Repellency Index Research Articles

Evaluation of soil properties in variously aged Scots pine plantations established on sandy soil

Abstract Pines are widely planted for sand dune stabilization and their cultivation results in the changes in physical, chemical, hydro-physical and water repellency properties. Soil properties were evaluated at three Scots pine plantations (PF1, PF2 and PF3) close to Studienka village, Borská nížina lowland (southwestern Slovakia) during hot and dry summer period. The PF1 site is a newly established plantation, the PF2 site is about 30 years old plantation, and the PF3 site is about 100 years old plantation. Here, we estimated the differences in pH, soil organic carbon content, Cox, particle size distribution, PSD, saturated, ks, and unsaturated, k(–2 cm), hydraulic conductivity, water, Sw , and ethanol, Se , sorptivity, water drop penetration time, WDPT, and repellency index, RI. It was found that Cox varies most significantly with plantation age, and relative differences in PSD and pH were lower than the relative difference in Cox. The PF3 site differs the most from the other two, especially in Cox and in the content of sand fraction. It can be attributed to the older age of the plantation, which represents a more advanced stage of succession accompanied by an accumulation of soil organic matter. Relationships between Cox, k(–2 cm), RI, and WDPT and pine forest age were described by appropriate mathematical models. We found a similarity between k(–2 cm) and RI relationships vs. pine forest age (exponential models), and between Cox and WDPT relationships vs. pine forest age (first and second-order polynomial models). The latter similarity can be supported by the fact that soil water repellency is induced by the hydrophobic and amphiphilic components of soil organic matter.

Natural and Synthetic Repellents for Pest Management of the Storage Mite Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae).

Simple SummaryThe ham mite is the major pest of dry-cured hams, aged cheeses, and specialty pet foods that are high in fats and proteins. Ham mites are also known to cause allergies in some cases for humans. The toxic fumigant gas methyl bromide had been used for years to control this mite pest, but it is being phased out of use due to its impact on the protective ozone layer of the earth’s upper atmosphere. Ham producers now require alternatives to methyl bromide for controlling mites. We conducted laboratory experiments with food-safe synthetic and plant-derived chemical repellents to keep mites away from dry cured hams. Our results showed that several of these repellents could effectively prevent ham mites from contacting and staying on treated pieces of ham, and that they would readily go to untreated ham pieces when given a choice. Further experiments found that mites would not feed on nor produce offspring when held on ham pieces coated with oils from thyme, lemon grass, rose, or a mixture of naturally occurring fat molecules. Our experiments suggest that these food-safe repellents might protect dry-cured hams from mites during their time in aging rooms by application to racks on which hams are aged or to the nets and packaging in which hams are held.The fumigant pesticide methyl bromide (MB) was used for stored products, but it is now banned for most uses in many countries as an ozone-depleting substance. MB was the only pesticide used to manage the ham mite, Tyrophagus putrescentiae, which is the most significant pest of dry cured hams. Effective alternatives to MB are needed to develop integrated pest management (IPM) programs for this pest. This study evaluated plant essential oils and food-safe compounds as repellents to directly protect hams from infestation. Experiments to assess the repellency to orientation, oviposition, and population growth of mites on pieces of aged country hams were conducted. Test compounds at different concentrations were dissolved in respective solvents and compared to the solvent control. Results showed that C8910, a mixture of three short-chain fatty acids, and the sesquiterpene ketone nootkatone had repellency indices of (RI) of 85.6% and 82.3%, respectively, at a concentration of 0.1 mg/cm2, when applied to a Petri dish arena. DEET and icaridin were also tested but performed poorly with RIs below 70% even at 0.1 mg/cm2.The monoterpene alcohol geraniol had the highest RI of 96.3% at 0.04 mg/cm2. Ham pieces dipped in C8910 and nootkatone at 150 ppm each had RIs of 89.3% and 82.8%, respectively. In general, as the concentrations of test compounds increased, the numbers of eggs that were laid on these treated ham cubes decreased after the 48 h exposure time. Ham pieces dipped in different concentrations of test compounds and then inoculated with 20 adult mites showed a significant decrease in mite population growth compared to control pieces after 14 days. The results of these experiments suggest that some plant secondary metabolites and synthetic food-safe compounds could serve as potential alternatives for managing mites on hams.

Influence of crested wheatgrass on soil water repellency in comparison to native grass mix and annual spring wheat cropping

Crested wheatgrass (CWG) [Agropyron cristatum (L.) Gaertn.] is a commonly introduced grass in the Canadian prairies, but concerns remain about its possible long-term effects on soil quality, and its influence on soil water repellency (SWR) has not been determined. The long-term (24 yr) effects of CWG on SWR in comparison to seeded native grasses and annual cropping were determined for a clay loam soil in southern Alberta, Canada by measuring SOC concentration and SWR using soil hydrophobicity (SH) and soil water repellency index (RI) methods. The cropping treatments were CWG, seeded native grass mix (NGM), continuous wheat, and wheat–fallow rotation, each with fertilized (nitrogen) and non-fertilized subplots, replicated four times. Mean SOC concentration, SH, and RI in samples of surface soil were similar (P > 0.05) for CWG and seeded NGM, and they did not support our hypothesis (seeded NGM > CWG). Mean SOC was significantly greater for seeded perennial grasses than annual crops by 1.7–2 times and SH by 2.1–2.5 times, which supported our hypothesis, but RI was similar among treatments. As expected, nitrogen fertilization significantly increased SOC concentrations, but the effects on SH and RI were undetectable. A strong positive correlation occurred between SOC concentration and SH (r = 0.92) but not for RI (r = 0.10). Our findings suggested that SWR was similar for CWG and seeded NGM. The SWR as measured using SH was greater for seeded perennial grasses than annual cropping but was similar using RI.

INSECTICIDAL AND REPELLENT ACTIVITIES OF CITRUSSINENSIS (L.) LEAF EXTRACT AGAINST TROGODERMA GRANARIUM EVERTS (COLEOPTERA: DERMASTIDAE IN STORED GROUNDNUT

Groundnut production has been reported to be threatened by storage insect pests which caused significant damage in storage. The repellent and efficacy activities of Citrus sinensis leaf extract were assessed on Trogoderma granarium in stored groundnut. The treatment was laid in a Completely Randomized Design with 3, 5, and 7% concentration level of methanolic and petroleum ether Extract for insecticidal activities. The results of C. sinensis leaf extract toxicity obtained was significant at 7% concentration at 24, 48 and 72 hours after treatment with 100% and 80% mortality in methanolic and Pet. ether extracts respectively in adults. Half disc experiment was carried out to determine the repellency activities with 1, 2, and 3% concentration of methanolic and pet. ether extract. It was observed that at 2HAT the insects moved towards the extract with the Index of Repellency of 1.13 at 3 % concentration for methanolic and pet ether extract, as the hours increase from 4 to 6HAT it was observed that the extract acted as repellant towards the insect with methanol and petroleum ether extract of 3 % concentration having the highest repellency index of 0.47. Petroleum ether at 1 % concentration with the value of 1.47, 1.40 and 1.20 repellency index across the 2, 4 and 6HAT showed that the extract remains an attractant towards T. granarium. The results obtained from this study is an indication of the potential of methanolic and petroleum ether crude extract of C. sinensis in groundnut storage

The Use of Apple Pomace as a Soil Amendment Enhances the Activity of Soil Microorganisms and Nitrogen Transformations and Affects Crop Growth

Apple pomace (AP) is an abundant waste causing environmental problems. Therefore, the aim of the study was to evaluate the impact of AP on soil and plant growth under optimum and limited water availability. Two laboratory experiments were conducted to evaluate the impact of AP on: (i) hydrophysical properties, respiration, and N transformations in soil aggregates and (ii) the growth of wheat and faba bean in soil with addition of AP under optimum and limited water availability. The soil respiration rate increased rapidly after the introduction of AP, and the effect was dependent on the aggregate size. The reduction of nitrate and the increase in ammonium content in response to the AP addition were more pronounced in the larger aggregates. Reduced growth of wheat was noted in the dry soil supplemented with AP. Faba bean maintained its unchanged rate of growth after the application of AP, irrespective of water availability. An increase in the chlorophyll content was observed in faba bean grown in the AP-enriched soil. The apple pomace reduced the water wetting rate and increased the repellency index but did not affect the tensile strength of the soil aggregates. Disposal of AP as a soil amendment affects many indicators of soil quality. The application of AP to the soil has an impact on respiration and N transformations in the soil aggregates; moreover, it differently influences the growth of spring wheat and faba bean.

Influence of continuous application of feedlot manure and legacy treatments on soil organic carbon, soil hydrophobicity, and soil water repellency

Continuous or discontinued manure applications to agricultural soils may impact soil organic carbon (SOC) and water balances because of manure carbon inputs and the potential for manure-induced soil hydrophobicity (SH) and soil water repellency (SWR). A laboratory study was conducted using a long-term (44 yr) field experiment on a clay loam soil to determine the effect of application rate of feedlot manure under dryland (0, 30, 60, and 120 Mg·ha−1 wet weight) and irrigation (0, 60, 120, and 180 Mg·ha−1) on SOC, SH, and SWR. In addition, we compared the effect of 44 yr of continuous annual manure applications (C44) to legacy treatments which had discontinued applications for 14 (D14) or 30 yr (D30). Laboratory measurements were conducted on air-dried and sieved (<2 mm) soil to determine SOC, SH using Fourier transform infrared spectroscopy, and SWR using the repellency index (RI) method. Mean RI values for all treatments ranged from 2.20 to 13.0, indicating subcritical (RI > 1.95) SWR. Manure application rate had a significant (P ≤ 0.05) and positive effect on SOC and SH, and both followed an exponential model. In contrast, RI had a negative response to the application rate under dryland and had no response under irrigation. Overall, positive responses of SOC and SH to application rate supported our hypothesis, but it was not supported for RI. The hypothesis of greater SOC, SH, and RI for continuous versus discontinued treatments was also supported for SOC and SH but not for RI.

Toxicity and repellency of four plant essential oils against Tribolium castaneum(Herbst) (Coleoptera: Tenebrionidae)

Essential Oils (EO) from four different plants viz., Cinnamomum cassia ( L .) J. Presl, Foeniculum vulgare Mill ., Murraya koenigii (L.) Sprengel and Pogostemon cablin (Blanco) Benth . were tested for their efficacy by Residual film technique for toxicity and Repellency by Area preference method against adult Red Flour Beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The repellency was recorded as an index of repellency (IR) at 30 min, 12 and 24-h’ time point. IR at 24 h time point with 1% v/v concentration for C. cassia and P. cablin was 0.1, 0.2 for F. vulgare and 0.5 for M. koenigii. The sub-lethal concentration (LC20) in % v/v for mortality to T. castaneum after 72 h was observed as 0.172 for C. cassia, 0.345 for P. cablin, 0.632 for M. koenigii and 0.712 for F. vulgare. The median lethal concentration (LC50) in % v/v for mortality to T. castaneum after 72 h was observed as 0.098 for C. cassia, 0.123 for P. cablin, 0.427 for M. koenigii and 0.304 for F. vulgare. It indicates that the P. cablin and C. cassia oil exhibits significant repellency and C. cassia oil exhibits significant toxicity against T. castaneum. Results obtained from this study indicate the important role of botanicals may be as pesticides against stored product pests in the modern world.

Impact of climate, soil properties and grassland cover on soil water repellency

Numerous soil water repellency (SWR) studies have investigated the possible causes of this temporal phenomenon, yet there remains a lack of knowledge on the order of importance of the main driving forces of SWR in the context of changing environmental conditions under grassland ecosystems. To study the separate and combined effects of soil texture, climate, and grassland cover type on inducing or altering SWR, four sites from different climatic and soil regions were selected: Ciavolo (CI, IT), Csólyospálos (CSP, HU), Pwllpeiran (PW, UK), Sekule (SE, SK). The investigated parameters were the extent (determined by repellency indices RI, RIc and RIm) and persistence (determined by water drop penetration time (WDPT) and water repellency cessation time, WRCT) of SWR, as well as field water (Sw) and ethanol (Se) sorptivity, water sorptivity of hydrophobic soil state (Swh) water sorptivity of nearly wettable soil state (Sww) and field hydraulic conductivity (K). Our findings showed an area of land has a greater likelihood of being water repellent if it has a sandy soil texture and/or a high frequency of prolonged drought events. Water infiltration was positively correlated with all the sorptivities (r = 0.32–0.88), but was mostly negatively correlated with RI (r = – 0.54 at CI), WDPT (r = – 0.47 at CI) and WRCT (r = – 0.58 at CI). The importance of natural and synanthropized vegetation covers with regards to SWR was not coherent; moving to regions having coarser texture or moving to drier climatic zones led to higher risk of SWR conditions. Climate change has been predicted to lead to more frequent extreme weather events and prolonged dry periods across Europe, which will most likely increase the extent of SWR-affected areas and increase the role of SWR in water management of grassland ecosystems. Therefore, there is a need to determine SWR risk zones to prevent decreases in soil moisture content, soil fertility, carbon and nitrogen sink potentials, as well as biomass production of the related agro-ecosystems.

Development of a universal microinfiltrometer to estimate extent and persistence of soil water repellency as a function of capillary pressure and interface chemical composition

Abstract Microinfiltrometers to assess soil water repellency (SWR) are limited to small tension ranges and have different technical setups, hindering a comparison between results from different laboratories. Hence, a microinfiltrometer which considers various aspects like extent and persistence of SWR is needed. The technical update suggested here uses glass tubes (e.g., 3 mm inner diameter), a fabric of mesh size 15 µm around the tip to enable good contact between soil surface and tip, ultrapure degassed water, and an evaporation protection for tip and reservoir during long-term infiltration. The adjustment of a continuous range of pressures and tensions (i.e., +0.5 to –40 cm) was done using glass tubes of various lengths connected to the tip. Three soil samples with initial contact angles, CA, of 18°, 62°, and 91° after 25°C treatment were additionally treated at 80°C to increase SWR persistence and CA. The soil particle interface chemical composition was determined by X-ray photoelectron spectroscopy (XPS). The hydrophysical properties evaluated included water and ethanol sorptivity as well as very important aspects of SWR, i.e. water drop penetration time, water repellency cessation time, repellency index, and modified repellency index. The results derived from the technically modified microinfiltrometer setup showed consistent differences between initial wettability and the water repellency cessation time as a parameter describing the development of SWR with time. The interface O/C ratio as derived from XPS data was negatively correlated with CA (p <0.05), thus proving the close relationship between interface chemistry and wettability. Our findings illustrated a strong positive correlation (R 2 = 0.99, p < 0.05) between sorptivity and O/C ratio under –2 cm tension which can be considered as the universal tension for different aspects of SWR.

Factors governing soil water repellency under tillage management: The role of pore structure and hydrophobic substances

AbstractSoil water repellency (SWR) has significant effects on soil degradation by changing some soil processes (e.g., carbon sequestration and soil erosion). Understanding the influence factors of SWR under conservation agriculture are playing a vital role in the sustainable development for improving soil quality. However, how soil pore structure influence on SWR remains unclear. We aim to assess the impact of hydrophobic substances and pore structure on SWR. Here we conducted two long‐term experimental fields with three treatments: conventional tillage (CT), reduced tillage (RT), and no‐tillage (NT). X‐ray tomography and the sorptivity method were used to measure soil pore structure and SWR, respectively. We found that soil organic carbon (SOC) and microbial biomass carbon (MBC) were higher in RT and NT treatments than in CT. MBC had significant influences on soil water sorptivity (Sw) and water repellency index (RI; p < 0.001), whereas SOC had no influence on Sw (p > 0.05). MBC also showed a closer relationship with SWR than SOC in redundancy analysis. The RT and NT increased the porosity of 55–165 μm that had a positive relationship with ethanol sorptivity and RI (p < 0.05). Ethanol sorptivity increased with an increase in soil pore porosity and connectivity under RT and NT treatments. However, increasing the pore surface area could decrease Sw due to enhance contact area between hydrophobic substances and soil water. Overall, the RT and NT treatments increased the water repellency index, which was a result of the interactions between pore structure and hydrophobic substances.

Long-term cropping and fertilization influences soil organic carbon, soil water repellency, and soil hydrophobicity

Long-term (58 yr) cropping and fertilization effects on soil water repellency were determined for a clay loam soil in southwestern Ontario, Canada by measuring soil organic carbon (SOC), soil water repellency index (RI), and soil hydrophobicity (SH). The 12 treatments (non-replicated) included fertilized and non-fertilized legume-based crop rotation (ROT) with four phases (corn–oat–alfalfa–alfalfa), continuous corn (CC), and continuous Kentucky bluegrass (KBG). We hypothesized that SOC, RI, and SH would be greater for each phase of the ROT versus CC, KBG versus CC and ROT, and fertilized versus non-fertilized treatments. Surface (0–10 cm) soil samples were collected in the spring of 2017. Laboratory measurements were conducted to determine SOC, RI (ratio of soil sorptivity to ethanol and water), and SH (ratio of hydrophobic CH– to hydrophilic CO– functional groups). Mean SOC and SH were greater (P ≤ 0.05) for each phase of the ROT versus CC (33% to 2.4 times), KBG versus CC (3.2–6 times) and each phase of ROT (2.2–2.8 times), and fertilized versus non-fertilized rotation oats and KBG (15%–30%). Mean RI was greater for KBG versus CC (4.8 times) and KBG versus each phase of the ROT (3.0–5.5 times) under fertilization only, greater for fertilized versus non-fertilized KBG (6.8 times), but similar for each phase of ROT versus CC. In general, legume-based rotations, perennial grass, and fertilizer enhanced SOC and SH, and to a lesser extent soil RI.

Comparative Studies on the Efficacy and Mode of Action of Chlorpyrifos, Cypermethrin and ‘Tofeto’ Against Anopheles spp (Diptera: Culicidae)

The efficacy of ‘Tofeto’ and two synthetic insecticides, chlorpyrifos and cypermettrin were compared as fumigants and repellants against Anopheles spp. Knockdown, mortality and repellency responses were noted and compared. ‘Tofeto’ had a significantly higher knockdown effect on mosquitoes, while chlorpyrifos had the least. Cypermethrin had the fastest mortality time. ‘Tofeto’ compared favourably with cypermethrin and chlorpyrifos as a repellant having the highest percentage repellence and repellency index.
 
 Keywords: Synthetic insecticides, Repellants, Haematophagus, Anthropophilic, Knockdown

Differences in moisture pattern, hydrophysical and water repellency parameters of sandy soil under native and synanthropic vegetation

The main goal of the study was to estimate the differences in moisture pattern, hydrophysical and soil water repellency (SWR) parameters of sandy soil profiles at two grassland sites, separated by a distance of about 100 m, near Sekule village (southwest Slovakia). Site S1 was covered with natural vegetation formed by a process of primary succession on a sand dune, whilst site S2 was covered by a synanthropic vegetation, formed by spontaneous secondary succession. Soil sampling and infiltration experiments were performed at designated plots during June 2017 to determine hydrophysical and SWR parameters. Higher measured value of organic carbon content at site S2 resulted in the greater values of repellency index (RI) and lower values of hydraulic conductivity, k(−2 cm), and sorptivity of water, Sw(−2 cm) compared to S1. For evaluating the differences between estimated hydrophysical and SWR parameters of S1 and S2, a Welch’s test of means (allowing for unequal group variances) was used, revealing significant differences in Sw(−2 cm), and RI, at p < 0.05. Simultaneously designed infiltration experiments pointed out altered distribution in wetting pattern across the soil profile with different penetration depths: below 100 cm and 80 cm at S1 and S2, respectively. Although the observed moisture patterns showed different shapes and extensions, difference in the cumulative increase in soil water storage between 0 and 50 cm was not significant (35.1% and 36.8% of applied water) at S1 and S2, respectively. According to the results we can state that grasslands at sites S1 and S2 have different soil water repellency parameters and shape of moisture pattern, induced probably by finger flow. Nevertheless, the soil water retention capacity of site S2, formed by spontaneous secondary succession is nearly the same as the retention capacity of native grassland S1.

Impact of secondary succession in abandoned fields on some properties of acidic sandy soils

Abstract Abandonment of agricultural lands in recent decades is occurring mainly in Europe, North America and Oceania, and changing the fate of landscapes as the ecosystem recovers during fallow stage. The objective of this study was to find the impact of secondary succession in abandoned fields on some parameters of acidic sandy soils in the Borská nížina lowland (southwestern Slovakia). We investigated soil chemical (pH and soil organic carbon content), hydrophysical (water sorptivity, and hydraulic conductivity), and water repellency (water drop penetration time, water repellency cessation time, repellency index, and modified repellency index) parameters, as well as the ethanol sorptivity of the studied soils. Both the hydrophysical and chemical parameters decreased significantly during abandonment of the three investigated agricultural fields. On the other hand, the water repellency parameters increased significantly, but the ethanol sorptivity did not change during abandonment. As the ethanol sorptivity depends mainly on soil pore size, the last finding could mean that the pore size of acidic sandy soils did not change during succession.

The effect of 12-year ecological farming on the soil hydraulic properties and repellency index

The objective of this study was to elucidate the influence of long-term ecological farming on selected soil properties by comparing results obtained in the field with continuous conventional farming (CT) and those obtained in the field where the original CT was converted into ecological farming system with no-till practice (NT) twelve years earlier. Soil water retention curves were obtained for 100 cm3 undisturbed soil samples using a pressure plate apparatus. Hydraulic conductivity and the repellency index were assessed directly in the field using a mini disk infiltrometer. The examined soil properties showed that NT mostly had a positive influence on the soil quality. The soil water retention capacity represented by the saturated soil water content of 0.32 and 0.40 cm3 cm−3 and the reciprocal of the air-entry pressure head of 0.0227 and 0.0187 cm for CT and NT, respectively, was higher in the NT field than in the CT field. The soil physical quality, represented by the slope of the soil water retention curve at the inflection point of 0.033 (CT) and 0.047 (NT), was better under NT than CT. The hydraulic conductivity at the pressure head of –2 cm was higher in the NT field (0.97 cm hr.−1) than in the CT field (0.17 cm hr.−1). On the other hand, ecological farming increased water repellency (repellency index of 6.73 and 18.91 for CT and NT, respectively).

Land Suitability Evaluation of The Wetland Soils of Obukiyo, Oju LGA of Benue State, Nigeria For Rice (Oryza Sativa) Production.

The effect of different rates of poultry manure application on water characteris- tics of Oforola soils was studied. The different poultry manure rates were 0, 10, 20, and 30 t/ha, while the soil properties studied were particle size distribution, bulk density, porosity, organic matter, saturated hydraulic conductivity, volumet- ric water content, volumetric infiltration rate, sorptivity and water repellence in- dex. Data were subjected to multiple correlation (p = 0.05 and p = 0.01) and anal- ysis of variance (p = 0.05) using RCBD. The results show that the particle size distribution and water repellence index did not differ significantly among the different treatment rates. Soil porosity and organic matter were observed to in- crease with increasing treatment rate but were not significantly influenced by the different treatment rates. Bulk density was significantly influenced in the 30 t/ha treated plot. Both the saturated hydraulic conductivity and volumetric water con- tent were significantly influenced in the 20 and 30 t/ha treated plots, while both volumetric infiltration rate and sorptivity were significantly influenced in all the treated plots. The result of the correlation analysis showed that the treatments had positive influence (p = 0.01) on porosity (r = 0.982), organic matter (r = 0.967) and volumetric water content (r = 0.976) but negatively influenced (p = 0.01) bulk density (r = -0.982), saturated hydraulic conductivity (r = -0.989), volumet- ric infiltration rate (r = -0.990) and sorptivity (r = -0.994). Also, the treatments correlated positively but non-significantly with water repellence index (r value), which correlated negatively and significantly with the percent clay content (r value). Based on the findings, a further study is recommended to establish a standard and beneficial poultry manure rate that would enhance soil water char- acteristics for sustainable productivity. o improve the soil constraints to maintain and sustain the productivity of the soils.

Tillage system influences hydrophobicity but not water repellency of a clay loam soil in southwestern Ontario

A 21 yr field study comparing zone tillage (ZT), no-tillage (NT), and moldboard plow tillage (MP) was used to elucidate tillage effects on soil hydrophobicity (SH) and soil water repellency index (RI) in a cool, humid clay loam soil in southwestern Ontario. The SH was 38% (P ≤ 0.05) greater for ZT and NT than MP, and it was similar between crop row (0.34) and crop inter-row (0.37) for ZT. The RI values were not different among tillage systems, or between the crop row versus crop inter-row positions under the three tillage systems.

Influence of crop residues and nitrogen fertilizer on soil water repellency and soil hydrophobicity under long-term no-till

Crop residues and N fertilizer under no-till may increase soil water repellency (SWR) and soil hydrophobicity, but few studies have examined these two treatment factors and their interaction. A laboratory study was conducted using a long-term (since 1999) field experiment on a clay loam soil to determine the effect of three crop residues and two N fertilizer levels on SWR and soil hydrophobicity under no-till within the Dark Brown soil zone of the semi-arid Canadian prairies. The three residue treatments were residues removed from soil (Rx0), residues returned to soil (Rx1), and residues supplemented to soil (Rx2). The two fertilizer N treatments were 0 (N0) and 45 kg N ha−1 (N1). Surface (0–10 cm) soil samples were taken in the spring of 2017 after 17 yr. Laboratory measurements were conducted on air-dried and sieved (&lt;2 mm) soil to determine SWR using the repellency index method (RI), soil organic C, hydrophobic CH and hydrophilic CO functional groups, and soil hydrophobicity (CH/CO ratio). Mean RI values ranged from 2.19 to 2.75, indicating subcritical (RI &gt; 1.95) SWR. Similar (P &gt; 0.05) RI values were found for the three residue and two N fertilizer treatments, but the trend was for greater RI with increased residue addition (by 12%–26%) and N fertilizer (by 8%). Soil hydrophobicity was significantly greater by 47%–82% for straw returned or supplemented than straw removed treatments, and by 33% for fertilized than unfertilized treatments. Overall, greater residues and N fertilizer had no effect on SWR, but significantly increased soil hydrophobicity.

Soil stabilisation by water repellency under no-till management for soils with contrasting mineralogy and carbon quality

No-till soil management is common around the globe, but the impacts on soil structural quality varies depending on cropping practice and inherent soil properties. This study explored water repellency as a driver of soil stabilization, as affected by soil mineralogy, granulometry and organic carbon quality in three Mollisols and one Vertisol under no-till management and with different levels of cropping intensity. The studied soils were located along a west-east textural gradient in the northern part of the Pampean region of Argentina. Cropping intensity treatments evaluated in each one of the soils were: Poor Agricultural Practices (PAP) close to a monoculture, Good Agricultural Practices (GAP) involving a diverse crop rotation and more targeted inputs, and the soil in the surrounding natural environment (NE) as a reference. NE had the greatest aggregate stability (MWD) of all cropping intensities, with GAP being more stable than PAP for Mollisols and PAP being greater than GAP for the Vertisol. This trend matched the Repellency Index (Rindex), with greater Rindex associated with greater MWD, including the difference between the Mollisols and Vertisol. However, the persistence of water repellency, measured by the Water Drop Penetration Time (WDPT) test followed the trend NE > GAP>PAP regardless of soil type. The increases in Rindex and MWD were related to higher intensification as measured by the Crop Sequence Index, and decreased with greater soybean occurrence in the sequence. Both WDPT and Rindex were closely related to aggregate stability, particularly for Mollisols. These results highlight the importance of considering the inherent soil characteristics texture and mineralogy to understand aggregate stabilization mediated by water repellency. Good correlations between soil water repellency, organic carbon fractions and aggregate stability were found. Under no-till, crop rotations can be altered to increase soil stability by inducing greater water repellency in the soils. The findings suggest that water repellency is a major property influencing soil structure stabilization, thus providing a useful quality indicator.

Insecticidal, Behavioral and Biological Effects of Chlorantraniliprole and Chlorfluazuron on Cotton Leafworm (Spodoptera littoralis).

The cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae) is the most destructive pests and causing a great loss for several vegetables and field crops. So, the present study was aimed to evaluate and compare the effects of chlorantraniliprole and chlorfluazuron on certain behavioral and biological aspects of S. littoralis at different stages. Under laboratory conditions, the toxicity of chlorantraniliprole and chlorfluazuron against the egg masses, 2nd and 4th larval instars of S. littoralis were evaluated. The impact of tested insecticides on the feeding, oviposition of females and biological aspects of S. littoralis was also carried out. Overall, chlorfluazuron was more toxic than chlorantraniliprole. According to repellency index (RI %), tested insecticides have a repulsive effect for the feeding of 2nd and 4th larval instars as well as for oviposition of females. Sublethal concentrations significantly reduced larval and pupal weight, adult survival, percent of pupation and adult emergence, female fecundity, fertility percentage, weight and protein content of ovaries. While, larval and pupal durations were increased. It was concluded that chlorantraniliprole and chlorfluazuron have insecticidal, behavioral and biological effects on S. littoralis stages and may be used as alternatives to conventional insecticides in IPM programs.