Variability Of Aggregate Stability Research Articles

Carbon balance of sandy loam soils in arid landscapes of the Chechen Republic

The spatial variability of the stability of soil aggregates and its relationship with runoff and soil erosion were studied in a semi-arid environment in the field in order to assess the validity of the stability of structures as an indicator of soil erosion in soils of sandy loam ridges. The influence of soil and relief properties on the variability of aggregate stability was also investigated. Significant relationships were found in the number of water droplets required to break down the aggregate, as well as the rate of runoff and erosion. The most significant correlation was found between the number of droplet impacts and the soil organic matter content. The stability of aggregates in the upper soil layer is apparently a valuable indicator of field runoff and inter-season soil erosion of sandy loamy ridges in semi-arid conditions.

Effects of Organic Amendments on Soil Aggregate Stability and Microbial Biomass in a Long-Term Fertilization Experiment (IOSDV)

The effect of two types of organic amendment (manure and straw incorporation) and various doses (0–200 kg N*ha−1) of mineral N fertilization on microbial biomass C (MBC), aggregate stability (AS), soil organic C (SOC) and grain yield were investigated in an IOSDV long-term fertilization experiment (Keszthely, Hungary). This study was conducted during years 2015–2016 in a sandy loam Ramann-type brown forest soil (Eutric Cambisol according to WRB). Organic amendments had a significant effect on AS, MBC and SOC, increased their values compared to the unamended control. The organic amendments showed different effects on AS and MBC. AS was increased the most by straw incorporation and MBC by manure application. The magnitude of temporal variability of AS and MBC differed. Presumably, the different effects of organic amendments and the different degrees of temporal variability explain why there was only a weak (0.173) correlation between AS and MBC. AS did not correlate with SOC or grain yield. MBC correlated (0.339) with SOC but not with the grain yield. The N fertilizer dose did not have a significant effect on AS and MBC, but had a significant effect on SOC and grain yield.

Soil survey reveals a positive relationship between aggregate stability and anaerobically mineralizable nitrogen

Abstract Soil health status should be monitored to allow planning sustainable management, but indicators available do not encourage frequent soil health evaluation because of the complexity, time-consumption, and expensiveness of the methodologies. Aggregate stability (AS) is a good soil physical health indicator associated with soil (SOC) and particulate (POC) organic carbon but is difficult to monitor. Anaerobically mineralizable nitrogen (AN) has been proposed as soil health indicator because is cheap, simple, and safe to measure, is sensitive to soil-use changes, is also related to soil (SOC) and particulate (POC) organic carbon, and is frequently determined by farmers in Mollisols of the Southeastern Argentinean Pampas to support soil fertility diagnosis. We hypothesize that AN is positively related to and can be used as indicator of AS. Soil samples were taken at 0–5 and 5–20 cm depths from 46 sites throughout the southeastern Buenos Aires province, Argentinean Pampas. In each site, we sampled Mollisols under continuous cropping (CC) and others that had not been disturbed for many years (pseudo-pristine, PRIS). We determined texture, SOC, mineral-associated organic C, POC, AS and AN. We also calculated variable values for 0–20 cm. Soil organic carbon, POC, AN and AS were reduced by continuous cropping. Anaerobically mineralizable N was positively related to SOC (R2 = 0.74, 0.46, and 0.62 at 0–5, 5–20, and 0–20 cm) and POC (R2 = 0.73, 0.33, and 0.60, respectively). An important proportion of the total variability in AS was explained by SOC (R2 = 0.77, 0.65, and 0.73 at 0–5, 5–20, and 0–20 cm, respectively), POC (R2 = 0.75, 0.63, and 0.73, respectively), and AN (R2 = 0.78, 0.69, and 0.81, respectively). The AS increased with the increase of SOC, POC, and AN at all three depths, with slopes that did not differ between CC and PRIS, but with intercepts that differed. Neither sand nor clay contents significantly contributed to explain the variations in AS as a function of SOC, POC, and AN. An independent validation of the regression model relating AS and AN at 0–20 cm was done and the output was very good (RPIQ (ratio of performance to interquartile distance) = 2.20). Results support our hypothesis because AN was positively related to AS. Consequently, AN would be a good indicator of AS, SOC, and POC. Based on our results, we consider that a simple and cheap soil analysis as AN can not only be used to diagnose soil fertility, but to monitor soil physical and biochemical health status.

Variabilidade espacial da estabilidade de agregados e estoque de carbono em Cambissolo e Argissolo

O avanço de atividades agropecuárias, sem considerar as condições estruturais do solo, finda no detrimento destes ambientes. Este trabalho objetivou avaliar a variabilidade espacial da estabilidade de agregados, densidade do solo, carbono orgânico total (COT) e estoque de carbono de áreas de campo natural e floresta, na região de Humaitá (AM). Os solos foram amostrados nos pontos de cruzamento de uma malha de 70 m x 70 m, em intervalos regulares de 10 m, às profundidades de 0,0-0,05 m; 0,05-0,10 m; e 0,10-0,20 m, totalizando 64 amostras por profundidade. Os resultados da análise geoestatística mostraram dependência espacial dos atributos avaliados. Os menores alcances foram decorrentes das constantes variações na forma do relevo da área de campo natural. Os valores médios respectivos do índice de estabilidade diâmetro médio ponderado (DMP) e COT, em torno de 3,0 mm e 29,0 g kg-1 da camada superficial, similares aos das áreas de campo natural e floresta, confirmam a correlação proporcional entre os teores de COT e o DMP. Todavia, os níveis de densidade do solo superiores a 1,40 kg dm-3 expressam a ineficiência das funções estruturais do solo da área de campo natural. Os valores de estoque de carbono, nas diferentes profundidades, mostraram-se mais favorecidos pelos teores de COT que em razão dos diferentes níveis de adensamento dos solos estudados.

Spatial variability of aggregate stability in latosols under sugarcane

The spatial variability of soils under a same management system is differentiated, as expressed in the properties. The spatial variability of aggregate stability of a eutrophic Red Latosol (ERL) and a dystrophic Red Latosol (DRL) under sugarcane was characterized. Samples were collected in a regular 10 m grid, in the layers 0.0-0.2 and 0.2-0.4 m, with 100 points per area, and the following properties were determined: geometric mean diameter (GMD) of aggregates, mean weight diameter (MWD) of aggregates, percent of aggregates in the > 2.0 mm class and organic matter (OM) content. The eutrophic Red Latosol (ERL) had a higher aggregate stability thn the dystrophic Red Latosol (DRL), which may be attributed to the higher clay and OM content and the gibbsitic mineralogy of this soil class. The differentiated evolution of the studied Oxisols explains the wider range and lower variation coefficient and variability, for all properties studied in the eutrophic Red Latosol.

Aggregate stability in range sandy loam soils Relationships with runoff and erosion

Abstract The spatial variability of soil aggregate stability and its relationship to runoff and soil erosion were examined in a catena of soils and vegetation in a semiarid environment at the Rambla Honda field site (Tabernas, Almeria, SE Spain) to evaluate the validity of structural stability as a soil erosion indicator in sandy loam range soils. The influence of soil properties and topography on the variability of aggregate stability was also examined. Methods include: 1) aggregate stability assessment at 12 sites (3 repetitions per site) on the hillslope by two methods: a) aggregate size distribution by dry sieving b) water drop test; 2) soil organic carbon content; 3) particle size distribution determination; 4) terrain attributes derived from a digital elevation model (1-m resolution); 5) monitoring runoff and erosion for nearly 3 years in eight (10 × 2 m) plots distributed over the hillslope. Results: 41% of the average soil mass is formed by > 2-mm aggregates. However, wet aggregate stability is poor, with a mean (of a total of 1440 aggregates) of only 26 drop impacts necessary to break up a wet aggregate (pF = 1). Significant relationships were found in the number of water drops required for aggregate breakdown and runoff and erosion rates. However, no significant relationships between the mean weight diameter of aggregates under dry conditions and runoff or erosion rates were observed. The relationships of aggregates with other soil properties, hillslope position and proximity to plants are also analysed. The most significant correlation found was between the number of drop impacts and soil organic matter content. The stability of topsoil aggregates seems to be a valuable indicator of field-assessed runoff and inter-rill erosion of sandy loam range soils under semiarid conditions.

Carbohydrates and aggregation in lowland soils of Nigeria as influenced by organic inputs

We evaluated the influence of several organic matter management practices on the characteristics of carbohydrates in water-stable aggregates and soil aggregate stability at three Nigerian locations (Abakiliki, Nsukka and Umudike) where forests had been converted to arable farming. The effect of management practices to enhance aggregate stability was site-specific. The highest aggregate stability was obtained with Gliricidia sepium at Abakiliki, with Cajanus cajan followed by rice mill wastes (RW) at Nsukka and with the forested soil at Umudike. While none of the treatments at all sites was able to enhance the C and N contents of the soils to the levels obtained in the forested sites, a net improvement in carbohydrate and organic carbon (OC) content was found for some management practices. The carbohydrate status increased with G. sepium at Abakiliki, and with Dactylodenae bacterii alone or in combination with Pentaclethra species at Umudike, while at Nsukka all organic inputs increased carbohydrate content over the control and forested soils. However, neither total OC nor the carbohydrate content were significantly correlated to the variability in aggregate stability of these soils. The δ 13 C values found for acidic hydrolysates were constant within the soil aggregate sizes and generally distributed around −29 to −30‰, suggesting that the OC from these sites originated from C3 plants. Our results indicate that in these tropical Nigerian soils, aggregate stability and OC content are generally preserved by alley-cropping in well structured soil, whereas treatments with organic wastes are sustainable management practices in more fragile soils.

Título en español.

Se presenta en este trabajo una evaluación matemática del efecto de factores tales como el contenido de arcilla, limo, materia orgánica, calcio + magnesio y sodio soluble sobre la estabilidad de los agregados de un grupo de Vertisols del Valle de Lajas, Puerto Rico. Las relaciones entre la estabilidad de los agregados y el contenido de arcilla y limo no fueron significativas. Cuando se incluyó el contenido de materia orgánica como otra variable independiente se obtuvo un coeficiente de correlación de 0.66 que resultó ser altamente significativo. Por lo tanto, se logró explicar casi el 43 porciento de la variabilidad en estabilidad de los agregados a base de esta sola variable. Cuando se trató de explicar una mayor proporción de la variabilidad en términos del contenido de Ca + Mg y de sodio soluble se obtuvieron coeficientes de correlación de 0.70 y 0.74, respectivamente. De manera que, solamente una pequeña, pero significativa, porción adicional de la variabilidad puede atribuirse a estas variables.

Título en español.

Se informan aquí los resultados de estudios estadísticos realizados con la intención de evaluar el grado de estabilidad de los agregados o unidades estructurales de un número seleccionado de suelos del Valle de Lajas en términos de los contenidos de materia orgánica, arcilla o limo. Los análisis de regresión sencilla revelaron que no hay correlación entre la estabilidad de los agregados y el contenido de arcilla o limo. Sin embargo, cuando el contenido de materia orgánica se consideró como la variable independiente se encontró una correlación altamente significativa. A pesar del alto nivel de correlación, solamente es posible explicar un 16 por ciento de la variación en estabilidad de los agregados a base del contenido de materia orgánica. Esto limita considerablemente la utilidad posible de hacer estimados por medio de la ecuación matemática desarrollada.