Evaluation of residual plastic film pollution in pre-sowing cotton field using UAV imaging and semantic segmentation

To accurately evaluate residual plastic film pollution in pre-sowing cotton fields, a method based on modified U-Net model was proposed in this research. Images of pre-sowing cotton fields were collected using UAV imaging from different heights under different weather conditions. Residual films were manually labelled, and the degree of residual film pollution was defined based on the residual film coverage rate. The modified U-Net model for evaluating residual film pollution was built by simplifying the U-Net model framework and introducing the inception module, and the evaluation results were compared to those of the U-Net, SegNet, and FCN models. The segmentation results showed that the modified U-Net model had the best performance, with a mean intersection over union (MIOU) of 87.53%. The segmentation results on images of cloudy days were better than those on images of sunny days, with accuracy gradually decreasing with increasing image-acquiring height. The evaluation results of residual film pollution showed that the modified U-Net model outperformed the other models. The coefficient of determination(R²), root mean square error (RMSE), mean relative error (MRE) and average evaluation time per image of the modified U-Net model on the CPU were 0.9849, 0.0563, 5.33% and 4.85 s, respectively. The results indicate that UAV imaging combined with the modified U-Net model can accurately evaluate residual film pollution. This study provides technical support for the rapid and accurate evaluation of residual plastic film pollution in pre-sowing cotton fields.

Steroidobacter gossypii sp. nov., isolated from cotton field soil

A Gram-negative bacterium, designated S1-65^T, was isolated from soil samples collected from a cotton field located in the Xinjiang region of PR China. Results of 16S rRNA gene sequence analysis revealed that strain S1-65^T was affiliated to the genus Steroidobacter with its closest phylogenetic relatives being 'Steroidobacter cummioxidans' 35Y (98.4 %), 'Steroidobacter agaridevorans' SA29-B (98.3 %) and Steroidobacter agariperforans KA5-B^T (98.3 %). 16S rRNA-directed phylogenetic analysis showed that strain S1-65^T formed a unique phylogenetic subclade next to 'S. agaridevorans' SA29-B and S. agariperforans KA5-B^T, suggesting that strain S1-65^T should be identified as a member of the genus Steroidobacter. Further, substantial differences between the genotypic properties of strain S1-65^T and the members of the genus Steroidobacter, including average nucleotide identity and digital DNA-DNA hybridization, resolved the taxonomic position of strain S1-65^T and suggested its positioning as representing a novel species of the genus Steroidobacter. The DNA G+C content of strain S1-65^T was 62.5 mol%, based on its draft genome sequence. The predominant respiratory quinone was ubiquinone-8. The main fatty acids were identified as summed feature 3 (C_16:1ω6c/C_16:1ω7c), C_16 : 0 and iso-C_15 : 0. In addition, its polar lipid profile was composed of aminophospholipid, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Here, we propose a novel species of the genus Steroidobacter: Steroidobacter gossypii sp. nov. with the type strain S1-65^T (=JCM 34287^T=CGMCC 1.18736^T).

[Effects of continuous cropping with straw return on particulate organic carbon and Fourier transform infrared spectroscopy in cotton field]

A long-term field experiment was conducted to investigate the effects of continuous cotton production years (0 as control, 5, 10, 15 and 20 years) and straw return on soil organic carbon (SOC) structure and stability by using Fourier transform infrared spectroscopy (FTIR) in Manas River valley of Xinjiang. The results showed that the relative peak intensity of polysaccharide and aromatics decreased with increasing continuous cropping years, whereas the aliphatic and alcoholic phenols relative peak intensity and the CH/C=C increased. The content of soil particulate organic carbon (POC) increased significantly in the 5-yr of cotton production farmland and then decreased with the increases of continuous cropping years. POC content was 5.11 times higher in 5-yr than that of the control. The content of mineral-bound organic carbon (MOC) was the highest in 10-yr farmland, being 1.84 times higher than that of the control. The highest value of the ratio of POC and MOC content (ω(POC)/ω(MOC)) was observed in 5-yr farmland. Together, long-term continuous cotton production with straw return led to SOC structure aliphatic and soil mineral binding increased the protection of organic matter, thus increasing the stability of soil organic matter.

[Comprehensive method for evaluating soil quality in cotton fields in Xinjiang, China]

To evaluate the soil quality in the main cotton growing regions of Xinjiang, 11 soil quality indices were measured in representative locations: Hami, Bole, Changji, Shihezi, Aksu, Kashgar and Kuitun. The indices included soil pH, salt, organic matter, total N, available P and available K for soil physicochemical properties, and Cr, Cu, Zn, As, and Pb for soil heavy metal pollution. Based on these indices, a comprehensive soil quality index (SQI) was developed to analyze the soil quality in the cotton fields of Xinjiang. The results showed that the soils in Xinjiang's cotton fields were alkaline, with an average pH of 7.87. The soils were mildly saline, with an average salt content of 3.44 g·kg^-1. Soil organic matter and total N concentrations were generally low, whereas available P and available K concentrations were relatively high. Soil available P concentrations were significantly higher than that of the second national soil survey, whereas soil pH, salt content, organic matter, and total N were less. Soil available K was greater in some regions but lower in others compared with the second national soil survey. The average heavy metal concentrations were as follows: Cr, 45.88 mg·kg^-1; Cu, 40.66 mg·kg^-1; Zn, 68.30 mg·kg^-1; As, 12.88 mg·kg^-1; and Pb, 16.68 mg·kg^-1. These values were all below the national standards. However, the Cu, Zn, and As concentrations were greater than the background values in Xinjiang, indicating the accumulation of those elements in the soils. When the Nemerow comprehensive pollution index (PN) of heavy metals was less than 0.5, the comprehensive soil quality improved as the soil physicochemical properties improved. Soil organic matter, total N, Cu, Zn, As and Pb were the main variables affecting soil quality in the main cotton cropping regions of Xinjiang. The cotton growing areas in Xinjiang generally had medium soil quality. Changji and Kuitun had the highest SQI (0.52) whereas Aksu had the lowest value (0.31). Soil quality was generally highest in northern Xinjiang, followed by western area, and then southern area.

Field Trapping of Predaceous Insects With Synthetic Herbivore-Induced Plant Volatiles in Cotton Fields

Nine herbivore-induced plant volatiles (HIPVs) and one methyl jasmonate were field-tested for their attractiveness to the main predators in cotton fields of North China in 2 yr. The main predators including ladybird beetles (Propylaea japonica (Thunberg), Harmonia axyridis (Pallas)), green lacewings (Chrysoplera sinica (Tjeder), Chrysopa spp.), predatory bugs (Geocoris pallidipennis (Costa), Orius spp., Nabis spp.) and spiders (Misumenops tricuspidatus (Fabricius), Erigonidium graminicolum (Sundevall)) were investigated. Two-way ANOVA indicated that the volatile compound, year, and the volatile compound × year interaction affected the behavioral responses of predators. It was found that indole significantly attracted the ladybird beetle P. japonica, H. axyridis. Linalool could attract P. japonica. Green lacewing C. sinica was significantly attracted by α-pinene and β-pinene, whereas indole significantly attracted Chrysopa spp. Methyl jasmonate and α-pinene showed significant attraction to small-flower bug Orius spp. In addition, the attraction of α-humulene to C. sinica, attractiveness of β-pinene to Orius spp. and Chrysopa spp., were observed only in one of the two years. However, the big-eyed bug G. pallidipennis, damsel bug Nabis spp., spiders M. tricuspiata and E. graminicolum did not respond to any of the tested HIPVs. These results are discussed with respect to possible applications of a synthetic attractant for main predators in cotton fields.

[Effects of enhanced-efficiency nitrogen fertilizers on nitrous oxide emissions from cotton field under plastic mulched drip irrigation in Xinjiang,China]

The effect of enhanced-efficiency nitrogen (N) fertilizers on emissions of nitrous oxide (N₂O) from the grey desert agricultural soils of Xinjiang is uncertain. In this study, the enhanced-efficiency fertilizers, polymer-coated urea (ESN), and stabilized urea with urease and nitrification inhibitors (U+I) were compared to conventional urea (U) for N₂O emissions from cotton under plastic mulch drip irrigation near Urumqi, Xinjiang. ESN was added once at planting but the other treatments were added multiple times with drip irrigation during the growing season. Gas samples were collected and analyzed twice per week during the growing season, using the static chamber-chromatography methodology. The results showed that generally, ESN significantly increased soil cumulative N₂O emissions during the growing season by 47%-73% compared to other treatments. In the first four months after fertilization, soil ammonium (NH₄⁺-N) and nitrate (NO₃^--N) concentrations under ESN treatment were generally higher than under other treatments. Thereafter, NH₄⁺-N and NO₃^--N concentrations under all treatments gradually decreased to similar levels. ESN all added at planting was likely responsible for high NH₄⁺-N and NO₃^--N concentrations and highest N₂O emissions. The U+I treatment reduced soil N₂O emission by 9.9% in comparison with U, whereas the difference was not statistically significant. In addition, soil NO₃^--N contents of the U+I treatments were generally lower than those of the ESN and the U treatments. The cumulative N₂O emissionsover the growing season ranged from 300 to 500 g N₂O-N·hm^-2, generally lower than emissions reported for other agricultural ecosystems. Drip irrigation successfully kept moisture conditions below levels for appreciable N₂O emissions. Multiple applications of N via drip irrigation seemed to be effective to lower emissions than all N applied at planting. Therefore, for cotton field under plastic mulch drip irrigation in arid land of Northwest China, the benefit of enhanced efficiency N ferti-lizers on N₂O mitigation is limited.

Resurgence of the cotton bollworm Helicoverpa armigera in northern Greece associated with insecticide resistance

Helicoverpa armigera has been controlled effectively with chemical insecticides in the major cotton crop production areas of northern Greece for many years. However, a resurgence of the pest was observed in 2010, which significantly affected crop production. During a 4-year survey (2007-2010), we examined the insecticide resistance status of H. armigera populations from two major and representative cotton production areas in northern Greece against seven insecticides (chlorpyrifos, diazinon, methomyl, alpha-cypermethrin, cypermethrin, gamma-cyhalothrin and endosulfan). Full dose-response bioassays on third instar larvae were performed by topical application. Lethal doses at 50% were estimated by probit analysis and resistance factors (RF) were calculated, compared to a susceptible laboratory reference strain. Resistance levels were relatively moderate until 2009, with resistance ratios below 10-fold for organophosphates and carbamates and up to 16-fold for the pyrethroid alpha-cypermethrin. However, resistance rose to 46- and 81-fold for chlorpyrifos and alpha-cypermethrin, respectively in 2010, when the resurgence of the pest was observed. None of the known pyrethroid resistance mutations were found in the pyrethroid-resistant insects. The possible association between resistance and H. armigera resurgence in Greece is discussed.