Soils Of Arid Regions Research Articles

Random Forest Modeling of Soil Properties in Saline Semi-Arid Areas

The problem of salinization/spreading of saline soils is becoming more urgent in many regions of the world, especially in context of climate change. The monitoring of salt-affected soils’ properties is a necessary procedure in land management and irrigation planning and is aimed to obtain high crop harvest and reduce degradation processes. In this work, a machine learning method was applied for modeling of the spatial distribution of topsoil (0–20 cm) properties—in particular: soil organic carbon (SOC), pH, and salt content (dry residue). A random forest (RF) machine learning approach was used in combination with environmental variables to predict soil properties in a semi-arid area (Trans-Ural steppe zone). Soil, salinity, and texture maps; topography attributes; and remote sensing data (RSD) were used as predictors. The coefficient of determination (R2) and the root mean square error (RMSE) were used to estimate the performance of the RF model. The cross-validation result showed that the RF model achieved an R2 of 0.59 and an RMSE of 0.68 for SOM; 0.36 and 0.65, respectively, for soil pH; and 0.78 and 1.21, respectively for dry residue prediction. The SOC content ranged from 0.8 to 2.8%, with an average value of 1.9%; soil pH ranged from 5.9 to 8.4, with an average of 7.2; dry residue varied greatly from 0.04 to 16.8%, with an average value of 1.3%. A variable importance analysis indicated that remote sensing variables (salinity indices and NDVI) were dominant in the spatial prediction of soil parameters. The importance of RSD for evaluating saline soils and their properties is explained by their absorption characteristics/reflectivity in the visible and near-infrared spectra. Solonchak soils are distinguished by a salt crust on the land surface and, as a result, reduced SOC contents and vegetation biomass. However, the change in saline and non-saline soils over a short distance with mosaic structure of soil cover requires high-resolution RSD or aerial images obtained from unmanned aerial vehicle/drones for successful digital mapping of soil parameters. The presented results provide an effective method to estimate soil properties in saline landscapes for further land management/reclamation planning of degraded soils in arid and semi-arid regions.

Does biochar addition improve soil physicochemical properties, bacterial community and alfalfa growth for saline soils?

AbstractBiochar addition has been proven to have great potential for improving soil physicochemical properties and crop growth in salt‐affected soils. However, whether adding biochar could affect alfalfa growth and soil bacterial community in salt‐affected soils of arid regions remains poorly understood. A pot experiment was carried out to investigate the effects of corn straw biochar addition on soil physicochemical properties, bacterial community and alfalfa yield in saline soils. There were 12 treatments in total, combining three biochar addition rates of 0, 20 and 40 g kg−1 (referred to as B0, B2 and B4, respectively) and four salinity levels of 0, 2, 4 and 6 g kg−1 (referred as to S0, S2, S4 and S6, respectively). The results indicated that biochar addition significantly increased soil organic carbon (SOC), electrical conductivity (EC), soil water content (SWC), available nitrogen (AN) and phosphorus (AP) and mesopores fraction, but decreased soil bulk density (BD), pH and macropores fraction for different salinity levels. In general, biochar addition had an adverse effect on alfalfa yield due to the aggregated stresses from the increased EC and mesopores fraction, especially at high salinity levels. On average, biochar addition decreased the total yield of the two years by 14.2%, 25.3%, 38.3% and 60.4% for S0, S2, S4 and S6, respectively. Biochar addition significantly changed bacterial community composition with higher relative abundances of Proteobacteria and Bacteroidetes but lower relative abundances of Actinobacteria and Acidobacteria under S2–S6. On average, both soil salinity and biochar treatments decreased soil bacterial richness by 5.7–14.6% and 4.1–8.8% compared with S0 and B0, respectively, but they did not significantly affect the bacterial diversity. The redundancy analysis (RDA) suggested that EC, SWC, pH, AN and AP were the most critical factors driving the change of soil bacterial community structure accounting for 69.9%, 64.7% 61.6%, 57.0% and 51.8% of the variation, respectively. Therefore, our results provided valuable insight into how biochar addition would affect alfalfa yield and soil properties, including bacterial community richness and composition and structure of saline soils in arid regions.

Geochemical evidence of fluoride behavior in loess and its influence on seepage characteristics: An experimental study

High background levels of fluorine in groundwater and soil in arid and semi-arid loess regions pose a severe threat to socio-economic development and human health, necessitating the evaluation of fluorine migration in loess. In this study, static leaching and dynamic seepage tests as well as scanning electron microscopy, mercury intrusion porosimetry, and X-ray fluorescence analyses were conducted using loess as the porous medium. Additionally, simulations using PHREEQC software were performed. The results indicated that the studied loess had a high background level of fluorine. Geochemical processes closely related to fluorine include dissolution of gypsum and dolomite, precipitation/dissolution of calcite and fluorite, and ion exchange between CaX and NaX. Under seepage of water with high fluorine levels, soil particles flocculated and formed aggregates; furthermore, the contact area between soil particles reduced, resulting in point-to-point contact between particles. Consequently, pores changed from small (intra- and inter-particle pores) to large (intra- and inter-granular pores) scale pores. Permeability initially decreased rapidly, then remained relatively stable, and subsequently rapidly increased with the passage of time. This was attributed to the dissolution of calcium minerals in loess, yielding Ca2+, which induced the precipitation of fluorite and promoted the dissolution of carbonates. Cation exchange and dissolution of other components were also important factors influencing permeability. The findings of this study can elucidate the coupling between loess microstructure, seepage behavior, and geochemical actions under the influence of high‑fluorine water, and are of great significance for in-situ regional research in loess areas.

Efficiency assessment of the environmental variables in the Qanat systems based on major hydrological basins in Iran

Qanat system, as a great human heritage, contributes to the sustainable management of groundwater in the arid and semiarid regions of the world. The main aim of this paper was to efficiency assessment of the environmental variables in the construction of the Qanat system in Iran. Using the geographical information system (GIS) and statistical method of receiver operation characteristic (ROC), the efficiency of 20 environmental variables was assessed based on divisions of 30 major hydrological basins. Results revealed that most physical parameters and anthropogenic characteristics have significant effects on the construction of Qanat water lines with an AUC index > 0.6. The Pearson correlation test also confirmed the positive and significant relationships between the Qanat system and mentioned environmental parameters. From a geological viewpoint, the results highlighted the effective role of Quaternary aged alluvial sediments with very high permeability and low density of crust rocks in arid soils of arid and semiarid regions, such as playa fields in NamakTehran, Kavir, Lut, and Siahkuh basins. Regarding the spatial expansion of the Qanat system in Iran, the higher effects of some test variables, such as the climatic element of temperature, fault density, and drainage density, were rejected due to poor discrimination values of the AUC index < 0.6.

Advances of coupled water-heat-salt theory and test techniques for soils in cold and arid regions: A review

Soil salinization is a global problem that severely restricts agriculture as well as the engineering and construction industry. Understanding water and salt transport laws is key to soil salinity improvement and prevention. This paper divides the development of the theory of water-salt migration into positive and negative temperature effects, taking temperature as the boundary. A review of the coupling of heat, salt, mechanics, and gas based on water-salt migration is included, and the generation of positive and negative temperature driving forces is analyzed along with the numerical models proposed in their development and the development of indoor experiments. In the end, a review of indoor tests and in situ soil salinity monitoring techniques is presented, and the shortcomings of soil salinity at this stage are summarized. Based on the above, an outlook on the future direction of soil salinization in a carbon–neutral environment is presented.

An index of environmental and cultural suitability for the cultivation of climate-resilient castor bean in rainfed low-productivity common lands in Mexico

Castor bean plants yield commercially important oilseeds with multiple uses; they are characterised by tolerance to drought and adaptation to marginal soils in arid and semi-arid regions. In northern Mexico, a large amount of arid land is categorised as “ejidos”: a system of mixed land ownership managed under a specific legal system, where land users have access to common or individual (parcelled) land. This work aimed to examine the suitability of castor bean cultivation on unused marginal land in ejido land. To determine the environmental suitability of the ejido lands of Coahuila, Mexico, we adapted a land Productivity Index (PI) from an existing method; it consisted of a set of biophysical indicators (edaphic factors, climate, and topography) adapted to castor bean cultivation. We then complemented this index with a “cultural component”, assessing the ethnobotanical knowledge of the people, their willingness to implement a new crop type, and the type and current use of the land. As a result, we found that 114,300 ha of ejido land (1.76% of the total) were very suitable for castor bean cultivation according to the Environmental-PI and that 808,524 ha of ejido land (12.4% of the total) was very suitable according to the Cultural-PI. We also hypothesised that the willingness of “ejidatarios” to cultivate castor beans was related to their degree of knowledge about the plant and the land available for its cultivation; however, their willingness was mostly related to differences in land tenure: “ejidatarios” who own parcelled land were more interested in obtaining benefits from the land through the implementation of novel crops, compared to those who only have access to common land. Highlights • In Mexico, the “ejido” is a unique land ownership and management system where users have access to common or individual (parcelled) land. • According to our Environmental Productivity Index, 114,300 ha of ejido land in Coahuila, México, were very suitable for castor bean cultivation. • This index was complemented with a “cultural component” gauging the people’s perception and willingness to introduce castor bean as a new crop. • 808,524 ha (12.4%) of ejido land were very suitable for castor bean cultivation according to the cultural component of our index. • Differences in land tenure most strongly influence the willingness of the ejido people to cultivate castor beans.

An index of environmental and cultural suitability for the cultivation of climate-resilient castor bean in rainfed low-productivity common lands in Mexico

Castor bean plants yield commercially important oilseeds with multiple uses; they are characterised by tolerance to drought and adaptation to marginal soils in arid and semi-arid regions. In northern Mexico, a large amount of arid land is categorised as “ejidos”: a system of mixed land ownership managed under a specific legal system, where land users have access to common or individual (parcelled) land. This work aimed to examine the suitability of castor bean cultivation on unused marginal land in ejido land. To determine the environmental suitability of the ejido lands of Coahuila, Mexico, we adapted a land Productivity Index (PI) from an existing method; it consisted of a set of biophysical indicators (edaphic factors, climate, and topography) adapted to castor bean cultivation. We then complemented this index with a “cultural component”, assessing the ethnobotanical knowledge of the people, their willingness to implement a new crop type, and the type and current use of the land. As a result, we found that 114,300 ha of ejido land (1.76% of the total) were very suitable for castor bean cultivation according to the Environmental-PI and that 808,524 ha of ejido land (12.4% of the total) was very suitable according to the Cultural-PI. We also hypothesised that the willingness of “ejidatarios” to cultivate castor beans was related to their degree of knowledge about the plant and the land available for its cultivation; however, their willingness was mostly related to differences in land tenure: “ejidatarios” who own parcelled land were more interested in obtaining benefits from the land through the implementation of novel crops, compared to those who only have access to common land. Highlights • In Mexico, the “ejido” is a unique land ownership and management system where users have access to common or individual (parcelled) land. • According to our Environmental Productivity Index, 114,300 ha of ejido land in Coahuila, México, were very suitable for castor bean cultivation. • This index was complemented with a “cultural component” gauging the people’s perception and willingness to introduce castor bean as a new crop. • 808,524 ha (12.4%) of ejido land were very suitable for castor bean cultivation according to the cultural component of our index. • Differences in land tenure most strongly influence the willingness of the ejido people to cultivate castor beans.

Studies on Growth, Yield and Soil Fertility Status in Cluster Bean [Cyamopsis tetragonoloba (L.) Taub] cv. Pusa Navbahar under Natural Farming Practice in Comparison with Conventional Farming

Background: The cluster bean [Cyamopsis tetragonoloba (L.) Taub.] is a bushy annual herb having a deep rooted system and drought resilient leguminous crop grown on sandy soils of arid and semiarid regions. The production list of cluster bean is dominated by India as leading producers of the crop in the world contributing to around 75-82% of the total production. Methods: Field experiment was conducted in Block-I at The Regional Horticulture Research and Extension Center, Kumbapur, Dharwad. The authentic source of Cluster bean seeds of Pusa Navbahar were purchased from Nadakatti seeds, Dharwad. Treatments are imposed as T1 (Package of Practice: FYM @ 10 t/ha, 25:75:60 NPK Kg/ha), T2 (Farmers Practice: FYM @ 10 t/ha, 12.5:37.5:30 Kg/ha), T3 (Natural Farming: Ghanajeevamrutha @ 1000 Kg/ha and liquid jeevamrtha @ 500 l/ha every fortnightly interval, with organic mulching) and T4 (Organic Farming: FYM @ 15 t/ha). Result: Among four different farming practices, higher plant height at harvest was recorded in package of practice (80.0 cm). The higher number of pods per plant and higher dry biomass production was recorded in organic farming (102.3 and 2.14 t/ha) respectively. 26.8 per cent higher yield was recorded in organic farming (OF) over PoP. Nitrogen, phosphorus and potassium content and uptake in cluster bean was found significantly higher in PoP (2.13, 0.58 and 1.17%) and (42.20, 11.51 and 23.11 Kg ha-1) respectively. Natural farming treatment recorded significantly lower nutrients content and uptake.

The Effect of Salty Groundwater Levels on the Grass Yield of Some Pasture Crops and Soil Salinity

F. elatior, Puccinellia distans, Lotus strictus have been tested at 4 different water table depths which grow under natural conditions in salt-affected soils of arid and semi-arid regions. The trial was carried out for 3 years with split plots test design in randomized blocks. The salt concentration of the groundwater where irrigation has been made was between 3.1-4.4 dS m-1. The effect of water table depths on dry grass yields of the cultivars was found statistically significant in the first trial year (P

Analysis of CYGNSS coherent reflectivity over land for the characterization of pan-tropical inundation dynamics

The monitoring of flood and wetland dynamics at global scale is hampered by several limitations, including a reduced data availability in tropical areas due to the presence of clouds affecting visible and infrared imagery, or low spatial and/or temporal resolutions affecting passive and active microwave Earth Observation (EO) data. As a consequence, surface water extent estimates and their temporal variations remain challenging especially in equatorial river basins. Global Navigation Satellite System Reflectometry (GNSS-R) L-band signals recorded onboard Cyclone GNSS (CYGNSS) mission, composed of 8 Low Elevation Orbit (LEO) satellites, provide information on surface properties at high temporal resolution from 2017 up to now. CYGNSS bistatic observations were analyzed for detecting permanent water and seasonal floodplains over the full coverage of the mission, from 40°S to 40°N. We computed CYGNSS reflectivity associated to the coherent component of the received power, that was gridded at 0.1° spatial resolution with a 7-day time sampling afterwards. Several statistical metrics were derived from CYGNSS reflectivity, including the weighted mean and standard deviation, the median and the 90th percentile (respectively Γmean,Γstd,Γmedian and Γ90%) in each pixel. These parameters were clustered using the K-means algorithm with an implementation of the Dynamic Time Warping (DTW) similarity measure. They were compared to static inundation maps, and to dynamic estimations of surface water extent both at the global and regional scales, using the Global Inundation Extent from Multi-Satellites (GIEMS) and MODIS-based products. The difference between Γ90% and Γmedian shows the best sensitivity to the presence of water. The river streams and lakes are correctly detected, and a strong seasonality is identified in CYGNSS reflectivity over the largest floodplains, with the exception of the Cuvette Centrale of Congo which is covered by dense vegetation. This seasonal reflectivity signal correlates well with inundation maps: Pearson’s correlation coefficient between Γmedian and surface water extent from both GIEMS and MODIS is over 0.8 in the largest floodplains. The spatial patterns of reflectivity are consistent with static inundation maps: at the time of maximum flooding extent, a spatial correlation coefficient around 0.75 with Γmedian is obtained for several basins. We also evaluated the dependence of CYGNSS-derived clusters and reflectivity on the dominant land cover type and on the density of Above Groud Biomass (AGB) in the pixel. On the one hand, misclassifications of flooded pixels were observed over vegetated regions, probably due to uncertainties related to the attenuation by the vegetation in both CYGNSS and reference datasets. On the other hand, flooded pixels with a mean AGB up to ∼300 Mg/ha were correctly detected with the clustering. High reflectivity values are also observed over rocky soils in arid regions and create false alarms. Finally, strong winds on large lakes cause surface roughness, and lower reflectivity values are observed in this case which weaken the detection of open water. While these constraints are to be taken in account and corrected in a future model, a pan-tropical mapping of surface water extent dynamics using CYGNSS can be envisaged.

Nitrogen enriched chemically produced carbon supplementary impacts on maize growth under saline soil conditions

Poor organic matter and nitrogen (N) deficiency along with salinity in arid and semiarid region soils are major hurdles to optimization of cereal's yield. In different cereals, maize productivity is significantly decreased due to less availability of N in low organic matter soils. Scientists suggest the incorporation of organic fertilizers to overcome this issue. That’s why the current study was conducted to explore the effectiveness of chemically produced nitrate blended acidified carbon (NBC). There were 3 levels of NBC i.e., 0, 0.50 and 1.00% applied under naturally normal and saline soils having EC 2.75 and 6.19 dS/m respectively. Results showed that the addition of 1.00NBC was significantly better compared to 0NBC for improvement in maize growth attributes i.e., root (32.86 and 77.84%) and shoot (74.17 and 67.57%) length, shoot fresh (53.98 and 97.42%) and dry weight (53.20and 84.20%), root dry (45.97 and 53.66%) and fresh weight (45.62 and 25.14%) in normal and saline conditions respectively. A significant enhancement in chlorophyll a, b, total and carotenoids of maize leaves also validated the imperative role of 1.00NBC than 0NBC in saline and normal soil. Application of 1.00BC also significantly decreases leaves electrolyte leakage and Na concentration in root and leaves over 0NBC in saline soils. In conclusion, 1.00NBC is an effective amendment to improve maize growth in saline soil. More investigations are suggested on different cereal crops under variable agroclimatic zones to declare 1.00NBC as the most effective amendment for alleviation of salinity stress.

A Review on Challenges and Opportunities in Management of Soils of Arid and Semi-Arid Regions of Kenya

Arid and semi-arid lands occupy currently 88% of arable land mass in Kenya, a region with significant diversity of production systems and economic opportunities. However, these areas are characterised by low and erratic rainfall, hence challenges to agriculture and socioeconomic development in the wake of an increasing population and the impacts of climate change. This review seeks to identify key challenges and opportunities associated with the management of agricultural soils in these arid and semi-arid communities. Arid and semi-arid regions in Kenya are dominated by 10 soil types; Solanchaks, Solonetz, Cambisols, Arenosols, Leptosols, Vertisols, Fluvisols, Phoezems, Calcisols, and Gypsisols. Among the main soil fertility challenges in these soils are moisture stress, high erodibility, and low organic matter content, salinity, and sodium toxicity, the deficiencies of mainly N, P, Zn, and Fe, hence the vulnerability of over 14 million inhabitants to the shocks of low crop and pasture production. Moreover, the adoption of soil conservation practices remains low as existing soil fertility management technologies have been criticized for being too abstract and not providing context and site-specific solutions. Improving soil fertility and moisture levels enhances soil ecosystem functions and food and pasture production in these regions. Encouraging farmers to join soil and water conservation groups, while providing economic incentives, could potentially accelerate the adoption of soil and water practices at the farm level through pulling resources together. Future research to validate a site and context-specific integrated soil fertility improvement technologies for these soils is evitable to enhance soil functions, agricultural production and livelihood at house hold level.

Zinc toxicity response in Ceratoides arborescens and identification of CaMTP, a novel zinc transporter.

Zinc (Zn) is an essential micronutrient for several physiological and biochemical processes. Changes in soil Zn levels can negatively affect plant physiology. Although the mechanism of Zn nutrition has been studied extensively in crops and model plants, there has been little research on steppe plants, particularly live in alkaline soils of arid and semiarid regions. Ceratoides arborescens is used in arid and semiarid regions as forage and ecological restoration germplasm, which is studied can enrich the mechanism of Zn nutrition. The plants were exposed to three different Zn treatments, Zn-deficient (-Zn 0 mM L−1), Zn-normal (Control, 0.015 mM L−1), and Zn-excess (+Zn, 0.15 mM L−1), for 3 weeks. Individual biomass, ion concentrations, photosynthetic system, and antioxidant characteristics were measured. High Zn supply significantly decreased plant biomass and induced chlorosis and growth defects and increased Zn concentration but decreased Fe and Ca concentrations, unlike in controls (p < 0.05). High Zn supply also reduced plant chlorophyll content, which consequently decreased the photosynthesis rate. Increased concentrations of malondialdehyde and soluble sugar and activities of peroxidase and superoxide dismutase could resist the high-level Zn stress. In contrast, low Zn supply did not affect plant growth performance. We also identified a novel protein through RNA transcriptome analysis, named CaMTP, that complemented the sensitivity of a yeast mutant to excessive Zn, which was found to be localized to the endoplasmic reticulum through transient gene expression in Nicotiana benthamiana. The gene CaMTP identified to be highly sensitive to Zn stress is a potential candidate for overcoming mineral stress in dicot crop plants.

Effect of Compost and Synthetic Fertilizer on Soil Fertility, Yield and Nitrogen Use Efficiency of Broccoli Crop in Arid Region of Morocco

Background: Soils in arid regions like Morocco are becoming increasingly degraded and polluted because of the high use of synthetic chemical fertilizers linked to population growth. Organic fertilizers such as compost remain a good alternative to improve soil quality and crop yields. Broccoli is a crop that is beginning to develop in Morocco. It is very nitrogen demanding crop; therefore, it is necessary to know nitrogen use efficiency in broccoli. Methods: In this field experimental conducted during 2015 at the horticultural complex of Agadir - Agronomy and Veterinary Institute Hassan II, different treatments were tested on broccoli as follows:TC8t/ha: compost, 8 t/ha (equivalent 200 kgN /ha), TC12t/ha: compost, 12 t/ha (equivalent 300 kg N /ha), TSYN: Synthetic chemical fertilizer (200kg N/ha), TC+SYN: 50% compost, 4t/ha+50% Synthetic fertilizer (equivalent 200 kg N/ha) and T0: control, in order to optimize nitrogen use efficiency of compost and synthetic fertilizer. Result: Our research showed that the combination of compost and synthetic fertilizer: TC+SYN improved the growth and yield parameters of broccoli; the best main head yield of broccoli was 13.5 t/ha for TC+SYN. Compost improved the chemical properties of soil. Total N content was 266 kg/ha for TC+SYN, 253 kg/ha for TSYN, 244 kg/ha for TC8 t/ha and 234 kg/ha forTC12 t/ha. For Nitrogen use efficiency, apparent recovery efficiency (ARE) was higher with TSYN: 0.91 followed by TC+SYN: 0.88 followed by TC8t/ha with 0.77and T C12 t/ha: 0.48.

Soil Contamination by Phthalate Esters in Cultivated and Non-Cultivated Soils in North African Arid Regions: A Tunisian Case Study

Over the last decades, several studies showed that phthalic acid esters (PAEs) were ubiquitous environmental contaminants and became a major threat to human health. This study provided the first case study about the concentration and the potential sources of soil’s PAEs, both in Tunisia and North Africa. Soil samples were collected from four cultivated (CS) and two adjacent native soils (NS) at 0-10 cm and 10-30 cm layers in southeastern Tunisia. The PAEs concentrations were analyzed using a gas chromatography-mass spectrometry (GC-MS) system. Results showed that the total concentration of PAEs ranged from 2.40 to 11.05%. Higher values were detected in NS in the 0-10 cm layer contrary to CS which showed higher PAEs concentration in 10-30 cm depth. The di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were the most abundant PAEs. In the 0-10 cm layer, PAEs concentration was highly related to the age of the plastic film in CS. We observed a positive association between PAEs concentration and conductivity (EC) values. The PAEs concentrations were affected by the presence of soil organic matter (SOM) in CS. This decrease of PAEs in CS compared to the NS may be related to the microbial decomposition activity stimulated by the presence of fresh organic residues and fertilizers. These results showed that CS and adjacent NS in the studied regions were contaminated by PAEs which is probably a result of agricultural activities. More investigations on PAEs concentrations in various soil managements are needed to confirm these results.

Role of composted organic material in reducing hazardous effect of salinity stress on biological nitrogen fixation and plant growth in salt affected soils of arid region

Application of organic matter (OM) has shown positive effects on growth and yield of crop grown under soil salinity stress. The present study was conducted to estimate effectiveness of OM in enhancing Biological Nitrogen Fixation (BNF) in soil and in return improving growth and yield of cowpea. Therefore, role of (OM) in alleviating impact of salinity stress on (BNF) in soils of arid region was evaluated in medium textured soils of different content of salts content. Experiment was conducted in pots under greenhouse conditions. Salinity range studied was 3.5, 8.2 and 12.4 dSm-1 in J1, J2, and J3 soil respectively. Compost as OM was added at 15, 25 and 50 g Kg-1 soil. Cowpea local variety was used as a test crop. Total nitrogen in soils without the addition of organic matter after harvesting was the least at the highest salinity level and the highest was in the soil of the least salinity level. Number of root nodules reduced by 27.0% and 49.0% when soil salinity increased to 8.2 and 12.4 dSm-1, respectively, compared to that in soil of 3.5 dSm-1. Total N in Cowpea plant linearly increase with the increase of level of (OM) addition. Rate of Increase in total N was the highest at the lowest salinity level soil and was the least at the highest salinity level soil. Weight of root nodules decreased by 45% when soil salinity increased by 42%. Addition of OM at a rate of 25 g OM Kg-1 soil to J1 soil of (3.5 dSm-1) and soil J3 of 12.4 dSm-1 weight of root nodules increased by 47.0%. and 21.7%, respectively. Dry weight of Cowpea plant grown in the three soils received different levels of OM decreased with the increase of soil salinity irrespective of level of OM addition. Addition of OM at a rate of 15, 25, and 50 g kg-1 soil of 3.5 dSm-1 seed yield increased by 65%,130%, and 136% respectively. These results had confirmed the role of OM in alleviating salinity stress on BNF process in soil.

Ensemble HYDRUS-2D modeling to improve apparent electrical conductivity sensing of soil salinity under drip irrigation

Monitoring and mapping soil salinity are valuable for irrigation management and reclamation of salt-affected agricultural soils in arid and semi-arid regions. Proximal measurements of apparent soil electrical conductivity (ECa) can help characterize soil salinity spatial distributions. However, ECa is not solely a function of salinity. ECa is strongly influenced by soil salinity, water content, and edaphic properties such as texture and bulk density. Consequently, monitoring and mapping salinity based on geospatial ECa measurements is challenging in fields with dynamic and spatially complex patterns of salinity and water content, such as occurs under drip irrigation. We conducted a numerical modeling study to evaluate protocols for using proximal ECa sensing in drip irrigated systems, focusing specifically on the measurement distance from the drip-line that consistently identifies areas of high salinity in the rootzone. The measurement distance was evaluated as a function of six irrigation management parameters: soil hydraulic conductivity, irrigation discharge, irrigation interval, solute concentration, root-zone volume, and leaching fraction. HYDRUS-2D was used to run a 729 member ensemble of drip irrigation simulations of water and solute dynamics under different irrigation management scenarios. Two case studies were simulated for clay loam soil: (1) low salinity soil irrigated with high salinity irrigation water and (2) high salinity soil irrigated with low salinity water. Depth-averaged ECa measurements down to the 75 and 150 cm depths, such as can be obtained using an electromagnetic induction (EMI) sensor, were evaluated in the simulations. According to the ensemble results, a reliable EMI measurement distance from the drip-line was about 100 cm for the case of low salinity irrigation in saline soil and adjacent to the drip-line for the high salinity irrigation. The ensemble ECa and EC of saturated paste extract (ECe) distributions were twice as sensitive to the irrigation water salinity level as compared to the other irrigation management parameters. The probabilistic ensemble approach can be extended to a variety of case studies to aid soil scientists and agricultural consultants monitoring and mapping soil salinity with ECa-directed soil sampling for micro-irrigation systems.

Halophytes play important role in phytoremediation of salt-affected soils in the bed of Urmia Lake, Iran

Soil salinity is a major threat in agriculture even in semi-arid regions of the world which can accelerate land degradation and desertification and decrease agricultural productivity and consequently jeopardize environmental and food security. Halophytes play important role in phytoremediation. This study is assessed the potential of Halocnemum strobilaceous, Atriplex verruciferae, Salsola crassae, and Salicornia europaeae in phytoremediation of saline soils occurred after water level desiccation of Urmia Lake. Three distances from the water body (500, 1000, and 1500 m) was selected for evaluating. Soils and plants were analyzed using standard methods. The mean values of salinity indices of the saline-sodic soil samples were identified as pH 8.6 and electrical conductivity (ECe) 65.34 dS m−1, also sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) were higher than 13 and 15%, respectively. The maximum soil exchangeable Na+, K+, and Ca2+ concentrations (7200, 1900, and 1400 mg kg−1, respectively), also the concentrations of Mn2+ (12.5 mg kg−1), Fe2+ (5.5 mg kg−1), and Cu2+ (1.5 mg kg−1), were significantly different at various distances. However, the highest amounts were obtained at 500 m. In addition the concentration of Fe2+ (511.85 mg kg−1), Zn2+ (99.97 mg kg−1), and Na+ (25.65 mg kg−1) was the highest, especially in shoots. Furthermore, Salicornia and Halocnemum were more effective in salinity-remediation in comparison to other halophytes. The maximum dry matter (38%), protein (16%), and oil percentage (3.5%) were found in Salicornia, followed by Halocnemum. The findings indicated that salt-accumulating halophytes could be considered as the suggestions for phytoremediation saline soils and desalinating soil in arid and semi-arid regions.

Update on the Epidemiology, Diagnosis, and Treatment of Coccidioidomycosis.

Coccidioidomycosis is a fungal infection caused by Coccidioides immitis and Coccidioides posadasii. The dimorphic fungi live in the soils of arid and semi-arid regions of the western United States, as well as parts of Mexico, Central America, and South America. Incidence of disease has risen consistently in recent years, and the geographic distribution of Coccidioides spp. appears to be expanding beyond previously known areas of endemicity. Climate factors are predicted to further extend the range of environments suitable for the growth and dispersal of Coccidioides species. Most infections are asymptomatic, though a small proportion result in severe or life-threatening forms of disease. Primary pulmonary coccidioidomycosis is commonly mistaken for community-acquired pneumonia, often leading to inappropriate antibacterial treatment and unnecessary healthcare costs. Diagnosis of coccidioidomycosis is challenging and often relies on clinician suspicion to pursue laboratory testing. Advancements in diagnostic tools and antifungal therapy developments seek to improve the early detection and effective management of infection. This review will highlight recent updates and summarize the current understanding of the epidemiology, diagnosis, and treatment of coccidioidomycosis.

Does Phosphorus Fertilization Increase Biomass Production and Salinity Tolerance of Blue Panicum (Panicum antidotale Retz.) in the Salt-Affected Soils of Arid Regions?

High soil salinity, drought, and poor soil fertility, especially phosphorus (P) deficiency, are serious challenges for crop production in arid and desert climate regions. In these regions, irrigation water (mostly groundwater) is saline, and fertilization is one of the strategies used to cope with salinity stress. Crop livestock is one of the major agricultural activities in marginal regions, and blue panicum (Panicum antidotale Retz.), the perennial forage grass, has the potential to furnish forage demand. Thus, a field experiment testing the combination of three levels of irrigation water salinity and three P rate was carried out to evaluate the potential of P fertilizer to enhance yield and salinity tolerance of blue panicum grass. The experiment was conducted for two years between 2019 and 2020 in Foum el Oued, Laayoune, Morocco. It was implemented in a split-plot design with three replications considering irrigation water salinity as the main plot and P rates as sub-plot treatments. The evaluated P rates were 0, 90, and 108 kg P2O5 ha−1 (P1, P2, and P3, respectively), and the irrigation water salinities were 5, 12, and 17 dS·m−1. The results revealed that increasing irrigation water salinity significantly decreased the biomass production and stomatal conductance of blue panicum. Increasing irrigation water salinity from 5 to 12 and 17 dS·m−1 decreased fresh biomass production by 20 and 29%, respectively. Irrigation water salinity also decreased (p &lt; 0.05) leaf N, P, K, Ca, and Zn concentration. However, supplementation of P fertilization enhanced (p &lt; 0.05) biomass production and stomatal conductance mainly by improving leaf OM, Zn, and Fe content. P fertilization at 108 kg P2O5 ha−1 increased fresh biomass by 27%, 32%, and 19% under 5, 12, and 17 dS·m−1, respectively. Considering increased fresh biomass yield, P application at the rate of 108 kg P2O5 ha−1 can be suggested for saline drylands. P application is recommended to reduce the adverse effects of high salinity on growth and productivity and improve salinity tolerance of blue panicum in salt-affected arid and desert regions.