Water-stable Aggregate Stability Research Articles

Accumulative Effect of Soil Organic Carbon and Nitrogen in Water-Stable Aggregates and Soil Stability Characteristics of <i>Robinia pseudoacacia</i> Plantation in the Loess Hilly-Gully Region

Soil water-stable aggregates (WSAs) are the basic unit of soil constitution and can contribute to remaining the stable soil constitution. The objective of this study was to clarify the distribution and stability of WSAs and the soil organic carbon (SOC), the total nitrogen (TN), and the total phosphorus (TP) concentrations in 0 - 20 cm and 20 - 40 cm soil layers under the different ages of Robinia pseudoacacia plantations. The 20, 25, 40, and 50 years-old Robinia pseudoacacia plantations were selected. Stepwise regression analysis showed that >5 mm and 1 - 2 mm WSAs, SOC concentration in 2 - 5 mm WSAs, and TN and TP concentrations in < 0.25 mm WSAs were dominant independent variables affecting aggregate stability and that SOC in 0.25 - 0.5 mm WSAs, TN in <0.25 mm and 1 - 2 mm WSAs and TP in 2 - 5 mm WSAs were dominant independent variables affecting SOC, TN, and TP concentrations in bulk soils.

Effect of biochar on reclaimed tidal land soil properties and maize (Zea mays L.) response

Reclaimed tidal land soil (RTLS) often contains high levels of soluble salts and exchangeable Na that can adversely affect plant growth. The current study examined the effect of biochar on the physicochemical properties of RTLS and subsequently the influence on plant growth performance. Rice hull derived biochar (BC) was applied to RTLS at three different rates (1%, 2%, and 5% (w/w)) and maize (Zea mays L.) subsequently cultivated for 6weeks. While maize was cultivated, 0.1% NaCl solution was supplied from the bottom of the pots to simulate the natural RTLS conditions. Biochar induced changes in soil properties were evaluated by the water stable aggregate (WSA) percentage, exchangeable sodium percentage (ESP), soil organic carbon contents, cation exchange capacity, and exchangeable cations. Plant response was measured by growth rate, nutrient contents, and antioxidant enzyme activity of ascorbate peroxidase (APX) and glutathione reductase (GR). Application of rice hull derived biochar increased the soil organic carbon content and the percentage of WSA by 36–69%, while decreasing the ESP. The highest dry weight maize yield was observed from soil which received 5% BC (w/w), which was attributed to increased stability of water-stable aggregates and elevated levels of phosphate in BC incorporated soils. Moreover, increased potassium, sourced from the BC, induced mitigation of Na uptake by maize and consequently, reduced the impact of salt stress as evidenced by overall declines in the antioxidant activities of APX and GR.

Exogenous application of EE-GRSP and changes in citrus rhizosphere properties

Mycorrhization-induced secretion of glomalin-related soil protein (GRSP) is known to contribute in improving soil fertility and aggregate stability. But, there is hardly any evidence that exogenous GRSP could produce the similar type of response. The present study was, therefore, carried out to extract easily extractable GRSP (EE-GRSP) from citrus rhizosphere soils and evaluate the response at 1/4, 1/2 and full strength EE-GRSP solutions watered into the rhizosphere of 27-year-old Satsuma mandarin (Citrus unshiu) grafted on the rootstock of Poncirus trifoliata. After ~5 months, exogenous EE-GRSP treatments produced significantly positive responses on endogenous EE-GRSP, difficultly-extractable GRSP (DE-GRSP), total GRSP production and soil organic carbon (SOC) content. A significantly positive correlation of these endogenous GRSP fractions with SOC indicated an active participation of GRSP on soil C pool. Exogenous GRSP showed a key role in binding water-stable aggregate (WSA) at 2–4, 1–2, 0.5–1, and 0.25– 0.5 mm size and enhancing WSA stability through changes in mean weight diameter (MWD). A stronger correlation of EE-GRSP and total GRSP with MWD was observed than DE-GRSP fraction. On the other hand, exogenous EEGRSP showed a positive effect on soil phosphatase activity, and soil endogenous EE-GRSP was significantly and positively correlated only with neutral phosphatase. Our studies suggest that exogenous EE-GRSP could be used as an effective regulator to affect soil fertility and soil structure within citrus rhizosphere.

The effect of different fire-intensity on soil organic matter and aggregates stability

DOI: 10.15414/afz.2015.18.01.01–05 Received 09. January 2015 ǀ Accepted 16. MArch 2015 ǀ Available online 31. March 2015 Fire affects many of physical, chemical and biological soil properties directly by the transport of the heat to the soil or indirectly because of the vegetation changes and dynamic of nutrients and organic matter. This impact depends on many factors therefore the aim of this study was to consider the impact of different severity of fire on the changes in quantity and quality of soil organic matter (SOM) and soil structure in sandy dystrict Fluvisol. The samples were taken in the Zbehy district (autumn 2012) from three localities: 1. unburned soil – the control, 2. Higher severity of fire, and 3. Lower severity of fire. The results showed the increase of SOM content due to higher severity of fire; on the other hand, the SOM quality was decreased. The stability of water-stable aggregates was clearly decreased because of higher fire-severity. Overall, our results indicate that the breakdown of soil structure was affected by higher severity of fire.  Keywords: fire, stability of water-stable aggregates, soil structure

Effects of soil structural properties on saturated hydraulic conductivity under different land-use types

Soil structure has important influences on edaphic conditions and environment, is often related to aggregate stability. The saturated hydraulic conductivity (Ks) is an important soil hydraulic property that affects water flow and transport of dissolved solutes. The objective of this study was to analyse the impact of water-stable aggregate stability on Ks under different land-use types. Using a range of aggregate stabilities in disturbed soil columns, Ks was measured and relationships between the mean weight diameter (MWD) of aggregates and Ks for three different conditions (three soil layers, four land use types, two water supply methods) were determined. Differences between soil aggregate characteristics and organic matter content among the land use types were significant. Using both both top and bottom water supply methods, MWD was related to Ks by a non-linear function (coefficient of determination &gt;0.95), and land-use type and water supply method were significant factors. When undisturbed soil columns were investigated, the relationship between MWD and Ks was obscured by other soil environmental factors.

Land Use Patterns Effect on Soil Anti-Erodibility in Low Mountain-Hilly Region

Land use patterns effect on soil anti-erodibility was studied by the combinative means of field investigation and laboratory analysis in low mountain-hilly region. The results showed that he five land use patterns had high proportion of aggregates at the size of &gt;2 mm after dry sieving and had high proportion of aggregates at the size of &lt;0.5 mm after wet sieving. Soil dispersion was mainly reflected in aggregate at the size of 0.05- 0.001 mm under different land use patterns. It was significantly different to land use patterns effect on soil anti-erodibility. Soil anti-erodibility in Chinese fir plantation and Eucalyptus plantation were stronger than those of tea plantation, loquat orchard and abandoned farmland. Water-stable aggregate stability was the highest in Chinese fir plantation, followed by eucalyptus plantations and tea plantations, and water-stable aggregate stability was the lowest in loquat orchards and abandoned farmland. Except for coarse dust, the other soil particle content of the same size had the different change under different land use patterns. The change of status of aggregate and degree of aggregation was opposite to the change of dispersive coefficient under different land use patterns. Water stability index and soil organic matter content in Chinese fir plantation, eucalyptus plantation and loquat orchard was higher than that of abandoned farmland and tea plantation. So, land use patterns of Chinese fir plantation and eucalyptus plantation was reasonable in study area.

Effect of land use patterns on stability and distributions of organic carbon in the hilly region of Western Sichuan, China

Soil aggregation is important for the resistance of land surfaces to erosion, and it influences the ability of soils to remain productive. At the same time, it is also an important process of carbon sequestration. The objectives of this study were to elucidate the effects of different land use patterns on soil aggregate stability and the distribution of organic carbon in different aggregate fractions in order to prove that the different land use patterns enhance soil aggregate stability. Five kinds of soil samples were collected from the hilly area of western Sichuan under different land use patterns, such as abandoned farmlands, eucalyptus plantations, Chinese fir plantations, tea plantations and loquat orchards. The results demonstrated that the five land use patterns had high proportions of aggregates at the size of >2 mm after dry sieving, and had high proportions of aggregates at the size of < 0.5 mm after wet sieving. The aggregation abilities of the soils were significantly different depending on land use patterns. Waterstable aggregate stability was highest in the Chinese fir plantations, followed by eucalyptus plantations and tea plantations. Water-stable aggregate stability was the lowest in loquat orchards and abandoned farmlands. Except for coarse particle, soil particle contents of the same size were affected according to the different land use patterns. As the size of aggregates decreased, the organic carbon content of the soil aggregates in tea plantations increased after a decrease, and then reduced again. However, the organic carbon contents of soil aggregates in other land uses increased continuously with the decreasing size of aggregates. Organic carbon content of the soil aggregates was strongly increased in land areas that had been converted from abandoned farmland to Chinese fir plantations, tea plantations and loquat orchards, while it was decreased when abandoned farmland was converted to eucalyptus plantations. The results provided the basis of implementation of returning farmland to forest and the process of carbon sequestration in the study areas.

Microbial Activity and Long-Chain Aliphatics in the Formation of Stable Soil Aggregates

Under intensive farming, restoration of organic matter levels and soil structure may depend on the amount and nature of the organic amendment added. The effect of three types of aliphatic compounds on the water aggregate stability of a chemically altered lacustrine heavy clay was studied in a 35-d incubation experiment. Water-stable aggregates were determined before and after unbound lipids were extracted. The addition of ethyl ether insoluble aliphatic produced 0 to 50 mg C kg−1 as CO2 and increased water-stable aggregates by 7 to 17.5%. The acid and neutral fractions produced 0.32 to 12.93 g C kg−1 as CO2, and resulted in acceptable aggregate stability. Stability may be attributed to the binding of aliphatic compounds to the inorganic component through polyvalent cation bridges. High correlation coefficients (P ≤ 0.001) for the acid and neutral fractions were found between the amounts of aliphatic compounds added, bound organic compounds extracted, CO2 evolved, and water-stable aggregate stability. The increase in soil aggregate stability appears closely related to bound aliphatic compounds incorporated into the aggregates as a result of microbial activity, and that the effect of aliphatic compounds on soil aggregate stability is associated with both their quantity and chemical nature.