Increased Aggregate Stability Research Articles

Vermikompostun Farklı Tekstürlü Toprakların Agregat Stabilitesi, Hacim Ağırlığı ve Bazı Kimyasal Özelliklerine Etkisi

This study was conducted to investigate the effects of vermicompost treatments on physical and chemical characteristics of two soils with different textures. Experiment was conducted in 30 pots with two different soil types, 5 vermicompost doses and 3 replications. Vermicompost doses were placed into 5 kg pots in dry bases and soil-vermicompost mixtures were incubated under laboratory conditions for about 90 days. Vermicompost treatments had significant effects on organic matter content, pH, electrical conductivity (EC) and cation exchange capacity (CEC) of both soils. Increasing organic matter contents and salinity values were observed with increasing vermicompost doses. As compared to the control treatment, soil salinity greatly increased with the greatest vermicompost dose (16 t da-1). With vermicompost treatments, pH of acidic loamy soils increased and pH of clay soils with relatively high pH levels decreased. Since vermicompost has high organic matter content, it increased soil CEC values significantly. There were significant positive correlations between organic matter content and CEC values of the soils. Vermicompost treatments had positive effects also on soil physical characteristics, increased aggregate stability (AS) and decreased bulk density (BD) of the soils. While vermicompost treatments increased aggregate stability of loamy soils remarkably, such effects were not remarkable in clay soils.

Effects of cover crops on soil hydraulic properties and yield in a persimmon orchard

ABSTRACT This study evaluated the effects of cover crops on yield and soil hydraulic properties of a persimmon orchard in Turkey. Soil samples were taken from 0-20 and 20-40 cm. Profiles of a clay soil and field capacity, permanent wilting point, available water capacity and saturated hydraulic conductivity of the samples were determined. Festuca rubra subsp. rubra, Trifolium repens, Festuca arundinacea, a mixture of them [Trifolium repens (40%) + Festuca rubra rubra (30%) + Festuca arundinacea (30%)], Vicia villosa R., and Trifolium meneghinianum were used as the cover crops. The experiment was conducted in a randomized complete blocks design with four replications including a mechanically cultivated and herbicide treated control plots. The greatest mean persimmon yield (16.2 Mg·ha-1) was observed in the Vicia villosa treatment and the lowest mean yield (3.6 Mg·ha-1) was observed in the bare control. The cover crops increased soil hydraulic properties, with increased aggregate stability, total porosity, reduced bulk density, and penetration resistance. The greatest increases in organic matter contents at 0-20 cm soil depth in the persimmon orchard were observed in the Vicia treatments (73.4% in the first and 74.5% in the second year). The highest aggregate stability (67.4%) and total porosity (60.9%) values were obtained on the Vicia treatments. To increase persimmon yield and improve soil physical and hydraulic properties, cover crops, especially Vicia villosa and Trifolium repens are suggested for clay soils.

Water stable aggregates and the associated active and recalcitrant carbon in soil under rubber plantation

Rehabilitation of the degraded soil is imperative to minimize the effects of soil degradation. It is in this context that stable soil aggregates, essential to providing physical protection to the organic residues, are important indicators of soil restoration or degradation. Thus, the present study was aimed at determining the soil aggregate stability and associated carbon fractions under rubber (Hevea brasiliensis) plantations. The study was conducted on 10, 15, 25, and 34-year-old rubber plantation established on Imperata grassland. Soil samples were collected from 0 to 10, 10–20, 20–50, 50–100 cm depths from different aged rubber plantation and native forest (NF) using a soil core of 5.6 cm inner diameter. Soil aggregates from each depth were separated by the wet-sieving technique, and grouped into three fraction size classes: macro-aggregates (>2 mm), meso-aggregates (0.25–2 mm), and micro-aggregates (<0.25 mm), and analyzed for carbon concentrations. The results showed that macro-aggregates dominated soil under different plantation ages and decreased with an increase in soil depth. The Mean Weight Diameter (MWD) and the Geometric Mean Diameter (GMD) increased with an increase in the age of the plantation and decreased with increase in soil depth. The MWD was the highest in the forest soil (5.8 mm) and the lowest (3.0 mm) under 10-year-old rubber plantation. The highest GMD was found under 34-year-old rubber plantation (2.1 mm) and the lowest under 10-year (1.4 mm) plantation. The SOC concentration under the recalcitrant pool increased with the increase in plantation age, and the highest amount was observed under 34-year old plantation. The increase in aggregate stability, recalcitrant carbon pool, and SOC stock with age chronosequence suggests the ecological role of mature rubber plantations in soil rehabilitation by minimizing the process of soil degradation.

Effects of biochar and phosphorus fertilizer rates on soil physical properties and wheat yield on clay textured soil in middle Nile Delta of Egypt

ABSTRACTBiochar has not been adequately used by farmers to improve the clay textured soil productivities in the world. Therefore, the objective of this study is to investigate the effect of the co-application of biochar with different rates of phosphorus (P) fertilizer on selected soil physical properties and wheat yield on clay textured soil over two growth seasons. Biochar treatments occupied the main plots at a rate of 0.0 and 10 t ha−1, while the sub-plots were devoted to phosphorus rates at rates of 0%, 50%, 100%, and 150% of recommended P fertilizers. Biochar (10 t ha−1) and P at different rates decreased soil bulk density significantly. Meanwhile, it increased aggregate stability, saturated hydraulic conductivity and soil water retention significantly at (p < .05), and it improved the grain yield of wheat. More grain yields in the soil treated with biochar than untreated soil under all P application rates for both years were probably caused partially by more nutrients (N, P, and K) were applied from biochar itself. Grain yield of wheat in the soil-amended biochar and P did not increase significantly between the application at 50%, 100% and 150% P. The results of this study indicate that phosphorus blends with biochar can be used to decrease the bulk density of clay textured soils and to improve crop production in these soils.

Influence of Biochar Applications on Modulus of Rupture and Aggregate Stability of the Soil Possessing Crusting Problems

Protecting and improving the structural properties of soil constitutes the basis for the efficient and sustainable utilization. The purpose of this research was to determine the effects of biochar application with different rates on aggregate stability (AS) and modulus of rupture (MR) of a poorly structured soil under laboratory conditions. During the experiment, 0 (control), 5, 10, 20, and 40 g/kg biochar rates were applied to soil and then incubated for 30 days. According to the results, biochar applications significantly affected both modulus of rupture and aggregate stability values of the soil. However 5, 10, 20 and 40 g/kg rates of biochar decreased soil modulus of rupture by 9%, 26%, 42% and 61% respectively, increased aggregate stability values by 3%, 27%, 178% and 189% respectively compared with the control. According to finding obtained from the research, biochar which is known as a soil amendment was determined to be a promising agricultural practice for improving soil structure in the short period of time.

Assessing of the influence of organic and inorganic amendments on the physical-chemical properties of a red soil (Ultisol) quality

Many highly weathered soils in subtropical environments have low organic matter contents that limit the aggregation, plant available water (PAW) and have acidity issues, increasing the risk of erosion and limiting plant growth. The objective of this study was to determine the influence of gypsum, lime, fused calcium-magnesium phosphate (fertilizer) (CaMgP), and biochar on soil physical and chemical properties in two types of red soil (Ultisol). In a laboratory study, two types of red soil aggregate stability, PAW, the saturated hydraulic conductivity (Ksat), pH, and Fe/Al oxides were measured after 21, 60, 180, and 365 days application. The soil amendments increased soil pH and the amount of amorphous Fe/Al oxides for two soils. The clayey red soil amorphous Fe/Al oxides (ammonium oxalate extracted oxides) were significantly (P < 0.05) positively correlated with the small macroaggregate fraction (0.25–2 mm) and hence increased the mean weight diameter (MWD). Consistent with the increased clayey red soil aggregation stability compared to control, the PAW was significantly increased after amendments where CaCO3 and CaMgP resulted in greater PAW than biochar followed by CaSO4. Ksat was not obviously changed after all amendments except for biochar. However, for granite red soil, the oxides and aggregates exhibited no change overtime under each amendment except for Al oxides compared to clayey red soil, resulting in a slight increase in PAW but a significant increase in Ksat. Application time for two red soils was also significant (P < 0.05), displaying substantial change 60 days after application. These findings suggest that amendments are helpful to red soil quality through their positive increase in aggregate stability, PAW and Ksat over time as influenced by the pH and soil amorphous oxides, probably beneficial for future crop yields.

Short-Term Effects of Olive Mill Wastewater Land Spreading on Soil Physical and Hydraulic Properties

In this study, we investigated the effect of olive mill wastewater on selected soil physical and hydraulic properties. Olive mill wastewater was added to each column every week at different loading rates (0, 50, 100, and 200 m3 ha−1). Physicochemical and hydraulic properties were determined for surface (0–8 cm) and subsurface layers (8–16 and 16–24 cm). The highest loading rate (200 m3 ha−1) showed an increase in aggregate stability from 18% (control) to 31 and to 38%, penetration resistance from 1.8 kg cm−2 (control) to 3.5 and to 4.5 kg cm−2, hydraulic conductivity from 43 cm day−1 (control) to 15.3 and 3.3 cm day−1, and water repellency from < 5 s (control) to 120 and 261 s in the first and second months for the surface layer, respectively. The opposite was observed for the infiltration rate, where it decreased from 39.01 mm h−1 (control) to 1.26 and 0.42 mm h−1 for the first and second months, respectively. This study showed that application of olive mill wastewater deteriorated the physical and hydraulic properties of soil proportional to loading rates and more specifically at the surface layer.

Using soil aggregate stability and erodibility to evaluate the sustainability of large-scale afforestation of Robinia pseudoacacia and Caragana korshinskii in the Loess Plateau

Revegetation in fragile ecosystems is an efficient means to increase aggregate stability and thus reduce soil erosion. However, the influence of large-scale afforestation on soil aggregate stability and erodibility in the Loess Plateau is not well understood. To assess the sustainability and suitability of widespread, long-term planting of plantations in terms of soil aggregate stability (mean weighted diameter (MWD) and geometric mean diameter (GMD)) and erodibility (K), we performed a large-scale investigation of soil aggregate stability and soil erodibility of Robinia pseudoacacia (RP) and Caragana korshinskii (CK) plantations on the Loess Plateau. The results showed that the soil macroaggregate fraction (>0.25 mm) content under RP and CK plantations had a decreasing trend with increasing latitude. Moreover, soil aggregate stability and soil organic carbon (SOC) and total nitrogen (TN) contents in RP and CK plantations decreased with increasing latitude. RP and CK plantations did not always result in improvement of soil aggregate stability and the accumulation of SOC and TN, which depended on the latitude and precipitation conditions. Specifically, RP planting in the south warm temperate forest subzone (STFZ) and north warm temperate forest subzone (NTFZ) could enhance the macroaggregate content (>5 mm), soil aggregate stability and soil nutrients, while CK planting for the improvement of the soil macroaggregate content, soil aggregate stability and soil nutrients in the temperate forest steppe subzone (TFSZ) was more effective than was RP planting. Correlation analysis showed that the latitude, longitude and mean annual precipitation (MAP) were significantly correlated with soil MWD, GMD, K values, SOC and TN across the RP and CK plantations, and soil MWD, GMD, and K values were significantly correlated with SOC and TN in RP and CK plantations. The changing trends of SOC and TN with latitude and longitude were consistent with that of soil aggregate stability with latitude and longitude under RP and CK plantations, indicating that changes in the SOC and TN concentrations will cause changes in soil aggregate stability and erodibility. Additionally, the effects of RP and CK plantations on the soil aggregate stability, erodibility, SOC and TN content were different and distinguished by latitude and MAP. RP plantation resulted in more SOC and TN accumulation, enhanced the soil aggregate stability and decreased erodibility compared with CK plantation in areas with MAP >500 mm or latitude <36° N; in contrast, in sites with MAP <500 mm or latitude >36° N, CK plantation had slight advantages over RP plantation. This study indicated that the changes in soil aggregate stability, erodibility, SOC and TN accumulation following RP and CK plantations had different patterns along latitude and precipitation gradients. Therefore, the 36° N or 500 mm precipitation threshold may be the dividing line for planting RP and CK plantations. Overall, our study produces unique insights into the relative significance of environmental factors that influence aggregate stability at large scales and is useful for selecting suitable afforestation species and locations to optimize forest management with sustainable production.

Composting modifies the patterns of incorporation of OC and N from plant residues into soil aggregates

In order to understand if and how composting modifies the dynamics of incorporation of organic carbon and nitrogen to soil aggregates during residue decomposition, we studied samples of a soil amended with fresh or composted plant residues in the laboratory. Samples from the surface horizon of a Luvisol (representative of large agricultural regions in northern Europe) were amended with fresh or composted 13C–15N-labelled wheat, corn and rapeseed residues and incubated in the laboratory during three years. Aggregates of samples taken at the initial time, after 45 days and after three years of incubation were fractionated by size; OC and N concentrations plus isotopic signatures of C and N were analysed in each aggregate fraction. Both fresh and composted residues addition increased aggregate stability at 45 days, but the effect almost disappeared after three years. The addition of the residues increased OC and N contents with respect to the control soils after three years. The additional OC and N coming from residues were initially incorporated preferentially into 0.05–0.2-mm aggregates, as indicated by isotopic signature analyses, and later redistributed homogeneously among all size fractions. After three years of incubation, 11% of plant residue OC remained in soil when these were added fresh, and 22% if they were previously composted, whereas similar N percentages (26–27%) remained for fresh or composted residues. Overall, a higher amount of inputs from plant residues remained in the soil in the long term when they were previously composted, with respect to non-composted residues.

The potential of recycling wool residues as an amendment for enhancing the physical and hydraulic properties of a sandy loam soil

PurposeClimate change and global food demand in coming decades urge effective actions for more efficient uses of water and soil resources. This paper reports the preliminary findings of a study assessing the potential of sheep scoured wool residues (SWRs) as soil amendments to enhance the physical and hydraulic properties of a sandy loam soil under rain conditions.MethodsTwo different SWRs were used: scoured residues (white wool, WW) and carbonized scoured residues (black wool, BW) at different SWRs/soil ratios (0.0, 0.5, 1.0 and 2.0%). Soil bulk density (BD), total porosity (TP), aggregates stability, aggregate size distribution, saturated hydraulic conductivity, and water retention properties were determined under rain conditions, in addition to rainwater balance (storage, percolation and runoff).ResultsBoth WW and BW, particularly at the high wool/soil ratio (2%), significantly reduced soil BD by 11.98% and 9.85%, respectively. Moreover, WW and BW increased TP by 16.45% and 13.57% and available water capacity by 6.5% and 18.1%, respectively. SWRs increased the formation of macro-aggregates and increased aggregate stability. The results of rainwater balance showed higher percolation percentages and less rainwater storage in the wool-treated soil.ConclusionsThe increase in water percolation is in line with the increased total porosity and the higher saturated hydraulic conductivity of wool-treated soil. Despite the high capacity of absorbing water, SWRs affected the water movement of the soil more than its water retention.

Soil Health Changes Over a 25-Year Chronosequence From Forest to Plantations in Rubber Tree (Hevea brasiliensis) Landscapes in Southern Côte d'Ivoire: Do Earthworms Play a Role?

The agro-ecological drawbacks of the spread of rubber tree plantations in Cote d’Ivoire since 1990’s are obvious even though they have not been properly investigated. They consist of biodiversity loss, land degradation and food insecurity, which have extended to the existing cocoa-led degraded areas whose rehabilitation has unfortunately not started. This situation increases not only the threat on soil health status but also undermines the capability of soils to deliver ecosystem services that are key to sustainable agricultural production. The current study took advantage of a chronosequence in rubber tree landscapes to assess soil health deterioration in general and possibly earthworm-mediated role in soil heath changes. The hypothesis underpinning the current study was that earthworms can contribute to mitigating soil health deterioration in rubber-dominated landscapes due to their key role in soil functioning. This study confirmed that the conversion of forest into rubber tree plantations has significantly impaired all soil biological, physical and chemical parameters at the beginning (7 years) of the chronosequence followed further by a restorative trend taking place beneath the plantations in, or after, 12 years. This is due to an enabling microenvironment caused by an improved SOC storage, increased aggregate stability, exchangeable K, total phosphorus concentration in aged rubber tree plantations and the development of geophageous mesohumic earthworms. However, this study failed to evidence a direct role of earthworms in soil health rehabilitation over time. Mesoscale studies along with the use of appropriate models could help unravel this “black box” and shed some light on the contribution of earthworms as key soil ecosystem engineers.

Tillage and residue management drive rapid changes in soil macrofauna communities and soil properties in a semiarid cropping system of Eastern Colorado

Tillage and stover harvest are common management practices in maize-based cropping systems around the globe. However, frequent soil disturbance and biomass export are likely to have negative long-term impacts on soil biological activity and a range of associated soil properties, and thus, there is great concern surrounding the sustainability of these practices. To address this issue, we examined soil macrofauna communities and a suite of soil chemical and physical properties in a recently established experiment (2.5 yrs. old) in Akron, Colorado. No-tillage and residue retention practices were included in a full factorial randomized block design with the following treatments: no-till + residue retention (NT/R); no-till + residue harvest (NT/RH); conventional tillage + residue retention (CT/R); and conventional tillage + residue harvest (CT/RH). In year three of the experiment, soil health parameters were assessed including: soil macrofauna diversity and abundance, aggregate stability, potential infiltration, and chemical fertility measures. The combined practice of residue retention with no-tillage (NT/R) resulted in greater macrofauna abundance, including a five-fold increase in earthworm abundance and biomass. Greater earthworm populations were associated with an increase in aggregate stability and a trend towards greater water infiltration under NT/R. While univariate tests did not reveal significant treatment differences in arthropod taxa, multivariate analyses indicated clear treatment effects on macrofauna communities, with tillage generally separating communities more than residue management. Soil chemical parameters indicated relatively less dramatic differences between treatments, but with some notable impacts of both residue retention and tillage on soil C and N dynamics. Findings from our study, among the first to examine whole soil macrofauna communities in the semi-arid Great Plains, suggest that no-till and residue retention practices offer promise for improving soil biological activity and soil structural properties of soil, especially when these two practices are employed in combination.

Influence of vegetation restoration on matrix structure and erosion resistance of iron tailings sites in eastern Hebei, China

The effects of vegetation restoration on matrix structure and erosion resistance of iron tailings were studied at dump sites in Malanzhuang, Qian’an, Hebei province, China. The restoration process involved soil spray sowing restoration model with Rhus typhina, soil and iron tailings admixture spray sowing restoration model with Amorpha fruticosa Linn. and six-hole brick restoration model with Pinus tabulaeformis Carriere.–Amorpha fruticosa Linn. mixed-forest, and direct restoration model with Hippophae rhamnoides and Sabina vulgaris. Results show that the composition and distribution of particles and aggregates were closely related to erosion resistance (P A. fruticosa soil and iron tailings admixture spray sowing > mixed-forest six-hole brick > H. rhamnoides direct restoration > S. vulgaris direct restoration. The R. typhina soil spray sowing restoration model resulted in the greatest improvement in matrix structure of iron tailings, increasing the clay (10.6%) and large particle aggregates (18.7%) contents significantly (P < 0.01). Simultaneously, particle population, grading conditions (Cu = 28.86, Cs = 1.65), and aggregate stability (6.02) were significantly improved. The A. fruticosa soil and iron tailings admixture spray sowing restoration model, which effectively improved particle distribution (Cu = 8.51, Cs = 1.07), increased the number of large aggregates considerably (9.6%), thereby increasing aggregate stability (6.2). The six-hole brick model significantly increased the number of large aggregates (4.0%) and improved the stability of aggregates (6.2). H. rhamnoides direct restoration improved the stability of aggregates (5.1) but showed no other significant improvements. The effect of S. vulgaris direct restoration on matrix structure of iron tailings was not significant. Due to its dependence on matrix structure of iron tailings, the erosion resistance of R. typhina soil spray sowing restoration model was the greatest, while that of S. vulgaris direct restoration was the weakest. There was no significant difference in the erosion resistance of the other models. Overall, vegetation restoration supplemented by soil spray sowing restoration and engineering measures is superior to in situ direct vegetation restoration in the short-term. In-situ direct restoration has long-term ecological significance because of its advanced concept of near-natural restoration and the advantages of low cost, easy operation, and low secondary damage.

Influence of woody vegetation on the content of humus in chernozem soils

The literature sources on the influence of woody vegetation on the content of humus in chernozem soils were analyzed. In scientific literature, there are many articles from scholars from around the world on the study of the content of organic matter in the soil under various types of plantings. Proceeding from this, there is a need for comprehensive research on humus of reference black soil common. Separately there is the question of the influence of artificial forest plantations of different wood structure and light structure on the complex characteristics of ascending ordinary black soil. The importance of these studies is due to the complex ecological role played by humus in soils. As a result of the analysis of literary data, it was discovered that woody vegetation increases the content of organic matter and positively affects the black soils. Regularities of change in the humus state are connected, first of all, with the type of land use. Under each tree species there is a characteristic and peculiar humus distribution in the soil profile, which differs significantly from the quantitative or qualitative distribution of humus in the soil horizons. In general, under the forest vegetation, the content of humus increases, as well as the structure of the soil improves, the permeability and porosity of the upper layer of soil increases. In the course of the literary analysis it became clear that the older the tree plantations, the greater the thickness of the humus horizon below them. In the monitoring sites under the Tilia cordata, there is a tendency to increase the content of humus, hygroscopic moisture, absorption capacity and granulometric composition, indicating improvement of soil conditions. Plantation of Acer platanoides leads to a decrease in the content of total humus in a 0-30-centimeter layer of soil, but with depth this index is gradually increasing. Under the Quercus robus plantations in the surface layer of soil, scientists observed a decrease in humus content, and in the middle layers of soil, on the contrary, an increase in this indicator. With a depth observed leaching of humus. The indicator of humus under Quercus robus is characterized by a significantly higher level of humus, than in black soil. So, the results are typical for humus in zonal chornozems. The data of some authors show that it is in natural forests that the best conditions for the humus accumulation in black soils are formed in comparison with the soils of artificial forests and soils under zonal vegetation (motley grass, Bromus spp., Stipa spp.). Under forest vegetation, leafy deposits form a litter. The Robinia pseudoacacia litter results in improved physical and chemical properties of soils, increases the content of organic matter, exchangeable potassium, absorption capacity, increases aggregate stability and moisture content, decreases pH and density. Scientific literature notes that the creation of Robinia plantations in soils that have previously lost its forest cover provides an increase in the content and storage of soil organic carbon compared to the Caragana korshinskii plantations. According to our literature data, the most rational measure to increase the soil fertility is the creation of an effective system of protective forest plantations, which are characterized by a favorable integrated influence on the steppe soils.

Effect of inorganic fertilisers and organic amendments on soil aggregation and biochemical characteristics in a weathered tropical soil

Highly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances for its cultivation. Providing proper nutrient management is important for balancing the nutrient removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM + biofertiliser consortia; FYM, rock phosphate and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ composting using recyclable cashew biomass and weeds + green manuring; vermicomposting of recyclable cashew biomass; FYM + organic cakes + recyclable cashew biomass + biofertiliser consortia; recommended dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser + FYM; and control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples were fractionated into three aggregate sizes, i.e., >2 mm (large macroaggregates), 0.25–2 mm (small macroaggregates), 0.053 to 0.25 mm (microaggregates) and <0.053 mm (silt + clay size fraction) using wet sieving. The results indicated that the organic sources of nutrient application increased the proportion of large and small macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly higher silt + clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates (47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the application of organic sources of nutrients. Aggregates in the silt + clay size faction and microaggregates recorded significantly higher carbon compared to small and large macroaggregates. Compared to control, the application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt + clay size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.

Temporal dynamics of paddy soil structure as affected by different fertilization strategies investigated with soil shrinkage curve

The paddy soil presents strong structural dynamics due to tillage and frequent Wetting/Drying (WD) cycles. Fertilization practices can affect soil structure and therefore may alter their dynamics. The aim of this study was to investigate the temporal dynamics of paddy soil structure as affected by fertilization strategies using soil shrinkage characteristics. Four long-term fertilization treatments were selected: no fertilization as a control (CK), mineral fertilizer (NPK), mineral fertilizer plus green manure (GM), mineral fertilizer plus green manure and swine manure (GSM). Undisturbed soil cores and bulk soil samples were collected four times during WD cycles. Soil physical properties and shrinkage curves were measured. The results showed that soil bulk density and aggregate stability increased during drying and decreased during wetting, while soil shrinkage capacity was on the contrary. Relative to CK and inorganic fertilization, the application of organic manure decreased soil bulk density and increased aggregate stability, but had no impact on soil shrinkage capacity. Detailed shrinkage analyses manifested the different shrinkage patterns for the different treatments. The GSM treatment had more structural shrinkage than the CK, NPK, and GM treatments because more inter-aggregate pores developed in the GSM treatment. The shrinkage behavior of organic fertilizer treated soils (GSM and GM treatments) was more stable during WD cycles than the NPK and CK treatments. Besides, the CK and NPK treatments had greater slopes at the inflection point (slopeinflection), indicating the soil structure of the GM and GSM treatments was more stable than that of the CK and NPK treatments, which was confirmed by soil aggregate stability data. These results suggest manure should be used to improve soil structure and increase soil stability. We also recommend soil shrinkage curves as a useful tool to study the structural properties, dynamics, as well as the quality of the paddy soil with a high shrinkage capacity.

Soil physical properties and abundance of soil fauna in conventional and organic rice field

Land management affected the physical, chemical and abundance of soil fauna. The aim of the study was to know differences of soil physical properties and abundance of soil fauna in conventional and organic rice field. Another aimed to know long term effect of organic farming to soil physical properties and abundance of soil fauna inrice field. This experiment used nested design which 3 location of sampling. The first location was in Imogiri Subdistrict with conventional rice field and 6 years of organic rice field applied. The second location was in Mojogedang Subdistrict with conventional rice field and 4 years of organic rice field applied. The third location was in Sawangan Subdisctrict with conventional rice field, 4 years and 10 years of organic rice field applied. Soil sample was taken in condition of after plough before planting, maximum plant vegetative phase and after harvesting. Organic rice field gave trend increased percentage of silt fraction and reduced percentage of sand fraction, increased aggregate stability of soil, increased abundance of earthworm, reduced abundance of plant parasitic nematode and increased non-parasitic nematode and increased soil respiration. Organic farming gave trend improving soil physical, chemical and biological parameters.

Interactions between humic substances and organic amendments affecting soil biological properties and growth of Zea mays L. in the arid land region

Application of organic amendments to the arid land soils is a sustainable tool to improve soil fertility. A greenhouse experiment was conducted to find the effect of humic acid (HA), alfalfa residues (AR) (Medicago sativa L.), and sheep manure (SM) on soil respiration, soil organic carbon content, soil structure, total bacteria, total fungi, and growth of corn plant Zea mays L. Results showed that the highest aggregate stability was 44.2% for the HA + SM treatment whereas it was 9% for the HA treatment. The higher stability was associated with higher organic carbon 4.60%, and higher bacterial and fungal densities of 190 × 106 g−1 dry soil and 101 × 106 g−1, respectively. The HA + AR treatment did not increase aggregate stability significantly (27.7%), nor did the AR treatment (25.9%). Soil respiration over 70 days was significantly (p < 0.05) higher in the SM (42.9 CO2–C mg g−1) compared to the AR treatment (33.3 CO2–C mg g−1). In contrast, the HA + SM treatment had lower soil respiration (27.4 CO2–C mg g−1) compared to the SM treatment (42.9 CO2–C mg g−1). The HA + AR treatment recorded higher plant weight (20.6 g) compared to HA (10.2 g) and control treatments (8.11 g). This study proved that HA did not enhance soil structure or the microbial community, whereas the combination of HA with SM or AR is more effective at promoting the soil microbial community, soil aggregation, organic carbon content and plant growth in the saline, arid land.

Influence of vegetation restoration on soil physical properties in the Loess Plateau, China

Extensive vegetation recovery has been implemented to control severe soil erosion on the Loess Plateau, China. However, no systematic study has been done on the soil improvement benefit and preferable pattern of vegetation rehabilitation. In this study, the effects of vegetation restoration on soil physical properties at ten sites with different vegetation types and varying restoration periods were investigated. The experiment was carried out in the Yanhe river basin in the hilly-gully region of the Loess Plateau. Ten sites, including two replanted arboreal forests for 25 and 35 years, three replanted scrubland for 15, 30, and 45 years, four secondary natural grassland for 10, 20, 30, and 40 years, and one farmland, were selected for soil sampling. Sampling was conducted at 0–20 cm and 20–40 cm layers. Vegetation restoration significantly decreased bulk density, and increased aggregate stability and saturated hydraulic conductivity (Ks), while their effects on porosity was complicated. The soil texture class did not change with vegetation succession, but minor differences in sand, silt, and clay components were observed. Bulk density, macroporosity, and > 0.25 mm aggregate stability were the principal physical parameters that affected Ks. Moreover, bulk density had the most effect on Ks (− 0.84), while > 0.25 mm aggregate stability had the lowest impact (0.38). Bulk density and Ks were correlated with most of the other soil physical properties. Replanted scrubland and secondary natural grassland had higher soil physical quality index (SDexter) than replanted arboreal forests and farmland. It is reasonable to take bulk density and Ks as the indicators to evaluate the effect of vegetation restoration on soil physical properties. Planting shrubs and grassland is better than forest for eco-environment rehabilitation in the study area. Results of this study provide a reference to regional eco-environmental rehabilitation and conservation.

Effects of agricultural management practices on soil quality: A review of long-term experiments for Europe and China

In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.