Water-stable Aggregates Research Articles

Impact of wood-derived biochar on the hydrologic performance of bioretention media: Effects on aggregation, root growth, and water retention

Bioretention systems are one example of green stormwater infrastructure that may mitigate the hydrologic impact of stormwater runoff. To improve water retention while maintaining rapid stormwater infiltration, conventional bioretention soil media (BSM) might be augmented with biochar. Biochar may improve the BSM's structure by increasing soil aggregation, which might improve water retention and increase stormwater infiltration while also improving root growth. Pots with BSMs representing high and moderate sand content media were amended with a wood-derived biochar, planted with switchgrass, and subjected to weekly storms for 20 weeks, followed by a 10-week drought. In the high sand content medium (NC mix), biochar amendment increased hydraulic conductivity (Ksat), and this effect increased with time. At 0 weeks, 2% and 4% (w/w) biochar increased Ksat by 4 ± 2% and 10 ± 4%, respectively, while at 30 weeks the increase was 30 ± 10 and 70 ± 20%, respectively, above biochar-free media. Similar improvements were seen in plant available water (PAW) in NC mix. However, minimal improvements in Ksat and PAW from biochar amendment were found in the moderate sand content BSM that contained compost and mulch (DE mix). Where biochar promoted Ksat, this was correlated with increased water-stable aggregate size (r = 0.86), fine root volume (r = 0.88), and below ground biomass (r = 0.83). Important factors affecting Ksat and aggregation in the NC mix were biochar's influence on organo-mineral association, fungal hyphae length, and plant roots. Wood-derived biochar amendment to BSM may obviate the need for compost/mulch since biochar has similar effects on improving BSM hydrology and root growth without the risk of undesired nutrient leaching.

Agricultural soil aggregation is affected by the crop root biomass rather than morphological characteristics

AbstractBackgroundIn areas prone to water erosion, crop selection strategies should be based on assessment of their effects on soil structural properties.AimsThe present study compared the effects of the cultivation of forage maize (Zea mays L.) and forage oat (Avena sativa L.) and their cultivars on soil aggregation relative to potato (Solanum tuberosum L.) or wheat (Triticum aestivum L.) at a hydrothermally limited site on the Loess Plateau, China.MethodsThe water‐stable aggregate (WSA) distribution in soil was measured under three cultivars in each of maize, oat, wheat, and potato (a total of 12 cultivars from four crops) in their flowering stage of three cropping seasons, when root biomass was largest.ResultsIn each year, the water‐stable macroaggregates (>0.25 mm) content and mean weight diameter (MWD) of WSAs in the top 20 cm of soil did not differ between tested cultivars of every crop but increased under maize and oat, compared with those under wheat or potato. The increased soil aggregation under maize and oat, compared with wheat or potato, was consistent with the pattern of change in root biomass but was not consistent with the changes in root length density, root surface area, or root mean diameter across the crops. The water‐stable macroaggregates content and MWD of soil was positively correlated with root biomass across cultivars and crop species within each cropping season.ConclusionsWe suggest that increased root biomass under maize and oat relative to potato or wheat resulted in increased soil aggregation in maize and oat cultivated soils. It is demonstrated that, in areas prone to soil water erosion, planting high‐biomass‐yielding crops such as maize and oat is more beneficial for increasing soil aggregation and stability, compared with low‐biomass‐yielding crops such as wheat or potato.

Short-Term Effects of Experimental Fire on Physicochemical and Microbial Properties of a Mediterranean Cambisol

Little is known about the bonfire impact on microbial properties in soil. This work aimed to study moderate- to high-severity experimental burning (250 °C) compared to unburned Cambisol in a natural Mediterranean environment (Croatia) on selected soil properties. The soil was sampled immediately and 1, 2, 4, and 6 months after the fire. The fire increased the mean weight diameter, water stable aggregates, and water repellence in different soil fractions, and the observed effect was the strongest immediately after the fire. It also altered soil pH, electrical conductivity, total nitrogen carbon, and sulphur content, and completely destroyed carbapenem-resistant bacteria, but did not significantly affect the soil’s mineralogical properties. Six months after the fire, most microbial properties (save for pH) returned to near control values. Heterotrophic, sporogenic, and phosphate-solubilising bacteria started to recover after a month, whereas the population of carbapenem-resistant bacteria was destroyed initially, but recovered by the fourth month after the fire. Dehydrogenase activity was not significantly affected, but proper recovery started four months after the fire. Even though Cambisol showed some resilience to fire and its properties mostly returned to normal by the sixth month, and a full recovery is expected to occur later, as vegetation returns.

Organic Materials and AMF Addition Promote Growth of Taxodium ‘zhongshanshan’ by Improving Soil Structure

Soil salinization is considered a type of global-scale soil degradation, whereby excessive salinity severely diminishes soil health, which is primarily manifested through disrupted soil structures and reduced fertility. Furthermore, plant growth capacity is inhibited, and productivity is diminished. Consequently, the improvement of saline soils is regarded as a particularly important aspect of enhancing land production. To elucidate the roles of organic amendments and mycorrhizal fungi in the improvement of saline soils, seven treatments were set up, including biochar alone (B), straw alone (S), arbuscular mycorrhizal fungi alone (A), biochar in combination with arbuscular mycorrhizal fungi (BA), straw in combination with arbuscular mycorrhizal fungi (SA), and a control (CK). The results revealed that the seedling height growth rate under the BA treatment was significantly higher than that of the CK by 31.66%. The capillary porosity of the soil under the addition of BA was significantly higher than the CK by 3.17% in the 0–20 cm soil layer. The BA treatment reduced the fractal dimension of soil aggregates considerably by 19.06% in the 0–20 cm soil layer, and 13.71% in the 40–60 cm soil layer in contrast to the CK, respectively. In addition, the positive effects of the BA treatment were significant in the 20–40 cm soil layer. Overall, the application of biochar alone promoted the water stability of soil aggregates. The combination of arbuscular mycorrhizal fungi and biochar promoted plant growth, improved soil pore structures, promoted agglomerate water stability, and led to improved microbial activities. The results showed that organic amendments applied in conjunction with AMF improved the environment of salinized soil, which is a key factor in the promotion of plant growth and the long-term stability of soil health. This study provides a key technical basis for remediation of salinized soil.

Effects of cyanobacteria- and moss-biocrusts on soil aggregate stability and splash erosion in croplands of the China Mollisols area.

To investigate the effects of biocrusts development on aggregate stability and splash erosion of Mollisols and to understand its function in soil and water conservation, we collected biocrusts (cyano crust and moss crust) samples in croplands during the growing season and measured the differences in aggregate stability between biocrusts and uncrusted soil. The effects of biocrusts on reduction of raindrop kinetic energy were determined and splash erosion amounts were obtained with single raindrop and simulated rainfall experiments. The correlations among soil aggregate stability, splash erosion characteristics, and fundamental properties of biocrusts were analyzed. The results showed that compared to uncrusted soil, the cyano crust and the moss crust decreased the proportion of soil water-stable aggregates <0.25 mm by 10.5% and 21.8%, respectively, while their soil water-stable aggregates 5-10 mm were 4.0 and 8.8 times as that of uncrusted soil. In contrast to uncrusted soil, the macroaggregate content (R0.25), mean weight diameter (MWD), and geometric mean diameter (GMD) of biocrusts were 31.5%, 76.2%, and 33.5% higher, respectively. In addition, biocrusts reduced raindrop kinetic energy by an average of 0.48 J compared to uncrusted soil. The breakthrough raindrop kinetic energy of cyano crust and moss crust were 2.9 and 26.2 times as that of uncrusted soil, while the reduction of raindrop kinetic energy by cyano crust with high biomass was 1.3 and 6.6 times as that of medium and low biomass, respectively. Under the single raindrop and simulated rainfall conditions, biocrusts reduced splash erosion amounts by 47.5% and 79.4%, respectively. The proportion of aggregates >0.25 mm in the splash soil particles of biocrusts (37.9%) was 40.3% lower than that of uncrusted soil, while the proportion of aggregates >0.25 mm decreased as biocrust biomass increased. Moreover, the aggregate stability, splash erosion amount, and fundamental properties of biocrusts were significantly correlated. The MWD of aggregates was significantly and negatively correlated with the splash erosion amount under single raindrop and simulated rainfall conditions, indicating that the improved aggregate stability of surface soil caused by biocrusts accounted for reducing splash erosion. The biomass, thickness, water content, and organic matter content of biocrusts had significant effects on aggregate stability and splash characteristics. In conclusion, biocrusts significantly promoted soil aggregate stability and reduced splash erosion, which had great significance to soil erosion prevention and the conservation and sustainable utilization of Mollisols.

Effect of Long-Term Organic Cropping Systems on Physico-Chemical Properties of the Soils of Indian Punjab

Organic farming is gaining momentum because of awareness among consumers for quality food. The long term effects of organic cropping systems on soil quality yet not have been studies in details. Therefore the present study the long term effect of five cropping systems viz. Poplar (Populus deltoids) + turmeric (Curcuma longa), sugarcane (Saccharum officinarum Linn )+ bottle gourd (Lagenaria siceraria) - broccoli (Brassica oleracea), basmati rice (Oryza sativa) - wheat (Triticum aestivum), sugarcane fodder and maize (Zea mays) + summer moong (Vigna radiate) - wheat on soil physico-chemical properties was studied at Bhagat Puran Singh Natural Agriculture Farm and Research Centre, Amritsar, Punjab (31.5730 N, 75.0660 E). The depth wise soil samples from these cropping systems were collected after rabi (2018-19) and kharif (2019) seasons. Poplar + turmeric cropping system has significantly higher soil organic carbon(SOC), soil carbon stock(SOCS), soil aggregate associated carbon(AAC), water stable soil aggregates (WSA) and mean weight diameter(MWD) of soil than other cropping systems. Sugarcane fodder cropping system has significantly higher soil pH than other cropping systems while basmati rice - wheat cropping system has significantly lower electrical conductivity (EC) and higher soil bulk density (BD) compared to other cropping systems. In the top soil (0-7.5 and 7.5-15 cm depths) SOC, SOCS, AAS, EC, WSA and MWD were significantly higher than subsurface layers (15-22.5 cm and 22.5-30 cm depth) whereas soil pH and BD were significantly lower in surface soil than subsurface soil.

Vliv zalesnění orné půdy a různého věku lesního porostu na tvorbu vodostabilních půdních agregátů (WSA)

Research was focused on determination of water-stable aggregates (WSA) distribution in soil (cambisol) under different land use (forest, arable land) taking into account also the age of forest stand. Soil samples were collected at three localities separately for arable and forest soil. The localities were selected from map in places where arable land had been afforested in the past. Afterwards 30 samples were dry sieved and then wet sieved to determine the percentage of individual soil fractions of WSA, which allowed comparison of localities. Results showed that from the land use perspective, no prominent differences were evident after dry sieving. However, after the subsequent wet sieving, there was a distinct change. For arable soil, the fraction larger than 2 mm was almost entirely (98.22–98.88%) dissolved into smaller fractions, while the results of forest soil showed much better soil properties, as the largest fractions (&gt;2 mm and 2–1 mm) were still represented in the sample in the range of 34.18% to 69.14%. From the results, it is possible to conclude that aggregation already occurs between 10 and 24 years after the establishment of the forest stand, which should be more investigated during the following research.

Post-farming land restoration schemes exhibit higher soil aggregate stability and organic carbon: Evidence in the Three Gorges Reservoir Area, China

The Three Gorges Reservoir Area was dominated by a farming landscape but has been the target of restorative land management schemes over recent decades, wherein croplands have been converted to forests or citrus woodlands run by commercial enterprises or, alternatively, abandoned for natural vegetation succession. How these ongoing restorative land management schemes imprint soil systems remains poorly understood. Accordingly, in this study, a space-for-time substitution approach was applied to compare soil aggregate stability and organic carbon stocks between lands used for ongoing arable production and areas subjected to restorative practices. Composite soil samples from reforestation woodlands, abandoned croplands, citrus woodlands, and present-day croplands were collected, and a variety of soil metrics (i.e., water-stable aggregate percentage, mean weight diameter, geometric mean diameter, erosion resistance of the aggregates, bulk soil organic carbon and aggregate-specific soil organic carbon) were used as a basis for comparison. Reforestation woodlands and abandoned croplands exhibited a higher mass percentage of macro-aggregates, higher values of mean weight diameter and geometric mean diameter, and higher organic carbon content within the sampled 0–40 cm depth soil profiles. Reforestation and cropland abandonment significantly increased the stability of soil aggregates and organic carbon stocks. Moreover, abandoned cropland samples exhibited higher soil aggregate stability and organic carbon stocks than reforestation woodlands. In contrast, soil aggregate stability for all sampled soil depths and organic carbon content except for the topsoil (0–10 cm) of citrus woodlands exhibited lower values than those for present day croplands. Exclusion of crop farming and reestablishment of restorative vegetation have therefore contributed to changes in soil physical structure and organic carbon stocks, with reforestation and cropland abandonment being more beneficial for soil aggregate stability and soil organic carbon stocks in the Three Gorges Reservoir Area.

Impacts of Soil Erosion on Soil Quality and Agricultural Sustainability in the North-Western Himalayan Region of India

Erosion by water reduces soil quality and hence crop yield. Understanding the response of crop yields to soil erosion is vital in assessing agriculture’s vulnerability to erosion. However, these effects are difficult to quantify. The study presents a quantitative relationship between soil erosion and soil quality and productivity of rainfed wheat (Triticum aestivum) by comparing field plots with different degrees of erosion in some sub-tropical alfisols in the Doon Valley region of India. By comparing the topsoil depth with the reference site as the control, erosion severity was classified into different phases such as slight, moderate, severe, and very severe. A quantitative, weighted additive model was used to evaluate soil quality for different phases of erosion using soil clay content, water holding capacity, soil aggregate, soil organic carbon, pH, CEC, total N, available P, and available K. The synthesis of long-term experimental data revealed that the mean soil erosion rate varied from 5.5 Mg ha−1 yr−1 in slightly eroded plots to 33.4 Mg ha−1 yr−1 in very severely eroded plots. Compared with the reference forest, the soil organic carbon (SOC) declined by 81.4% and water holding capacity by 31% in severely eroded soils. A substantial loss of total N, extractable P, and available K was also observed. Water stable aggregates (WSA) decreased from 86% to 12.6%, and the cation exchange capacity (CEC) from 25 to 12.6 c mol(+) kg−1. The soil quality index was 0.7 in slightly eroded compared with 0.4 in severely eroded soil. Similarly, the sustainable yield index for wheat was 0.9 and 0.6 for slightly and severely eroded soils, respectively. Thus, there is a strong need to identify land management systems that reduce erosion risks, restore eroded soils, and enhance soil quality.

Impact of Land Capability Classes and Land Use on Properties and Erodibility Behaviour of Soil of Ghatampur Watershed

The study was carried out in Ghatampur Watershed district Kanpur under National Watershed Development Project Area. The soils of Ghatampur watershed region are erodible in nature. Soil erodibility increased from land use capability class II to VI in the project area. Fallow land is most erodible followed by Rangeland, woodlots, cultivated land while orchard &amp; grooves lands are erodible on the basis of water stable aggregates, dispersion and erosion ratio as principal indices of erodibility, soil under various land use capability classes may be arranged in the order of class VI &gt; class V &gt; class III &gt; class II. The erodibility of soil under different present land use was found in the order Fallow land &gt; Rangeland &gt; Wood lots &gt; Cultivated land &gt; Orchard &amp; grooves land, Erosion ratio was significantly and negatively correlated with clay (r = -0.920***) moisture equivalent (r= -0.669), water holding capacity (r=-0.685**), water stable aggregate (r=- 0.834***), organic carbon (r=-0.780***) and clay/moisture equivalent ratio (r=- 0.660***) but a positive correlation was recorded with sand (r-0.777***), Bulk density (r=0.709**), easily dispersible silt+clay (r= 0.888***), clay ratio (r=0.745***),dispersion ratio (r= 0.908***), Erosion index (r=0.432**),the correlation between erosion ratio and silt (r=-0.432**) was recorded to be negative but significant. Among various land use capability classes, soil erodibility decreased substantially with increasing clay content but increased with increasing advancing capability class and fallow land use. Soil of Ghatampur watershed area in erodible nature and require warrant and prompt attention for implementing intensive soil conservation measures in the entire watershed in order to subside the havoc of soil erosion within safe limits because adapted soil conservation measure variably effective to control the erosion.

Short-Term Crop Residue Management in No-Tillage Cultivation Effects on Soil Quality Indicators in Virginia

The use of crop residues for biofuel production has the potential to provide environmental and economic benefits to modern societies. Because of the profound impacts that crop residues have on agricultural productivity and soil health, a sustainable utilization of these residues is required. Thus, we determined crop yield and quality response for a range of biomass retention rates in grain cropping systems. Combinations of corn (Zea mays L.) stover (0, 3.33, 6.66 and 10 Mgha−1) and wheat (Triticum aestivum L.) straw (0, 1.0, 2.0, and 3.0 Mgha−1) were soil applied in a corn-wheat/soybean (Glycine max L. Merr.) rotation in Virginia’s Coastal Plain. Corn stover (0, 3.33, 6.66, 10 and 20 Mg ha−1) was applied in a continuous corn cropping system in the Ridge/Valley province. For each system, residues were applied following grain harvest over two production cycles. Each experiment was conducted as a randomized complete block design with four replications. Two cycles of crop residue management, with retention rates of up to 20 Mg ha−1 of corn stover retention in Blacksburg, and up to 13 Mg ha−1 of corn stover and wheat straw in New Kent, had no effect on total nitrogen (TN) and carbon (TC) concentrations, CN ratios, bulk density (BD), soil pH, field capacity, permanent wilting point, plant available water and water aggregate stability across soil depths and aggregate sizes in Virginia. In one situation when residue management slightly affected BD (0–2.5 cm depth, NK1), differences across the sixteen total retained residues treatments were less than 5%, thus rendering them not biologically or environmentally meaningful. Overall, results of this study did not show any clear short-term impact, resulting from various rates of crop residue retention in Virginia cropping systems. These incipient negative impacts resulting from very low rates of residue return warrant further studies to corroborate whether these results are to be found following long-term scenarios of crop residue management.

Impact of long-term fertilization on soil organic carbon dynamics and biological health of soils under Pearl millet -mustard-cowpea cropping sequence in an inceptisol of Gujarat

The study was undertaken by utilizing an ongoing long-term experiment on continuous cropping at Anand Agricultural University that began in 1980. From 1994 onwards, a modification was made by including Farmyard Manure (FYM) treatments for studying the following objectives: long-term effect of fertility levels with and without FYM on changes in soil organic carbon pools for assessing the role of organics and chemical fertilizers on soil organic carbon buildup and their interrelationship with soil aggregate stability under the pearl millet-mustard-cowpea (F) cropping sequence. Under F1 (FYM @ 10 t/ha) and FL3 (NP application @150 percent of RDF), there was a considerable improvement in the status of Walkley and Black C (WBC), Soil Microbial Biomass Carbon (SMBC), and Total Organic Carbon (TOC) compared to the control in both depths (0-15 and 15-30 cm). Long-term manuring and fertilization practices affect aggregate development and stabilization. In all depths, the highest soil macroaggregates and microaggregates were found when FYM @ 10 t/ha and FL3 (150 percent NP) were applied. Under FYM treated plots and with the greater dose of NP (NP application @150 percent of RDF) in both the surface and sub-surface layers, the maximum water-stable aggregate expressed as mean weight diameter (MWD) was recorded. Furthermore, a significantly positive correlation was observed between SMBC and enzymatic activities (phosphatase, urease, and dehydrogenase) in both the soil depths; indicating the effect of labile C on the biological activities of soil which might be achieved by means of changes in microbial diversity of the soil.

Effects of five years conservation tillage for hedging against drought, stabilizing maize yield, and improving soil environment in the drylands of northern China.

Continuous tillage cultivation positioning trials can provide the basis for maintaining soil health, improving resource utilization efficiency and crop productivity, and achieving sustainable agricultural development. In this study, changes in soil stability and water-holding capacity characteristics were measured under different tillage cultivations from a multi-year microscopic perspective and analyzed to evaluate selected key indicators. Continuous monitoring of rainfall utilization efficiency and yield was carried out for five years. Here, we discuss the role of conservation tillage in buffering and stabilizing rainfall precipitation pattern on the fluctuation and uncertainty of soil water retention and water supply capacity and soil quality. The study was carried out on dryland areas of the Loess Plateau in northern China with eight tillage systems established in 2016: no-tillage (NT); no-tillage and straw (NTS); subsoiling (SU); subsoiling and straw (SUS); rotary tillage (RT); rotary tillage and straw (RTS); conventional tillage (CT); and conventional tillage and straw (CTS). All treatments were applied in conjunction with continuous cropping for five years. The evaluated soil parameters were mean weight diameter (MWD), geometric mean diameter (GMD), >0.25 mm aggregate content (R0.25) of water-stable aggregates (WSAs), soil moisture characteristic curve (SMCC), specific soil water capacity (Cθ), soil organic matter (SOM), rainfall utilization efficiency (RUE), and maize yields for five consecutive years. The MWD, GMD, and R0.25 of SUS were 27.38%, 17.57%, and 7.68% more than CTS (control), respectively. Overall, SOM, average annual RUE, and average annual yields increased by 14.64%, 11.89%, and 9.59%, respectively, compared with 2016. Our results strongly suggest that conservation tillage can considerably improve these characterization indicators. SUS was more effective than CTS in the 0-40 cm soil layer at hedging against drought in the area, stabilizing crop production, and achieving sustainable agricultural development.

Organic carbon accumulation and aggregate formation in soils under organic and inorganic fertilizer management practices in a rice–wheat cropping system

Soil organic carbon (C) and aggregates are the important components of soil fertility and the foundation of sustainable agriculture. The storage and protection of SOC in aggregates is widely regarded as the material basis of soil organic C accumulation. However, current understanding of soil aggregate and its associated organic C is insufficient to elucidate the regulation mechanism of soil organic C. A nine-year field experiment including chemical fertilizer (FR) and organic manure (OM) treatments was set up in the eastern plain of Funiu Mountain, central China. Using chemical analysis, physical sieving as well as nuclear magnetic resonance (NMR) methods, we mainly probed into the response of soil organic C concentration and composition, and C functional groups, water-stable aggregates to different treatments. Furthermore, scanning electronic microscopy (SEM) and partial least square structural equation modelling (PLS-SEM) was conducted to characterise the different size aggregates and to analyse the mechanism of soil organic C accumulation and stabilisation at aggregate scales. After nine years of farming, OM treatment substantially increased soil organic C content (by 3.77 g kg−1) and significantly enhanced the formation of macro-aggregates (> 250 μm), while FR had no significant influence on soil organic C. At the aggregate scale, the amounts of soil organic C, C physical fractions (particulate and mineral-associated organic C), total nitrogen and microbial biomass carbon associated in macro-aggregates (> 250 μm) were obviously higher than that in micro-aggregates and silt + clay fraction, and OM treatment greatly increased the accumulation of soil organic C and its components in macro-aggregates. Moreover, microbial biomass carbon (MBC) amounts in aggregates were remarkably increased (27–116%) by the application of OM. And MBC had a positively effect on the physical fractions of SOC but not on the C chemical structure within aggregates. The present study indicated that soil organic C accumulation mainly rely on macro-aggregates (> 250 μm). Intra–particulate organic carbon (POC) and mineral-associated organic carbon (MOC) within macro-aggregates played an important role in soil organic C accumulation. Meanwhile, soil microbes were a driving force for the accumulation of soil organic C physical fractions (POC and MOC). We concluded that OM treatment accelerated the synergistic process between organic C sequestration and soil aggregation, and showed great potential to increase soil organic C accumulation.

Wetting and drying cycles, organic amendments, and gypsum play a key role in structure formation and stability of sodic Vertisols

Abstract. In the natural environment, soils undergo wetting and drying (WD) cycles due to precipitation and evapotranspiration. The WD cycles have a profound impact on soil physical, chemical, and biological properties and drive the development of structure in soils. Degraded soils are often lacking structure, and the effect of organic amendments and WD cycles on structure formation of these soils is poorly understood. The aim of this study was to evaluate the role of biotic and abiotic factors on aggregate formation and stabilization of sodic soils after the addition of gypsum and organic amendments (feedlot manure, chicken manure, lucerne pallets, and anionic poly acrylamide). Amended soils were incubated at 25 ∘C over four WD cycles, with assessment of soil microbial respiration, electrical conductivity, pH, sodium adsorption ratio (SAR), aggregate stability in water (ASWAT), aggregate size distribution, and mean weight diameter. Our results demonstrate that WD cycles can improve aggregate stability after the addition of amendments in sodic Vertisols, but this process depends on the type of organic amendment. Lucerne pellets resulted in highest soil microbial respiration, proportions of large macroaggregates (&gt;2000 µm), and mean weight diameter. In contrast, dispersion was significantly reduced when soils were treated with chicken manure, whilst anionic polyacrylamide only had a transient effect on aggregate stability. When these organic amendments were applied together with gypsum, the stability of aggregates was further enhanced, and dispersion became negligible after the second WD cycle. The formation and stability of small macroaggregates (2000–250 µm) was less dependent on the type of organic amendments and more dependent on WD cycles as the proportion of small macroaggregates also increased in control soils after four WD cycles, highlighting the role of WD cycles as one of the key factors that improves aggregation and stability of sodic Vertisols.

Agrophysical indicators of ordinary chernozem depending on the methods of its tillage in the Northern Steppe of Ukraine

Topicality. The spread of negative processes in the soil associated with the aggravation of the economic situation in modern Ukraine, the rapid rise in prices for equipment, fuels and lubricants, the replacement of energy-intensive traditional tillage systems with non-moldboard and other resource-saving ones, requires further and deeper research on their impact on her agrophysical indicators. Purpose. To study the influence of the primary tillage on the agrophysical indicators of ordinary chernozem in the link of the field grain-fallow-row crop rotation (winter wheat after maize of milk-wax ripeness - peas for grain - winter wheat) in the conditions of the Northern Steppe of Ukraine. Materials and Methods. Methods of primary tillage based on moldboard plowing and non-moldboard loosening against the background of moldboard plowing for corn were studied. In experimental studies, we used field, laboratory and statistical-mathematical methods. The agrophysical parameters of the soil were determined according to generally accepted methods. Results. No significant difference has been found in the influence of the primary tillage methods on the soil density in the 0–30 cm layer under the crops of the crop rotation link in spring and at their harvesting. In 2011 and 2012, there was a significant increase in the number of water-stable aggregates (over 0.25 mm) in the soil under non-moldboard tillage, compared with plowing, under all crops of the crop rotation link in the spring and during harvesting, mainly in the 0–10 and 10–20 cm layers. This was more often observed in the spring – on average for 2010–2012, the difference in this indicator in the soil layer of 0–30 cm for the crops of the crop rotation link was: winter wheat after maize of milk-wax ripeness – 1.9, peas – 4.4 and winter wheat after peas – 3.0 %, and on average for the crop rotation link – 3.1 It is established that moldboardless tillage contributes to a significant reduction in moisture consumption for unproductive evaporation in conditions of frequently repeated drought events. Conclusions. The studied methods of primary tillage of ordinary heavy loam chernozem equally affect the bulk density and do not cause deterioration of this indicator. The non-moldboard tillage improves the water resistance of the arable soil layer under crops in the crop rotation link and reduces moisture consumption for evaporation, compared to plowing. Key words: tillage, density, water resistance, productive moisture, winter wheat, peas

Natural &lt;sup&gt;13&lt;/sup&gt;C Abundance of Organic Matter in Water-Stable Aggregates of Haplic Chernozem under Conditions of Contrasting Land Uses

Natural 13C abundance of different organic matter (OM) pools in water-stable macro- and free microaggregates of Haplic Chernozem in contrasting land use variants (steppe and long-term bare fallow) are described. Fractionation of 13C at certain stages of the formation of OM pools is relatively constant, regardless of the level of structural organization. This is demonstrated by the presented conceptual scheme, which allows one to quantify the fluxes of carbon (C) in the system of aggregate/OM pool. It was revealed that the main C fluxes in the OM pools go from the free OM (LFfr) to the Residue fraction through microaggregates within water-stable aggregates (mWSA), the components of which are the occluded OM (LFocc) and the Clay. With a high degree of probability, C flows from macroaggregates (WSAma) to free microaggregates (WSAmi). At the same time, the higher probability of the C flux into the Residue from the mWSA as compared to the direct C fluxes from the LFocc and the Clay, testifies in favor of the hypothesis that the Residue is represented, to a large extent, by parts/fragments of disintegrated mWSAs of 50–1 μm in size. Regardless of the size, the WSA contains a labile OM (as the components of mWSA, along with LFfr – only in macroaggregates) and a stable OM (Residue). Labile OM (LFocc and Clay) within WSAmi is characterized by a lower degree of microbial processing (“lighter” isotopic signature) compared to that within WSAma, which is due to its greater “physical” protection against microbial attacks. However, the most stable OM pool, concentrated in the Residue within WSAmi is enriched in 13C compared to that within WSAma. Considering that the Residue determines the total isotopic composition of C in WSA, the organic matter of free microaggregates is characterized by a higher degree of microbial processing in comparison with that of macroaggregates. Free microaggregates are parts of disintegrated macroaggregates.

Natural 13C Abundance in the Organic Matter of Water-Stable Aggregates of Haplic Chernozem under Contrasting Land Uses

Natural 13C Abundance in the Organic Matter of Water-Stable Aggregates of Haplic Chernozem under Contrasting Land Uses

IRRIGATION AND MINERAL FERTILIZER EFFECTS ON PHYSICAL PROPERTIES OF LIGHT CHESTNUT SOIL USED IN THE CULTIVATION OF SUGAR BEET (BETA VULGARIS L.)

This work studied the effect of irrigation and mineral fertilizers on the physical properties of light chestnut soil used in cultivating sugar beet (Beta vulgaris L.). The experiment happened in 2021 on an irrigated field with an area of 2 ha in the territory of the Kazakh Research Institute of Agriculture and Plant Growing, District Karasai, Almaty region, Kazakhstan. A sugar beet hybrid (obtained from domestic selection ‘Aksu’ and foreign selection ‘Yampol’) cultivation used four levels of mineral fertilizers, i.e., 0:0:0 (control), 90:90:60, 120:120:90, and 150:150:120 NPK kg ha-1. During the sugar beet growing season, all periods of observations recorded an increase in the bulk density in the upper, middle, and lower soil layers, from 1.14–1.27 g/cm3 to 1.31–1.48 g/cm3. The content of agronomically valuable aggregates in 0–10 cm, 10–20 cm, and 20–30 cm soil layers decreased from the germination phase to harvesting of sugar beet in extensive technology (10.0%–15.7%) and intensive technologies (2.3%–13.1%). In these soil layers, the number of water-stable aggregates decreased from the beginning of renewal to the end of the growing season of sugar beet in technology without the use of fertilizers (2.9%–6.4%) and in technologies with the application of mineral fertilizers (1.6%–7.6%). In the soil layers, the noted highest content of productive moisture occurred in the phase of closing the leaves in the rows with the extensive technology of sugar beet cultivation (51.5–213.2 mm). Irrigation during the sugar beet growing season reduces the content of agronomically-valuable and water-stable aggregates in soil layers to the minimum values for harvesting in technology without the use of fertilizers (50.5%–54.4% and 12.9%–14.2%) and technology with the use of mineral fertilizers (52.3%–54.4% and 10.9%–13.5%), respectively.

A Combined Ridging and Cover Crop Tillage System for Sustainable Coffee Plantation in Kenya

The introduction of ridge tillage and beans as a cover crop was investigated as a means of management for mitigating soil erosion and increasing the physical functionalities of soil. In a completely randomized design, four treatments were applied to twelve plots, three with ridges introduced (T1), three with beans as the cover crop (T2), three with cover crops combined with ridges (T3), and another three as controls without intervention (T4). Four physical properties were monitored, i.e., soil moisture content, bulk density, infiltration rate, and aggregate stability. Data were collected from two seasons with beans as the cover crop, with each season lasting three months. The results showed that T3 resulted in the highest soil moisture content at 34.87 ± 6.78%, followed by T2 and T1 with 34.20 ± 0.65% and 32.65 ± 1.71%, respectively, while T4 had the minimum value of 28.28 ± 5.30%. The bulk density of the soil was found to be lowest at T2 and T3, both having a value of 0.92 g cm−3 with standard deviations of ±0.03 and ±0.11, respectively. This was followed by T1 with 0.98 ± 0.05 g cm−3 while T4 had the highest bulk density of 1.17 ± 0.13 g cm−3. A similar trend was observed for both the basic infiltration rate and aggregate stability, except that, in terms of the latter, T1 was ranking second after T3, with 64.07% of water stable aggregates greater than 0.25 mm diameter. The interventions introduced in coffee plantations had significant effects on the bulk density and infiltration rate; however, there was no significant difference in the moisture content and aggregate stability. Further investigation is needed to quantify the environmental effects of these interventions, e.g., greenhouse gas emissions and yields.