Improvement Of Aggregate Stability Research Articles

Sustainable soil management: Insights from a 47-year maize-wheat cropping system study

Continuous monitoring of soil quality is vital to understand the effects and to identify best management practices for sustainable agroecosystems. This study focuses on evaluating the soil quality and crop yield sustainability in a long-term maize-wheat cropping system experiment spanning 47 years. Physical, chemical, and biological soil quality indicators were assessed at two soil depths (0–0.15 m and 0.15–0.30 m) under eleven fertilizer and amendment regimes i.e., 50 % NPK, 100 % NPK, 150 % NPK, 100 % NPK + Zn, 100 % NPK+ hand weeding, 100 % NP, 100 % N, 100 % NPK + farmyard manure (FYM), 100 % NPK(S), 100 % NPK + lime and control, laid out in a completely randomized block design. Principal component analysis (PCA) was employed to select a minimum data set (MDS) of indicators for soil quality assessment, followed by weighted additive approach to calculate the soil quality index (SQI). Results showed that balanced dose of NPK fertilizers, in combination with FYM or lime, enhanced average wheat grain yield by 39.9 and 29.4 % over sole 100 % NPK fertilizers, respectively. Treatment 100 % NPK + FYM recorded a significant improvement in aggregate stability, available nutrients, microbial biomass over control and 100 % NPK. The highest value of SQI (0–0.15 m) was recorded in 100 % NPK + FYM (0.99), followed by 100 % NPK + lime (0.86) and lowest in 100 % N (0.41). Omission of NPK, PK, K and S from fertilizer regime caused a decline of respective 33, 39, 22 and 6 % in the SQI, whereas, all the treatments recorded a decline in SQI in sub-surface layer. The average contribution of MDS towards the SQI of 0–0.15 and 0.15–0.30 m depth was labile carbon (LC) (30 %) > microbial biomass N (MBN) (28 %) > mean weight diameter (MWD) (17 %) > pH (16 %) > available K (6 %) and LC (33 %) > N mineralization (24 %) > MWD (22 %) > pH (21 %), respectively. The SQI positively correlated with average grain yield and SYI, highlighting the importance of soil quality for sustainable crop production. This research underscores the significance of continuous soil quality monitoring and use of balanced fertilization, organic manure and lime in maintaining soil health and crop productivity in agroecosystems.

The effect of organic matter amendments on soil surface stability in conventionally cultivated arable fields

AbstractIn this study, new and traditional organic wastes (green waste compost, farmyard manure (FYM), anaerobic digestate or straw) were ploughed into an arable field experiment at a range of rates (1–3 t C ha−1) and under spring and winter cropping rotations for 5 years. The stability of the soil surface structure (<5 cm) was assessed in Years 3, 4 and 5 to guide the use of organic wastes in arable field management. Aggregate stability was determined by immersing each soil sample in water (fast‐wetting test, relevance to summer storms) and measuring the size distribution of the aggregates (mean weight diameter, MWD). The MWD value was compared with the different classes of aggregate stability (very stable, stable, medium, unstable or very unstable) to classify each result. All the arable field samples were classified as unstable, and there were no significant differences (p > .05) in MWD after any treatment. Potentially, this approach is too imprecise to detect differences, so pore‐scale analyses using CT scanning were used. There were no significant differences in porosity or pore shape (features associated with microbial activity) between the control and organic waste treatments. The results contradicted published data from the Broadbalk experiment (established in 1843), which was the basis for this study, so its soils were studied to understand this discrepancy. Broadbalk soils were classified as unstable, including soils treated with annual FYM applications. Instead, we found a significant relationship between MWD and clay content and previous interpretations had not taken this variable (23%–39% clay content) texture into consideration. In conclusion, to achieve a stable soil surface structure, a 150% improvement in aggregate stability would be needed here and ploughing in organic wastes was not a successful management approach on these arable field experiments.

Working with UK farmers to investigate anecic earthworm middens and soil biophysical properties

AbstractThe conversion from conventional tillage to no‐tillage soil management practices is generally associated with an improvement in aggregate stability and anecic earthworm populations. We worked with UK farmers who measured Lumbricus terrestris midden area (%) and earthworm numbers associated with middens compared to the general soil. They found that middens covered up to 42% of the soil surface. Middened soil (i.e., soil underlying the middens) was associated with significantly more earthworms than the general soil (i.e., non‐middened soil) in agreement with research from scientific field trials. We compared the biophysical properties of middened soil to general soil across an experimental field trial recently converted to no‐tillage soil management practices. We measured water‐stable aggregation, soil porosity at scales relevant to water storage and gas diffusion and invertebrate feeding activity. Middened areas covered up to 13% of the field trial and were associated with significantly improved aggregate stability and porosity compared to the general soil. Our findings highlight the importance of considering middens when surveying soil quality and health in arable systems.

Effects of fire on the aggregate stability of clayey soils: A meta-analysis

Fire is a natural phenomenon that affects the Earth's biogeochemical cycle. Wildland fires are increasing in frequency and magnitude, possibly owing to climate change. In addition, fire is applied as a tool in agro-ecosystem management. However, several detrimental effects on soil properties, particularly on soil aggregate stability, might occur. A general explanation is that “the effects of fire on soil aggregate stability in soil with high clay content, calcium carbonate, and Fe and Al oxides as the principal cementing substances cause gradual improvement in aggregate stability, following fire-heating severity.” In short, the higher the fire severity, the higher is the aggregate stability. A meta-analysis was conducted for assessing the laboratory and field studies to verify this concept. The Scopus® platform was used to search for the literature related to “soil aggregate stability” AND fire OR heating AND clay OR “clayey soil.” A total of 10 studies were selected with 16 soil types, 244 burned or heated samples, and 160 control samples. The meta-analysis was performed using RevMan 5.3 software. Meta-analysis was delineated according to the following assumptions: a) field and laboratory studies were tested as two independent subgroups, and a pooled effect was subsequently calculated; b) a random-effects model was used; c) mean differences with 95% confidence intervals were computed for continuous variables. Laboratory and field measurements showed dissimilar effects on soil aggregate stability and evidenced positive effects in the laboratory experiments compared with those in the field. Aggregate stability measured in the laboratory increased by 2.80% after heating. Fire effects measured in the field did not show a significant increase in soil aggregate stability (−0.16%). The overall effects of combined subgroups showed an aggregate stability improvement of 1.49% (confidence intervals 0.80% to 2.17%). However, the weight of the results from the laboratory studies played an important role in the overall effect. The soil clay content was found to be inversely associated with aggregate stability, i.e., the lower the clay content the higher the aggregate stability in soil subjected to fire heating. In conclusion, the aggregate stability of clayey soils rich in Al and Fe oxides does not necessarily improves following fire heating.

Impact of biochar and compost on aggregate stability in loamy sand soil

Biochar and compost are important organic amendments which act as cementing agents and increase the aggregate stability in the sandy soils. The main idea of this study was to investigate the impact of date palm waste biochar, compost and their mixture on soil aggregate stability at the rate of 1, 2, 3 and 4%. The objectives were to evaluate the changes in indicators of aggregates stability to water due to biochar, compost, and biochar-compost addition and to study the impact of biochar and compost on sandy soil erodibility. Water stable aggregates (WSA), macroaggregates (WSA>0.25), mean weight diameter (MWD), geometric mean diameter (GMD) and erodibility factor (Kerodibility) were measured and evaluated. The results showed that the indicators of WSA, WSA>0.25, MWD, GMD and Kerodibility were 76.35, 15.94%, 0.19, 0.39 mm and 0.09 for control (unamended soil), respectively. The WSA, WSA>0.25, MWD, GMD and Kerodibility were enhanced with different rates of biochar and compost. However, biochar exhibited a significant improvement in aggregate stability and their effect was slightly better than compost. Accordingly, biochar increased WSA (24.6-31%), WSA>0.25 (69.9-164.2%), MWD (57.5-121.6%), GMD (24-44.2%), and decreased Kerodibility (18.8-31.1%). Compost increased WSA (7.8-45.3%), WSA>0.25 (11.1-45.3%), MWD (9.7-36.5%), GMD (5.1-17.5%) and deceased Kerodibility (4.7-14.5%) compared with unamended soil. Therefore, the amendment materials reduced the soil erosion and led to increased aggregation stability against erodibility. The results of this study can be helpful in predicting the behavior of biochar and compost amendments towards aggregate stability in loamy sand soils.

Effects of combined organic manure and mineral fertilization on soil aggregation and aggregate-associated organic carbon in two agricultural soils

The effect of organic manure and inorganic fertilizer on soil aggregate size distribution and stability, and associated carbon (C) within aggregates varies greatly in previous studies because of the differences in soil conditions, cropping systems, and management practices. This study was conducted as two field fertilization experiments, with different cropping systems, under a subtropical climate in China. The two field experiment sites were located in Jinhua (established in April 2011) in the Jinqu basin in Zhejiang province and Jintan (established in October 2010) in the low-middle Yangtze River plain in Jiangsu province. Both experiments consisted of four treatments, including unfertilized (CK), mineral fertilizer nitrogen (N)–phosphorus (P)–potassium (K) (NPK), NPK plus straw (NPK + SR), and NPK plus cattle manure (NPK + FYM) or half NPK plus cattle manure (1/2NPK + FYM). Water stable aggregate size classes (>5, 2–5, 1–2, 0.5–1, 0.25–0.5, and <0.25 mm) and associated soil organic C (SOC) at 0–15 cm depth were measured. The mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregates (WSA) > 0.25 mm were also determined. The results showed that aggregate-size distribution varied with soil types. Combined application of NPK and organic matter (straw residue or cattle manure), unlike the CK and NPK treatments, significantly increased the WSA >0.25 mm, MWD, and GMD, while obviously reducing the proportion of <0.25 mm aggregates. However, no differences in WSA >0.25 mm, MWD, GMD, and associated C were observed between CK and NPK at both sites. The addition of FYM to the NPK treatment yielded the highest SOC contents in bulk soil, and showed significantly higher associations of C within all size aggregates at both sites. In contrast, NPK + SR significantly increased SOC within aggregate classes (2–5 mm, 0.5–1 mm, 0.25–0.5 mm, and <0.25 mm) at Jinhua and (>5 mm and 1–2 mm) at Jintan compared to the CK and NPK treatments. Overall, the combined application of FYM and mineral NPK was the best sustainable management practice for the improvement of aggregate stability and SOC sequestration.

The effect of straw and wood gasification biochar on carbon sequestration, selected soil fertility indicators and functional groups in soil: An incubation study

Annual removal of crop residues may lead to depletion of soil organic carbon and soil degradation. Gasification biochar (GB), the carbon-rich byproduct of gasification of biomass such as straw and wood chips, may be used for maintaining the soil organic carbon content and counteract soil degradation if applied to soil. This study investigated the effect of straw removal and GB addition on soil biological, chemical and physical properties in a 22-months soil incubation study with a temperate sandy loam soil.Soil application of wood and straw GB (WGB and SGB) resulted in very low CO2 emissions, confirming the stability of the material against microbial degradation. Both GBs increased total organic carbon, cation exchange capacity and pH of the soil. The application of SGB and WGB did not affect aggregate stability, whereas SGB did not affect and WGB decreased clay dispersibility. In contrast, the addition of straw resulted in a high soil respiration rate, and about 80% of the added carbon was respired at the end of the incubation. However, the addition of straw increased aggregate stability and decreased clay dispersibility. Results from Fourier transformed infrared photoacoustic spectroscopy revealed a lower content of O–H and aliphatic C–H together with a higher content of aromatic groups in soils amended with GB compared to soils amended with straw. This suggested that the improvement in aggregate stability in straw treatments could be related to microbial derived aliphatics and simple sugars, and that increased stability against microbial degradation in biochar amended soil was related to highly condensed aromatic groups. Addition of nutrients (N, P and S) together with straw resulted in higher soil respiration compared to the straw treatment, but did not cause differences in other soil processes.Results from this study suggest that GB has a potential for increasing soil carbon sequestration, CEC and pH. However, the straw turnover process plays a vital role for aggregate stability and clay dispersibility. Thus, annual straw removal on loamy soil needs to be considered with care in order to avoid soil degradation and risk of soil compaction or erosion.

Structure alteration of a sandy-clay soil by biochar amendments

The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. 1H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased as the amount of biochar was raised up. The 1H NMR relaxometry revealed a unimodal T 1 distribution for both the sole sandy-clay soil and the biochar. Conversely, a bimodal T 1 distribution was acquired for all the different f bc samples. Improvement in aggregate stability was obtained as biochar was progressively added to the sandy-clay soil. A dual mechanism of water retention has been hypothesized. In particular, intra-aggregate porosity was indicated as the main responsible for molecular water diffusion when f bc comprised between 0 and 0.33. Conversely, inter-aggregate porosity resulted predominant, through swelling processes, when f bc overcame 0.33.

Effects of Poultry Manure and NPK Fertilizer on Physical Properties of a Sandy Soil in Ghana

Field experiment was conducted during the rainy season at the experimental field of the Department of Horticulture, Faculty of Agriculture, Collage of Agriculture and Renewable Natural Resources, Kwame Nkrumah University of Science and Technology to test the effects of poultry manure and NPK fertilizer on the physical properties of a sandy soil. There were five treatments with five replications. The experiment was laid in Randomized Complete Block Design. Data were collected on the following soil physical properties: bulk density, total porosity, aeration porosity, volumetric water content, aggregate stability. The results suggest that the poultry manure decreased the dry bulk density, increased the total porosity and increased the moisture content. However, there were no significant improvement in aggregate stability and aeration porosity. The mineral fertilizer did not show any significant improvement in any of the parameters. In the short term Poultry manure was therefore found to improve some physical properties of the sandy soil.

Changes in soil properties and nematode population status under planted and natural fallows in land use systems of southern Cameroon

Changes in soil properties and nematode population status under Flemingia macrophylla [(Willd.) Merrill], Pueraria phaseoloides (Roxb.) Benth, and natural bush fallows were assessed in three villages in southern Cameroon. In each village, experiments were set up in a 4–5 year-old bush fallow dominated by Chromolaena odorata (L.) R. M. King and H. Rob and a more than 20 year-old secondary forest. Total aboveground biomass production of P. phaseoloides was 7.45 Mg ha−1, 4.2 times higher than F. macrophylla (1.78 Mg ha−1; P < 0.05). In two years (24 MAP), the soil bulk density under P. phaseoloides, F.macrophylla and the natural regrowth in both bush and forest land use systems decreased (P < 0.05). Within the same period, there was a general improvement in aggregate stability. The particle size distribution changed over 3 years (36 MAP), such that at 0–10 cm depth, the percent sand content had reduced whiles the percent clay content had increased under all the fallow systems in both bush and forest land use systems (LUSs). Soil N also increased significantly (P < 0.05) after cropping under all the fallow systems in both LUS. In contrast, soil organic carbon decreased, but the extent was lower under P. phaseoloides and F. macrophylla compared to the natural regrowth. Soil P also decreased after cropping under all the fallow systems in both LUS whereas decrease in Mg was only observed under P. phaseoloides. F. macrophylla had Mg content after cropping similar to the initial in both LUS. Soil contents of K and Ca were not significantly different over time under all the fallow systems. Comparing the initial Helicotylenchus multicinctus population to that at 12 MAP, both P. phaseoloides and F. macrophylla reduced density of H. multicinctus (P < 0.05). However, when the initial population density was compared to that at 24 MAP only under P. phaseoloides was the reduction maintained. The study concluded that the general improvement in the soil physical properties, impacted positively on the N and organic carbon contents which were sustained to a larger extent under the planted fallows than the natural regrowth. Furthermore, P. phaseoloides could be used as one component for the biological control of Helicotylenchus multicinctus, a phytopathogenic nematode.

Dynamics of aggregate stability and biological binding agents during decomposition of organic materials

SummaryThe relative importance of different binding mechanisms and associated biological binding agents on aggregate stability is still unclear. The aim of this study was to evaluate the role of various aggregate binding agents during the decomposition of cauliflower residues, wheat straw, cattle manure and poultry woody compost. We measured aggregate stability, hot‐water extractable polysaccharide, C mineralization, fungal and microbial biomass dynamics in an amended silt loam soil, under controlled conditions. Soil aggregate stability was measured using three methods involving fast wetting, slow wetting and mechanical breakdown. Aggregate stability to slow wetting followed the same dynamics as C mineralization and was well correlated with polysaccharide content for cauliflower residues and wheat straw. This relationship is in agreement with the hypothesis that the rapid microbially induced improvement in aggregate stability that follows fresh organic residue additions at least partly involves labile polysaccharides. The transient increase in the two other types of stability was not directly related to C mineralization dynamics and seemed to be influenced by fungal hyphal length. Fungi would provide resistance to mechanical breakdown and slaking. The dynamic behaviour of biological binding agents was only partly explained by the initial quality of the organic materials, as characterized by Van Soest proximal fractionation.Dynamique de la stabilité structurale et des facteurs agrégeants biologiques associée à la décomposition de produits organiques.RésuméL’importance relative des différents mécanismes d’agrégation et des facteurs agrégeants biologiques associés n’est toujours pas clairement établie. L’objectif de cette étude est d’évaluer l’effet de différents facteurs agrégeants sur la stabilité structurale au cours de la décomposition de produits organiques: de résidus de chou‐fleur, de paille de blé, d’un fumier de bovin et d’un compost de fientes de volailles et d’écorce de peuplier. Nous avons mesuré les dynamiques de stabilité des agrégats, de minéralisation du C et des biomasses microbienne et fongique d’un sol limoneux amendé pour des conditions contrôlées. La stabilité structurale est mesurée par trois traitements d’intensités différentes correspondant à une humectation rapide, une humectation lente et une désagrégation mécanique sur des agrégats. La stabilité structurale soumise à l’humectation lente suit les mêmes dynamiques que la minéralisation du C et est bien corrélée avec la concentration en polysaccharides pour les résidus de chou‐fleur et la paille de blé. Cette corrélation confirme l’hypothèse que les polysaccharides labiles participent au moins partiellement à l’amélioration rapide de la stabilité des agrégats induite par l’activité microbienne à la suite d’apports de produits organiques frais. L’augmentation transitoire des deux autres types de stabilité structurale n’est pas directement liée aux dynamiques de minéralisation du C et est plutôt influencée par la longueur des hyphes mycéliens. Le rôle des champignons serait alors d’accroître la résistance des agrégats soumis à des forces de désagrégation plus importantes. Le comportement des différents agents agrégeants biologiques n’est que partiellement expliqué par la composition initiale des produits organiques, caractérisés par la méthode de fractionnement Van Soest.

Effects of winter cover crops and successive spring tillage on soil aggregation

In the Fraser River Delta of British Columbia, Canada, one in three farms faces soil problems associated with poor structure and low organic matter content. Surface soil structure usually degrades in early spring due to prolong wet conditions and a lack of surface cover during winter. Rates of change of surface soil aggregation under different overwinter cover crops followed by spring tillage operations were studied on a lowland soil in the Fraser River. Cover cropping treatments were bare control, winter-killed spring barley ( Hordeum vulgare L.) (cv. Virden), fall rye ( Secale cereale L.) (cv. Danko) and annual ryegrass ( Lolium multiflorum Lam.) (cv. Westerwolds). Aggregate stability, expressed as mean weight diameter (MWD) and the 2–6 mm aggregate-size fraction, decreased from fall to spring, then increased again over summer months. This seasonal variation in MWD was much more pronounced in the least stable bare soil than in the more stable cover cropped soils. In spring, overwinter cover crops had significantly higher MWD and the proportion of 2–6 mm water-stable aggregates up to 0.75 mm and 0.27 kg kg −1, respectively, when compared to bare control soil. Improved aggregate stability with cover crops was related to increasing organic carbon in the soil. After the plots were cultivated in spring, winter cropped soils had lower proportion of > 6 mm clods up to 0.28 kg kg −1 than did soils left bare over winter. On the other hand, tilled plots had higher MWD and 2–6 mm aggregates for all cover cropping treatments due to lower aggregate water content at sampling, when compared to no-tilled plots. Overall, the greatest improvement in aggregate stability was observed under annual ryegrass, followed by fall rye and winter-killed spring barley. The results suggest that winter cover crops, such as annual ryegrass, may protect aggregate breakdown during winter and result in better structure after spring tillage operations when compared to the bare soil.

Effects of coal derived humic substances on water retention and structural stability of Mediterranean soils

Abstract. The potential for using coal‐derived humic substances to improve the available water holding capacity (AWC) and aggregate stability of typical Mediterranean soils was evaluated in the laboratory using an agricultural surface (0–20 cm) soil from each of three regions of Italy, (Sicily, Tuscany and Venetia) and five rates of humic acids (HA), 0,0.05,0.10,0.50 and 1.00 g/kg. There were significant (P &lt; 0.05) differences between the field capacity (FC), permanent wilting point (PWP), and available water capacity (AWC) values of the controls and those treated with 0.05 g/kg of the HA. Beyond this rate, differences in these properties were not significant. At the 1.00 g/kg HA rate, the relative improvements in AWC over the three controls were 30%, 10% and 26%. Low rates (0.05 to 0.10 g/kg) of HA were also needed to obtain a 40 to 120% improvement in aggregate stability of these soils relative to the controls. These results indicate that the addition of highly humified organic matter such as coal‐derived humic substances can improve the structural and water retention properties of degraded arable soils. However, since there is not yet any direct evidence that these humic materials can ameliorate soils under field conditions, field studies will be needed to validate these results.