organic C (SOC) was the only indicator positively correlated with both the SMAF and CASH indices, indicating its importance in maintaining the health of the tested soils. Moreover, CASH index recommended improving soil structure and SOC as the management priority to maintain or improve the overall soil health. Increasing organic inputs along with CST is seemingly the optimal management option.

Comparison of Carbon Dioxide (CO2) Fluxes between Conventional and Conserved Irrigated Rice Paddy Fields in Myanmar

Rice (Oryza sativa. L.), a major food crop widely grown in Myanmar, is the most prominent cause of greenhouse gas (GHG) emissions in agriculture. Moreover, as a result of modification in agricultural management practices (such as soil tillage), the soil organic matter is exposed to more oxidizing conditions, releasing CO2 into the environment, contributing to global warming. Therefore, we studied the effects of both conventional and conservation soil tillage management practices on CO2 fluxes on an experimental rice paddy field in Myanmar. Total CO2 emissions during the night from paddies farmed under conventional practices were significantly higher than those from paddies farmed under conservation practices; however, no net CO2 flux differences were found between practices. Total net CO2 fluxes ranged from −59 to 1614 mg CO2 m−2 h−1 in conventional practices and from −282 to 1082 mg CO2 m−2 h−1 in conservation practices, respectively. Significantly higher rice biomass and grain yields were observed in conventional practices when compared to those in conservation practices, causing a significant rise in both CO2 uptake and emissions during the day and night, respectively. In addition, the results of this study revealed that CO2 emissions in rice fields could be much higher than expected, requiring further study to elucidate key factors driving the dynamics of CO2 in rice paddy systems.

Phosphorus balance in typical rainfield of black soil region in northeast China

This research aimed to evaluate the phosphorus balances at field level in black Soil Region in northeast China, which is one of three black soil regions in world and is one of the most important agricultural production regions in China. By using the soil nutrient balance method, the phosphorus balances were calculated for 11 fields representing four tillage practices [Conventional tillage system (TCT), No-tillage with straw covered system (TNT), Reduced tillage system (TRT) and Contour tillage system (TTT)], three vegetation recovery measures [Conventional tillage management (TCT), Vegetation recovery management (VVR) and Bare management (VB)], three land’s slope (3°, 5° and 7°) and three land’s length (20 m, 40 m and 60 m). Processes quantified included mineral fertilizer, organic matter and atmospheric deposition (inputs) and harvested products, surface runoff and soil erosion (outputs). Measurements of phosphorus flows were made in the 11 fields and the phosphorous balance of various experiment plots was assessed in a quantified manner in 2013. Moreover, the rainfall, the tillage practices, the flow output and sand output of experiment plots of different slope gradients and lengths and the relations between dissolved phosphorus and particulate phosphorus of 2013 were also analyzed. Results shows that VVR and VB are phosphorus deficiency and the others are phosphorus surplus. Rainfall are the main sources of phosphorus inputs for VVR and VB among the 11 experiment plots, while chemical fertilizers are the main sources for the other 9 zones. Crop harvest and soil erosion are the main outputs of phosphorus in the 11 zones, except in VVR and VB. This research provides support to the farmland nutrient management and the prevention and control of non-point source pollution within the region.

Coberturas vegetais do solo e manejo de cultivo e suas contribuições para as culturas agrícolas

The objective this work was to evaluate the agronomic performance of beans, corn and soybean cultivated under no - tillage system and conventional tillage management. The work consisted of 12 experiments, divided three agricultural crops, with the cultivation of species of vegetal cover in a consortium or in an isolated way, and later sowed the summer crops, besides the crop in conventional preparation, where the soil remained fallow during the winter period. Aerial dry mass of soil cover and yield components of beans, maize and soybean were evaluated. The turnip along with the species present in the fallow were those that demonstrated the lower production of dry mass of the aerial part. All soil cover, except turnip, did not show a decrease in bean yield components. The growth of corn crop was shown to be higher when grown in succession to vetch in isolation or in consortium with black oat or turnip. There was superiority in soybean yield as a function of the cultivation system, in at least one soil cover. It was concluded that beans did not promote reduction in yield components for conventional tillage management, but corn and soybean yielded benefits in grain yield components only when in succession the species of soil cover in the planting system conventional.

Effective carbon sequestration in Italian agricultural soils by in situ polymerization of soil organic matter under biomimetic photocatalysis

AbstractFacing an exploding population growth with consequent increase of agriculture intensification, new chemical technologies are being sought to limit organic matter losses and reduce land degradation. Here, we report that an effective organic carbon sequestration in different cropped soils of Italy is obtained by an in situ photo‐oxidative coupling among soil humic molecules, when catalyzed under solar irradiation by a water‐soluble biomimetic iron‐porphyrin catalyst amended to field soils. A 3‐year long field study showed that the catalyst‐assisted in situ photochemical polymerization of humic matter enabled a yearly sequestration of soil organic carbon that ranged from 2.2 to 3.9 t ha−1 y−1, despite the periodical soil disturbance due to a conventional tillage management. This significant stabilization of organic matter was observed not only in bulk soils but also in water‐stable aggregates, whose loss of organic carbon during separation was limited in catalyst‐treated soils. Although crop yields were the same in treated and control soils, measurements of phospholipids fatty acids and soil enzyme activities indicated that the catalyzed in situ photo‐oxidative coupling of humic molecules did not alter the structure and activity of microbial communities and the biological functions of soils. This innovative and ecologically safe catalytic technology may be developed as a useful soil management practice to stabilize organic matter in situ in arable soils, while concomitantly ensuring soil functions and sustainability of crop production.

Influence of Soil Properties in Different Management Systems: Estimating Soybean Water Changes in the Agro-IBIS Model

AbstractThe water balance in agricultural cropping systems is dependent on the physical and hydraulic characteristics of the soil and the type of farming, both of which are sensitive to the soil management. Most models that describe the interaction between the surface and the atmosphere do not efficiently represent the physical differences across different soil management areas. In this study, the authors analyzed the dynamics of the water exchange in the agricultural version of the Integrated Biosphere Simulator (IBIS) model (Agro-IBIS) in the presence of different physical soil properties because of the different long-term soil management systems. The experimental soil properties were obtained from two management systems, no tillage (NT) and conventional tillage (CT) in a long-term experiment in southern Brazil in the soybean growing season of 2009/10. To simulate NT management, this study modified the top soil layer in the model to represent the residual layer. Moreover, a mathematical adjustment to the computation of leaf area index (LAI) is suggested to obtain a better representation of the grain fill to the physiological maturity period. The water exchange dynamics simulated using Agro-IBIS were compared against experimental data collected from both tillage systems. The results show that the model well represented the water dynamics in the soil and the evapotranspiration (ET) in both management systems, in particular during the wet periods. Better results were found for the conventional tillage management system for the water balance. However, with the incorporation of a residual layer and soil properties in NT, the model improved the estimation of evapotranspiration by 6%. The ability of the Agro-IBIS model to estimate ET indicates its potential application in future climate scenarios.

English

The production and emission of CO2 in native, pasture and cultivated areas is a result of microbiological activity and mineralization of organic matter, and depends on favorable environmental factors, such as temperature, availability of water and of land use. The results of this work show that the no tillage system (NT) has the potential to mitigate 37.7% of C-CO2 efflux from cultivation of soy compared to conventional tillage (CT). The temperature of the soil accounted for 65% of the variability of the flux of CO2-C in CT. The variation of soil moisture explained 73 and 51% of the flux of CO2-C in CT and NT, respectively. These results indicate that soil moisture and soil temperature were controlling factors of CO2-C emissions from soil to atmosphere because these parameters directly affect soil microbial activity. The results also show that the active pasture had the highest outflows of soil CO2-C to the atmosphere in relation to forests and degraded pasture in Western Para. Furthermore, it was shown that both the pastures and forests have seasonality in the fluw, which mainly related to precipitation patterns and water potential between soil and air. We observed a strong correlation between the efflux and soil moisture of both capoeira and in the pastures, as the soil temperature was a controlling factor of the active efflux only in the pasture. The average fluw of CO2-C obtained in pasture active was 218.9 mg C m-2 h-1 value of 40.7% higher than the primary forests and 155.5 mg C m-2 h-1. Finally, the results presented here suggest that the conventional tillage and pasture management are activities strongly associated to human enhance biogeochemical changes in the balance of carbon in these ecosystems, since the efflux of CO2-C is related to soil primary productivity of these ecosystems. Key words: Greenhouse effect, land use change, carbon cycle, soil CO2-C efflux.

Impact of no tillage vs. conventional tillage on the soil bacterial community structure in a winter wheat cropping succession in northern China

A comprehensive evaluation of the impacts of different tillage managements on bacterial community structure is fundamental to better understand their roles in maintaining soil health. The objective of this study was to assess the impact of no tillage (NT) vs. conventional tillage (CT) management on soil properties, bacterial community structure in a 22-year experiment established on the Loess Plateau of China, under a winter wheat cropping succession. Our results showed that the long-term application of NT caused a significant increase in bacterial alpha-diversity as indicated by the significantly greater number of unique operational taxonomic units (OTUs), richness (Chao), evenness (ACE), and Shannon index and a lower Simpson index compared to CT. Moreover, the NT treatment changed certain soil physicochemical properties, e.g., soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon (DOC), microbial biomass C (MBC), microbial biomass N (MBN) and nitrate nitrogen (NO3-N) were greater under CT. The bacterial communities differed significantly between the different tillage treatments, and NT harboured relatively higher abundances of the dominant genera Sphingomonas and Pseudomonas and a lower abundance of Acidobacteria than CT. A redundancy analysis (RDA) revealed that the bacterial community structure was strongly correlated with variations of SOC, DOC and TN. Thus, based on these findings, it is concluded that NT management is a more sustainable faming practice to improve soil properties and bacterial diversity.

Changes in the composition and diversity of topsoil bacterial, archaeal and fungal communities after 22 years conventional and no-tillage managements in Northern China

ABSTRACTA comprehensive comparison about microbial community (bacterial, archaeal and fungal) response to different tillage managements in Northern China remain little studied, in this study we compared no-tillage (NT) versus conventional tillage (CT) management on topsoil microbial community diversity and composition in field experiment. We found that NT practice significantly increased the soil moisture content (SMC), bulk density, stocks of soil organic carbon (SOC), total nitrogen (TN), and microbial biomass carbon and nitrogen (P < 0.05). Moreover, higher levels of bacterial and archaeal alpha diversity were observed in NT relative to CT while unexpectedly, there was no significant difference found in fungal diversity between two treatments. The most pronounced shifts in the composition of the different microbial groups were found for the archaeal community, which followed by bacterial and fungal. NT practice markedly enhanced abundances of Proteobacteria (belongs to bacteria) phyla, Thaumarchaeota phyla (belongs to archaea) and Glomeromycota phyla (belongs to fungi). Redundancy analysis revealed that the factor that most closely correlated with bacterial, archaeal and fungal composition were SMC, TN and SOC, respectively. Considering NT enhanced both microbial composition and C storage in topsoil, we suggest that NT offers significant promise to improve topsoil health in this region.

Soil nitrogen dynamics and leaching under conservation tillage in the Atlantic Coastal Plain, Georgia, United States

Conservation tillage (CsT) involves management that reduces soil erosion by maintaining crop residue cover on farm fields. Typically, both infiltration and soil organic matter increase over time with CsT practices. We compared the impact of a commonly used CsT practice, strip tillage (ST), to conventional tillage (CT) management on soil nitrogen (N) dynamics and leaching and examined associations to soil N availability and microbial biomass. A winter cover crop was used in both tillage treatments. The study was conducted over a five-year period during rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production in the Atlantic Coastal Plain region in Georgia, United States. Fertilizer and poultry litter were applied ahead of the cotton crops. Sets of PVC cylinders were filled with soil from each of six plots, three in ST and three in CT, and maintained in situ in their respective plots for 16 intervals of about 90 days. After retrieval, the soil in each cylinder was analyzed for inorganic N (ammonium and nitrates [NH4+ and NO3−]), total N, total carbon (C), and microbial biomass. Leached NO3−-N was captured on anion exchange resin-filled bags attached to the bottom of each cylinder. After the five-year study period, the ST and CT soil C content increased by 22% and 23%, respectively. Total soil N content increased 27% with ST compared to 22% with CT. Temporal patterns in NO3−-N leaching were not different between CT and ST treatments, and a high amount of NO3−-N leaching was observed after the application of poultry litter. The cumulative amount of NO3−-N leached from soils throughout the five-year study was 141 and 122 kg N ha−1 (126 and 109 lb N ac−1) with CT and ST practices, respectively. Results suggest that leaching from the top 15 cm (6 in) of soil may be an important pathway of N loss from both CT and ST cropping systems in the region. Regardless of tillage, soil microbial biomass N was equal to or higher than the total inorganic N, but still represented a small percentage (up to 9%) of the total soil N. Overall, microbial biomass N was higher in ST compared to CT. Minimizing NO3−-N in the soil from reaching ground and surface waters while increasing crop productivity represents a major challenge. The use of ST in conjunction with winter cover crops may improve plant N availability by more than 27 kg ha−1 y−1 (24 lb ac−1 yr−1) in the sandy landscapes of the southeastern Coastal Plain region through microbial cycling of organic N while reducing subsurface NO3−-N losses.

SOIL QUALITY IN RELATION TO FOREST CONVERSION TO PERENNIAL OR ANNUAL CROPPING IN SOUTHERN BRAZIL

Many forested areas have been converted to intensive agricultural use to satisfy food, fiber, and forage production for a growing world population. There is great interest in evaluating forest conversion to cultivated land because this conversion adversely affects several soil properties. We examined soil microbial, physical, and chemical properties in an Oxisol (Latossolo Vermelho distrófico) of southern Brazil 24 years after forest conversion to a perennial crop with coffee or annual grain crops (maize and soybeans) in conventional tillage or no-tillage. One goal was to determine which soil quality parameters seemed most sensitive to change. A second goal was to test the hypothesis that no-tillage optimized preservation of soil quality indicators in annual cropping systems on converted land. Land use significantly affected microbial biomass and its activity, C and N mineralization, and aggregate stability by depth. Cultivated sites had lower microbial biomass and mineralizable C and N than a forest used as control. The forest and no-tillage sites had higher microbial biomass and mineralizable C and N than the conventional tillage site, and the metabolic quotient was 65 and 43 % lower, respectively. Multivariate analysis of soil microbial properties showed a clear separation among treatments, displaying a gradient from conventional tillage to forest. Although the soil at the coffee site was less disturbed and had a high organic C content, the microbial activity was low, probably due to greater soil acidity and Al toxicity. Under annual cropping, microbial activity in no-tillage was double that of the conventional tillage management. The greater microbial activity in forest and no-tillage sites may be attributed, at least partially, to lower soil disturbance. Reducing soil disturbance is important for soil C sequestration and microbial activity, although control of soil pH and Al toxicity are also essential to maintain the soil microbial activity high.

Soil aggregate geometry: Measurements and morphology

Aggregates provide physical microenvironments for microorganisms, the vital actors of soil systems, and thus play a major role as both, an arena and a product of soil carbon stabilization and dynamics. The surface of an aggregate is what enables exchange of the materials and air and water fluxes between aggregate exterior and interior regions. We made use of 3D images from X-ray CT of aggregates and mathematical morphology to provide an exhaustive quantitative description of soil aggregate morphology that includes both intra-aggregate pore space structure and aggregate surface features. First, the evolution of Minkowski functionals (i.e. volume, boundary surface, curvature and connectivity) for successive dilations of the solid part of aggregates was investigated to quantify its 3D geometrical features. Second, the inner pore space was considered as the object of interest. We devised procedures (a) to define the ends of the accessible pores that are connected to the aggregate surface and (b) to separate accessible and inaccessible porosity. Geometrical Minkowski functionals of the intra-aggregate pore space provide the exhaustive characterization of the inner structure of the aggregates. Aggregates collected from two different soil treatments were analyzed to explore the utility of these morphological tools in capturing the impact on their morphology of two different soil managements, i.e. conventional tillage management, and native succession vegetation treatment. The quantitative tools of mathematical morphology distinguished differences in patterns of aggregate structure associated to the different soil managements.

Long-term changes in soil aggregation comparing forest and agricultural land use in different Mediterranean soil types

The formation and stabilization of soil aggregates have a key role to play in adequate soil functioning. Aggregate stability (AS) is considered by some authors to be a property that provides information on soil quality. It's also a property that is highly influenced by land use and management. This study aims to identify the long-term changes in soil aggregation and related properties comparing forest and agricultural land use in Mediterranean calcareous soils. For the research, seven study sites with different soil characteristics located in Alicante Province (E Spain) were chosen to compare the overall effect of land use change from agriculture to forestry on soil aggregation. At every site, samples of the same soil type were collected from agricultural land (dry crops with conventional tillage management using ploughing), and nearby forest, where agriculture was abandoned between 20 and 50years ago. Selected physical and chemical properties like: texture, total content of aggregates (TCA), aggregate stability (AS), organic matter content (OM), carbonates, mean weight diameter (MWD) of aggregates and water repellency (WR) were analysed on the collected soil samples.As expected, in all soils, the AS was significantly lower in agricultural sites than in forest sites. But in some cases the differences were much higher than in others. In forest sites the AS varied between 46 and 82% while in agricultural sites it ranged between 14 and 45%. The results showed strong positive correlation of AS with OM. The lowest values of AS in forest areas were found in wettable sandy soils. The relative increase of AS in forest soils compared to agricultural land use ranged from 39 to 79%. These differences can be explained mainly by some soil properties, such as OM content, texture, and WR. In particular, the lower OM content and absence of WR are responsible for the lower values of AS in agricultural land use due to the long-term conventional tillage management. Soil WR was found in three of the sites, and its presence plays a key role in soil aggregation and its stability, especially for sandy soils. The MWD was in most cases higher in forest than in agricultural sites, except for two wettable sandy soils with the lowest initial AS. In the case of carbonates, no correlations were found with AS, and only in the group of sandy soils, significant positive correlations between carbonates and TCA and with MWD were found.In conclusion we can say that the prolonged use of conventional tillage management using ploughing has a strong influence on AS in all types of soils studied in this research. The recovery after decades of land use abandonment not only is dependent on how is the increase of soil OM content, but also is controlled by some soil properties such as the texture and the presence of WR. In some cases the presence of hydrophobic substances can play a key role in the formation and stabilization of soil aggregates, contributing to maintaining good levels of OM and avoiding higher levels of soil degradation.

Modelling soil organic carbon storage with RothC in irrigated Vertisols under cotton cropping systems in the sub-tropics

The performance of the Rothamsted Carbon Model (RothC) in simulating soil carbon (SOC) storage in cotton based cropping systems under different tillage management practices on an irrigated Vertisol in semi-arid, subtropics was evaluated using data from a long-term (1994–2012) cotton cropping systems experiment near Narrabri in north-western New South Wales, Australia. The experimental treatments were continuous cotton/conventional tillage (CC/CT), continuous cotton/minimum tillage (CC/MT), and cotton-wheat (Triticum aestivum L.) rotation/minimum tillage (CW/MT). Soil carbon (C) input was calculated by published functions that relate crop yield to soil C input. Measured values showed a loss in SOC of 34%, 24% and 31% of the initial SOC storages within 19 years (1994–2012) under CC/CT, CC/MT, and CW/MT, respectively. RothC satisfactorily simulated the dynamics of SOC in cotton based cropping systems under minimum tillage (CC/MT and CW/MT), whereas the model performance was poor under intensive conventional tillage (CC/CT). The model RothC overestimated SOC storage in cotton cropping under conventional intensive tillage management system. This over estimation could not be attributed to the overestimation of soil C inputs, or errors in initial quantification of SOC pools for model initialization, or the ratio of incoming decomposable plant materials to resistant plant materials. Among other different factors affecting SOC dynamics and its modelling under intensive tillage in tropics and sub-tropics, we conclude that factors for tillage and soil erosion might be needed when modelling SOC dynamics using RothC under intensive tillage management system in the tropics and the sub-tropics.