Soils Of Semi-arid Regions Research Articles

Drought and its legacy modulate the post-fire recovery of soil functionality and microbial community structure in a Mediterranean shrubland.

The effects of drought on soil dynamics after fire are poorly known, particularly its long-term (i.e., years) legacy effects once rainfall returns to normal. Understanding this is particularly important for nutrient-poor soils in semi-arid regions affected by fire, in which rainfall is projected to decrease with climate change. Here, we studied the effects of post-fire drought and its legacy on soil microbial community structure and functionality in a Cistus-Erica shrubland (Spain). Rainfall total and patterns were experimentally modified to produce an unburned control (natural rainfall) and four burned treatments: control (natural rainfall), historical control (long-term average rainfall), moderate drought (percentile 8 historical rainfall, 5months of drought per year), and severe drought (percentile 2, 7months of drought). Soil nutrients and microbial community composition (ester-linked fatty acid approach) and functionality (enzyme activities and C mineralization rate) were monitored during the first 4years after fire under rainfall treatments, plus two additional ones without them (six post-fire years). We found that the recovery of burned soils was lower under drought. Post-fire drought increased nitrate in the short term and reduced available phosphorus, exchangeable potassium, soil organic matter, enzyme activities, and carbon mineralization rate. Moreover, drought decreased soil total microbial biomass and fungi, with bacteria becoming relatively more abundant. Two years after discontinuing the drought treatments, the drought legacy was significant for available phosphorus and enzyme activities. Although microbial biomass did not show any drought legacy effect, the proportion of fungi and bacteria (mainly gram-positive) did, being lower and higher, respectively, in former drought-treated plots. We show that drought has an important impact on soil processes, and that some of its effects persist for at least 2years after the drought ended. Therefore, drought and its legacy effects can be important for modeling biogeochemical processes in burned soils under future climate change.

Characterization and Classification of Soils in Semi-arid Region of Tatrakallu Village of Anantapuramu District in Andhra Pradesh

Characterization and Classification of Soils in Semi-arid Region of Tatrakallu Village of Anantapuramu District in Andhra Pradesh

Characterization, Classification and Evaluation of Soils in Semi-arid Region of Mahanandi Mandal in Kurnool District of Andhra Pradesh

Ten representative pedons from surroundings of Mahanandi mandal in Kurnool district, Andhra Pradesh were studied for their morphological and physicochemical properties, and nutrient status. These soils were deep to very deep, neutral to moderately alkaline (pH 7.3–8.3), non-saline (0.19–1.00 dS m−1), low to medium in organic carbon (0.2–7.5 g kg−1) and low to high in CEC [4.31–52.11 cmol(p+)kg−1 soil]. Soils were low to medium in available nitrogen (62.7–545.7 kg ha−1), low to high in available phosphorus (2.7–65.7 kg ha−1), high in available potassium (149–1125 kg ha−1) and deficient to sufficient in available sulphur (1.3–79.2 mg kg−1). The DTPA extractable Zn (0.02–4.97 mg kg−1), Fe (0.46–22.56 mg kg−1), Cu (0.02–0.55 mg kg−1) and Mn (0.27–30.80 mg kg−1) were deficient to sufficient. Pedon 2 having argillic (Bt) horizon was classified as Typic Haplustalfs and other pedons with cambic horizon (Bw) were classified as Fluventic Haplustepts (pedons 1, 4, 6, 8, 9 and 10), Aridic Ustorthents (Pedon 5), Typic Haplustepts (Pedon 3) and Vertic Calciustepts (Pedons 7).

Microbiomes of Top and Sub-Layers of Semi-Arid Soils in North-Eastern Nigeria Are Rich in Firmicutes and Proteobacteria with Surprisingly High Diversity of Rare Species

Borno state is the second largest state in Nigeria with over 70,000 square kilometers of diverse ecosystems including parts of the fertile Lake Chad basin. However, more than 2/3 of this landmass is threatened with drought, advancing desertification and degraded soils. Most restoration efforts involve revegetation, which in the past has met with limited success. Microbial communities of soils play a pivotal role in soil fertility and plant cover. We conducted the first metagenomic amplicon sequencing study, comparing two soil depths to determine whether soil bacteria abundance and diversity in the harsh bare soils were sufficient to sustain greening efforts. The goal was to glean insights to guide microbial inoculant formulation needed in the region. Samples from top (0 - 15 cm) and sub (16 - 65 cm) soils were collected from five strategic locations in the state. Using next generation Illumina sequencing protocols, total DNA extracted directly from the soils was sequenced and analyzed by QIIME. Metadata collected from site showed scorching temperatures of over 46˚C, near zero moisture level and a pH of about 6 for top soil. At 65 cm depth, the temperature averaged 32˚C with a pH of 5 and significantly higher soil moisture of 0.1%. The bacterial community structure was unexpectedly very diverse at both soil depths samples, recording a ChaO1 index ranging from 909 to 4296 and a Shannon diversity range of 3.54 to 6.33. The most abundant phyla in both soil depths were the Firmicutes and Proteobacteria; however the relative abundance of composite lower taxa was strikingly different. Operational taxonomic units and diversity indices were highest for top soils and were dominated by members of resilient groups of Actinobacteria, Firmucutes, Acidobacteria and numerous other less well-known taxa whose individual relative abundance did not exceed 3% of total population. The high diversity and richness of Proteobacteria (at 65 cm depth), some of which are key to soil fertility, suggest that revegetation efforts could be improved by shifting the gradient of these microbiota upwards using shades and micro-irrigation. Soils in semi-arid regions in Nigeria contain numerous operational taxonomic bacterial groups with potential thermophilic and drought genetic resources to be mined. Microbial community structure beneath the top soil appears stable and should be the target sample for the assessments of climatic change impact on microbial community structure in environments like this.

Potentialities and limitations of agricultural use in soils of semi-arid region of the state of Bahia.

The objective of this study was to evaluate the potentialities and limitations of the agricultural use of representative classes of semi-arid regions of the state of Bahia, based on the pedological and evaluation of their soil characteristics. Five areas were selected where trenches were opened to collect samples for the analyses: Eutric Haplustept which presents vulnerability to physical and chemical degradation due to poor drainage with risks of erosion, waterlogging, salinization and compaction but having good natural fertility; Abrupt Kandiustalf with high vulnerability to physical degradation due to the presence of gravel and pebbles which may limit the development of deep rooting plants and mechanization but also with good natural fertility; Typic quartzipsaments and Typic Eutrustalf with no limitations related to drainage as low risk of compaction but featuring limitation of low moisture-holding capacity and nutrients; and Arenic Haplustulf wose characteristics are high vulnerability to degradation due to the drainage limitation related to the Btx horizon cementing in addition to low natural fertility and therefore is not recommended to agricultural use. However, in general, they feature no serious impediments for agricultural use. The amounts of OM is low in all soils but the use of management systems aiming at their accumulation and maintenance in appropriate levels will contribute to the CEC increase as well as to improve the chemical and physical properties.

Environmental controls and long-term changes on carbon stocks under agricultural lands

Improved understanding of changes in soil organic carbon (SOC) stocks is critical for developing strategies that ensure effective climate change mitigation and the long-term productivity. Changes in SOC are likely to vary across soil and climate conditions, yet long-term data to elucidate these trends across different ecosystems remains limited. In this study we evaluated long-term changes in SOC across a gradient of climate conditions (from arid to hyper humid), soil orders, and land uses (non- cultivated, woody perennial, and cultivated) in central Chile. Thus, we sought to find evidence for SOC changes in the agricultural lands over past three or four decades. Surface soils (8–29 cm depth) were sampled between 2014 and 2016 and analyzed for total C and N content, aggregate stability, texture, bulk density, pH as well as spectral properties using Mid-infrared (MidIR) and Near-infrared spectroscopy. SOC stocks were compared to those previously measured at the same sites between 1968 and 1994, covering a wide range of SOC values (from 12 Mg C ha−1 to 128 Mg C ha−1). Our findings show that the largest SOC losses occurred in semiarid and subhumid areas for the time frame considered, decreasing from their initial C stocks by 24.7% and 26.1%, respectively. Moreover, cultivated soils in semiarid regions were more vulnerable than those in arid regions to SOC losses. The results also indicated that in cooler and humid regions, SOC stocks were stable or increased over time. Among soil orders, Mollisols showed the largest losses (29.9% reduction between sampling dates). The MidIR results indicate that the mineral bands for clays and silicates were associated with these sites demonstrating SOC conservation, suggesting that mineral protection played an important role in the long-term SOC storage in semiarid areas. This study provides a better understanding of temporal changes of SOC to address the restoration of degraded land and adaptation for future trends in global change.

Preliminary study on phosphate solubilizing Bacillus subtilis strain Q3 and Paenibacillus sp. strain Q6 for improving cotton growth under alkaline conditions.

BackgroundLow phosphorus availability limits crop production in alkaline calcareous soils in semi-arid regions including Pakistan. Phosphate solubilizing bacteria may improve crop growth on alkaline calcareous soils due to their ability to enhance P availability.MethodsTwenty rhizobacterial isolates (Q1–Q20) were isolated from rhizosphere of cotton and characterized for their growth promoting attributes in vitro. The selected phosphate solubilizing isolates were further screened for their ability to improve cotton growth under axenic conditions (jar trial). The phosphorus solubilization capacities of selected strains were quantified and these strains were identified through 16S rDNA sequencing.ResultsIsolates Q2, Q3, Q6, Q7, Q8, Q13 and Q14 were able to solubilize phosphate from insoluble sources. Most of these isolates also possessed other traits including catalase activity and ammonia production. The growth promotion assay showed that Q3 was significantly better than most of the other isolates followed by Q6. Maximum root colonization (4.34 × 106 cfu g−1) was observed in case of isolate Q6 followed by Q3. The phosphorus solubilization capacities of these strains were quantified, showing a maximum phosphorus solubilization by Q3 (optical density 2.605 ± 0.06) followed by the Q6 strain. The strain Q3 was identified as Bacillus subtilis (accession # KX788864) and Q6 as Paenibacillus sp. (accession # KX788865) through 16S rDNA sequencing.DiscussionThe bacterial isolates varied in their abilities for different growth promoting traits. The selected PGPR Bacillus subtilis strain Q3 and Paenibacillus sp. strain Q6 have multifarious growth promoting traits including ability to grow at higher EC and pH levels, and phosphorus solubilizing ability. These strains can efficiently colonize cotton roots under salt affected soils and help plants in phosphorus nutrition. It is concluded that both strains are potential candidates for promoting cotton growth under alkaline conditions, however further investigation is required to determine their potential for field application.

Soil-landscape relationship as indicated by pedogenesis data on selected soils from Southwestern, Iran

Soils of semiarid regions of Dehdasht and Choram in Southwestern Iran have formed on alluvium derived from mixed calcareous-gypsiferous materials from Lower Miocene to Upper Pliocene. In order to characterize and classify the soils and to determine the soil-landscape relationship in the area, nine pedons located on different physiographic positions including plateau, river alluvial plain, piedmont plain, alluvial plain and alluvial fan have been described, sampled and analyzed. Physicochemical analyses, clay mineralogy and micromorphological studies were performed. The results showed that topography and parent material were two important soil forming factors affecting soil formation in the area. The soils were dominated by carbonate, gypsum, and clay illuviation and accumulation. More developed soils were found on the stable plateau and piedmont plain. Clay illuviation and argillic horizon development in soils of the more stable alluvial plain were assumed to be relict features from presumably more humid climates. Palygorskite, illite, chlorite, smectite, kaolinite, and quartz clay minerals were identified in almost all physiographic surfaces, but more palygorskite and less smectite were found in the soils with gypsiferous parent materials. Observations by SEM revealed the occurrence of neoformed palygorskite as thread-like faces and coating of gypsum crystals and marly matrix. Coating and infilling of gypsum and calcite crystals in voids and channels were common pedofeatures observed in the soils studied. Two different distribution patterns of Fe-Mn oxides were identified in aquic and non-aquic soils.

Combination of plastic film mulching and AMF inoculation promotes maize growth, yield and water use efficiency in the semiarid region of Northwest China

Plastic film mulching (PFM) plays a critical role in improving crop production and sustainable development of agroecosystem in semiarid agriculture. Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with the vast majority of plant roots and have been shown to contribute to host growth in harsh conditions. Yet, whether the integrated application of PFM and AMF inoculation have an interactive effect on crop growth and production in semiarid regions with poor soil nutrients and water shortage has received rather less attention. Therefore, we performed a two-year field study to investigate the effects of PFM and AMF inoculation on spring maize growth, yield and water use efficiency (WUE). Four treatments, including non-mulching and non-AMF inoculation (CK), plastic film mulching (PFM), arbuscular mycorrhizal fungi inoculation (AMF) and combination of plastic film mulching and arbuscular mycorrhizal fungi inoculation (PAMF), were compared in 2014 and 2015 at Shenmu Country on the semiarid Loess Plateau of Northwest China. Our results indicated that AMF inoculation contributed to increased plant biomass and height, although its effectiveness was lower than PFM alone or combined practice. Compared with the non-mulched control (CK), the mulched treatments significantly increased the average soil water content by 43.2% at the depth of 0–60 cm in 2014 and by 30.3% at the depth of 0–30 cm in 2015. The combination of PFM and AMF inoculation had the greatest soil water content at different soil depths in both years. AMF inoculation significantly improved root mycorrhizal colonization and external hyphal length in both years. Meanwhile, mycorrhizal plants under PFM had significantly greater root tip number and surface area when compared with the control. PAMF treatment had the highest yield and WUE among all treatments. Compared with the CK, PAMF treatment increased the yield and WUE by55.6% and 43.1% in 2014 and by 39.3% and 45.6% in 2015, respectively. Moreover, the mycorrhizal dependency of maize yield was more notable in mycorrhizal plants grown in mulched soils than in bare soils. In conclusion, the combined application of PFM and AMF inoculation is an effective and favorable agricultural practice in nutrition-deficiency soil in semiarid regions of China because of improved root morphological traits and enhanced topsoil water content that increase crop productivity.

Changes in attributes of soils subjected to fallow in desertification hotspot

ABSTRACT Soils in semi-arid regions have been degraded by overgrazing, which reduces the production capacity and, in certain situations, leads to desertification. An alternative to recover degraded areas is the fallow period, which works through the resilience of the soil itself, increasing the supply of organic matter and improving soil physical properties. Thus, the objective of this study was to test the hypothesis that 14-year grazing exclusion improves soil physical and chemical attributes in degraded areas under desertification. The study was conducted in Iraucuba, Ceara State, Brazil. The experimental design was completely randomized, in a 4 x 2 factorial scheme corresponding to four areas and two managements (overgrazing and fallow), with four replicates, plus an area with native vegetation (reference), with characteristics of secondary vegetation. Fallow led to improvements in soil physical and chemical attributes after 14 years; however, in comparison to the study conducted in the same area with a 7-year fallow period, there were few alterations. Organic carbon content was higher in fallow areas than in overgrazing areas, and the fraction in highest proportion was the mineral-associated organic carbon.

Effects of planting patterns and sowing densities on grain-filling, radiation use efficiency and yield of maize (Zea mays L.) in semi-arid regions

The ridge-furrow rainwater harvesting system is a valuable technique for collecting runoff water and increasing radiation use efficiency to improve crop production. Field experiments were conducted over two consecutive years (2015–16) on a loess soil in semi-arid regions of China. Three different planting densities (L: 52500 plant ha−1; M: 75000 plant ha−1; H: 97500 plant ha−1) and three different planting patterns (RF: ridge and furrow rainfall harvesting system; FM: flat planting with plastic film mulching; CP: conventional planting without plastic film) were used to measure various maize characteristics. The objectives were to enhance the water use efficiency (WUE), radiation use efficiency (RUE), and promote the grain-filling process and yields of maize. The results showed that under the same densities, there was no significant differences between the average filling rate (Gmean) and the maximum filling rate (Gmax) (P>0.05) during the normal-precipitation year (2015). However, the Gmean and Gmax in the RF and FM treatments were significantly higher than the CP treatment in dry year (2016). Under the same densities, the number of grains per row, number of kernels per ear, and kernel yield per plant of RF and FM treatments were significantly higher than those of the CP treatment. These maize yield components decreased with increased planting densities under the same planting patterns. Compared to the CP treatment, the average annual grain yield under the RF and FM treatments increased by 33.4% and 30.0%, respectively. Compared to the CP treatment, the average annual RUE in the RF and FM treatments increased by 12.4% and 11.5% before silking and increased 17.7% and 14.7% after silking, respectively. Under the RF system with a middle planting density (M-RF) promoted grain-filling rate, grain yield, yield components, WUE, and RUE. Therefore, we concluded that M-RF model is the most suitable for increases maize yield and RUE in the semi-arid regions of China.

Towards prediction of soil erodibility, SOM and CaCO3 using laboratory Vis-NIR spectra: A case study in a semi-arid region of Iran

Soil Visible–Near-Infrared (Vis-NIR) spectroscopy has become an applicable and interesting technique to evaluate a number of soil properties because it is a fast, cost-effective, and non-invasive measurement technique. The main objective of the study to predict soil erodibility (K-factor), soil organic matter (SOM), and calcium carbonate equivalent (CaCO3) in calcareous soils of semi-arid regions located in south of Iran using spectral reflectance information in the Vis-NIR range. The K-factor was measured in 40 erosion plots under natural rainfall and the spectral reflectance of soil samples were analyzed in the laboratory. Various soil properties including the CaCO3, soil particle size distribution, SOM, permeability, and wet-aggregate stability were measured. Partial least-squares regression (PLSR) and stepwise multiple linear regression (SMLR) were used to obtain effective bands and develop Spectrotransfer Function (STF) using spectral reflectance information and Pedotransfer Function (PTF) to predict the K-factor, respectively. The derived STF was compared with developed PTF using measurable soil properties by Ostovari et al. (2016) and the Universal Soil Loss Equation (USLE) predictions of the K-factor. The results revealed that the USLE over-predicts (0.030thMJ−1mm−1) the K-factor when compared to the ground-truth measurements (0.015thMJ−1) in the semi-arid region of Iran. Results showed that developed PTF had the highest performance (R2=0.74, RMSE=0.004 and ME=−0.003thMJ−1mm−1) to predict K-factor. The results also showed that the PLSR method predicted SOM with R2 values of 0.67 and 0.65 and CaCO3 with R2 values of 0.51 and 0.71 for calibration and validation datasets, respectively. We found good predictions for K-factor with R2=0.56 and ratio of predicted deviation (RPD)=1.5 using the PLSR model. The derived STF (R2=0.64, RMSE=0.002 and ME=0.001thMJ−1mm−1) performed better than the USLE (R2=0.06, RMSE=0.0171 and ME=0.0151thMJ−1mm−1) for estimating the K-factor.

CHARACTERIZATION OF DISSOLVED ORGANIC MATTER IN AN AGRICULTURAL WASTEWATER-IRRIGATED SOIL, IN SEMI ARID MEXICO

Most agricultural soils in semi-arid regions present a deficiency of organic matter (SOM). In order to improve this soil, wastewater is used due to its high organic carbon content. The objective of the present work was to characterize the dissolved organic matter in five residual water samples and ten soil samples from the agricultural area of the municipality of San Luis Potosi by 3D fluorescence spectroscopy. The changes in some physical and chemical properties of the soil were also analyzed. The soil samples were collected at different depths to observe the anthropogenic organic matter presence, their retention in the soil profile, their fluorescence intensity changes and their migration into the aquifer. Temperature, electrical conductivity, dissolved oxygen, oxidation- reduction potential and total dissolved solids were determined in situ. The major anions and cations: Na + , K + , Mg 2+ , Ca 2+ , PO 4 3– , SO 4 2– , NO 3– , NO 2 – , were analysed in laboratory. The results show the great contribution of organic matter (>2020 mg/L) in the residual water used for irrigation, as well as, the low content of SOM. The physical and chemical results indicate that the high electrical conductivity of the water, represents a risk of salinization for soils, but not of short term sodicity. The 3D fluorescence spectra of the soil profile, shows the presence of humic and fulvic acids, aromatic proteins and products of microbial degradation. The latter observed in that depth where there is a greater percentage of clay.

The effects on soil aggregation and carbon fixation of different organic amendments for restoring degraded soil in semiarid areas

SummaryThe addition of organic wastes as a strategy to restore degraded soil in semiarid regions can increase soil aggregation and carbon fixation. These processes can be affected by both the characteristics of the organic amendments and the soil microbial community structure. This study examines the effect of single additions (150 t ha−1) of different organic residues for soil restoration (fresh and composted sewage sludge, vegetal residue and farmyard manure) on aggregation and carbon (C) retention in a semiarid degraded soil. Changes in the distribution of microbial biomass in soil aggregates were also evaluated. Sewage sludge compost was added at rates of 150 and 300 t ha−1 to determine the effect of the amount applied on the distribution processes. Large macroaggregates (2000–8000 μm), small macroaggregates (250–2000 μm), microaggregates (53–250 μm) and the < 53‐μm soil fraction were obtained, and organic carbon (Corg) concentration was determined in these fractions in addition to the total phospholipid‐derived fatty acids (PLFAs). Both the characteristics of the amendments and the amount applied affected soil aggregation and Corg concentration in the aggregate size classes. The manure and the compost added at 300 t ha−1 contributed to the fixation of stable Corg in soil aggregates to a greater extent than the fresh sludge, vegetal residue or compost added at 150 t ha−1. In all soil fractions, the total concentration of PLFAs was larger in restored soil than in the control soil, and increases depended on the aggregate size class and characteristics of the amendment. The largest microbial abundance occurred in both large and small macroaggregates.Highlights Effects of type and amount of amendment on aggregation and C fixation in semiarid soil are elucidated. We explored distribution of the microbial community in soil aggregates in response to new soil C pools. Carbon fixation and microbial abundance of aggregates are affected by type and amount of amendment. Restored and degraded soils differ in terms of the breakdown of new organic matter inputs.

Response of pomegranate (Punica granatum) to drip irrigation system in light textured soils of semi-arid regions

The study was designed to evaluate numbers and different arrangements of emitters under surface drip irrigation system in pomegranate (Punica granatum L.) cv. Bhagwa orchard grown on light textured soil. A field experiment was conducted at National Research Centre on Pomegranate, Solapur for three consecutive years (2010 to 2013). The treatments consisted of irrigation with 2 online emitters (8 lph) on single lateral (T1), 3 online emitters (4 lph) on single lateral (T2), 4 emitters (4 lph), 2 online, 2 through microtube on single lateral placed on four sides of plant (T3), 6 emitters (2 lph) on double laterals placed 50 cm apart on both side of plants (T4) and inline lateral having 8 emitters (2 lph) placed in the form of ring encircling the plant (T5). Experiment was laid out in randomized block design with four replications. Equal quantity of irrigation equivalent to 0.80 E. Pan was applied on every alternate day. The results revealed that irrigation with 6 emitters (2 lph) on double laterals placed 50 cm apart on both sides of plants provide higher and uniform distribution of water in the root zone of the plants, resulted in better nutrient uptake, growth and yield performance of pomegranate plants. Highest leaf content of N (2.36%) and P (0.17%) was observed in this treatment which reflected in highest increase in plant height (20.4%) and plant spread (22.7%) producing highest yield in terms of numbers (36.1) and weight (6.889 kg) of fruits/plant. Plants irrigated with inline lateral having 8 emitters (2 lph) placed in the form of ring encircling the plant recorded highest leaf chlorophyll content (57.2) and maintained cool plant canopy as indicated by lowest leaf temperature during all the fruiting months. Flowering intensity was high in the plants irrigated with 2 dripper (8 lph) on one lateral system but it does not reflected in producing fruit yield due to limited wetting zone inducing moisture stress to the plants as indicated by highest fruit cracking (11.1%) in this system. It can be concluded that irrigation with 6 emitters (2 lph) fixed on two laterals placed on both sides of plants 50 cm away from the trunk along the rows system should be provided to pomegranate grown on light textured soils of semi-arid regions.

The Geochemistry of Natural Radionuclides in Saline Soils from Brazil Treated with Phosphogypsum Imbituba

The soil saltiness in the Brazilian semiarid environment is a common problem caused by incorrect agricultural practices, allied to the local weather and soil condition. The use of phosphogypsum (PG) to recover these soils still is a concern since this material has in its composition natural radionuclides. An experiment was conducted to study the use of phosphogypsum to reduce the salinity and evaluate the bioavailability of radionuclides on the Brazilian semiarid region soils. The radionuclide content of phosphogypsum samples were previously analyzed by gamma spectrometry. Three differents doses of phosphogypsum were mixed with samples of surface soil in the greenhouse, and after a reaction time and irrigation, controlled soil samples + phosphogypsum underwent simple extractions based on the sequential extraction method by Tessier et al. Ra isotopes and 210Pb in the extracted fractions were analyzed by counting alpha and beta. The higher concentration of Ra isotopes and 210Pb were associated to residual fraction, followed by exchangeable fraction due to the low levels of carbonates, organic matter, and manganese and iron oxides. The use of phosphogypsum studied did not contribute to increase the 226Ra activity on the analyzed soils. 226Ra levels in phosphogypsum were lower than those recommended by the USEPA to allow the use of phosphogypsum in agricultural soils, but can contribute to the accumulation of 228Ra and 210Pb. The phosphogypsum Imbituba promoted a satisfactory reduction of electrical conductivity in the soils, which indicates the possibility of recovery of these soils.

Roots Density and Activity of Pomegranate Grown in Light Textured Soil of Semi-Arid Region

Root distribution pattern forms the crux for optimum utilization irrigation, fertilizers and other inputs. Therefore, root distribution in terms of root mass and root activity (i.e. root length) in pomegranate cv. Bhagwa was studies in light textured, shallow soil types on four year old trees of pomegranate. Roots were collected from six radial distances (0-30, 30-45, 45-60, 60-75, 75-90 and 90 cm and above) and seven depths (0-15, 15-30, 30-45, 45-60, 60-75, 75-90 and above 90 cm). The results revealed that total dry mass of feeder roots (diameter up to 5 mm) was 992.7 g plant-1 while cumulative root length (activity) was 2332.4 m plant. On weight basis, contribution of small roots (2 < to < 5 mm) in total weight was the highest whereas, on the basis of root length, contribution of very fine roots (< 0.5 mm ) was exceptionally high compared to other categories of the roots. Root growth or root activity of pomegranate plants was observed in 0-60 cm radial distance and 0-45 cm vertical distance. Therefore fertilizers and water may be applied in this zone for better utilization of inputs by the tree roots..

Plant growth, nutrient uptake, water use efficiency and yield of pomegranate as affected by irrigation scheduling in loamy soils of semi-arid regions

A field experiment was conducted on loamy soil of National Research Centre on Pomegranate, Solapur, Maharashtra for three consecutive years (2010 to 2013) to assess the water requirement of pre-bearing and bearing plants of pomegranate cv. Bhagwa. The treatments consisted of replenishment of irrigation water equivalent to 30, 40, 50, 60, 70, 80 and 90% of cumulative pan evaporation (CPE) on alternate day laid out in randomized block design with four replications. The results of the study showed that during pre-bearing year, maximum plant growth can be achieved with the application of irrigation equivalent to 60% of CPE, while during bearing period it should be 70% of CPE. In three-year-old plants, maximum fruit yield (6.79 kg/plant) and irrigation efficiency (0.473 t/ha-cm) was observed in 70% CPE treatment. Leaf content of N (2.25%), Cu(124.9 ppm) and Mn (80.7 ppm) was also highest in this treatment. Fruit cracking to the extent of 58.8, 45.3 and 37.7% was recorded from the plants supplied with 30, 40 and 50% of CPE irrigation, respectively which reduced fruit yield drastically.

Effect of irrigation frequencies on nutrient uptake, growth and yield of pomegranate (Punica granatum) grown on heavy textured soils of semi-arid region

Effect of irrigation frequencies on nutrient uptake, growth and yield of pomegranate (Punica granatum) grown on heavy textured soils of semi-arid region

Multi locus sequence analysis and symbiotic characterization of novel Ensifer strains nodulating Tephrosia spp. in the Indian Thar Desert

Phylogenetically diverse Ensifer strains associated with five species of Tephrosia growing in alkaline soils of semi-arid regions of the Thar Desert were characterized using multi locus sequence analysis. Based on 16S rRNA and four protein-coding housekeeping gene (recA, atpD, glnII and dnaK) sequences, the Tephrosia–Ensifer strains were genetically different from the type strains of Ensifer saheli, Ensifer kostiensis, Ensifer terangae (African origin) and Ensifer psoraleae (Asiatic origin). One strain, Ensifer sp. TL4, showed maximum similarity (99%) to Ensifer adhaerens LMG 20216T and formed a separate lineage close to it. Phylogenetic incongruence between sym and housekeeping genes was observed. The monophyletic origin of symbiotic genes from Asia in the Tephrosia–Ensifer strains from the Thar Desert suggests that they might have been acquired from a common ancestor and horizontally transferred. These novel strains are promiscuous, cross-nodulating some papilionoid crop species, mimosoid trees and the caesalpinioid Chamaecrista pumila. This study improves understanding of the distribution of Ensifer in unexplored and threatened alkaline arid regions of the Thar Desert and how this relates to other similar regions in the world.