Soil Mean Weight Diameter Research Articles

Unraveling the impact of global change on glomalin and implications for soil carbon storage in terrestrial ecosystems

Glomalin-related soil protein (GRSP) is a potential byproduct of arbuscular mycorrhizal fungi (AMF) and a major contributor to the passive soil organic carbon (SOC) pool. Despite its crucial role in SOC storage, we know little about the response of GRSP to anthropogenic global change factors (GCFs). Here, using 530 observations from 107 primary studies, we conducted a global meta-analysis to unravel the effects of multiple GCFs (climate change, plant invasion (PI), wildfire, urbanization, land-use change (LUC), and nutrient addition (nitrogen; N, phosphorus; P, and potassium; K) on two functional GRSP fractions (easily extractable- (EE-) and total- (T-) GRSPs) in terrestrial ecosystems. We found that elevated carbon-dioxide increased T-GRSP by 28%, combined NP addition by 39.9%, and NPK addition by 29.5%. Climate warming and alone N addition increased EE-GRSP solely by 2.4% and 13.6%, respectively, but did not influence T-GRSP. However, urbanization and drought decreased T-GRSP by 26% and 15%, respectively. The LUC from natural ecosystems to cropland decreased T-GRSP by 40%, while afforestation in croplands increased it by 32%. Other GCFs (PI, wildfire, and P) had non-significant effects on GRSP probably because of (i) minor changes in AMF activity and (ii) the counterbalancing of effects by opposite processes. GCF impacts were robust when applied at higher intensities for medium-to-long durations (3–10＋ years) in humid conditions and clay-rich soils. The sandy soils experienced greater T-GRSP losses during LUC. Increases in T-GRSP were positively correlated with AMF-root colonization, soil mean-weight diameter, and SOC content. Further, our structure equation model confirmed that GCFs directly influence SOC by altering AMF-GRSP production and indirectly affecting soil aggregate formation and protection, suggesting that optimizing GRSP production can enhance SOC sequestration.

Does biochar combined with cover crops improve health and productivity of sandy, sloping, and semi‐arid soils?

AbstractBiochar may improve the health of environmentally sensitive soils (i.e., low C, sandy, sloping) especially if combined with cover crops (CCs), but research is scant. We assessed how wood biochar (836 g C kg−1) applied at 0, 6.25, 12.5, 25, and 50 Mg ha−1 to sandy, sloping, and semi‐arid soils with and without CCs affects soils and crop yields in the central US Great Plains for 3 years. We measured crop yields and CC biomass each year, and most soil properties in Years 1 and 3. Biochar did not interact with CCs, suggesting the combination was no better than biochar or CC alone. In the semi‐arid soil, crop and CC did not establish due to persistent droughts. Biochar benefits were highly site‐specific. Biochar improved some soil properties but only in the sandy and sloping soils and at the biochar application depth (0‐ to 15‐cm soil depth). The 50 Mg biochar ha−1 improved the soil's ability to sorb water (0.08 cm s−1/2). Also, in the sandy soil, it increased soil organic matter concentration (2.5 g kg−1), soil pH (0.65 units), and available water (0.07 m3 m−3) only in Year 1, suggesting a biochar benefit in sandy soils is short‐lived. In the sloping soil, >25 Mg biochar ha−1 reduced bulk density (0.16 Mg m−3) and increased soil mean weight diameter of water‐stable aggregates (0.58 mm), organic matter concentration (11.42 g kg−1), infiltration (9.35 cm), CC biomass production (0.27 Mg ha−1), and some microbial biomass groups. Biochar did not affect crop yields. Overall, >25 Mg biochar ha−1 improved properties in some soils without interacting with CCs.

Enhancing Soil Aggregate Stability and Organic Carbon in Northwestern China through Straw, Biochar, and Nitrogen Supplementation

Enhancing soil stability through the incorporation of straw and biochar is well documented. Nevertheless, the combined impact of straw, biochar, and nitrogen supplementation on soil aggregates and organic carbon still needs to be explored, with limited attention given to various sieving methods in the existing literature. Therefore, the current experiment used four sieving methods—routine wet sieving (RoutW), fast-wetting sieving (FastW), slow-wetting sieving (SlowW), and wetting–stirring sieving (WetS)—to investigate the effects of adding straw (0 or 4.5 t ha−1), biochar (from maize straw, 0 or 15 t ha−1), and N (0 or 100 kg ha−1) on soil aggregate stability and soil organic C in silt–loam soil of rainfed farmland in northwest China. The field experiment was started in 2014; soil samples were collected in 2021. The results revealed that straw returned, biochar, and N addition significantly increased soil mean weight diameter (MWD) and soil organic C (SOC). Compared to CN0 (zero-amendment) plots, straw returned with nitrogen addition (SN100) significantly increased the MWD of aggregates by 130.3% (RoutW), 121.66% (FastW), 73.94% (SlowW), and 91.78% (WetS) in the 0–30 cm soil layer. The addition of biochar and nitrogen (BN100) treatment showed the most significant effects on the relative slaking index (RSI), relative mechanical breakdown index (RMI), and SOC; compared with CN0 treatment, BN100 plots can reduce RSI and RMI by 42.90% and 54.66% and increase SOC by 53.27% for all soil layers. Therefore, adding organic materials with N can enhance the stability of soil aggregates and SOC of silt–loam soils in northwest China. Integrating biochar as an organic soil amendment in the agricultural practices of northwest China presents a multifaceted solution that addresses soil health, crop productivity, and environmental sustainability. The current study provides valuable insights that support adopting this innovative approach, paving the way for future sustainable agricultural practices that can benefit both the region and the global community.

Experimental and Modeling Evaluation of Impacts of Different Tillage Practices on Fitting Parameters of Kostiakov’s Cumulative Infiltration Empirical Equation

The evaluation and modeling of the water infiltration rate into the soil are important to all aspects of water resources management and the design of irrigation systems for agricultural purposes. However, research focused on experimental studies of infiltration rates in clay soils under different tillage practices remains minimal. Therefore, an empirical prediction model for cumulative water infiltration needs to be created to estimate water depth under different tillage practices. Thus, the present research investigated the impacts of different tillage practices, including plow type (three tillage systems: moldboard, disk, and rotary plows), tillage depth (100 and 200 mm) and four soil compactions levels (0, 1, 3, and 5 tractor wheel passes), on cumulative infiltration behavior in a clay soil under a randomized complete design with three replications. Double-ring infiltration experiments were conducted to collect infiltration data. The research was conducted in three different stages. The first stage was performed through a field test to obtain infiltration data, the second stage involved using a Kostiakov empirical equation (Z = q × tb) for cumulative infiltration to acquire the fitting parameters of “q” and “b”, and in the last stage, we predicted the fitting parameters of “q” and “b” based on soil mean weight diameter, tillage depth, and four soil compaction levels by applying regression data mining approaches in Weka 3.8 software. The results show that the effects of relevant factors on the cumulative water infiltration depth of the soil could be statistically significant (p < 0.05). The Kostiakov model, with an average coefficient of determination of 0.939, had a good fitting effect on the cumulative water infiltration depth process of the investigated soil. The average, lowest, and maximum values of the “q” parameter were 2.7073, 2.2724, and 3.1277 mm/minb, respectively, while for the “b” parameter, they were 0.5523, 0.5424, and 0.5647, respectively. Furthermore, the evaluation of several regression data mining approaches determined that the KStar (K*) data mining approach, with a root mean square error of 0.0228 mm/minb, a mean absolute error of 0.0179 mm/minb, and a correlation coefficient of 0.997, was the most accurate method for fitting parameter “q” using the testing dataset. The most accurate method for fitting the parameter “b” estimation was determined to be the Multilayer Perceptron method, with a root mean square error of 0.0026, a mean absolute error of 0.0013, and a correlation coefficient of 0.962, using the testing dataset. Therefore, this research, which consisted of in situ field observation experiments and infiltration modeling of the infiltration process in a clay soil, provides an essential theoretical basis for improving models of the rate of cumulative infiltration. Moreover, the proposed methodology could be employed for simulation of the fitting parameters “q” and “b” for soil water cumulative infiltration processes, not only for irrigation management purposes under regular crop production conditions, but also for the selection of the most suitable tillage practices to modify the soil during the agriculture season to conserve water and prevent yield declines. The results support the understanding of the infiltration processes in a clay soil and demonstrate that tillage practices could reduce the water infiltration rate into the soil.

Agricultural soil aggregation is affected by the crop root biomass rather than morphological characteristics

AbstractBackgroundIn areas prone to water erosion, crop selection strategies should be based on assessment of their effects on soil structural properties.AimsThe present study compared the effects of the cultivation of forage maize (Zea mays L.) and forage oat (Avena sativa L.) and their cultivars on soil aggregation relative to potato (Solanum tuberosum L.) or wheat (Triticum aestivum L.) at a hydrothermally limited site on the Loess Plateau, China.MethodsThe water‐stable aggregate (WSA) distribution in soil was measured under three cultivars in each of maize, oat, wheat, and potato (a total of 12 cultivars from four crops) in their flowering stage of three cropping seasons, when root biomass was largest.ResultsIn each year, the water‐stable macroaggregates (>0.25 mm) content and mean weight diameter (MWD) of WSAs in the top 20 cm of soil did not differ between tested cultivars of every crop but increased under maize and oat, compared with those under wheat or potato. The increased soil aggregation under maize and oat, compared with wheat or potato, was consistent with the pattern of change in root biomass but was not consistent with the changes in root length density, root surface area, or root mean diameter across the crops. The water‐stable macroaggregates content and MWD of soil was positively correlated with root biomass across cultivars and crop species within each cropping season.ConclusionsWe suggest that increased root biomass under maize and oat relative to potato or wheat resulted in increased soil aggregation in maize and oat cultivated soils. It is demonstrated that, in areas prone to soil water erosion, planting high‐biomass‐yielding crops such as maize and oat is more beneficial for increasing soil aggregation and stability, compared with low‐biomass‐yielding crops such as wheat or potato.

Long-term manure fertilization increases rill erosion resistance by improving soil aggregation and polyvalent cations

Application of organic fertilizers is a potential practice to prevent soil erosion by changing the physicochemical properties of the soil, such as macroaggregates, soil organic carbon (SOC) content, and exchangeable cations. However, the practical performance of organic fertilizer in soil erosion after a long-term application has scarcely been reported. To reveal the response of soil erosion resistance (i.e., the soil susceptibility to resist external erosion force) to 43 years of organic fertilization, five treatments were investigated: (1) CK (no fertilizer), (2) NPK (mineral fertilizer), (3) M (pig manure), (4) MN1 (pig manure + 138 kg N ha−1), and (5) MN2 (pig manure + 276 kg N ha−1). The results showed that NPK, M, MN1, and MN2 significantly increased soil critical shear stress (τc) by 54 %, 87 %, 101 %, and 67 %, respectively, compared to CK. However, rill erodibility (kd) was increased significantly only in the MN2 treatment. The optimal partial least squares regression model showed that the increase in soil exchangeable Ca2+ was the dominant contributor to the τc increase, while soil mean weight diameter (MWD) had the greatest negative effect on kd. Compared with CK, the soil exchangeable Ca2+ in M and MN1 increased significantly by 123 % and 135 %, respectively. The MWD in M and MN1 increased by 86 % and 83 %, respectively, compared with that in CK. The application of pig manure was beneficial for decreasing exchangeable Na+ and increasing SOC content, which could improve MWD. Manure with a high N content did not increase MWD due to SOC decomposition. Our results indicate that the long-term application of manure, alone or combined with moderate N, improves rill erosion resistance.

Inclusion of fractal dimension in four machine learning algorithms improves the prediction accuracy of mean weight diameter of soil

The study of soil mean weight diameter (MWD), essential for sustainable soil management, has recently received much attention. As the estimation of MWD is challenging, labor-intensive, and time-consuming, there is a crucial need to develop a predictive estimation method to generate helpful information required for the soil health assessment to save time and cost involved in soil analysis. Pedotransfer functions (PTFs) are used to estimate parameters that are ‘difficult to measure’ and time-consuming with the help of ’easy to measure’ parameters. In the current study, empirical PTFs, i.e., multi-linear regression (MLR), and four machine learning based PTFs, i.e., artificial neural network (ANN), support vector machine (SVM), classification and regression trees (CART), and random forest (RF) were used for mean weight diameter prediction in Karnal district of Haryana, India. A total of 121 soil samples from 0‐15 and 15‐30 cm soil depths were collected from seventeen villages of Nilokheri, Nissing, and Assandh blocks of Karnal district. Soil parameters such as bulk density (BD), fractal dimension (D), soil texture (i.e., sand, silt, and clay), organic carbon (OC), and glomalin content were used as the input variables. Two input combinations, i.e., one with texture data (dataset 1) and the other with fractal dimension data replacing texture (dataset 2), were used, and the complete dataset (121) was divided into training and testing datasets in a 4:1 ratio. The model performance was evaluated by statistical parameters such as mean absolute error (MAE), mean absolute percentage error (MAPE), root mean square error (RMSE), normalized root mean square error (NRMSE), and determination coefficient (R2). The comparison results showed that including the fractal dimension in the input dataset improved the prediction capability of ANN, SVM, and RF. MLR and CART showed lower predictive ability than the other three approaches (i.e., ANN, SVM, and RF). In the training dataset, RMSE (mm) for the SVM model was 8.33% lower with D than with texture as the input, whereas, in the testing dataset, it was 16.67% lower. Because SVM is more flexible and effectively captures non-linear relationships, it performed better than the other models in predicting MWD. As seen in this study, the SVM model with input data D is the best in its class and has a high potential for MWD prediction in the Karnal district of Haryana, India.

Long-Term Conservation Tillage Practices Directly and Indirectly Affect Soil Micro-Food Web in a Chinese Mollisol

Soil micro-food webs play an essential role in maintaining or improving the stability of agricultural soils, and they can be influenced by tillage. However, little is known with respect to soil microbial and faunal communities and their relationships shaped by long-term tillage practices. The goal of this study was to investigate the impact of 38 years of no-tillage (NT), subsoil tillage (ST), moldboard plow tillage (MP), and rotary and ridge tillage (CT) practices on soil microbial and faunal communities, and their relationships with soil properties using high-throughput sequencing technology and structural equation modeling (SEM) at 2 soil depths (0–20 cm and 20–40 cm). The results indicate that, after the 38-year (1983–2020) period, the bacterial, fungal, protozoan, and metazoan gene copy numbers under the NT treatment at 0–20 cm were 1.31–6.13 times higher than those under the other treatments. Conversely, the microbial and protozoan alpha diversities were reduced under the NT treatment compared with the CT treatment. However, MP significantly increased microbial and faunal gene copy numbers at 20–40 cm. Moreover, the bacterial community composition remarkably varied relative to the community composition of the fungi and fauna in response to the tillage practices and soil depths. Additionally, the highest and lowest average connectivities of the soil micro-food web networks were observed under the ST and MP treatments, respectively. The SEM demonstrated that tillage practices and soil depths explained 73–98% of the microbial and faunal abundances, diversities, and compositions. Additionally, tillage and depth demonstrated direct quantitative effects and indirect quantitative effects by altering the soil mean weight diameter of aggregates, soil organic carbon, and total nitrogen. Overall, subsoil tillage is recommended as the optimal practice for application in northeast China, and it could improve soil properties and aid in forming a more complex soil micro-food web structure.

Nitrogen fertilization degrades soil aggregation by increasing ammonium ions and decreasing biological binding agents on a Vertisol after 12 years

Degraded soil aggregation arising from nitrogen (N) fertilization has been reported in many studies; however, the mechanisms have not yet been clarified. Elucidating the impact of N fertilization on soil aggregation would help to improve soil structure and sustain high crop production. The objective of this study was to determine the impact of long-term N fertilization on soil aggregation and its association with binding and dispersing agents. A 12-year (2008–2019) N fertilization field experiment on a Vertisol was performed, covering a wide range of N application rates (0, 360, 450, 540, 630, and 720 kg ha-1 year-1) and including straw management (straw return and straw removal) in a wheat (Triticum aestivum L.)-maize (Zea mays L.) cropping system. Soil samples of 0–20 cm depth were collected from 12 field treatments with 3 replications in 2019. Soil aggregate stability (mean weight diameter (MWD)) and contents of soil organic carbon (SOC), glomalin-related soil protein (GRSP), microbial biomass carbon (MBC), and mineral N (NH4+ and NO3-) were determined. Long-term N fertilization under straw removal conditions reduced soil MWD by 12%–18% at N rates from 0 to 720 kg ha-1 compared to that under straw return (P < 0.05). Soil MWD was positively associated with pH (P < 0.05) and MBC (P < 0.05), but negatively correlated with NH4+ (P < 0.05) and NO3- (P < 0.05). Compared with the straw removal treatment, the straw incorporation treatment significantly improved the contents of aggregating agents (SOC, GRSP, and MBC) (P < 0.001), but did not affect that of the dispersing agent (NH4+) (P > 0.05); consequently, it improved soil aggregation. Overall, our results indicate that long-term N fertilization may degrade soil aggregation because of the increases in monovalent ions (H+ and NH4+) and the decrease in MBC during soil acidification, especially when the applied N dose exceeded 360 kg ha-1 year-1. Our finding can minimize the negative structural impacts on Vertisol.

Distribution of phosphorus fractions in soil aggregates in Chinese fir plantations with different stand ages

Exploring the distribution of phosphorus (P) fractionsin soil aggregates is helpful to improve soil P availa-bility during Chinese fir planting. In this study, soil samples were collected in the 0-20 cm soil layer from Chinese fir plantations with different stand ages (9 a, 17 a, and 26 a) and one nearby abandoned land (CK) in Rongshui County, Guangxi, China. Soil aggregates were classified into &gt;2 mm, 1-2 mm, 0.25-1 mm, and &lt;0.25 mm size classes through dry-sieving process, and then soil P fractions in different sized aggregates were measured. These results showed that: 1) The composition of soil aggregates showed significant difference among different stand ages. As the major aggregate fractions in soil, the contents of &gt;2 mm aggregates increased firstly and then decreased over time, and peaked in the 17 a Chinese fir plantation. The changes of soil mean weight diameter (MWD) and geometric mean diameter (GMD) during Chinese fir planting were the same as the content of &gt;2 mm aggregates. 2) Soil total P, inorganic P, and organic P contents did not differ among different sized aggregates. However, soil available P content was mainly distributed in &gt;2 mm aggregates with a range of 1.23-7.33 mg·kg-1. Compared with CK, soil total P, available P, and inorganic P contents were significantly higher in Chinese fir plantations, and their contents increased firstly and then decreased over time. Soil total P (322.40 mg·kg-1) and available P (7.33 mg·kg-1) contents were the highest in the 9 a plantations, and soil inorganic P content (114.05 mg·kg-1) was the highest in the 17 a plantation. Moreover, soil organic P content showed an order of 9 a &gt; 26 a &gt;17 a &gt; CK, with the highest content (210.00 mg·kg-1) in the 9 a plantation. 3) The distribution of P stock in soil aggregates was related to the contents of different sized aggregates, with &gt;2 mm aggregates having the highest P stock. Except for organic P, soil P stock increased firstly and then decreased with the increases of stand age. In conclusion, Chinese fir planting was helpful to improve soil aggregate stability and to promote the increase of soil P level before the stand age of 17 a. However, Chinese fir planting could result in the degradation of soil aggregates and in the decrease of soil P level after 17 a. The formation and stabilization of &gt;2 mm aggregates played an important role in the maintenance of soil quality and soil P supply level after 17 a Chinese fir planting.

The Edaphic and Vegetational Properties Controlling Soil Aggregate Stability Vary with Plant Communities in an Arid Desert Region of Northwest China

The stability of soil aggregates is the basis for supporting ecosystem functions and related services provided by the soil. In order to explore the mechanism of the influence of soil and vegetation properties on the stability of soil aggregates in desert communities, the particle size distribution and aggregate in different communities were compared, and the contribution of soil physical and chemical properties (soil salinity, soil water content, soil pH, soil organic carbon, soil total phosphorus, soil total nitrogen, etc.) and vegetation properties (species richness, phylogenetic richness, plant height and coverage, etc.) to the stability of soil aggregates was determined by using a structural equation model. The results show the following: Soil water content, organic carbon, and salt in river bank plant communities have significant direct positive effects on the mean weight diameter of soil, with path coefficients of 0.50, 0.11, and 0.24, respectively (p &lt; 0.01). Water also indirectly affects soil stability by affecting plant height, soil salt, and soil organic carbon; species richness and vegetation coverage have significant direct positive effects on the soil stability index, with path coefficients of 0.13 and 0.11, respectively (p &lt; 0.01). In the desert marginal plant community, the plant coverage and species richness have significant positive effects on soil stability, with path coefficients of 0.43 (p &lt; 0.001) and 0.35 (p &lt; 0.001), respectively. Phylogenetic richness has a significant direct negative effect on soil stability (p &lt; 0.05), with an effect value of −0.27. Phylogenetic richness indirectly affects soil stability by adjusting the coverage, with an indirect effect value of 0.23. Moisture, ammonium nitrogen, and nitrate nitrogen have significant direct positive effects on soil stability, with effect values of 0.12, 0.09, and 0.15, respectively. Our research shows that the process of soil stabilization is mainly controlled by soil factors and vegetation characteristics, but its importance varies with different community types.

Organic carbon distribution and soil aggregate stability in response to long-term phosphorus addition in different land-use types

Understanding the relationships among phosphorus (P), soil organic carbon (SOC) and aggregate stability is vital for improving soil fertility and P and C cycling in different land-use types. Here, we assessed the responses of SOC distribution in different aggregate fractions to P addition in two different land-use types categorized in either a P-limitation or non-P-limitation status based on the stoichiometric ratios of microbial enzymes. Four different long-term fertilization managements (no fertilizer [control, non-P limitation]; nitrogen and potassium [NK treatment, P limitation]; phosphorus [P treatment]; and nitrogen, phosphorus, and potassium [NPK treatment]) were established in upland and paddy soils to compare the effects of pre-assessed non-P- and P-limited soil conditions in combination with different fertilizer additions. A wet-sieving method was used to obtain four sizes (> 2-, 0.25–2-, 0.053–0.25- and < 0.053-mm) of soil aggregates. The concentrations of SOC and iron and aluminum (Fe/Al) oxides in the forms extractable by DCB (Fed/Ald), oxalate (Feo/Alo) and polyphosphate decahydrate (Fep/Alp) were measured. The results showed that compared to the non-P-limited control, the P treatment reduced soil mean weight diameter (MWD) by 13.1% in upland and 9.7% in paddy soils. The MWD of NPK treatment was significantly higher by 24% than that of the P-limited NK treatment in upland soil, while the difference between the same two fertilization treatments was not significant in paddy soil. Compared with that of the control, SOC concentration in each size was greater in the P-treated upland soil, while in the paddy soil, SOC concentration of the >2-mm size were lower in the P and NPK treatments than in the control and NK treatments, respectively. Phosphorus addition decreased Fep/Alp of each aggregate size in upland soil, while it increased Fep/Alp of each aggregate size in paddy soil. To better quantify the effects of P on SOC and aggregate stability, we used a partial least squares path model (PLS-PM). The results indicated that P addition had a direct negative effect on MWD (−0.797, P < 0.01) under the non-P limitation condition (control vs. P treatment). The addition of P in upland soil had a high positive effect on MWD (0.565, P < 0.05) under the P-limitation condition (NK vs. NPK treatments), but the effect was not significant in paddy soil (0.047, P > 0.05). Thus, strategies aiming to improve soil carbon cycling and aggregate stability by regulating phosphorus addition should consider land-use type and soil P-limitation status.

Soil organic C and total N as well as microbial biomass C and N affect aggregate stability in a chronosequence of Chinese fir plantations

Soil aggregation as one of the key processes can maintain soil quality. Revealing the relationships of soil aggregate stability with the relevant bio-chemical parameters could provide valuable guidance to maintain soil quality in the Chinese fir plantations. In this study, soil samples (0–20 cm and 20–40 cm depths) were collected from Chinese fir plantations with various stand ages (3 years, 9 years, 17 years, and 26 years) in Guangxi, China. Soil aggregates with four different sizes were obtained through the optimal moisture sieving method, including the >2 mm, 2-1 mm, 1–0.25 mm, and <0.25 mm fractions. For each fractions, the organic C (OC), total N (TN), microbial biomass C (MBC), microbial biomass N (MBN), and microbial respiration rate (MRR) were measured. Regardless of the Chinese fir plantation age, soil OC and TN contents were concentrated in the <0.25 mm fractions, while soil MBC, MBN, and MRR were relatively high in the 1–0.25 mm fractions compared with other fractions. Soil mean weight diameter (MWD) and geometric mean diameter (GMD) were higher in the 17-year Chinese fir plantations than other stand ages, which indicated stronger stability of soil aggregates in the 17-year Chinese fir plantations. In the process of Chinese fir planting, the peaks of soil OC, TN, MBC, MBN, and MRR were observed in the 17-year Chinese fir plantations. Based on the redundancy analysis (RDA) and Pearson's correlation analysis, soil aggregate stability was significantly positively correlated (P < 0.05) with the OC, TN, MBC, and MBN over time, particularly in the OC, which was the most important contributor of the chronological variation in soil aggregate stability. Overall, soil aggregate stability and aggregate-related OC, TN, MBC, and MBN are the highest in the 17-year Chinese fir plantations. With the growth of Chinese fir after 17 years, these factors decrease significantly. Therefore, it is necessary to adopt reasonable management methods (i.e., appropriate application of organic manure) to increase soil aggregate stability and maintain soil quality in Guangxi, China.

Strip Till-Planting Method for Coserving Power and Costs Through Faba Bean Planting نظام الحراثة والزراعة الشرائحي لتقليل الطاقة والتکالبف خلال زراعة الفول البلدي

The main objective of this study is to investigate the effect of using strip till-planting method as the minimum tillage system for reducing power and cost requirements of faba bean seedbed preparation and planting under Egyptian conditions. Field experiments were conducted in a clay soil. A split-spit-plot statistical experimental design with three replicates was conducted. Three tillage and planting systems were studied under various levels of planting depths and planting speeds. Measurements were taken for soil mean weight diameter, planting depth, planting speed, fuel consumption and the percentage of seed germination. Results indicated that the soil mean weight diameter were 19.63, 16.79 and 12.52 mm for traditional system (TS), mechanized system (MS) and strip till-planting system (STP), respectively. The strip till-planting system (STP) resulted in the lowest values for the energy requirements and total costs compared with the other two systems. The percentage of seed germination decreased as the planting speed increased for mechanized (MS) and strip till-planting (STP) systems. However, there is no appreciable change in the seed germination when the speed increased for traditional system (TS). From the results of this study, it could be concluded that the strip till-planting system (STP) conserved the power requirements for seedbed preparation and planting faba bean by 40% and 46% compared with the traditional (TS) and mechanized (MS) systems, respectively. It also reduced the total costs by 56% and 69%, respectively.

Soil organic carbon and soil aggregate stability associated with aggregate fractions in a chronosequence of citrus orchards plantations

Soil aggregates and their associated C may serve as accurate diagnostic markers for changes in soil characteristics in response to different agricultural management practices. However, there is limited knowledge regarding the effects of various chronosequences on soil organic C (SOC) pool in aggregates of different particle sizes in citrus plantations. Surface soil (0–20 cm) samples were collected from 120 citrus orchards (Yongxing County, Hunan Province, China) of different plantation ages (0-10y, 11-20y, and 21-30y). Plantation age dramatically affected the composition of soil aggregates of different particle sizes and their associated SOC, with the strongest macroaggregate fraction observed in the 0-10y orchards. Soil mean weight diameter (MWD) and geometric mean diameter (GMD) gradually decreased with plantation age (by 12.58% and 20.30% in 21–30y orchards, respectively). However, soil fractal dimension (D) and erodibility (K) gradually increased with plantation age (by 3.95% and 2.15% in 21–30y orchards, respectively). Furthermore, the SOC content and pool of aggregates and contribution of aggregates to SOC decreased with decreasing particle size. Multivariate analysis identified the aggregate fraction with a particle size over 2 mm as the main factor affecting the stability of soil aggregates in citrus plantations. The SOC content of aggregates was positively correlated with soil MWD and GMD but negatively correlated with soil D and K. The distribution of organic matter in soil aggregates can help us better understand the stability of soil structure and reduce the risk of soil erosion in successive citrus planting (<30y).

Root System and Its Relations with Soil Physical and Chemical Attributes in Orange Culture

Citrus companies have sought and developed alternative systems of tillage or implanting orchards so as not to significantly alter the physical and chemical attributes of the soil and, consequently, the root development of plants. Therefore, the aim of this study was to identify the physical and chemical attributes of the soil that most influence the root volume of the orange crop in different tillage systems. The experiment was carried out in the region of Avaré, state of São Paulo, Brazil, in Utissol and Oxisol. For the planting of the orange crop, the following tillages were made: minimum tillage, subsoiler tillage and soil tillage using a triple tillage implement. The physical and chemical attributes evaluated were bulk density, macroporosity, microporosity, total porosity, soil moisture, soil mean weight-diameter, soil resistance to penetration, sum of bases, cation exchange capacity, base saturation, pH, exchangeable cations, potential acidity, available phosphorus, analysis of micronutrients such as copper, iron, manganese and zinc, and organic carbon content. The root system was evaluated using SIARCS® software. For data classification, data mining techniques were used such as attribute selection and decision tree induction. Regardless of the soil type, the use of the triple operation implement provided greater root volume for orange plants. For the Utisol area, the pH value of 4.2 was the main attribute that provided a high root volume. For the Oxisol, the presence of copper, in levels that did not generate toxicity for the plants, provided a high volume of root for the crop.

Prediction of mean weight diameter of soil using machine learning approaches

AbstractEven though research shows that aggregate stability and mean weight diameter (MWD) are critical components of soil health, it is not routinely measured. An alternative approach to the physical measurement is to calculate these values based on routinely measured soil parameters. Therefore, the objective was to compare two artificial intelligence (AI)‐based machine learning approaches, that is, support vector machine (SVM) and artificial neural network (ANN) models in prediction of soil wet aggregate stability (quantified by MWD). Soil samples (120) from the Indo‐Gangetic Alluvium major soil group, that are characterized as Ustifluvents were used in the study. These samples were analyzed for sand, silt, clay, bulk density (BD), organic carbon (OC), and MWD. The correlation coefficient (r) was highest in case of SVM model with a percentage increase of 16.92 and 2.70 when compared with MLR and ANN respectively. The SVM and ANN models showed 6.36 and 2.12% decrease in RMSE in training dataset while a 14.28% decrease was found for SVM in testing dataset when compared to the multi‐linear regression (MLR) model. Results showed that ANN with two neurons (building blocks of ANN) in hidden layer had better performance in predicting MWD than MLR, whereas the radial basis Kernel function based SVM was found to be best for training and testing data of MWD. Soil texture, OC, and BD can be used to predict soil structural stability effectively using SVM. However, additional work is needed to confirm these findings with other soils.

Soil mechanical properties and wind erosion following conversion of desert to irrigated croplands in central Iran

Conversion of the virgin desert to agricultural lands can obviously alter some soil properties; however, little is known about how this conversion impacts soil mechanical properties and wind erosion. The present study therefore aimed at assessing the impacts of agricultural exploitation on aggregate stability, mechanical properties and wind erosion of desert soils in Abarkooh plain, central Iran. To do so, three land uses were assessed: (1) wheat (Triticum aestivum L.), (2) pistachio (Pistacia vera L.), and (3) the adjacent virgin desert soils. Ten sites including three land uses were selected. At the time of soil sampling, the vane shear test was performed. Then, the composite soil samples (0–20 cm depth) were taken for laboratory analyses. Soil organic carbon, bulk density, mean weight diameter, wind erosion rate, wind erodible fraction, shear strength value, cohesion (c), and angle of internal friction (φ) were measured. The results showed that soil organic carbon content in the croplands was greater than that of desert. Nevertheless, according to findings, soil gravel, electrical conductivity, and bulk density decreased with cultivation. Compared to the desert (0.21 mm), wheat (1.71 mm) and pistachio (1.34 mm) fields had a higher dry mean weight diameter of soil. The wind erosion rate in the desert (1.48 g m−2 s−1) was 16.4 and 13.5 times greater than those of wheat and pistachio fields, respectively. Also, the wind erodible fraction in the desert was significantly higher (85%) compared to the cultivated soils (52–58%). The value of φ was greater in wheat‒cropped soil (41.05°) than in the desert (36.90°). The c values (21.39–22.46 kPa), vane shear strength (14.36–14.78 kPa) and shear strength values (22.14–23.49 kPa) in the croplands were 5.2–5.4, 5.0–5.1, and 4.9–5.2 times greater than those of desert, respectively. These results revealed that sustainable use of irrigated desert lands could be an appropriate method which significantly improves soil mechanical resistance against wind erosion.

Soil nematode community and crop productivity in response to 5-year biochar and manure addition to yellow cinnamon soil

BackgroundManure and biochar soil amendments have shown many benefits to soil quality and crop productivity. This study aimed to reveal the effects of biochar and manure applications on soil fertility improvement and crop productivity in yellow cinnamon soil.ResultsThis study based on a 5-year field experiment. Four treatments were designed, included the control (CK), biochar amendment, manure amendment, and both biochar and manure amendment (BM). The results showed that: after five years, both biochar and manure treatment improved soil structure by increasing soil mean weight diameter (MWD), and soil water and nutrient supply was also increased by increasing the contents of water content, available potassium and available phosphorus. The productivity was also enhanced as wheat yield under the biochar, manure, and BM treatments increased by 3.59–11.32% compared with CK. In addition, biochar and manure treatment increased soil microbial biomass carbon (MBC) by > 15%, and soil total nematode abundance was significantly increased. Furthermore, the nematode community structure was significantly affected by biochar and manure treatment, dominant trophic group in CK was herbivores, but bacterivores were dominant in the biochar and manure treatments. The distribution of nematode genera was closely related to soil chemical properties and microbial biomass. Increases in the Shannon's diversity index, and decreases in the dominance index and summed maturity index after the 5-year treatment indicated a sustainable soil ecosystem after the biochar and manure applications.ConclusionsThese findings indicate that biochar and manure result in better soil quality and increased productivity in yellow cinnamon soil.

Effect of tillage practices at different levels of soil moisture on some soil properties and maize productivity

A field experiment was carried out during the early summer seasons of 2018, at Agricultural Research Centre (ARC) Giza, Egypt. This study aims to examine the effect of three tillage treatments under three different moisture contents on some soil properties and on maize crop production. The experiments included three moisture contents of (MC1, 27.2 %), (MC2, 15.4 %) and (MC3, 7.2 %); as well as three tillage treatments, no-tillage control (NT), minimum tillage (MT) and conventional tillage (CT). The experimental was laid out in split-split plot design with four replications. The results showed that, there was significant effect of tillage at different moisture levels on soil physical and chemical properties. It was also indicated that the effect of tillage practices was significantly on soil bulk density, total porosity, hydraulic conductivity and moisture constants, where the conventional tillage at soil moisture level 15.4% (MC2) helped in improving soil bulk density, hydraulic conductivity and total porosity. Soil organic C, cations exchange capacity CEC, available N, P and K were improved in the soil surface layer of NT and decreased with depth. Clod mean weight diameter of soil was improved with 15.4-% of soil moisture content regardless of tillage depth and enhanced root proliferation by increasing density roots compared with minimum and no tillage in maize plant. The grain yields of maize were improving more under conventional tillage at moisture content 15.4% compared with other treatments. It was found that plant height and roots value increased by using conventional tillage compared with other tillage treatments.