Distribution and release of phosphorus fractions associated with soil aggregate structure in restored wetlands

In article approaches for statistical estimation of composite variables are considered. The soil aggregate structure is described by indicators which concern a category composite variable, i.e. such which in the sum always compound the fixed number (in our case it is 100 %). Mathematical properties of composite variables is essential confine possibility of various types of mathematical actions, including statistical analysis, over the data on soil aggregate structure. For application of statistical and other mathematical methods of analysis of the data of aggregate structure this data should be preliminary transformed. The classical soil structure coefficient is closest on ideology to the transformed variables, but its mathematical form not to the full meets the requirements of the further statistical procedures as is somewhat arbitrary. In the literature there are various variants of bases of orthogonal log-transformation of the data, but there are no ecologically well-founded criteria for their choice. For a choice of the best basis of transformation we offer a method of comparison of transformation results with edaphic properties matrixes or matrixes of plants morphometry. The optimum decision represents such basis which gives the best correlation with matrix external in relation to a composite variable of properties. Ordinary and partial Mantel tests have allowed to establish that the variation of aggregation structure is at the bottom of variability morphometric indicators of corn from the sowings which are on given bedrock. In turn correlation of aggregation structure with other edaphic properties is a consequence of their co-ordinated variability owing to unity of soil as is natural-historical body. Keywords: composite variables, log-transformation, aggregation structure, soil properties.

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Quantification of Available Water Capacity Comparing Standard Methods and a Pedostructure Method on a Weakly Structured Soil

Transactions of the ASABE ◽

10.13031/trans.13073 ◽

2019 ◽

Vol 62 (2) ◽

pp. 289-301

Author(s):

Amjad T. Assi ◽

Rabi H. Mohtar ◽

Erik F. Braudeau ◽

Cristine L. S. Morgan

Keyword(s):

Water Content ◽

Soil Water ◽

Field Capacity ◽

Soil Aggregate ◽

Pedotransfer Functions ◽

Water Retention Curve ◽

Aggregate Structure ◽

Standard Methods ◽

Available Water ◽

Water Holding

Abstract. The purpose of this study was to evaluate the use of the pedostructure concept to determine the soil available water capacity, specifically the field capacity (FC). Pedostructure describes the soil aggregate structure and its thermodynamic interaction with water. Specifically, this work compared the calculation of soil water-holding properties based on the pedostructure concept with other standard methods for determining FC and permanent wilting point (PWP). The standard methods evaluated were the FAO texture estimate (FAO method), the Saxton-Rawls pedotransfer functions (PTFs method), and the water content at predefined soil suction (330 and 15,000 hPa) as measured with a pressure plate apparatus (PP method). Additionally, two pedostructure methods were assessed: the thermodynamic water retention curve (TWRC method) and the thermodynamic pedostructure (TPC method). Undisturbed loamy fine sand soil from a field in Millican, Texas, was analyzed at both the Ap and E horizons. The results showed that the estimated water content at FC and PWP for the three standard methods and for the TWRC method were in relative agreement. However, the TPC method used characteristic transition points in the modeled contents of different water pools in the soil aggregate and was higher for the Ap horizon, but in agreement with the other methods for the E horizon. For example, for the Ap horizon of the soil analyzed in this study, the FC estimated with the standard and TWRC methods ranged from 0.073 to 0.150 m3H2O m-3soil, while the TPC method estimate was 0.221 m3H2O m-3soil. Overall, the different methods showed good agreement in estimating the available water; however, the results also showed some variations in these estimates. It is clear that the TPC method has advantages over the other methods in considering the soil aggregate structure and modeling the soil water content within the aggregate structure. The thermodynamic nature of the TPC method enabled the use of both the soil shrinkage curve and the water retention curve in a weakly structured soil. It is expected that the TPC method would provide more comprehensive advances in understanding the soil water-holding properties of structured soils with higher clay contents. Keywords: Available water, Field capacity, Pedostructure, Pedotransfer functions, Permanent wilting point.

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Soil Aggregate Structure Effects on Dielectric Permittivity of an Andisol Measured by Time Domain Reflectometry

Vadose Zone Journal ◽

10.2136/vzj2003.9000 ◽

2003 ◽

Vol 2 (1) ◽

pp. 90-97 ◽

Cited By ~ 42

Author(s):

Teruhito Miyamoto ◽

Takeyuki Annaka ◽

Jiro Chikushi

Keyword(s):

Dielectric Permittivity ◽

Time Domain ◽

Soil Aggregate ◽

Time Domain Reflectometry ◽

Aggregate Structure

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Impact of different fallow durations on soil aggregate structure and humus status parameters

Soil and Water Research ◽

10.17221/174/2018-swr ◽

2019 ◽

Vol 15 (No. 1) ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Maksim Burdukovskii ◽

Irina Kiseleva ◽

Polina Perepelkina ◽

Yuliya Kosheleva

Keyword(s):

Organic Matter ◽

Soil Structure ◽

Russian Far East ◽

Arable Land ◽

Fulvic Acids ◽

Soil Aggregate ◽

Aggregate Structure ◽

Fallow Period ◽

Humus Status

Soil aggregate structure and soil organic matter are closely interrelated and commonly considered as key indicators of soil quality. The aim of this study was to evaluate the effects of different fallow durations on indices of soil structure and humus status indicators. Studies were conducted on abandoned agricultural fields (15, 20 and, 35 years after abandonment). As a reference site, we used a cultivated field in the area. The experimental soil fields are classified as Gleyic Cambisols. Soil macroaggregates were separated with the sieve (dry sieve) to seven aggregate size fractions, i.e.> 10, 10–5, 5–2, 2–1, 1–0.5, 0.5–0.25 and < 0.25 mm. The humus status parameters of soils included the following indicators: soil organic carbon (Corg), humus reserves (QH), the degree of humification of organic matter (SOMdh), fractions of humic acids (HA) (free and bound with monovalent cations and Al2O3, Fe2O3, bound with Са2+ which forms humates, bound with clay minerals), fulvic acids (FA) (free aggressive) and ratio of HA to FA (CHA : CFA). After a fallow period of more than 20 years on the surface formation of a sod layer. A long-term fallow period had an impact on the mean weight diameter of the aggregates (MWD) and agronomically valuable aggregates (AVA). Fallow soils have a significantly better structure than soils under a cultivated field. Long-term cultivation leads to the deterioration of soil structure and the formation of large aggregates (>10 mm). The Corg content remains at the level of the background content when the soils are left fallow for less than 15 years and increases over time. The Corg in the upper 0–20 cm soil layer has been shown to increase from 3.55 to 8.74% on arable land that has been fallow for 35 years and has been largely associated with significant accumulation of organic matter within the plant root mass. Mature sites are characterized by an increase of fulvic acids in the humus composition in comparison with their arable analogues. The abandonment of soil agricultural use and the cessation of mechanical tillage results in the restoration of the natural structure of soils and the improvement of their agrophysical properties. Such studies have not been previously conducted in the Primorsky region of the Russian Far East.

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Impact of maize cob and wood-derived biochar on soybean plant growth and soil aggregate structure in dry land

10.5194/egusphere-egu2020-13007 ◽

2020 ◽

Author(s):

Hua Ma ◽

Qirui Li ◽

Sonoko D. Bellingrath-Kimura

Keyword(s):

Plant Growth ◽

Grain Yield ◽

Soil Structure ◽

Clay Soil ◽

Soil Aggregate ◽

Mean Value ◽

Soybean Plant ◽

Aggregate Structure ◽

Dry Land ◽

The Mean

Soil structure plays important roles in land degradation, soil fertility, and agricultural productivity and thus has great ecological importance. Soil aggregation is a crucial soil function for maintaining soil porosity and enhancing the stability of soil structure to prevent soil erosion. Biochar was reported to be a binding agent for organic matter in aggregate formation and thus alleviate aggregates degradation. Therefore, this study attempts&#160;to a) investigate the impact of the biochar on soybean plant growth, plant nutrients content and soil chemical properties; b) analyze the effect of maize cob biochar (CB) and wood biochar (WB) on soil aggregate structure in vulnerable dry land area.Field trial was performed on two sandy soil fields (at MLZ and BDG village)&#160;and one loamy clay soil field (at RQ village) which located in Ningxia, China. Two treatments (20 t ha-1&#160;of CB&#160;and WB application) and control were repeated 7 times. In this study, we analyzed biomass, grain yield, and nutrients content of soybean plant while soil nutrients&#160;were&#160;observed as well. Nine soil aggregate size classes (ASCs) were obtained&#160;(>10, 10-7, 7-5, 5-3, 3-2, 2-1, 1-0.5, 0.5-0.25 and <0.25 mm)&#160;through&#160;dry sieving to analyze soil structure.&#160;In addition, soil dry mean weight diameter (dMWD), dry geometric mean diameter (dGMD), and structure coefficient (Ks) were measured&#160;to estimate the aggregate stability, erodible fraction, and agronomically valuable fraction. After that, redundancy analysis and ridge regression analysis were applied for further data processing.Our results&#160;indicated&#160;a)&#160;biomass&#160;and&#160;grain&#160;yield:&#160;both CB and WB significantly increased shoot biomass in loamy clay soil by 48.7% and 45.0%, respectively. In the two sandy soils, biochar indicated no significant enhancement on the plant growth and grain yield. Even though, the mean value of grain yield&#160;increased by 29.7% and 35.1% with the CB and WB application in the MLZ field, respectively. CB application also increased the mean value of&#160;grain yield by 34.2% in the BDG field. Although the data&#160;shows insignificant difference with high standard errors due to field heterogeneity,&#160;the mean values&#160;can&#160;still give insights&#160;into&#160;agricultural field practices;&#160;b)&#160;soil&#160;aggregate&#160;structure:&#160;soil type exerted stronger influence on soil aggregation and plant growth rather than biochar.&#160;The sandy field in MLZ showed high soil loss potential by wind erosion referring&#160;to a&#160;low value of dGMD, and the loamy clay field showed the highest dMWD, dGMD and Ks values&#160;for&#160;an ideal aggregate structure for crop growth. Findings indicate that biochar had no significant influence on aggregate structure in both sandy and loamy clay soils;&#160;c) soil&#160;nutrients:&#160;CB can significantly increase&#160;soil total carbon content in RQ and BDG fields. Soil potassium content can be&#160;enhanced by CB application in loamy clay soil.

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