Proportion Of Water-stable Macroaggregates Research Articles

Effects of the application of different improved materials on reclaimed soil structure and maize yield of Hollow Village in Loess Area.

In order to solve the soil problem of poor structure and low fertility after the abandoned homestead reclamation of Hollow Village in Loess Area and to improve the quality of the reclaimed soil in Hollow Village, a five-year field experiment was conducted here. In this experiment, the following seven treatments were applied: no modified material (CK), maturing agent (TM), fly ash (TF), organic fertilizer (TO), maturing agent + fly ash (TMF), maturing agent + organic fertilizer (TMO) and fly ash + organic fertilizer (TFO), and the effects of different improved materials on soil properties and crop yield were studied. The results showed that: soil organic matter (SOM) and total nitrogen contents increased significantly after the application of different improved materials, which promoted the cementation and aggregation of water-stable microaggregates (< 0.25 mm), and the water-stable macroaggregates showed an increasing trend. In the 0–0.15 m soil layer, the proportion of water-stable macroaggregates under TM, TF, TO, TMF, TMO, and TFO treatment increased by 328.2%, 130.0%, 87.8%, 81.1%, 36.7%, and 12.2% compared with CK, respectively. Meanwhile, TF, TO, TMF, TMO, TFO treatments significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD) values, reduced soil bulk density, the stable aggregate index (ELT) and fractal dimension (D) values (P < 0.05), and the stability of soil structure and the capacity of soil moisture retention has been significantly improved. The SOM content had a significant positive correlation with MWD, GMD, and > 2 mm water-stable aggregates and a significant negative correlation with the ELT, D, and water-stable microaggregates. In particular, the organic–inorganic coupling treatment of TFO showed the highest SOM content, soil moisture content, water-stable macroaggregates and maize yield, which was the most appropriate amendment for improving the reclaimed soil structure and fertility of Hollow Village in Loess Area.

Effect on Soil Properties and Crop Yields to Long-Term Application of Superabsorbent Polymer and Manure

Intensive farming leads to soil degradation, and poses a serious threat to agricultural yield sustainability and soil ecology. Superabsorbent polymer (SAP) and organic manure (OM) are amendments that can remediate the soil, and improve soil structure and soil pore characteristics, thereby enhancing soil quality and promoting crop growth. These benefits may be enhanced through long-term continuous application of the amendments. X-ray computed tomography (CT) was used to determine the number, connectivity, and locations of pores (160–1,000 μm, &amp;gt;1,000 µm) in the soil at depths of 0–100 cm. Soil organic carbon content, proportion of water-stable macroaggregates (&amp;gt;0.25 mm) (WSM), soil bulk density, field water capacity, available water content, wilting point content, and saturated hydraulic conductivity were also determined. Compared to the control, long-term SAP and OM treatments significantly increased the number of 160–1,000 µm and &amp;gt;1,000 µm soil pores (5–20 cm depths), &amp;gt;1,000 µm and &amp;gt;160 µm soil porosity (at 0–20 cm depths), total organic carbon (10–20 cm and 40–50 cm), field water capacity (0–20 cm), available water content (0–20 cm), wilting point (10–30 cm), saturated water content (10–70 cm), saturated hydraulic conductivity (0–90 cm), and WSM (0–30 cm and 40–50 cm) while decreasing the soil bulk density (0–70 cm). Compared to OM, SAP had greater beneficial effects on the total organic carbon, soil field water capacity, available water content, saturated water content, saturated hydraulic conductivity, and WSM in soil at 0–20 cm depth. The improvements to soil quality resulted in an increase in the yields of wheat and maize. Therefore, although SAP and OM were both effective at improving soil properties and increasing the economic yield of wheat and maize, the effectiveness of SAP was greater than that of OM.

Effect of salinity on soil structure and soil hydraulic characteristics

Revealing the influences of soil salinity on soil structure and hydraulic properties contributes to understanding the mechanism of salinity restraining rehabilitation of saline sodic soil in coastal area. After being passed through a 1 mm sieve, silt loam and silty clay were irrigated with saline water to achieve different soil salinities to highlight the effect of irrigation salinity on aggregate formation from primary particles. Three irrigation events with different saline water were conducted in the same 2 mo interval in soil columns; the soil columns were subjected to natural evaporation during the interval. The soil salinity, soil structure, soil–water characteristic curve, and saturated hydraulic conductivity (Ks) results were determined after the end of the third drying subprocess. The results showed that the proportion of water-stable macroaggregates (0.25–2 mm) in the silt loam and silty clay increased as the soil salt content (SSC) increased. Under the same matric suction, the retention capacity and plant-available water capacity (PAWC) of the silt loam first increased and then decreased, with the SSC increasing to a maximum of approximately 14.5 g kg−1. The retention capacity of the silty clay increased with the SSC, whereas the PAWC decreased with the SSC. The Ksof the silt loam increased with SSC. This study reveals the effects of soil salinity on aggregate formation from primary particles in wetting–drying cycles and describes the corresponding changes in hydraulic properties, which influence the rehabilitation of saline sodic soils in coastal areas.

Soil structure and soil organic matter in water-stable aggregates under different application rates of biochar

Soil structure and soil organic matter in water-stable aggregates under different application rates of biochar

Initiation of soil formation in weathered sulfidic Cu-Pb-Zn tailings under subtropical and semi-arid climatic conditions

Field evidence has been scarce about soil (or technosol) formation and direct phytostabilization of base metal mine tailings under field conditions. The present study evaluated key attributes of soil formation in weathered and neutral Cu-Pb-Zn tailings subject to organic amendment (WC: woodchips) and colonization of pioneer native plant species (mixed native woody and grass plant species) in a 2.5-year field trial under subtropical and semi-arid climatic conditions. Key soil indicators of engineered soil formation process were characterized, including organic carbon fractions, aggregation, microbial community and key enzymatic activities. The majority (64–87%) of the OC was stabilized in microaggregate or organo-mineral complexes in the amended tailings. The levels of OC and water soluble OC were elevated by 2–3 folds across the treatments, with the highest level in the treatment of WC and plant colonization (WC+P). Specifically, the WC+P treatment increased the proportion of water stable macroaggregates. Plants further contributed to the N rich organic matter in the tailings, favouring organo-mineral interactions and organic stabilization. Besides, the plants played a major role in boosting microbial biomass and activities in the treated tailings. WC and plants enhanced the contents of organic carbon (OC) associated with aggregates (e.g., physically protected OC), formation of water-stable aggregates (e.g., micro and macroaggregates), chemical buffering capacity (e.g., cation exchange capacity). Microbial community and enzymatic activities were also stimulated in the amended tailings. The present results showed that the formation of functional technosol was initiated in the eco-engineered and weathered Cu-Pb-Zn tailings under field conditions for direct phytostabilization.

The influence of soil organic matter fractions on aggregates stabilization in agricultural and forest soils of selected Slovak and Czech hilly lands

Because the stability of soil aggregates is affected by many factors, we studied aggregates formed in forest and agricultural soils in different soil types (Cambisols, Luvisols, Chernozems). We evaluated: (1) the differences in water-stable aggregates (WSA) as related to soil type and land management and (2) the relationships between quantitative and qualitative parameters of soil organic matter (SOM), particle-size distribution and individual size classes of WSA. Soil samples were taken from three localities (Soběsice, Bab, Vieska nad Žitavou). Each study locality included both a forest and an agricultural soil-sampling area. We found that in forest soils, the proportion of water-stable macroaggregates (WSAma) relative to water-stable microaggregates (WSAmi) was greater than in agricultural soils. When all soils were assessed together, positive statistically significant correlations were observed between the size classes WSAma > 1 mm and organic carbon (Corg) content; however, the WSAmi content was negatively correlated with Corg content. Favorable humus quality positively influenced the stabilization of WSAma > 5 mm; however, we found it had a negative statistically significant effect on stabilization of WSAma 1–0.25 mm. In agricultural soils, the stabilization of WSAma was associated with humified, i.e., stable SOM. The WSAma content was highly positively influenced mainly by fulvic acids bound with clay and sesquioxides; therefore, we consider this humus fraction to be a key to macroaggregate stability in the studied agricultural soils. On the other side, all fractions of humic and fulvic acids participated on the formation of WSAma in forest soil, which is a major difference in organic stabilization agents of macroaggregates between studied forest and agricultural soils. Another considerable difference is that WSAmi in agricultural soils were stabilized primarily with humic acids and in forest soils by fulvic acids. Moreover, in forest soils, a higher content of labile carbon in WSA had a positive effect on formation of WSAmi. The observed changes in individual size classes of WSA and interactions between SOM, particle-size distribution, and WSA have a negative impact on soil fertility and thereby endanger agricultural sustainability.

Effects of no-tillage systems on soil physical properties and carbon sequestration under long-term wheat–maize double cropping system

A thorough assessment of changes in soil quality associated with soil management practices is vital for the selection and establishment of sustainable agricultural management. The winter wheat (Triticum aestivum L.)–maize (Zea mays L.) double cropping system was used to study the integrated effects of a 9-year-old tillage coupled with fertilization on soil carbon sequestration and other physical properties in the Yellow River Delta (YRD). Three tillage systems were selected: no-tillage with straw cover plus recommended urea nitrogen rate (NTS), no-tillage with straw removed and manure applied plus recommended urea nitrogen rate (NTM), and conventional tillage with straw removed plus conventional urea nitrogen application rate (CT). There were three replicates of each treatment organized in a randomized block design. NTS and NTM treatments were found to result in a slightly decrease in the soil bulk density (BD), and significantly increased the proportion of water stable aggregates (WSA) (>2mm), as well as the water infiltration capacity. The proportion of water stable macroaggregates (>0.25mm), the mean weight diameter (MWD) and the geometric mean diameter (GMD) of aggregates in the 0–20cm layer were unchanged by NTS and NTM. The total soil organic carbon (SOC) stock at a depth of 0–60cm was not significantly different among the treatments. Both aggregate-associated SOC concentration and stocks (0–5cm) were significantly greater for NTS and NTM compared with CT, while CT led to a greater OC accumulation in the 20–60cm soil layer compared with NTS and in the 10–20cm compared with NTM. The mesoaggregate fraction (2–0.25mm) and its associated OC pool accounted for the highest percentages in the whole soil profile under the CT treatment. The NT system was found to have a positive effect on the investigated soil physical properties and increase soil carbon content in the soil surface layer. The CT system in conjunction with the wheat–maize double cropping system, however, improved soil aggregation in the soil profile (0–60cm) and also maintained a higher fraction of SOC in the subsoil compared with the NT systems.

POTENCIAL DE INÓCULO MICORRÍZICO E IMPORTÂNCIA DO COMPRIMENTO DO MICÉLIO PARA A AGREGAÇÃO DE SOLOS DE AMBIENTE FLUVIAL

Os fungos micorrízicos arbusculares (FMAs) desempenham importante papel nos ecossistemas naturais pelo seus impactos na nutrição vegetal e estrutura do solo. O objetivo deste estudo foi determinar o potencial do inóculo micorrízico e a relação do comprimento do micélio micorrízico (CMM) dos FMAs na agregação de solos de ambientes fluviais. Foram realizadas coletas em áreas de ambiente fluvial da bacia hidrográfica do rio Itajaí-Açu, entre os municípios de Gaspar e Navegantes, em Santa Catarina. Oito áreas foram amostradas em três classes de solos, sendo elas: Cambissolo (C), Gleissolo (G) e Organossolo (O). Nos solos coletados, foram avaliadas as seguintes variáveis: potencial de inóculo micorrízico, número de esporos, CMM e análise dos atributos físicos e químicos do solo. A porcentagem de colonização micorrízica da Brachiaria brizantha no ensaio do potencial de inóculo variou de 13,8 a 55,3 % e nenhum padrão foi observado de acordo com a classe de solo. O CMM no solo variou de 10,48 a 44,67 mg g-1. O número de esporos em 100 cm3 de solo variou de 2,4 a 80. Foi observada correlação negativa entre o CMM e a proporção de macroagregados estáveis em água e correlação positiva entre CMM com microagregados. Este trabalho demonstrou que os solos da bacia do rio Itajaí-Açu possuem potencial de inóculo micorrízico suficiente para iniciar a colonização das raízes das plantas em curto período de tempo, o que pode ser importante facilitador no crescimento de espécies arbóreas usadas no processo de recuperação desses ambientes.

Soil aggregation, and total and particulate organic matter following conversion of native forests to continuous cultivation in Ethiopia

Conversion of native forests to cultivation is usually accompanied by a decline in soil organic carbon (SOC) and nutrients, and deterioration of soil structure. The objectives of this study were: (i) to assess the effect of cultivation on soil aggregation and aggregate stability and (ii) to determine the effect of cultivation on total SOM, and the quantity and quality of POM in a Rhodic Nitisol at Munesa, in southeastern Ethiopia. Samples were collected from a cropland cultivated for 26 years and an adjacent natural forest. After cultivation, the proportion of water-stable macroaggregates was significantly reduced from >70% in the natural forest soil to 50% in the cultivated soil, being more pronounced in the >1 mm size aggregates. Cultivation also induced significant losses of OC and N both in bulk soil and water-stable aggregates. The amounts of free light fraction (free LF) C and N were more affected by cultivation than the amounts of intraparticulate organic matter (iPOM) C and N. The effect of cultivation was more pronounced on macroaggregate associated total and particulate organic matter than on microaggregate-associated fractions. The losses of POM C and N due to cultivation were highest in comparison to the total aggregate and whole soil OC and N suggesting that POM constitutes a more sensitive SOM fraction to the effects of cultivation. Soil aggregate stability and SOM could be used as indicators to apply the more appropriate management practices for increasing soil sustainability or productivity.

Water-stable aggregation of Québec silty clay soils: some factors controlling its dynamics

Despite a relatively high organic matter content, the heavy soils of the St-Lawrence lowlands of eastern Canada are susceptible to structural degradation in the form of compaction, surface crusting and sheet erosion. The resistance of these soil to degradation is largely controlled by the presence of stable macroaggregates. Several agronomic studies involving various combinations of management options such as organic additions, crop rotations and reduced tillage have allowed to intensively monitor the changes in aggregation of these soils through time. The proportion of water-stable macroaggregates (>1 mm) showed large temporal variation. Short-range variations (days or weeks) were attributable to climatic conditions and tillage operations as revealed by significant correlations between soil water content and aggregation within a growing season. Longer-term trends (>2 years) were a function mostly of carbon (C) management i.e. placement or location of the residues in the soil profile, and the amount and quality of the residues. The effect of C management was reflected by correlations between aggregation, C inputs, soil C content and organic matter (OM) fractions. Based on a study of the OM associated with the primary particles it is proposed that the clay and silt particles of these soils are relatively saturated in OM which leads to highly stable microaggregation. Any additional OM accumulation in the surface soil provided by reduced- or no-till conditions, perennial forage crops or manure additions would lead to increased macroaggregation and be related to the accumulation of particulate OM. This hypothesis helps to explain the relatively high responsiveness of soil structure, and in particular stable macroaggregation, to changes in cropping systems in these soils.

Soil organic structures in macro and microaggregates of a cultivated Brown Chernozem

The chemical composition of soil organic binders and their role in aggregate stability is largely unknown. The purpose of this study was to characterize soil organic matter (SOM) in soil macro and microaggregates by pyrolysis field ionization mass spectrometry (Py-FIMS). In comparison with a wheat-fallow (WF) rotation, a continuous wheat (CW) system stored more organic C, maintained a greater proportion of water stable macroaggregates > 250 μm and was characterized by greater molecular diversity of SOM. The highest concentration of molecular ions in all aggregate fractions were carbohydrates, lignin monomers, N compounds, and alkylaromatics (each representing from 9 to 15% of total detected molecular ions). Lipids, lignin dimers and sterols were the least abundant (each representing from 0.3 to 4% of total detected molecular ions). Linear regression models showed that the proportion of water stable macroaggregates was correlated with the concentration of lignin dimers ( r = 0.98), sterols ( r = 0.94), alkylaromatics ( r = 0.94) and lipids ( r = 0.90). Chemical classes of organic compounds were not correlated with the proportion of water stable microaggregates.