Experimental Field Plots Research Articles

Plasma-activated water for inactivation of Fusarium graminearum spores: An in-vitro wheat study

Fusarium graminearum (F. graminearum) as the major pathogen for Fusarium head blight (FHB) in wheat can cause severe yield loss and secrete mycotoxins to contaminate grain. Herein, this study prepared a novel green fungicide named plasma-activated water (PAW) by only using air, water and electricity via cold plasma activation, and investigated its antifungal effects against F. graminearum spores. The in-vitro results showed that PAW achieved a 1.98 to 3.98 log reduction of F. graminearum spores for treatment times ranging from 30 to 120 min. PAW also efficiently inhibited mycelial growth, spore germination and fungal pathogenicity of F. graminearum. Hydroxyl radicals and hydrogen peroxide were identified as the major antifungal agents in PAW, which destroyed the intracellular redox homeostasis and cell membrane of F. graminearum, eventually causing cell necrosis. PAW maintained a strong antifungal activity (4 log reduction) at a maximum dilution ratio of 6:4 and storage time of 2 h. The field-plot experiments verified that PAW effectively controlled wheat FHB via decreasing the disease incidence, FHB index, deoxynivalenol contamination and weight loss of wheat grains. The results demonstrated that PAW holds a great potential as an efficient, economical, and green fungicide for FHB control in wheats.

Symbiotic interaction between a mixture of Bradyrhizobium japonicum strains and different soybean cultivars

Aim. To study the mutual relations between different soybean cultivars and two Bradyrhizobium japonicum strains after mixed inoculation, to evaluate the impact of the introduced microorganisms on the local rhizobial communities in soil, the formation and functioning symbiotic systems, and productivity of soybean. Methods. Microbiological and serological methods; field experiment, gas chromatography and mathematical-statistical methods. Results. A small- plot field experiment demonstrated that the use of a mixture of B. japonicum 46 and B. japonicum КВ11 strains pro- moted a more even distribution of the local and introduced rhizobia in the nodule populations of 12 soybean cultivars of different geographic origin. There was no domination of particular strains in the nodules, and the symbiotic systems formed were more balanced than the control without inoculation. After inoculation of the above-mentioned mixture, in most cultivars there was a considerable increase in the number of nodules (10–45 % more) and their mass (11–86 % increase). There was also an increase in the level of symbiotic nitrogen fixation with 1.2–4.2 times and an increase in the weight of grain per plant by 6–29 % (depending on the cultivar). The efficiency of a mixture of B. japonicum 46 and КВ11 strains in a preparation Rizogumin was confirmed in extensive field trials with soybean on an area of about 60 thousand ha in different regions of Ukraine. In the background of the local populations of the soybean nodulating bacteria in the areas, the application of the formulated mixture of the two rhizobia strains ensured a stable increase by 15–33 % in the soybean yield as compared with the control without the inoculation. Conclusions. A novel approach was investigated, which lies in the application of a mixture of B. japonicum 46 (genetic group USDA 6) and B. japoni- cum КВ11 (genetic group USDA 123) strains for different soybean cultivars inoculation. Combining these two strains and their introduction into agrocenoses ensured the formation of a balanced symbiotic systems (without clear domina- tion of some strains in the nodules). This was expressed in an intensified nodulation, symbiotic nitrogen fixation, and increased yield of different cultivars of soybeans by 15–33 % as compared to the control (without inoculation).

Effects of Planting Pre-Germinated Buds on Stand Establishment in Sugarcane

Sugarcane (a complex hybrid of Saccharum spp.) is propagated vegetatively by using stem pieces of mature cane with healthy buds. Abiotic and biotic stress may cause pre-germination of these buds, which may have an impact on both emergence and plant cane stand establishment. There is very limited information available in the literature. A greenhouse study was conducted with single-budded seed pieces of three levels of bud germination (ungerminated buds, Pop-eyes, and Lalas) from three different cultivars (CP 96-1252, CPCL 05-1201, and CPCL 02-0926) planted in pots and repeated over time. Data on growth parameters (tiller count, primary shoot height, SPAD, and dry biomass of shoots and roots) at early growth showed that Lalas produced more tillers and higher shoot dry biomass than Pop-eyes and ungerminated buds. Both Lalas and Pop-eyes produced higher root dry biomass than ungerminated buds in one of the two experiments. The cultivar had a significant effect on primary shoot height and SPAD. A small plot field experiment was conducted with cultivar CP 96-1252 to validate the results of greenhouse experiments, and similar results were reported for tiller count. The results indicate that pre-germinated buds may have a neutral or positive effect on early sugarcane growth and establishment. Further on-farm research needs to be conducted to confirm these results before using pre-germinated buds as a potential seed source for the late season planting of sugarcane.

Influence of Number of Buried Nodes and Sources of Potassium Fertilizers on Sweet Potato Growth and Yield in Dodoma, Tanzania.

Inadequate knowledge on appropriate number of nodes of sweet potato vines to be planted and sources of potassium fertilizer to be used are among major factors resulted into low sweet potato productivity in central part areas of Tanzania. This research aimed at evaluating the effects of four levels of nodes buried and three potash fertilizer sources on growth and yield of three sweet potato varieties. Split-split plot field experiment in complete randomized block design was conducted at Hombolo, Dodoma during 2013/2014 cropping season. Main plot were three sweet potato varieties, Kiegeya, Mataya, and Ukerewe. Sub plot were, four level of buried nodes, (two above ground), five buried nodes (three above ground), seven buried nodes (three above ground) and eight buried nodes (four above ground). The sub - subplot treatments were potash fertilizer sources i.e control no fertilizer used, Potassium chloride (KCl), Potassium nitrogen phosphate (NPK) and Farm yard manure (FYM). Results indicated that there were no significant effects on the yield among varieties used. The number of tubers increased significantly in fertilized plots compared to control. The lowest number of tuber roots (3 tubers) was from control treatment while the highest number of tuber roots (6) was from KCl treatment. The effect of potassium fertilizer sources on root yield were also significant, use of KCl resulted to highest yield (18.84 t ha-1), followed by NPK (17.51 t ha-1), FYM (11.33 t ha-1) and control treatment where no fertilizer applied (8.82 t ha-1). Plating of different number of nodes resulted into significant increase in yield where the highest yield of (15.91 t ha-1) was from eight buried nodes and lowest total yield (11.68 t ha-1) was from four buried nodes. Seven and eight buried nodes with KCl and NPK fertilizers appeared to be appropriate for optimum sweet potato growth, yield and tuberous root quality in the study area and are therefore recommended.

In-field rice panicles detection and growth stages recognition based on RiceRes2Net

Accurate rice panicle detection and growth stages recognition are crucial steps in rice field phenotyping. However, conventional manual characterization of rice panicles is time consuming and labor intensive. In this study, a RiceRes2Net based on improved Cascade RCNN (Region-CNN) architecture was proposed to detect the rice panicle and recognize the growth stages under the complex field environment. RiceRes2Net first adopted the Res2Net network and Feature Pyramid Network （FPN） as the backbone network to generate and fuse multi-scale feature maps. Then, RiceRes2Net constituted a four IoU thresholds cascade RCNN to deal with multi-scale feature maps to give the target class prediction and coordinate regression of the bounding boxes. In addition, Soft non-maximum suppression (Soft NMS) and Generalized Intersection over Union (GIoU) loss function were also integrated into RiceRes2Net to better predict the bounding boxes of the occluded panicles. Datasets of the rice panicles were acquired by smartphone in two comprehensive field plot experiments under complex field background. Rice panicles differed in genotype, planting density, growing practices, planting season and growth stages, which constituted a comprehensive rice panicles phenotyping. The results showed that RiceRes2Net outperformed the traditional cascade RCNN in rice panicle detection, with average precision (AP) values of 96.8%, 93.7%, 82.4% at booting stage, heading stage, and filling stage, respectively. Furthermore, RiceRes2Net has a significant advantage in detecting the occlusion panicle thereby increase the accuracy. To test the robustness of RiceRes2Net, the counting results of RiceRes2Net was compared with the manual counting results with an independent test set. The RMSE values at three growth stages were 1.19, 2.56, and 3.13, respectively. In addition, the performance of the RiceRes2Net was compared to the widely used state-of-art deep learning models. The results showed that RiceRes2Net can learn a more representative set of features that helped better locate the rice panicles at three growth stages, and thus achieved better detection accuracy than the other deep learning models. In terms of panicle growth stages recognition, RiceRes2Net showed satisfactory results with high precision values of 99.83%, 99.34%, and 94.59% in recognition of booting stage, heading stage, and filling stage, respectively. The average accuracy of growth stages recognition was 96.42%. The overall results suggest that RiceRes2Net is a promising tool for detection of rice panicles and the growth stage, and has great potentials for field applications.

Effect of Magnetized Brackish Water Drip Irrigation on Water and Salt Transport Characteristics of Sandy Soil in Southern Xinjiang, China

Xinjiang is short on freshwater resources and rich in ones. The unregulated use of brackish water for agriculture leads to the aggravation of secondary salinization in soil; however, magnetization can improve the quality of brackish water. To evaluate the effects of magnetized brackish water drip irrigation on the water and salt transport characteristics of sandy soil in southern Xinjiang, China, a field plot experiment was carried out in which irrigation water was treated using one or two water magnetization events at different magnetization intensities. Water was treated at five magnetization intensities: 1000, 2000, 3000, 4000, or 5000 Gs, while unmagnetized water was used as the control. The results showed that the magnetization of brackish water used in drip irrigation decreased the water transport rate and increased the water holding capacity of the root layer soil. Magnetized irrigation water enhanced the leaching of soil salt and reduced the rate of salt accumulation. Compared with the control, the salt content of the magnetized water-irrigated soil decreased by 15.0%~33.7%, and the salt storage in the magnetized water-irrigated soil decreased by 44.99%~86.78%. The lowest rate of salt accumulation (4.96%) was observed at a magnetization intensity of 3000 Gs. Magnetized water irrigation changed the composition and proportions of soil ions, and Na+, Cl−, and SO42− leaching from the soil increased. The effect of magnetizing the irrigation water twice was greater than that of one magnetization event. Magnetizing the water twice at an intensity of 3000 Gs led to the largest decrease in the relative percentage contents of Na+ and Cl−, which were 80.90% and 82.36%, respectively. The magnetization intensity had a significant effect on the soil carbon and nitrogen contents, which showed a trend of first increasing and then decreasing as the magnetization intensity rose. The total carbon content after irrigation with magnetized water increased by 13.48%~63.35%, and the total nitrogen content increased by 11.73%~147.96%. The magnetization treatment of irrigation water can therefore reduce the risk of soil salinization and reduce salinity stress on crops in arid regions, providing a new method for alleviating the shortage of freshwater resources in Xinjiang and a means to use brackish water safely while improving salinized soil.

Nutritional value and agronomic traits of forage sorghum under drought stress

Drought negatively affects the crop yield and nutritional value of forage sorghum. The effect of drought on forage sorghum was investigated in a two-year, strip plot field experiment with a randomized complete block design. The vertical factor included four levels of drought stress (mild, moderate, severe, and extreme), and the horizontal factor consisted of four forage sorghum genotypes (Spidfid, Sugargraze, Jumbo, and Pegah). The results showed that drought stress negatively influenced plant height, number of leaves, biomass, leaf-to-stem ratio, and seed yield and yield components, as well as crude protein and prussic acid contents of sorghum. However, the different genotypes did not show the same responses to drought stress. The highest forage yield was observed in Spidfid genotype under mild stress by 121.6 ton/ha, the lowest related value (30.5) was obtained in Sugargraze genotype under extreme drought. The highest seed yields were recorded in the Spidfid genotype in mild and extreme stress treatments (7861 and 4839 kg/ha, respectively). The Sugargraze genotype showed the highest yield reduction under extreme stress. The nutritional value of forage was significantly higher in the Spidfid genotype, and the same genotype contained the lowest prussic acid content under mild and extreme stress conditions by 87 and 86 mg/kg, respectively. However, the crude protein content of the genotypes was not significantly different under severe stress. Therefore, using the Spidfid tolerant genotype and reducing the irrigation period in water shortage conditions, can be a promising solution to achieve the ideal quantitative and qualitative yield of sorghum forage.

Persistence of Hg-Contaminated Soil Stabilization in Typical Areas of Dehua County, Fujian Province, China

The in-situ stabilization remediation of Hg-contaminated soil in Qianyang, Dehua County, Fujian Province, was studied through the pre-experiments (stabilization orthogonal experiment and pot experiment) and field plot experiments for two consecutive years. The pre-experiments results showed that the main factors of the stabilization were the initial concentration of Hg in the soil and the amount of amendment added, followed by the amendment type, while the aging time had less effect. When the initial concentration of Hg in the soil was less than 10 mg·kg−1 and the amendment (modified biochar with modified attapulgite) added ratio was 0.2–0.4%, indicating optimized stabilization effect. After one-time application of 6750 and 11,250 kg·hm−2 amendment in low (1.38 mg·kg−1), medium (2.46 mg·kg−1), and high (8.52 mg·kg−1) Hg-contaminated soils, it could accelerate the transformation of Hg from exchangeable to residual and oxidizable Hg, enhance the activities of catalase, urease, and invertase in the soil. After one year of remediation, the case of adding 6750 kg·hm−2 amendment showed a significant stabilization effect. Compared to the control group, the available Hg content in the soil and Hg content in the water spinach reduced to 52.1–62.0% and 58.2–66.6%, respectively. When the application amount was increased to 11,250 kg·hm−2, the reduction rates were 43.2–46.0% and 58.2–62.0%, respectively. After two years of remediation, the stabilization effect was weakened, but the available Hg content in the soil and the water spinach was still significantly lower than that of the control, indicating that the persistence of the stabilization was good. For the soil contaminated slightly by Hg, the Hg content in the water spinach within two years was lower than the limit value of the Chinese standard (0.01 mg·kg−1). Although the Hg content in the water spinach for the soil contaminated highly by Hg was higher than the limit value, it could reduce to 67.3%, indicating an acceptable stabilization effect on heavily contaminated soil.

Biological Control Potential of Endophytic Fungi with Amelioration of Systemic Resistance in Sunflower and GC-MS Metabolic Profiling of Talaromyces assiutensis.

Endophytic fungi live inside plant tissues but do not cause any disease. Several reports have now revealed that they have great influence on host. In this study, the beneficial role of endophytic fungi is highlighted and explored. Endophytic fungi isolated from healthy plants were identified as Aspergillus terreus, Curvularia lunata, C. hawaiiensis, Macrophomina phaseolina, Fusarium solani, Talaromyces assiutensis, and T. trachyspermus using 18S rRNA gene sequencing. In vitro, fungi evaluated for antimicrobial activity, showed significant activity. These fungi were tested in field application by exploring their broad spectrum. Talaromyces assiutensis and T. trachyspermus were applied in pots and field plot experiments using sunflower as test plants, along with endophytic Cephalosporium sp., and Chaetomium sp. Endophytic fungi showed significant activity against root rot pathogens affecting sunflower and improved plant biomass. They also improved production of plant defense biochemical markers (polyphenolic content and salicylic acid) with improvement in antioxidant potential. These fungi are used as biological control agents, so their culture filtrates are used to check the presence of metabolites by GC-MS. Several new compounds were isolated from T. assiutensis. The major bioactive compounds are Coumarin, 3,4-dihydro-6-methoxy-4,4-dimethyl, 1-Monolinoleoylglycerol trimethylsilyl ether, 1,2-Propanediol, 3-(octadecyloxy), Ethyl iso-allocholate, and 1H-Pyrazole, which possess antioxidant, antitumor, antibacterial, anticancer, and antimicrobial properties. These findings will lead to further in-depth research toward the potential use of these endophytic fungi for their possible use in agriculture and drug formation.

The influence of fungicides on the growth, development and productivity of soybean

The paper presents the results of a two-year experiment on fungicide Deposit, muE (1.0 l/t and 1.2 l/t) and its combinations with fungicide Optimo, EC (0.5 l/ha). The experiment was conducted in the south of the Russian Far East in 2021-2022. The first step was a phytophathological inspection of the seeds treated with the fungicide in the laboratory conditions. Deposit was noted to have an antibacterial and antifungal effect. A rhizotron was used for further experimental work to observe the growth and development of soybean plants. It was established that Deposit did not have a negative effect on the crop and facilitated a slight increase in plant weight. The last step of the research was field plot experiments aimed at studying the efficacy of the fungicides against root rot and leaf and stalk diseases of soybean. Deposit was observed to inhibit root rots damaging the crop. At the stage BBCH 62, the fungicide decreased the intensity of infection progression by 11.0% (1.0 l/t) and 15.6% (1.2 l/t). Deposit and Optimo had a high antipathogenic activity against leaf and stalk diseases of soybean. It was established that the fungicides and their combinations were effective against Septoria blight (22.1-35.5%), Cercospora leaf blight (29.7-70.4%), and Ascochyta blight (20.4-58.4%). Additionally, they increased the thousand kernel weight (TKW) and soybean yield.

Beneficial Effects of Biochar Application with Nitrogen Fertilizer on Soil Nitrogen Retention, Absorption and Utilization in Maize Production

The irrational use of nitrogen (N) fertilizer has become a major threat to soil quality and food security, resulting in serious ecological and environmental problems. Holistic approaches to N fertilizer application are required to maintain a high N utilization efficiency (NUE) and sustainable agriculture development. Biochar is an efficient carbon-rich material for amending soil quality and promoting crop N uptake, but knowledge pertaining to the promoting effects of biochar application on N fertilizers is still limited. In this study, a field plot experiment was designed to detect the combined effects of biochar (0, 15 and 30 t ha−1) and N fertilizer (204, 240 and 276 kg N ha−1) on the soil nutrient levels, NUE, plant growth performance and crop production of maize. The results demonstrated that the combined application of N fertilizer and biochar can significantly decrease the soil pH and increase the contents of soil organic carbon, mineral N, available phosphorus and potassium. The crop N uptake and N content were largely promoted by the addition of N fertilizer and biochar, resulting in higher leaf photosynthetic efficiency, dry matter accumulation and grain yields. The highest yields (14,928 kg ha−1) were achieved using 276 kg N ha−1 N fertilizer in combination with 15 t ha−1 biochar, and the highest NUE value (46.3%) was reached with 204 kg N ha−1 N of fertilizer blended with 30 t ha−1 of biochar. According to structural equation modeling, the beneficial effects of N fertilizer and biochar on the plant biomass of maize were attributed to the direct effects related to soil chemical properties and plant growth parameters. In conclusion, N fertilizer combined with biochar application is an effective strategy to enhance the utilization of N fertilizer and crop production for maize by increasing soil fertility, improving plant crop uptake and promoting plant growth.

Deep vertical rotary tillage mitigates salinization hazards and shifts microbial community structure in salt-affected anthropogenic-alluvial soil

Soil tillage management is one of the major agricultural countermeasures to the ever-expanding soil salinization in arid and semiarid irrigated regions worldwide. However, how tillage implementations mitigate soil salinization hazard, improve soil quality and enhance microorganism function has not yet been clearly clarified. A two-consecutive-year field plot experiment with three tillage treatments, including CT (conventional rotary tillage, depth 25 cm), VRT (vertical rotary tillage, depth 25 cm) and DVRT (deep vertical rotary tillage, depth 50 cm), were conducted to examine the tillage effect on soil salinization and microbial communities. Dynamics of soil salinity (EC1:5), bulk density (ρb), saturated hydraulic conductivity (Ks), organic carbon (OC), water-stable aggregates (WSA), and bacterial and fungal community structures were measured. The results indicated that, compared with the CT and VRT treatments, the DVRT treatment had lower EC1:5 and ρb, but higher Ks at 0–40 cm soil layers. The promoted salt leaching was mostly attributable to the improved soil porosity and permeability under the DVRT treatment. The DVRT significantly increased soil total OC and percentage of > 2 mm (WSA1) and 2–0.25 mm (WSA2) aggregates, but decreased that of 0.053–0.01 mm (WSA4) aggregates. Soil bacterial richness and diversity was negatively responsive to the DVRT, whereas fungal richness and diversity showed positive responses to the DVRT. The DVRT did not alter the dominant microbial phyla but changed their relative abundance. At the genus level, the DVRT shifted bacterial community from Vicinamibacterales and Lysobacter -dominated to Vicinamibacterales, Geminicoccus and Marmoricola -dominanted, and transformed fungal community from Mortierella and Chaetomium -dominated to Mortierella and Aspergillus -dominated. Moreover, seasonal changes also showed significant direct and interactive influences on the above edaphic properties and microbial communities. Edaphic properties including EC1:5, OC, ρb and WSA1 explained the causal connection among tillage practices and microbial richness, diversity and community structure. It was concluded that the DVRT mitigated soil salinization hazards by promoting salt leaching and improving macro-aggregates and organic carbon, and shifted soil microbial communities by evolving the microbes better adaptable to the changed microhabitats.

Effects of Different Exogenous Organic Materials on Improving Soil Fertility in Coastal Saline-Alkali Soil

The coastal saline-alkali soil in eastern China is an important reserve arable land resource. Adding exogenous organic material is an effective way to improve soil fertility and promote the conversion of saline-alkali soil to agricultural soil. In this study, a field plot experiment was used to investigate the influences of different organic materials (vinegar residue, VR; sewage sludge, SS; vermicompost, VC) on the reduction in salinity-alkalinity barrier factors, the accumulation of soil organic carbon (SOC), and the improvement in soil fertility in saline-alkali soil. The results indicated that applying different types of exogenous organic materials reduced soil electrical conductivity (EC) and pH, promoted SOC accumulation, and increased the barley yield. With the same application rate, VR application was more beneficial in reducing soil EC and pH, accumulating SOC, and increasing barley yield compared to SS and VC applications. In particular, the barley yield with VR application was higher than that with SS and VC applications by 18.4% and 26.6% on average, respectively, during the two-year experiment. Correlation and path analysis revealed that the barley yield was significantly negatively correlated with soil barrier factors (EC and pH), but EC in SS and VC-treated soils had an indirect negative effect on barley yield, while EC in VR-treated soil had a direct negative effect (−2.24). In addition, the direct (−4.46) and indirect (5.39) contributions of SOC to barley yield were higher with VR than those with SS and VC, while the direct contribution of soil aggregate to barley yield was lower with VR than that with SS and VC. Therefore, compared with SS and VC applications, VR application led to a fast reduction in soil barrier factors and the rapid accumulation of SOC, which were more beneficial for increasing barley yields in saline-alkali soil.

Growth and Yield Responses of Leafy Vegetables Grown in Organic and Conventional Agriculture Systems

Several scientific reports indicate lower as well as higher relative yield stability in organic and conventional (chemical) agriculture systems. This study present results of on-farm trials conducted on leafy vegetables grown in in organic and conventional management systems. Four leafy vegetables collard green (Brassica oleracea cv. acephala), kale (Brassica oleracea cv. sabellica), lettuce (Lactuca sativa) and swiss chard (Beta vulgaris L. cv. cicla) were grown in organic and conventionally managed plots in the spring 2018 and 2020. United States Department of Agriculture (USDA), National Organic Program (NOP) standards were followed for cultural and management practices in organically managed experimental field plots. Synthetic chemical inputs (seeds and fertilizer) were applied in the experimental field plots managed in conventional production system. Data on plant height, leaf number and total fresh weight of leafy vegetables were measured at the end of the experiment. Results showed that maximum fresh weight per plant was obtained from conventionally grown kale and the lowest was recorded in conventionally grown lettuce. The fresh weight of collard (344.1 g/plant) and kale (475.6 g/plant) was significantly higher in conventional system relative to the organic management system in collar (184.9 g/plant) and kale (242.3 g/plant). In contrast, for lettuce, significantly greater fresh weight was obtained in the organic (266.5 g/plant) compared to conventional (189.3 g/plant). No difference recorded in fresh weight of swiss chard grown in organic (222.0 g/plant) and conventional (263.7 g/plant) production systems. No difference observed in plant height and number of leaf count between the two production systems. Findings suggest that growth and yield responses in organic and conventional production systems can vary with the individual crop species. Results presented could be helpful to growers in planning for the organic production of leafy greens vegetables.

Effect of Mechanized Ridge Tillage with Rice-Rape Rotation on Paddy Soil Structure

Ridge tillage is one of the essential tillage methods in China. It affects the soil structure by altering the soil-water environment. With the rapid development of agricultural mechanization, the mechanized ridge tillage technology that combines modern mechanized agriculture with conservation tillage has become a pertinent agricultural production technology in the hilly regions. However, to date, the effects of mechanized ridge tillage on soil structure have garnered little attention. In this study, a field plot experiment involving the following four treatments: conventional tillage with rice and winter fallow (CK1), conventional tillage with rice-rape rotation (CK2), wide ridge tillage with rice-rape rotation (BT), and narrow ridge tillage with rice-rape rotation (RT) was conducted to study the effects of mechanized ridge tillage with rice-rape rotation on soil aggregate stability and soil porosity. The results indicated that mechanized ridge tillage could reduce the porosity of pores > 30 μm in diameter and increase the porosity of pores < 0.5 μm. Furthermore, mechanized ridge tillage could increase soil aggregate stability; the order of average mass diameter and geometric average diameter was RT > BT > CK2 > CK1. The BT and RT treatments could increase the agglomeration degree of the soil particles, which followed the order of RT > BT > CK2 > CK1. Therefore, mechanized ridge tillage with rice-rape rotation is effective in enhancing soil structure.

Impacts of Long-Term Micronutrient Fertilizer Application on Soil Properties and Micronutrient Availability

Deficiencies of micronutrients in calcareous soils have been reported in different areas of China's Loess Plateau. The objective of this research was to study the influence of the continuous application of micronutrient fertilizers on soil properties and micronutrient availability in this region. The micronutrient fertilizer field plot experiment began in 1984. It included Zn, Mn and Cu fertilizer treatments and the control treatment. The crop system was continuously cropped winter wheat. The soil properties and available Zn, Mn, Cu and Fe were measured. Their relationships were analyzed through correlation and path analysis. After 31 years, the soil pH, CaCO3 and available P levels decreased; in contrast, the organic matter, fulvic acid, reducing substances and soil moisture levels in the surface soil increased in the micronutrient fertilized treatments compared to the control treatment. Cu and Zn fertilizers promoted the available Cu and Zn levels in the surface and deep soil, but available Mn was not significantly affected by Mn fertilizer. It can be seen from the interaction between the micronutrient availability and micronutrient fertilizers that Zn, Cu and Mn fertilizers can increase the available Fe level; Mn fertilizer can increase the available Cu level, and Cu and Mn fertilizers can increase the available Zn level. This means that Fe, Cu and Zn availability were easy to implement, whereas the soil-available Mn was difficult to improve in calcareous soils on the Loess Plateau. Fulvic acid and organic matter showed a significant and direct effect on the available Zn; the available Mn and Fe were mainly affected by the soil CaCO3 and moisture; the available Cu was mainly affected by the soil organic matter, available P and reducing substances. These results indicate the importance of organic matter in calcareous soils; it can not only directly affect the availability of micronutrients but also indirectly affect their availability through the indirect interaction with fulvic acid, reducing substances, available P and CaCO3. The above conclusions suggest that the long-term micronutrient fertilizers changed some important soil properties and increased the micronutrient availability in the loess-derived soil.

Calibration, validation, and evaluation of the Water Erosion Prediction Project (WEPP) model for hillslopes with natural runoff plot data

The Water Erosion Prediction Project (WEPP) model has been widely used for estimating runoff and soil loss. The evaluation of the latest version (version 2021.133) under a range of environmental conditions can provide confidence to its users. The objectives of this study were to evaluate the WEPP model for runoff and soil loss predictions using 1159 plot years of rainfall-runoff events data from field experimental plots with various climates, soils, topographies, and crops. WEPP runoff and soil loss predictions were compared to the observations before and after input parameter calibration. The results showed good predictions of runoff and soil loss were obtained with both the uncalibrated and calibrated WEPP model for all considered scales with Nash-Sutcliffe model efficiencies (NSE) over 0.4. The calibration of input baseline effective hydraulic conductivity (ke), baseline critical shear stress (τc), baseline rill erodibility (kr), and baseline interrill erodibility (ki) improved WEPP model performance with NSE values of 0.98 and 0.91 for average annual runoff and soil loss predictions, respectively. The WEPP model tended to underestimate the runoff and soil loss for large events with runoff over 100 mm and soil loss over 120 t/ha. Good event runoff and soil loss predictions (NSE ≥0.4) were obtained for the most common cropping/management systems considered, including corn, cotton, tilled fallow, and wheat after calibration. This study illustrates the most recent WEPP model's performance for runoff and soil loss predictions, and provides a comprehensive set of results.

Low-Cd wheat varieties and soil Cd safety thresholds for local soil health management in south Jiangsu province, east China

Wheat is the second most important staple food crop, therefore safe and environmentally friendly production of wheat is essential for human safety and health. Southern Jiangsu province is a very important wheat producing region that is highly industrialized with many soils polluted with potentially toxic metals, especially cadmium (Cd). Wheat varieties with low Cd bioconcentration factors (BCF) are often used to decrease Cd accumulation and increase the safety of products in field practice. In addition, the development of local soil safety thresholds, the main focus of soil health management, is also necessary to protect agricultural soil health and agricultural production. However, there is no published literature describing low-Cd-accumulating wheat varieties and soil safety thresholds in this region. Field plot experiments and field investigations at multiple experimental sites in southern Jiangsu province have therefore been conducted for several years to screen low-Cd-accumulating wheat varieties and to derive soil Cd safety thresholds. The varieties Yangmai 25, Zhengmai 12 and Yangmai 12 had stable and low Cd BCF. The deduced safe thresholds of total soil Cd concentrations for protecting 95 % of wheat varieties were 0.17, 0.18, and 0.31 mg kg−1 at 4.5 < pH ≤ 6.5, 6.5 < pH ≤ 7.5 and 7.5 < pH ≤ 9.0, stricter levels than the Chinese national risk screening values. The deduced thresholds were validated to increase the protection rates of wheat by field investigations. In conclusion, wheat varieties with low Cd BCF and soil thresholds can contribute to local soil health management and safe wheat production in southern Jiangsu province.

Screening Fungicides for Controlling Wheat Crown Rot Caused by Fusarium pseudograminearum across Hebei Province in China

Wheat Fusarium crown rot (FCR) is caused predominantly by Fusarium pseudograminearum across most wheat-producing countries; this fungal disease needs a specific combination of fungicides to control it. In this research, the efficacy of four fungicides against F. pseudograminearum is tested using in vitro assays. Our results showed that fludioxonil had an EC50 of 0.0447 mg/L, followed by difenoconazole (0.3845 mg/L) and tebuconazole (0.4919 mg/L). Azoxystrobin (2.6019 mg/L) was also effective. Commercially available fungicides with the first three ingredients as active ingredients were further tested for the control of FCR. Cruiser Plus and Celest presented higher efficacies in an environmentally controlled pot assay. Further testing in the field achieved a higher level of control by Cruiser Plus than Celest at the seedling (72.34% vs. 62.55%) and adult (56.76% vs. 47.78%) stages in a field plot experiment. When tested in naturally infected wheat fields in Linzhang, Hebei Province, applications of the two fungicides resulted in relative control efficacies of 45.17% and 38.57%, respectively, and grain yields were increased by dressing with Cruiser Plus (8.7%) and with Celest (5.3%). Furthermore, seed dressing combined with additional spraying in early spring resulted in significantly better control of FCR and higher grain yield than seed dressing treatment alone (10.4% and 7.4%, respectively). Similar results were obtained when tested in Xian County, Hebei Province, with a disease control efficacy of 40.36–59.91% and a yield increase of 4.2–7.5%. Integrated measures of dressing (Cruiser Plus and Celest) combined with spraying (Horizon) showed higher control efficacy to FCR.

S-metolachlor persistence in soil as influenced by within-season and inter-annual herbicide use

The ability to predict fate of pesticides in the environment is crucial for sustainable management. This process starts with a proper characterization of the dissipation of a parent compound under different sets of conditions. There is widespread use of S-metolachlor across multiple common cropping systems, modes of action among commercially available herbicides are limited, and concern is rising of increase in resistance to S-metolachlor in problematic weeds, including species such as Palmer amaranth (Amaranthus palmeri). Therefore, S-metolachlor dissipation was investigated in fortified soil collected from a field plot experiment in order to determine the influence of single or repeated within-season herbicide applications to accelerate dissipation. S-metolachlor dissipation in fortified soils was then investigated in samples collected from paired, commercial fields, all of silt loam soil texture. Producer fields from five Arkansas counties were categorized as low-use (0 to 2 years of application) or high-use (5 to 6 years of application within the past six years). S-metolachlor concentrations were extracted from soil during a 56-day incubation and S-metolachlor degradation was modeled to calculate half-life. Two within-season applications of S-metolachlor increased persistence in fortified soils, and dissipation was faster in soils collected 1 and 24 days compared to 59 days after planting soybean [Glycine max (L.) Merr.].The half-life of S-metolachlor did not decrease in soil from fields with high-use (5 to 6 years) compared to soil collected from fields with low-use (0 to 2 years) of herbicide application history. Dissipation of S-metolachlor in soil was not enhanced by repeated short-term intra-annual or longer-term inter-annual applications. Results highlight the importance of management practices and soil properties in assessing the fate of S-metolachlor.