Field Conditions In Soil Research Articles

The Development of a Draft Force Prediction Model for Agricultural Tractors Based on the Discrete Element Method in Loam and Clay Loam

In the field of agricultural machinery, various empirical field tests are conducted to measure design loads for the optimal design and implementation of tractors. However, conducting field tests is costly and time-consuming, with many constraints on weather and field soil conditions, and research utilizing simulations has been proposed as an alternative to overcome these shortcomings. The objective of this study is to develop a DEM-based draft force prediction model that reflects differences in soil properties. For this, soil property measurements were conducted in two fields (Field A in Daejeon, Republic of Korea, and Field B in Chuncheon, Republic of Korea). The measured properties were used as parameters for DEM-based particle modeling. For the interparticle contact model, the EEPA contact model was used to reflect the compressibility and stickiness of cohesive soils. To generate an environment similar to real soil, particle mass and surface energy were calibrated based on bulk density and shear torque. The soil property measurements showed that Field B had a higher shear strength and lower cone index and moisture content compared to Field A. The actual measured draft force was 19.47% higher in Field B than in Field A. In this study, this demonstrates the uncertainty in predicting draft force by correlating only one soil property and suggests the need for a comprehensive consideration of soil properties. The simulation results of the tillage operation demonstrated the accuracy of the predicted shedding force compared to the actual field experiment and the existing theoretical calculation method (ASABE D497.4). Compared to the measured draft force in the actual field test, the predictions were 86.75% accurate in Field A and 74.51% accurate in Field B, which is 84% more accurate in Field A and 37.32% more accurate in Field B than the theoretical calculation method. This result shows that load prediction should reflect the soil properties of the working environment, and is expected to be used as an indicator of soil–tool interaction for digital twin modeling processes in the research field of bio-industrial machinery.

Simulation of Mouldboard Plough Soil Cutting Based on Smooth Particle Hydrodynamics Method and FEM–SPH Coupling Method

In the field of agricultural machinery, various empirical field tests are performed to measure the tillage force for precision tillage. However, the field test performance is costly and time-consuming, and there are many constraints on weather and field soil conditions; the utilization of simulation studies is required to overcome these shortcomings. As a result, the SPH method and the coupled FEM-SPH method are used in this paper to investigate the mouldboard plough–soil interaction. In this paper, the finite element software LS-DYNA was used to build the SPH model and the FEM-SPH coupling model of soil cutting, as well as to investigate the change in cutting resistance during the soil cutting process. The simulation results are compared with those of the experiments, and the curves of the simulation and experiment are in good agreement, which verifies the reliability of the model. The validated simulation model was used to investigate the effects of the cutting speed, depth of cut, inclination angle, and lifting angle of the mouldboard plough on cutting resistance. The simulation studies show that the SPH model takes 5 h and 2 min to compute, while the FEM-SPH coupled model takes 38 min; obviously, the computational efficiency of the FEM-SPH coupled model is higher. The relative errors between the SPH model and the experiment are 2.17% and 3.65%, respectively. The relative errors between the FEM-SPH coupled model and the experiment are 5.96% and 10.67%, respectively. Obviously, the SPH model has a higher computational accuracy. The average cutting resistances predicted by the SPH model and the FEM-SPH coupled model, respectively, were 349.48 N and 306.25 N; these resistances are useful for precision tillage. The cutting resistance increases with the increase in cutting speed and is quadratic; the cutting resistance increases with the increase in cutting depth and is quadratic; the horizontal cutting resistance and the combined cutting resistance increase with the increase in inclination angle, while the vertical cutting resistance remains essentially constant with the increase in inclination angle; the horizontal cutting resistance and combined cutting resistance increase as the lifting angle increases, while the vertical cutting resistance decreases as the lifting angle increases.

Some Agronomical and Physiological Characteristics of Sang Yod Phatthalung Rice from In Vitro Regenerated Plant After Transfer to Clay Soil in Field Conditions

Sang Yod Phatthalung rice is indica rice and grown as Geographical Indications (GI) in Patthalung province. Its dark red color seed contains high antioxidant activity that helps reduction in the risk of some chronic diseases such as diabetes, cancer, and cardiovascular diseases. So far, yield per planting area of this rice is still low. Thus, application of PGRs might play an alternative role in agronomical and physiological characteristics leading to improving yield of this rice. First, shoot tips of Sang Yod Phatthalung rice were cultured to induce multiple shoots and root on liquified PGR-free oil palm culture medium (OPCM) with different concentrations of 6-benzyladenine (BA) (0, 0.5, 1, 1.5 mg/L) alone or in combination with 1-naphthaleneacetic acid (NAA) (0 and 0.5 mg/L). Complete plants were acclimatized to field condition at Phatthalung Rice Research Station (PRRS). After acclimatization for 120 and 140 days, some agronomical and physiological characteristics of rice plant obtained from different PGR containing OPCM were statistically compared. A 2×4 factorial design in RCBD with 4 replication was performed. The results were clearly demonstrated that adding BA in the culture medium increase plant height, number of panicles, panicle length and leaf chlorophyll content. Plantlets obtained from in vitro culturing shoot tip on 0.5 mg/L BA containing medium gave the highest results in average plant height at 189.50 cm, number of panicles at 34.00 panicles, panicle length at 32.50 cm and leaf chlorophyll content at 39.65 SPAD unit. The results from this present study indicated the production of new plant types or characteristics for Sang Yod Phatthalung rice for high yield in future. HIGHLIGHTS The effect of concentrations of PGRs, and culture conditions on agronomical and physiological characteristic were evaluated 5 mg/L BA-derived plants germinated in vitro gave higher results than ex vitro in agronomical and physiological characteristic Addition of 0.5 mg/L BA in the medium increases the plant height, number of panicles, panicle length and leaf chlorophyll content 5 mg/L BA-derived plants in vitro gave the highest plant height, number of panicles, panicle length, and leaf chlorophyll content at 189.50 cm, 34.00 panicles, 32.50 cm, and 39.65 SPAD units, respectively GRAPHICAL ABSTRACT

Farm structure and environmental context drive farmers’ decisions on the spatial distribution of ecological focus areas in Germany

ContextEcological Focus Areas (EFAs) were designed as part of the greening strategy of the common agricultural policy to conserve biodiversity in European farmland, prevent soil erosion and improve soil quality. Farmers receive economic support if they dedicate at least 5% of their arable farmland to any type of EFA, which can be selected from a list of options drawn up at the European Union level. However, EFAs have been criticized for failing to achieve their environmental goals and being ineffective in conserving farmland biodiversity, mainly because they are not spatially targeted and because they promote economic rather than ecological considerations in farm management decisions.ObjectivesWe used a spatially explicit approach to assess the influence of farm and field context as well as field terrain and soil conditions on the likelihood of whether or not a particular EFA type was implemented in a field.MethodsWe used a multinomial model approach using field-level land use and management data from 879 farms that complied with the EFA policy in 2019 in the Mulde River Basin in Saxony, Germany. Geospatial environmental information was used to assess which predictor variables (related to farm context, field context or field terrain and soil conditions) increased the probability of a field being assigned to a particular EFA. We tested the hypothesis that productive EFAs are more often implemented on fields that are more suitable for agricultural production and that EFA options that are considered more valuable for biodiversity (e.g. non-productive EFAs) are allocated on fields that are less suitable for agricultural production.ResultsWe found that farms embedded in landscapes with a low proportion of small woody features or nature conservation areas mainly fulfilled the EFA policy with productive EFAs (e.g. nitrogen fixing crops). Conversely, farms with a higher proportion of small woody features or nature conservation areas were more likely to adopt non-productive EFAs. As predicted, large and compact fields with higher soil fertility and lower erosion risk were assigned to productive EFAs. Non-productive EFAs were placed on small fields in naturally disadvantaged areas. EFA options considered particularly beneficial for biodiversity, such as fallow land, were allocated far away from other semi-natural or nature protection areas.ConclusionsOur results highlight that the lack of spatial targeting of EFAs may result in EFA options being assigned to areas where their relative contribution to conservation goals is lower (e.g. farms with higher shares of protected areas) and absent in areas where they are most needed (e.g. high intensity farms). To ensure that greening policies actually promote biodiversity in European agriculture, incentives are needed to encourage greater uptake of ecologically effective measures on intensively used farms. These should be coupled with additional measures to conserve threatened species with specific habitat requirements.

The effect of sulfur-containing compounds and thiobacillus bacteria on corn plants under field soil and soil contaminated by heavy metals lead and zinc conditions

Investigating the effect of various sources of sulfurous compounds along with the inoculation of Thiobacillus bacteria on corn plants under stress conditions of lead and zinc metals, an experiment executed at zanjan uni researching green house. The treatments include elemental sulfur (0.75, 1.25 and 2 g/kg soil), sulfur with Thiobacillus bacteria (1, 2 and 3 g/kg soil) and potassium sulfate (0.5, 1 and 1.5 g/kg soil ). The results showed that the traits were significant in all applied treatments except proline. The amount of morphological traits and physiological traits increased in sulfur treatment with thiobacillus bacteria in field soil conditions and heavy metal stress compared to the control. But the properties of soluble sugars and proline decreased in this treatment. On the other hand, with the increase in the concentration of elemental sulfur and potassium sulfate treatments that caused stress in the plant. However, under stress conditions, the amount of absorption of lead and zinc in the root and aerial part of the plant increased to a critical and damaging level, but by applying of treatments, the amount of absorption and damage decreased. it can be concluded that elemental sulfur and potassium sulfate treatments by reducing the absorption of all elements required by the plant caused stress, but sulfur with bacteria treatment reduces the absorption of these heavy elements, and the bacteria in the soil provides the conditions for absorbing more water and nutrients through the roots and improves the growth of the plant.

Evaluation of Tires Acting on Soil in Field Conditions Using the 3D Scanning Method

This research presents the results of tests conducted under field conditions and included measuring the footprint of tires on soil. Two agricultural tires of the same size but different internal structures were tested, 500/50R17 (radial) and 500/50-17 (bias-ply). The factors were tire inflation pressure (0.8 bar, 1.6 bar, and 2.4 bar) and tire vertical load (7.8 kN, 11.8 kN, and 15.7 kN). The footprint made on the soil was scanned with a 3D scanner, resulting in a digital image of the tire footprint on the soil to enable an analysis of the measured parameters: length, width, depth, and contact area (in 3D form). Statistical analysis showed that for radial tire footprints, both inflation pressure and vertical load had a significant effect on all analyzed parameters. For bias-ply tire footprints, it was shown that only inflation pressure had a significant effect on all of the analyzed parameters, while the significance of the effect of the vertical load was not confirmed for the footprint depth. Based on the results obtained, the suitability of models describing the relationship between operating factors and the actual footprint area was verified. It was found that for a radial tire, the model formulated based on laboratory tests can predict the contact surface under field conditions (the correlation coefficient R2 was equal to 0.9226). In the case of a bias-ply tire, the correlation coefficient R2 reached a value equal to 0.5828. This indicates a less accurate estimation of the surface area under field conditions based on the model designed after laboratory testing.

Screening germplasm and detecting QTLs for mesocotyl elongation trait in rice (Oryza sativa L.) by association mapping

BackgroundRice is one of the most important food crops in the world and mainly cultivated in paddy field by transplanting seedlings. However, increasing water scarcity due to climate change, labor cost for transplanting, and competition from urbanization is making this traditional method of rice production unsustainable in the long term. In the present study, we mined favorable alleles for mesocotyl elongation length (MEL) by combining the phenotypic data of 543 rice accessions with genotypic data of 262 SSR markers through association mapping method.ResultsAmong the 543 rice accessions studied, we found 130 accessions could elongate mesocotyl length under dark germination condition. A marker-trait association analysis based on a mixed linear model revealed eleven SSR markers were associated with MEL trait with p-value less than 0.01. Among the 11 association loci, seven were novel. In total, 30 favorable marker alleles for MEL were mined, and RM265-140 bp showed the highest phenotypic effect value of 1.8 cm with Yuedao46 as the carrier accession. The long MEL group of rice accessions had higher seedling emergence rate than the short MEL group in the field. The correlation coefficient (rGCC−FSC = 0.485**) between growth chamber condition (GCC) and field soil condition (FSC) showed positive relationship and highly significant (P < 0.01) indicating that the result obtained in GCC could basically represent that obtained under FSC.ConclusionNot every genotype of the rice possesses the ability to elongate its mesocotyl length under dark or deep sowing condition. Mesocotyl elongation length is a quantitative trait controlled by many gene loci, and can be improved by pyramiding favorable alleles dispersed at different loci in different germplasm into a single genotype.

Pelleting of Physical Dormancy Small-Seeded Species in Astragalus sikokianus Nakai

Astragalus sikokianus is a rare Japanese perennial of the seashore that was reported to be extinct in the wild. The small seed size and deep dormancy of A. sikokianus make it difficult for direct seeding restoration in aspects of seed handling, transport, planting, and seedling establishment. For the large-scale economic restoration of dormant small-seeded species, seed pelleting combined with the breaking of dormancy was studied. Physiological (prechilling and plant hormones) and physical (hot water, hydrochloric acid, and sulfuric acid) seed dormancy break treatments were evaluated. The dormant broken seeds were used for pelleting. The effects of the substrate, pellet sizes, and their interactions on germination were measured. The scarification of five rubs of seeds placed between sandpapers completely broke the physical dormancy of A. sikokianus. Seed coat impermeability inhibited germination. Pelleted seeds ranging from 2.0 to 4.0 mm in diameter showed more than 90% germination on filter paper. The germination of the pelleted seeds was measured in commercial, field, and sand soil conditions. The highest germination was shown in sand (70–74% GP), regardless of the pellet size, whereas unpelleted scarified seeds germinated only 48%. These results suggest that small-seeded species with physical dormancy can be used for seed-based restoration after seed pelleting.

MACRONUTRIENTS USE EFFICIENCY IN SANDY SOIL CULTIVATED BY MAGNETICALLY TREATED SEEDS PRE-SOWING AND SPRAYED BY N-FERTILIZER DISSOLVED IN MAGNETIZED WATER

Purpose: is to enhance the nutrients use efficiency (NUE) along with the crop yield and quality by magnetic treatment (MT) of the groundnut (Arachis hypogaea L.) seeds pre-sowing as well as the MT of water used to dissolve the nitrogen (N) fertilizer under sandy soil field conditions. Methods: Treatments were distributed in a split-plots design in triplicates. The control CL has received the recommended dose RD of the N-fertilizer while other treatments received a 50% of the RD applied to the surface soil 30 days after planting. The main factor (F1) was the N-application rates 1000, 2000, and 3000 mg kg-1 of urea dissolved in the magnetically treated water (MTW) then sprayed on the soil in the liquid form five times after planting. The sub-factor (F2) was the time of MT (15, 30, and 45 min) of the groundnut seeds exposed to a magnetic field MF 1.4 T intensity before planting. Results: The soil available N, P, K, Fe, Mn, and Zn (mg kg-1) were increased significantly by 34.8%, 23.0%, 3.49%, 9.4%, 22.2%, and 23.2% respectively, at P ≤ 0.05 by the 45 min MT and 3000 mg kg-1 N relative to its corresponding control (CL). The MT has increased the seeds yield (kg ha-1) significantly in the order 45 min &gt;30 min &gt;15 min for the N-rates 1000, 2000, and 3000 mg kg-1. At the 45-min time, it was increased by 17.5, 15.3, and 14.8% for the N-rates, respectively. Conclusions: The 2000 mg kg-1 rate with MT of seeds for 15 min can be recommended for an acceptable nutrients use efficiency (NUE).

Screening of finger millet genotypes for sodicity tolerance using the Na+/K+ ratio as a major physiological trait

Sodicity affects a larger area than salinity, but research on the sodicity tolerance mechanism is limited. The study was carried out to screen 120 finger millet genotypes under sodic soil conditions and identify sodicity-tolerant genotypes. The experimental field soil conditions were sandy clay loam with pH 8.9, electrical conductivity (EC) 0.94 dSm-1 and exchangeable sodium percentage (ESP) 21.5, which was naturally sodic. Grain yield per plant and Na+/K+ ratio were recorded for each genotype to screen sodicity tolerance among the genotypes. A significantly higher grain yield per plant than that of the sodicity-tolerant check variety TRY 1 (23.10 g) was observed in 30 finger millet genotypes. The analysis of sodium and potassium revealed that these 30 finger millet genotypes also recorded a significantly lower Na+/K+ ratio, which is comparatively lower than that of the sodicity-tolerant check variety TRY 1 (0.23 Na+/K+ ratio). The genotypes (FIN 3045, FIN 2875, FIN 3077, FIN 3015, FIN 3063, FIN 2861, FIN 3028, FIN 2867, FIN 2854, FIN 2860, FIN 2872, FIN 2896, FIN 4268, FIN 3034, FIN 3928, FIN 3104, FIN 3965, FIN 3091, FIN 2960, FIN 3994, FIN 4198, FIN 3174, FIN 3078, FIN 4288, FIN 4202, FIN 4238, FIN 3089, FIN 4205, FIN 3966 and FIN 3182) that recorded higher grain yield per plant and lower Na+/K+ ratio can be considered sodicity tolerant. These genotypes with a high grain yield per plant and a low Na+/K+ ratio could be utilized in stress breeding programs to develop sodicity-tolerant finger millet varieties.

Modeling paddy field soil conditions in East Java, Indonesia

Knowledge of soil conditions is a critical factor of effective land management to achieve optimum ecosystem services in agriculture. Digital soil modeling that incorporates soil spectral data has become a cost-efficient method compared to traditional wet-chemical soil analysis to produce high quality soil management data at the regional level. This research objective was to develop soil property prediction models to assess the characteristics of paddy field soil conditions in East Java, Indonesia. This study examined the utilization of a hybrid two-step regression (2Step-R) soil modeling approach that incorporates categorical soil-environmental variables and continuous visible-near-infrared (VNIR) spectral data. The integrative 2Step-R method was implemented in two modes—Partial Least Square Regression, PLSRmod, and Sparse Bayesian Infinite Factor, SBIFmod—with ‘mod’ referring to the fusion of important categorical soil-environmental parameters and soil VNIR spectral data. This research successfully developed reliable prediction models for soil organic carbon, nitrogen (N), pH, sum of bases (SB), and cation exchange capacity in the study area, with acceptable model performance (performance to interquartile ratio or RPIQ 1.77 to 2.54; performance to deviation ratio or RPD 1.45 to 1.89; and coefficient of determination or R2 0.53 to 0.72). The fused soil-environmental and VNIR spectral data approach (2Step-R) showed markedly improved model performances when compared to models that solely used VNIR spectra data (PLSR) for all modeled soil properties. This research underpins the utilization of cost-effective soil modeling to reveal existing soil conditions in securing soil ecosystem services for intensive agriculture in data sparse regions such as Indonesia.

Response of Organic Biostimulants and Silicon to Growth, Yield and Quality of Tomato under Soil Salinity Conditions

Abiotic stresses strongly affect plant growth, nutrient composition and quality of production; final crop yield can be really compromised if stress occurs in plants’ most sensitive phenological phases. The present field study was conducted to evaluate the effect of biostimulants on improvement of tolerance and yield of tomato plants exposed to salinity. The tomato field soil condition with pH- 8.7 and EC- 4 dS m-1 was recorded. After the first fruit set of tomato, Organic biostimulant (Organic mix with high concentration of carboxylic acids, containing calcium oxide (CaO), ammonium ligninsulfonate and Zinc) were given by soil drenching and Orthosilicic acid as silicon source by foliar spray at every 10 – 15 days interval. The treatments include Organic biostimulant at 0.3ml/plant &amp; 0.6ml/plant, Orthosilicic acid at 0.2% and 0.4%. The observations were taken during greener and red ripening stage. The biostimulants positively affected the plant height and chlorophyll fluorescence. Biostimulants were allowed to maintain the lower level of electrolyte leakage and osmotic potential within the plant. The activities of catalase (CAT) and superoxide dismutase (SOD) enzymes increased with the increases in salinity: biostimulants thereby kept the lower the level of reactive oxygen species. Under saline conditions due to the ionic imbalance, potassium and calcium content in both the shoots and roots were recorded lower, whereas the sodium content was found to be higher than the control plants. Similarly, a significant increase in total soluble solids and firmness of the fruit was recorded in tomato fruits. Yield characters like fruit number per plant, single plant yield, single fruit weight and flower to fruit ratio were positively affected by the application of biostimulants. The organic biostimulant and Orthosilicic acid administered at a greater dose appeared to be the most effective in our investigation.

The Synergic Effect of Whey-Based Hydrogel Amendment on Soil Water Holding Capacity and Availability of Nutrients for More Efficient Valorization of Dairy By-Products

Agricultural production is influenced by the water content in the soil and the availability of nutrients. Recently, changes in the quantity and seasonal water availability are expected to impact agriculture due to climate change. This study aimed to test an agricultural product with promising properties to improve soil quality and water-holding capacity during agricultural application. Most of the traditional hydrogels are low-biodegradable synthetic materials with under-researched long-term fate in field soil conditions. The novel, biodegradable hydrogel made from acid whey and cellulose derivatives cross-linked with citric acid was used. The soil-improving effects were tested under controlled experimental conditions with the sandy artificial soil consisting of 10% finely ground sphagnum peat, 20% kaolinite clay, and 70% quartz sand. Soil pH, the content of organic carbon (Cox), total nitrogen (N), available forms of the essential macronutrients (P, K, Ca, and Mg), the cation exchange capacity (CEC), the maximum water capacity (MWC) and water holding capacity (WHC) were determined. The results showed a positive effect on water retention and basic soil properties after the different levels of hydrogel had been introduced into the soil. Generally, the addition of whey-based hydrogel increases the available nutrients concentration and water retention in soil.

Back to the Future: Decomposability of a Biobased and Biodegradable Plastic in Field Soil Environments and Its Microbiome under Ambient and Future Climates.

Decomposition by microorganisms of plastics in soils is almost unexplored despite the fact that the majority of plastics released into the environment end up in soils. Here, we investigate the decomposition process and microbiome of one of the most promising biobased and biodegradable plastics, poly(butylene succinate-co-adipate) (PBSA), under field soil conditions under both ambient and future predicted climates (for the time between 2070 and 2100). We show that the gravimetric and molar mass of PBSA is already largely reduced (28-33%) after 328 days under both climates. We provide novel information on the PBSA microbiome encompassing the three domains of life: Archaea, Bacteria, and Eukarya (fungi). We show that PBSA begins to decompose after the increase in relative abundances of aquatic fungi (Tetracladium spp.) and nitrogen-fixing bacteria. The PBSA microbiome is distinct from that of surrounding soils, suggesting that PBSA serves as a new ecological habitat. We conclude that the microbial decomposition process of PBSA in soil is more complex than previously thought by involving interkingdom relationships, especially between bacteria and fungi.

DEM simulation for draft force prediction of moldboard plow according to the tillage depth in cohesive soil

In the field of agricultural machinery, various empirical field tests are performed to measure the design load for optimal design of tractors and implement. However, field test performance is costly, time-consuming, and there are many constraints on weather and field soil conditions, requiring simulation utilization studies to overcome these shortcomings. Therefore, the objectives of this study are to perform agricultural soil modeling, draft force prediction simulation in function of tillage depth using discrete element method (DEM) software, and to verify the prediction accuracy by comparing with field test results. In this study, soil property measurement test was performed by soil depth considering target tillage depth (0–200 mm) using soil mechanical properties measurement system for DEM soil modeling. DEM soil model calibration was performed using virtual vane shear test and cone penetration test values instead of the repose angle test. In addition, field tests to verify the accuracy of draft force prediction simulation were performed using a measuring tractor equipped with a draft force measurement system, a tillage depth measurement system and an RTK-GPS (travel speed). As a result of the DEM simulation, it was found that the prediction accuracy of the draft force was within 7.5% (5.1–9.9%) when compared to the measured draft force through field test. In addition, it was confirmed that the result was 5.3–61.6% more accurate than those obtained through existing theoretical methods used to predict draft force. On the other hand, the error of draft force prediction using DEM simulation considering only topsoil properties showed 20.3% lower prediction accuracy than the DEM soil model considering the soil properties of different soil layer. This study provides useful information for the DEM soil modeling process that consider the change in soil properties according to the tillage depth from the perspective of agricultural machinery research and it is expected to be utilized in agricultural machinery design research.

Contrasting Responses of Rhizosphere Bacterial, Fungal, Protist, and Nematode Communities to Nitrogen Fertilization and Crop Genotype in Field Grown Oilseed Rape (Brassica napus)

The rhizosphere microbiome is considered to play a key role in determining crop health. However, current understanding of the factors which shape assembly and composition of the microbiome is heavily biased toward bacterial communities, and the relevance for other microbial groups is unclear. Furthermore, community assembly is determined by a variety of factors, including host genotype, environment and agricultural management practices, and their relative importance and interactions remain to be elucidated. We investigated the impact of nitrogen fertilization on rhizosphere bacterial, fungal, nematode and protist communities of 10 contrasting oilseed rape genotypes in a field experiment. We found significant differences in the composition of bacteria, fungi, protist and nematode communities between the rhizosphere and bulk soil. Nitrogen application had a significant but weak effect on fungal, bacterial, and protist community composition, and this was associated with increased relative abundance of a complex of fungal pathogens in the rhizosphere and soil, including Mycosphaerella sp. and Leptosphaeria sp. Network analysis showed that nitrogen application had different effects on microbial community connectivity in the soil and rhizosphere. Crop genotype significantly affected fungal community composition, with evidence for a degree of genotype specificity for a number of pathogens, including L. maculans, Alternaria sp., Pyrenopeziza brassicae, Olpidium brassicae, and L. biglobosa, and also potentially beneficial Heliotales root endophytes. Crop genotype had no significant effect on assembly of bacteria, protist or nematode communities. There was no relationship between genetic distance of crop genotypes and the extent of dissimilarity of rhizosphere microbial communities. Field disease assessment confirmed infection of crops by Leptosphaeria sp., P. brassicae, and Alternaria sp., indicating that rhizosphere microbiome sequencing was an effective indicator of plant health. We conclude that under field conditions soil and rhizosphere nutrient stoichiometry and crop genotype are key factors determining crop health by influencing the infection of roots by pathogenic and mutualistic fungal communities, and the connectivity and stability of rhizosphere microbiome interaction networks.

Off-Site Calibration Approach of EnviroScan Capacitance Probe to Assist Operational Field Applications

Soil water content or soil moisture content is considered one of the most critical properties of the soil for crop production, irrigation, and environmental studies. The technical development of soil moisture measurement devices is swift, but calibration among field conditions is still not entirely resolved. Accurate calibration requires samples taken right next to the sensor that disturbs the site and changes the soil conditions. Real field operation requires the probe to represent larger areas that have undisturbed soils around the probe. These would describe the parcel’s general soil conditions and start providing data from the time of installation. This study aimed to compare several potential solutions for off-site calibration of an operational EnviroScan sensor (Sentek Technologies, Stepney South, Australia). The performances of the default and soil texture-specific equations provided by the manufacturer were compared with the field and laboratory calibration approaches. Two statistical parameters, coefficient of determination (R2) and root square mean error (RMSE) was used to determine logarithmic model results. The results show that the default calibration equations in all three classes have relatively low performances with RMSE values of around 10–15 and R2 values ranging from 0.4 to 0.8. However, significant refinement was achieved by selecting texture-specific equations from the manufacturer’s libraries. The soil texture-specific equations of the EnviroScan often yielded quite satisfactory results, with RMSEs ranging between 2 and 4. Similar RMSE values were achieved from the laboratory calibration exercises, but the reapplication potential of these equations was often questionable due to the severely changed soil conditions of the laboratory processed soil compared to the field soil conditions.

New sources of lentil germplasm for aluminium toxicity tolerance identified by high throughput hydroponic screening.

Aluminium (Al) toxicity in acid soils inhibits root elongation and development causing reduced water and nutrient uptake by the root system, which ultimately reduces the crop yield. This study established a high throughput hydroponics screening method and identified Al toxicity tolerant accessions from a set of putative acid tolerant lentil accessions. Four-day old lentil seedlings were screened at 5µM Al (pH 4.5) for three days in hydroponics. Measured pre and post treatment root length was used to calculate the change in root length (ΔRL) and relative root growth (RRG%). A subset of 15 selected accessions were used for acid soil Al screening, and histochemical and biochemical analyses. Al treatment significantly reduced the ΔRL with an average of 32.3% reduction observed compared to the control. Approximately 1/4 of the focused identification of germplasm strategy accessions showed higher RRG% than the known tolerant line ILL6002 which has the RRG% of 37.9. Very tolerant accessions with RRG% of > 52% were observed in 5.4% of the total accessions. A selection index calculated based on all root traits in acid soil screening was highest in AGG70137 (636.7) whereas it was lowest in Precoz (76.3). All histochemical and biochemical analyses supported the hydroponic results as Northfield, AGG70137, AGG70561 and AGG70281 showed consistent good performance. The identified new sources of Al tolerant lentil germplasm can be used to breed new Al toxicity tolerant lentil varieties. The established high throughput hydroponic method can be routinely used for screening lentil breeding populations for Al toxicity tolerance. Future recommendations could include evaluation of the yield potential of the selected subset of accessions under acid soil field conditions, and the screening of a wider range of landrace accessions originating from areas with Al toxic acid soils.

Growth and yield improvement of maize by ACC deaminase producing bacteria under dry soil conditions

The beneficial effects of plant-microbe interactions have been widely studied. This study aimed to examine the ability of ACC deaminase producing bacteria to improve maize plant growth and yield under dry soil conditions. The study consisted of laboratory analyses, a greenhouse trial, and field experiments. Eight strains of Pseudomonas and Bacillus from previous studies were formulated into four groups of bacterial consortia (PC1, PC2, PC3, and PC4) in peat-based carriers. The bacteria were evaluated for their ability to grow in osmotic stress conditions using Polyethylene Glycol. Greenhouse experiment tested the consortia to improve maize growth in soil with 50, 75, and 100% water-filled pore space (WFPS). A field experiment was conducted in a farmer’s field using bacterial consortia in combination with organic fertilizer. The results showed that most bacterial strains were able to grow in osmotic stress conditions up to -2.0 MPa. Under different WFPS levels, the four consortia tested appeared to prevent maize from further stress of water shortages, although not significantly different from the uninoculated. The highest increase of maize yield under field soil condition was shown by plants inoculated with PC3 consortium. Therefore, the PC3 consortium needs further evaluation as a promising biofertilizer for dry soil conditions.

Management of Ralstonia solanacearum (potato wilt disease) virulence by using bioactive compounds

Potato is an important vegetable crop of Bangladesh which is facing challenges worldwide due to a quarantine pathogen, Ralstonia solanacearum. It is a very successful bacterial pathogen against most of the traditional management practices. Suspension of ten bioactive compounds viz. propolis, honey, turmeric powder+oil, turmeric powder, magnesium chloride, boiled rice fluid, boiled rice fluid+iodine, sun dried cow dung powder, honey+iodine and sodium bicarbonate were evaluated and compared with control (sterile water), commercial bactericide (Krosin AG) and farmers practice (stable bleaching powder). In vitro assessment was done by comparing the inhibition zones produced on TZC (tetrazolium chloride) solid medium in disc diffusion method. All of those compounds produced larger inhibition zones as compared to control which indicated the effectiveness of the test compounds against the bacteria. To screen out the performances of those compounds in vivo, potato seedlings were inoculated in sterilized soil by soil soak method. Later, mature plants were inoculated in unsterilized soil to find the better resulting compound(s) in field soil condition against the disease. Finally, suspension of cow dung (@25%), propolis (@ 6mg/ml) and turmeric powder (@25%) were selected for trial as soil and seed treatment against the pathogen. It was found that, cow dung reduced 28.89% disease severity index which was followed by 26.67% in propolis and 22.22% in turmeric powder as compared to control (84.44%) in artificially inoculated potato plants against R. solanacearum.&#x0D; J. Biodivers. Conserv. Bioresour. Manag. 2020, 6(1): 65-76