Soil Texture Research Articles

Evaluation and development of pedotransfer functions of saturated hydraulic conductivity for subtropical soils

The determination of soil saturated hydraulic conductivity (Ks) is crucial in environmental and engineering fields. However, the current direct measurement methods of Ks are time-consuming and labor-intensive. As an alternative method, many researchers have developed a series of pedotransfer functions (PTFs) that estimate Ks based on easily accessible soil properties. Unfortunately, most existing PTFs of Ks focus on temperate and tropical regions in the United States and Europe. There is a lack of research discussing the applicability of Ks models in subtropical areas. To resolve this issue, we conduct a study using 515 subtropical soil samples to test the performance of existing PTFs of Ks. The Ks values of investigated soils range from 1.4 × 10-4 to 290 cm h−1. Among the affecting factors, soil bulk density (ρb) and effective porosity (φe) are found to be the most important variables. Current PTFs considering soil pore structural property (i.e., φe) or soil texture solely are not effective in assessing Ks of subtropical soils. To address this limitation, we integrate soil pore structural and textural properties and develop a new PTF based on the Kozeny-Carman equation. The performance and reliability of the new PTF are evaluated using independent Ks datasets from various regions. The results show a significant positive correlation between the measured Ks and the predicted Ks from the new PTF for subtropical soils with an R2 of 0.69, an average RMSE in log10Ks (cm h−1) of 0.496, and a mean bias value of 0.070. Besides, the new PTF is found to perform as well as widely used machine learning tools.

Variations in soil erodibility (K-factor) for the Chernozems depending on the method of texture determination

Soil erodibility (K-factor) is an important parameter in erosion modeling, is one of five factors of the Revised Universal Soil Loss Equation (RUSLE), and generally represents the soil's response to rainfall and run-off erosivity. The erodibility could be determined based on direct measurements of soil properties and mathematical calculations. In this study, the K-factor was calculated based on a formula from RUSLE, proposed by Renard et al. (1997). All input parameters: soil organic carbon (SOC), soil structure, and permeability classes were measured by one method, but particle size distribution – in two ways by sedimentation and laser diffraction methods to assess the impact the K-factor variability and the values of soil erosion rates. The 107 soil samples of Chernozems from Kursk Oblast (Russia) were studied. The texture for the most of samples was classified as silty loam in both analyses. However, the laser diffraction underestimates the clay content by an average of 13.2% compared to the pipette method. The average K-factor estimated based on laser diffraction data was 0.050, and 0.034 t ha h ha−1 MJ−1 mm−1 – sedimentation method. Thus, depending on the method of soil texture analysis, the RUSLE calculated soil loss could underestimated/overstated by 32% (or 4 t ha-1 yr-1 on average in the study site). Therefore, we propose a regression equation-based conversion method of laser diffraction data to sedimentation method data for Chernozems.The Laska-TM laser analyzer measured on ∼ 13% less clay fraction (more on ∼ 8% silt and ∼ 5% fine sand) compared with sedimentation method data.For erosional researchers/modelers it is suggested to state the method of soil texture analysis (based on sedimentation law or laser diffraction) was used for RUSLE K-factor calculations.To convert K-factor values (for Chernozems) calculated and based on data of the sedimentation method to laser sedimentation – it suggested utilize the coefficient 1.47 (0.68 – vice versa).

Wireworm species associated with corn and soybean agroecosystems in Ontario, Canada.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are often the target of insecticide seed treatments commonly used in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in North America. Nevertheless, there is a lack of knowledge of the species, life history, and economic impact of wireworms present in these agroecosystems. An extensive survey of wireworms was conducted in corn and soybean fields in Ontario, Canada, from 2014 to 2017 to document species distribution and co-occurrence and to identify risk factors related to their abundance. In total, 4,332 specimens were collected from 1,245 different sampling records. The dominant species collected was Limonius agonus (Say) (Coleoptera: Elateridae) comprising 71.5% of the specimens. The remaining wireworm specimens were identified as Hypnoidus abbreviatus (Say), Melanotus similis (Kirby), M. cribulosus (LeConte), M. depressus (Melsheimer), M. communis (Gyllenhal), Agriotes mancus (Say), Aeolus mellillus (Say), and Hemicrepidius spp (Germar). Multiple wireworm species were found to commonly occur within the same field and the same sample. Path analysis was conducted to investigate whether site, soil, and agronomic characteristics influenced wireworm distribution and abundance. Several significant relationships were found between wireworm species and geographic factors, soil texture, and agronomic practices. The results of this survey provide critical information that can be used to improve integrated pest management of the major wireworm genera found in corn and soybean agroecosystems in Ontario.

Rhizosphere hydraulic regulation in maize: tailoring rhizosphere properties to varying soil textures and moistures

Abstract Aims Motivated by recent studies highlighting the active role of plants in influencing the hydraulic properties of the rhizosphere through mucilage exudation, this study explored the effect of plant rhizosphere regulation on the emergent hydraulic properties of the rhizosphere under varying soil texture and moisture levels. Methods Maize (Zea mays) plants were cultivated in sand and loam soils exposed to varying moisture levels. Neutron radiography was employed to quantify the profile of water content ($${\theta }_{r})$$ θ r ) around lateral and crown roots. The $${\theta }_{r}$$ θ r were used to derive rhizosphere hydraulic indices such as rhizosphere extension ($${d}_{rh}$$ d rh ), water content at the root-soil interface ($${\theta }_{rs}$$ θ rs ), and water content in the rhizosphere ($${\theta }_{rh}$$ θ rh ). The latter two attributes were normalized by the respective bulk soil water contents ($${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ ). Results Results showed a higher $${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ and $${d}_{rh}$$ d rh in coarse-textured soil versus fine-textured soil. This indicates a more pronounced rhizosphere development in sand compared to loam, possibly via mucilage exudation to maintain better root-soil contact. In contrast, soil water content did not impact the rhizosphere properties of crown roots but impacted the rhizosphere properties of lateral roots. The derived rhizosphere water retention curves revealed a higher water-holding capacity of the rhizosphere in both soils compared to bulk soil. Conclusions Our study underscores that soil-grown maize plants dynamically adjust the hydraulic properties of their rhizosphere in response to external factors, primarily aiming to optimize root-soil contact. That leads to a more pronounced rhizosphere in coarser textures, interacting with the soil moisture.

Evaluation and comparison of infiltration models for estimating infiltration capacity of different textures of irrigated soils

Accurate estimation of infiltration rates is crucial for effective irrigation system design and evaluation by optimizing irrigation scheduling, preventing soil erosion, and enhancing water use efficiency. This study evaluates and compares selected infiltration models for estimating water infiltration rates in the Shillanat-iv irrigation scheme in northern Ethiopia. Soil samples were collected to determine textural classes using hydrometer soil texture analysis and the United States Department of Agriculture (USDA) textural triangle. The soil textural map of the study was created using the inverse distance weight interpolation technique in ArcGIS version 10.4. Infiltration rates were measured using the double-ring infiltrometer for five soil textures: clay loam, loam, sandy clay loam, clay, and sandy loam. Six infiltration models (Kostiakov, Modified Kostiakov, Revised Modified Kostiakov, Philip, Horton, and Novel) were employed and evaluated using statistical parameters. Model calibration and validation were conducted using data from 38 points within the study area. The parameter values of the infiltration models were optimized using SPSS statistical software using least-squares errors. The results showed that, Revised Modified Kostiakov, Modified Kostiakov, and Novel infiltration models demonstrated superior capability in estimating infiltration rates for clay loam, loam, and sandy loam soil textures, respectively. Horton's model outperformed other models in estimating infiltration rates for both sandy clay loam and clay soil textures. The appropriately fitted infiltration models can be utilized in designing the irrigation system to estimate the infiltration rate of soil textures within the selected irrigation scheme and at similar sites with comparable soil textures.

Comprehensive assessment for the seasonal variations of organic compounds and core soil microbiome in the simulated pilot-scale aquifer storage and recovery (ASR) system

Soil microbiome is responsible for crucial biochemical reactions by interacting with organic compounds in the injection wells in aquifer storage and recovery (ASR) processes. This study investigated seasonal variations in organic compounds and microbial communities in a simulated ASR system. For this purpose, eleven pilot-scale soil columns were operated in ASR mode over 13 months. River water was intermittently fed into the simulated ASR system after sedimentation pretreatment. As a result, the sand ratios in soil texture were slightly increased from 93.2-93.4 % to 96.6–98.1 % while the total organic carbon content in the soil was accumulated and maintained at < 0.2 % during the ASR operation. During the sedimentation process, 9–31 % of dissolved organic carbon (DOC) was removed in the water, while during the storage in the soil column, the DOC in water was fluctuated. However, the DOC concentration (less than 4 mg/L) in the effluent was stably maintained until the end of operational periods. High-throughput sequencing results showed that the predominant phylum was Proteobacteria. Interestingly, at the species level, the microbial community structure clearly shifted with elapsed time and column location; various organic degrading soil microbiome having different physiological characteristics (e.g., oxygen, substrate, and temperature) became predominant. Outcomes of this study suggest that soil microbiome can facilitate the establishment of stable ASR processes for river water treatment by contributing to bioattenuation.

Bacterial community composition of Hungarian salt-affected soils under different land uses

Salinization and sodification are serious and worldwide growing threats to healthy soil functions. Although plants developed a plethora of traits to cope with high salinity, soil bacteria are also essential players of the adaptation process. However, there is still lack of knowledge on how other biotic and abiotic factors, such as land use or different soil properties, affect the bacterial community structure of these soils. Therefore, besides soil chemical and physical investigations, bacterial communities of differently managed salt-affected soils were analysed through 16S rRNA gene Illumina amplicon sequencing and compared. Results have shown that land use and soil texture were the main drivers in shaping the bacterial community structure of the Hungarian salt-affected soils. It was observed that at undisturbed pasture and meadow sites, soil texture and the ratio of vegetation cover were the determinative factors shaping the bacterial community structures, mainly at the level of phylum Acidobacteriota. Sandy soil texture promoted the high abundance of members of the class Blastocatellia, while at the slightly disturbed meadow soil showing high clay content was dominated by members of the class Acidobacteriia. The OTUs belonging to the class Ktedonobacteria, which were reported mostly in geothermal sediments, reached a relatively high abundance in the meadow soil.

Characteristics of Orange-Footed Scrubfowl (Megapodius reinwoardt) Nests in Kerandangan Natural Tourism Park West Lombok

Orange-footed scrubfowl (Megapodius reidwardt) are protected species and need to be preserved. Orange-footed scrubfowl (Megapodius reidwardt) are terrestrial birds that build nests on the ground. To maintain its sustainability, it is necessary to have knowledge about the characteristics of orange-footed scrubfowl nests. Kerandangan Natural Tourism Park is one of the places where orange-footed scrubfowl are found, but until now there is still no information about the characteristics of orange-footed scrubfowl nests. So this study aims to analyze the characteristics of orange-footed scrubfowl nests in Kerandangan Natural Tourism Park. The method used in this research is descriptive exploration, the research variables include physical parameters of the nest, environmental parameters of the nest, chemical parameters of the nest mound and plant vegetation around the nest. The results showed that the diameter of the nest ranged from 400-590 cm with a nest height of 85-154 cm, the number of laying holes ranged from 1-3 holes and the soil texture class of the nest mound consisted of sandy loam and loam. Environmental parameters obtained average temperature outside the nest 27,9oC, average temperature inside the nest 28,6oC, average humidity outside the nest 80,3%, humidity inside the nest 81,2% and light intensity ranged from 98,1-834,1 lux in the morning, 437,8-4014,8 lux in the afternoon, and 45,7-653,8 lux in the afternoon. Chemical parameters obtained organic matter content ranged from 1,4%-3,2% and pH ranged from 6,8-7. Vegetation that had the highest INP in each nest was Voacanga foetida, Inga edulis, Artocarpus elasticus, and Bambusa bambos, these plant species act as materials for building nest mounds and potentially as food for orange-footed scrubfowl.

Soil Physicochemical Properties under Selected Avocado Cultivars in Ethiopian Smallholder Agroforestry

This study investigated the impact of three avocado cultivars on selected soil physicochemical properties in Central Ethiopia, to enhance the knowledge on the influence of avocado cultivars on soil physicochemical properties, and assist smallholders in cultivar selection in agroforestry. Trees planted in farmers´ fields 8 years earlier were revisited. Soil samples were collected from 0–20 cm and 20–40 cm depth at three radial distances from trees (1 m and 2 m from tree trunk, and at 5 m from the canopy edge as a control). Soil texture, bulk density, moisture content, pH, electrical conductivity, soil organic carbon, total nitrogen and available phosphorus were determined. Soil moisture content and electrical conductivity were overall higher and bulk density was lower (p < 0.05) under the canopies of the avocado trees than in the control and soil organic carbon, total nitrogen and available phosphorus tended to increase in spite of nutrient inputs to the control whilst the trees were unfertilized. Differences between the studied cultivars were small, but Hass tended to have the largest impact on soil nutrient levels, whilst Ettinger and Nabal tended to have a somewhat larger effect on the soil organic carbon concentration. Integrating these avocado cultivars on farms can improve soil fertility in the study area. However, for optimal agricultural soil health and sustainable avocado production, cultivar and site-specific soil management practices must be applied.

Geographic variations of aggregate mechanical stability controlled by inorganic cementing agents across the East Asian monsoon region

Soil aggregate mechanical properties are of vital importance for plant growth, tillage and soil erosion, and strongly conditioned by the amount and type of cementing agents that differ with soils. As most research focus at the site scale, how aggregate mechanical stability vary across different types of soils at regional scales and underlying mechanisms remain poorly understood. Herein, seven typical zonal soils in heavy textures with an increased status of soil development were collected under two land uses (arable and forest) and at three pedogenic horizons along the mid-temperate to south-subtropical climatic gradient in the East Asian monsoon region. Aggregate tensile strength (Y), specific rupture energy (Esp) and friability (FI) were measured on air-dried aggregates in a compression test, as well as soil cementing agents related to particle size distribution, organic matter and its components, metal oxides, phyllosilicates and exchangeable cations. Y and Esp were most affected by soil type (F = 37.7 and 21.4, p < 0.001), and less affected by land use and soil horizon (F < 8.2). Y and Esp were overall remarkably larger for temperate moderately (257 ∼ 700 kPa and 40 ∼ 261 J kg−1) than for subtropical highly developed soils (171 ∼ 329 kPa and 22 ∼ 52 J kg−1); FI (0.35 ∼ 1.30) showed no distinct geographic trend. Among soil properties, exchangeable polyvalent cations, crystalline Fe and Al oxides, and vermiculite had much larger and significant explanatory power (R2 = 0.33 ∼ 0.54, p < 0.01) than traditional soil properties (organic matter, soil texture and bulk density) (R2 < 0.25, p > 0.01), suggesting the predominant roles of the inorganic cementing agents in aggregate mechanical stability across soil types. Aggregate mechanical stability was increased by exchangeable polyvalent cations and vermiculite (r = 0.71 ∼ 0.81, p < 0.001), and weakened by crystalline Fe and Al oxides (r = −0.77 ∼ −0.74, p < 0.001). Additionally, mean annual precipitation and temperature were negatively correlated with aggregate mechanical stability (r = −0.80 ∼ −0.76, p < 0.001). This study demonstrates the remarkable geographic variations of aggregate mechanical stability under the influence of climate and highlights the importance of clay mineralogy (mainly swelling clay and crystalline Fe and Al oxides) and exchangeable cations at the regional scale.

Distribution of 210Po activity and soil texture in agricultural soil.

The assessment of 210Po in agricultural soil matrices in different regions of Kerala and Karnataka was studied. The wet ash method was used to find the activity concentration of 210Po. The alpha activity was counted using a silver-activated zinc sulfide counter of 30% efficiency, and the activity was calculated. The average concentration of 210Po activity in soil samples ranged from 0.09 to 20.52Bqkg-1, with an average value of 4.47Bqkg-1. The soil texture was measured using the International Pipette method. Using the IBM Statistical Package of Social Science Software, the frequency distribution curve of 210Po is plotted and found to be lognormal. The data of 210Po are highly skewed, and the Kurtosis has a significant positive value. The 210Po activity concentrations are substantially within the World Health Organization's recommended limits.

Vegetation resistance to increasing aridity when crossing thresholds depends on local environmental conditions in global drylands

The crossing of aridity thresholds triggers abrupt changes in multiple functional and structural ecosystem attributes across global drylands. While we understand the consequences associated with aridity thresholds, the key factors influencing dryland vegetation resistance when crossing them remain unclear. Here, we used field observations from 58 dryland sites across five continents and satellite remote sensing data (2000-2022) to show that plant richness, soil moisture dynamics and texture, and bare soil fraction are important variables contributing to vegetation resistance. Additionally, drought history (frequency and magnitude of past droughts) is important in interaction with plant richness and soil texture. Interestingly, plant species richness was negatively related to vegetation resistance, except in areas with higher drought history and in grasslands. Our results highlight that vegetation resistance depends on local environmental conditions. Enhancing our understanding of the factors important for vegetation resistance is an important step towards dryland conservation efforts and sustainable management strategies.

Effect of Different Levels of NPK, Biochar and Azotobacter on Physico-chemical Properties of Soil on Cowpea (Vigna unguiculata)

In light of this, the following goals are present in the experiment "Effect of Different Levels of NPK and Biochar, Azotobacter on Physico-chemical Properties of Soil and Yield Attributes of Cowpea to calculate the impact of various NPK, Biochar, and Azotobacter dosages on the physical-chemical characteristics of soil. An excavated soil sample from the experimental site revealed that the land topography ranged from nearly level to sloped by 1% to 6%, with soil area falling into the Inceptisol order. The soil texture was sandy loam, with sand percentages of 62.65%, silt percentages of 21.09, and clay percentages of 16.26. The pH of soil was 6.89, and its electrical conductivity (EC) was non-saline (0.42 ds m-1). Organic carbon content was low to medium, available nitrogen was low to medium (280.78 kg ha-1), available phosphorus was 17.34 kg ha-1, and available potassium was 168.16 kg ha-1. Two factors with three levels of @NPK 0, 50, and 100% ha-1, three levels of @Biochar 0, 50, and 100% ha-1, and a randomized block design were used in the statistical analysis. During field testing, nine different treatments were used; the best outcomes were significant. The results indicate that the physical and chemical parameters of the soil, including the cumulative mean values for bulk density (1.39 and 1.41 mg m-3), particle density (2.46 and 2.47 mg m-3), and soil pH (6.89 and 6.91), attained their maximum in T1 (Absolute control) at depths of 0-15 cm and 15-30 cm, respectively. Additionally, the percentage pore space was found to be 48.22% and 47.39%, and the water holding capacity was found to be 44.14% and 45.34%), electrical conductivity (EC) was measured at 0.49 ds m-1 and 0.52 ds m-1, the percentage of organic carbon was determined to be 0.40%), and the available nitrogen was found to be (299.78 kg ha-1 and 295.76 kg ha-1, available phosphorus was (23.78 kg ha-1 and 21.98 kg ha-1), and the available potassium was (179.25 kg ha-1 and 176.56 kg ha-1).

Enhancing the Performance of Machine Learning and Deep Learning-Based Flood Susceptibility Models by Integrating Grey Wolf Optimizer (GWO) Algorithm

Flooding is a recurrent hazard occurring worldwide, resulting in severe losses. The preparation of a flood susceptibility map is a non-structural approach to flood management before its occurrence. With recent advances in artificial intelligence, achieving a high-accuracy model for flood susceptibility mapping (FSM) is challenging. Therefore, in this study, various artificial intelligence approaches have been utilized to achieve optimal accuracy in flood susceptibility modeling to address this challenge. By incorporating the grey wolf optimizer (GWO) metaheuristic algorithm into various models—including recurrent neural networks (RNNs), support vector regression (SVR), and extreme gradient boosting (XGBoost)—the objective of this modeling is to generate flood susceptibility maps and evaluate the variation in model performance. The tropical Manimala River Basin in India, severely battered by flooding in the past, has been selected as the test site. This modeling utilized 15 conditioning factors such as aspect, enhanced built-up and bareness index (EBBI), slope, elevation, geomorphology, normalized difference water index (NDWI), plan curvature, profile curvature, soil adjusted vegetation index (SAVI), stream density, soil texture, stream power index (SPI), terrain ruggedness index (TRI), land use/land cover (LULC) and topographic wetness index (TWI). Thus, six susceptibility maps are produced by applying the RNN, SVR, XGBoost, RNN-GWO, SVR-GWO, and XGBoost-GWO models. All six models exhibited outstanding (AUC above 0.90) performance, and the performance ranks in the following order: RNN-GWO (AUC: 0.968) &gt; XGBoost-GWO (AUC: 0.961) &gt; SVR-GWO (AUC: 0.960) &gt; RNN (AUC: 0.956) &gt; XGBoost (AUC: 0.953) &gt; SVR (AUC: 0.948). It was discovered that the hybrid GWO optimization algorithm improved the performance of three models. The RNN-GWO-based flood susceptibility map shows that 8.05% of the MRB is very susceptible to floods. The modeling found that the SPI, geomorphology, LULC, stream density, and TWI are the top five influential conditioning factors.

SPATIAL DISTRIBUTION OF PHOMA LEAF SPOT OF COFFEE AND RELATIONSHIP WITH ENVIRONMENTAL AND HOST VARIABLES

The objective of this study was to evaluate the spatial distribution of Phoma leaf spot of coffee and its relationship with the environmental variables altitude, soil texture, and mineral nutrients. In addition, the relationship between disease and foliar nutrients, leafing, and plant production was evaluated. The study was carried out in a 7.65 ha coffee plantation for two years. A total of 86 points were georeferenced in this area. The incidence and severity of the disease were assessed monthly, and the data were transformed into annual values of “Area Under the Incidence Progress Curve” (AUIPC) and “Area Under the Severity Progress Curve” (AUSPC) of the disease. Likewise, the monthly data for the leafing were transformed into annual values of “Area Under the Leafing Progress Curve” (AULPC). Environmental and host variables significantly correlated with the AUIPC were subjected to geostatistical modeling. Higher AUIPC and AUSPC were observed in the second year of the study. The altitude, P-rem and Ca present in the soil, as well as the P and N present in the leaves, showed a positive correlation with the AUIPC. The K, Cu, and Mn present in the leaves, the AULPC and the production were negatively correlated with this variable. The exponential semivariogram model was the most appropriate to model the spatial autocorrelation of the variables analyzed, except for altitude.

Effects of Muddy Water Infiltration on the Hydraulic Conductivity of Soils

Despite the high sand content of Yellow River water in arid Northwest China, locals in the region opt to use muddy water to meet the demand for agricultural irrigation. Muddy water irrigation is a complex process and is still poorly understood. In this study, six sets of saturated soil column infiltration tests were designed, considering soil texture (silt loam, sandy loam, and sand) and muddy water sand content (3%, 6%, 9%, and 12%) as the influencing factors, with two sets of validation tests. Change in hydraulic conductivity (Kh), the average change rate of hydraulic conductivity (ΔK), and cumulative infiltration volume (I) were experimentally studied in the context of muddy water infiltration to respectively establish the separate functional models and developed to fit their relationship with time. The study results indicated that the hydraulic conductivity (Kh) decreased with increasing muddy water infiltration time. For silt loam and sandy loam, Kh stabilized at 0.0030 and 0.0109 cm/min, respectively, after 70 min of infiltration. In contrast, Kh in the saturated sandy soil column significantly declined throughout the muddy water infiltration, showing a 90.84% reduction after 90 min compared to the saturated hydraulic conductivity of the sandy soil. As the sand content of the muddy water increased from 3% to 12%, Kh decreased by 83.99%, 90.90%, 91.92%, and 92.21% for 3%, 6%, 9%, and 12% sand content, respectively, in the saturated sandy soil columns at the end of the infiltration period. The I values were 21.20, 9.29, 7.90, and 6.25 cm for 3%, 6%, 9%, and 12% sand content, respectively. The ΔK values were 0.0037, 0.0041, 0.0043, and 0.0044 cm/min2 for the respective sand contents, at an infiltration time of 80 min. The validation test demonstrated that the segmented function model accurately emulated the changes in hydraulic conductivity of sandy soil textures throughout the infiltration period. Results from this study provide a significant basis for understanding the mechanisms to hinder muddy water infiltration and to efficiently utilize muddy water for irrigation.

Contribution of the postharvest period to soil N2O emissions from arable Mediterranean crops

Soil nitrous oxide (N2O) emissions are a relevant contributor to the global warming potential of Mediterranean agro-ecosystems and therefore should be accurately quantified. Here, we investigated the quantitative relevance of considering postharvest N2O measurements when calculating annual soil N2O emissions from herbaceous crops (excluding rice). Data from 25 studies conducted in Mediterranean climates were compiled from a variety of crops and cropping systems, soil types, tillage practices, and nitrogen (N) fertilizer management practices. The differences between cumulative N2O emissions in the cropping period (preharvest emissions) and in the postharvest period were evaluated through a meta-analysis, as were the maximum N2O peaks in both periods and the resultant N2O emission factors (EFs). The relative contribution of the postharvest period to total cumulative N2O emissions was a mean 26%, but showed high variability. The average N2O EFs in the field experiments included in this study were 0.21% and 0.27% when not considering and when considering the postharvest period, respectively. The relative and absolute contribution of postharvest emissions was significantly greater for winter cereals than for either horticultural crops or maize. The maximum preharvest fluxes were higher than the maximum postharvest fluxes in 72% of the observations, but notable postharvest N2O peaks after soil rewetting were obtained in some studies. On average, postharvest emissions in nonfertilized plots were similar to those in fertilized winter crops. Other factors such as N source (greater relevance for organic fertilizers, particularly in summer crops), N rate, tillage intensity and soil texture significantly affected the amount of postharvest emissions. Taking measurements during the postharvest period in Mediterranean cropping systems are encouraged in studies that include winter crops, use of organic fertilizers or have unbalanced N rates. Our results may contribute to improving N2O measurement protocols and to re-evaluating N2O EFs in Mediterranean and semiarid areas.

Assessing soil degradation in Brazilian agriculture by a remote sensing approach to monitor bare soil frequency: impact on soil carbon

In countries with extensive agricultural practices, there is a significant risk of soil degradation, making it essential to develop techniques for understanding and detecting these changes. In this study, we used an earth observation system to identify the temporal bare soil frequency and thus, relate it with soil tillage and its impact on soil carbon degradation. The work was performed in two important agricultural states of Brazil, São Paulo and Paraná. For that, historical field and Remote Sensing (RS) data were analyzed to identify the relation between bare soil areas and their degradation. The frequency of bare soil was detected by Landsat images, in the last 36 years using the Geospatial Soil Sensing System (GEOS3). Historical soil surface temperature data was produced using the same images. In addition, legacy pedological and crops (i.e., soil cover) maps were used. Finally, soil texture information was spatialized based on a synthetic soil image (SISY). A total of 28,000 sites with topsoil organic carbon (SOC) were used as the reference for degradation. The soils of the state of Paraná presented significantly lower bare soil areas when compared to the state of São Paulo, mainly due to the wide use of the No-Tillage system. The advancement of sugarcane harvesting technologies together with the "boom" of the commodities after 2000s was responsible for the considerable increases in soil cover conservation. It was noticed that the more exposed the soil remains, the less carbon it has, having a negative correlation (r≈ −0.5). Sandy soils in both states proved to be the ones that were subject to the highest exposure rates and thus, more degraded. This fact is of concern, given that sandy soils are more susceptible to degradation factors, such as erosion. We observed important historical public policies related to the temporal tillage systems adopted by agro-community, which had a significant impact on carbon dynamics. The remote technique was able to infer how the soil has been managed. This information is crucial as it provides a solid basis for developing future public policies aimed at sustainable production.

Effects of Land Use Change on Soil Aggregate Stability and Erodibility in the Karst Region of Southwest China

Differences in land use type and chronological age affect soil properties and plant community characteristics, which may influence soil structural stability and erodibility. However, knowledge on the effects of soil physicochemical properties on soil aggregate stability and erodibility at different land use years is limited. This study selected five land use types: corn field (Year 38th-y), corn intercropped with cabbage field (Year 38th-y + b), fruit and meridian forest (Year 6th-jgl), naturally restored vegetation (Year 6th-zr), and artificial forest (Year 7th-rgl) in the karst landscape of the Chishui River Basin in Yunnan Province. We aimed to identify the influencing factors of soil stability and erodibility under different land use time series. The results indicated that the mean weight diameter (MWD), the geometric mean diameter (GMD), and soil structural stability index (SSI values) were highest in Y6th-zr and lowest in Y7th-rgl. Conversely, the erodibility K value was lowest in Y6th-zr, suggesting that the soil structure in Y6th-zr exhibited greater stability, whereas soil stability in Y7th-rgl was lower. Redundancy and throughput analyses revealed that organic carbon and water-stable aggregates &gt; 2.0 mm content had higher vector values. Soil bulk density, total nitrogen, organic carbon, and soil texture content were the main factors contributing to soil stability variation (0.338–0.646). Additionally, total nitrogen, organic carbon, total phosphorus, and soil texture content drove the variation in K values (0.15–1.311). Natural vegetation restoration measures can enhance soil structure to a certain extent. These findings highlight changes in soil aggregate stability and erodibility over different land use durations. The research results have important theoretical and practical significance for understanding the differences in soil erosion and soil restoration under different land use patterns in the karst landscapes of southwest China.

Effectiveness of Crop Farmers' Use of Indigenous Knowledge on Land Degradation Control Practices in Imo State, Nigeria

This study analyzed the effectiveness of the crop farmers' use of indigenous knowledge on land degradation control practices in Imo State, Nigeria. A multistage sampling procedure was used to select 180 crop farmers for the study. Data were collected using a structured questionnaire and analyzed using mean, percentages, and multiple regression analysis. Crop farmers perceived zero tillage to help in conserving soil texture (x̄=3.52), replanting of deforested areas enables them to maintain vegetative cover (x̄=3.45), use of organic manure to improve soil's organic matter contents (x̄=3.42) and controlling both water and wind erosions by making ridges (x̄=3.30) and rainwater harvesting (x̄=3.10) as highly effective in controlling soil degradation. Age, marital status, educational level, household size, monthly income, membership of association, extension contact and farm size) They significantly influenced their perceived effectiveness of using indigenous knowledge on land degradation control. The major constraints faced by crop farmers were inadequate funds to practice land degradation control practices (99.44%) and limited availability of farmland (98.31%), poor extension contact (86.44%), poor knowledge and education of land degradation control processes (86.44%), poor government support (81.92%) and poor access to information (75.14%). The study concludes that crop farmers experienced soil degradation and were practicing indigenous land degradation, although some factors constrained them. Therefore, crop farmers should come together to transform their indigenous knowledge and control practices, thereby discussing and looking for the best way to tackle their peculiar land degradation challenges.