To quickly and accurately extract vegetation coverage information of winter wheat in turning green period.

The field visible light images of winter wheat were obtained by UAV, and four common visible light vegetation indices were extracted. According to the principle of pixel dichotomy model, the vegetation coverage extraction models were established based on visible-band difference vegetation index(VDVI), excess green (EXG), normalized green-blue difference index (NGBDI) and normalized green-red difference index (NGRDI) respectively. The accuracies of four models were verified using the support vector machine (SVM) supervised classification results as the truth values.

The VDVI vegetation coverage extraction model had the highest accuracy and the best extraction effect to extract vegetation coverage among the four models. Compared with the supervised classification results, the extraction errors (E_F) of four vegetation coverage extraction models were 3.36%, 15.68%, 8.74% and 15.46% respectively, the values of R² were 0.946 1, 0.934 4, 0.695 3 and 0.746 0 respectively, and the values of root mean square error (RMSE) were 0.021 9, 0.059 5, 0.042 0 and 0.055 9 respectively.

The vegetation coverage extraction model based on visible vegetation index and pixel dichotomy has realized accurate and rapid extraction of vegetation coverage of winter wheat in turning green period, which provides a new way to extract vegetation coverage and a reference for UAV remote sensing monitoring vegetation coverage information.

As the main feed additive in breeding industry, Cu²⁺, Zn²⁺ and oxytetracycline contribute to high amounts of residues in livestock and poultry excrement and sewage, forming complex pollution. We are aimed at screening strains to degrade oxytetracycline under the stress of Cu²⁺ and Zn²⁺.

The strain DJ1 of oxytetracycline degrading bacteria was screened and isolated from culture wastewater using selective medium. The biodegrading conditions of oxytetracycline by strain DJ1 were optimized. The tolerances of strain DJ1 to other tetracycline antibiotics and chloramphenicol were determined.

The strain DJ1 was identified as Cutaneotrichosporon cutaneum based on morphology and 18S rDNA sequence alignment. The oxytetracycline degradation rate of DJ1 reached 78.83% after five days of culturations under the condition of pH7, 30 ℃ temperature, 50 mL liquid in 250 mL flask, 200 mg/L substrate and 1%(φ) inoculum size. In medium with lower concentration (50 mg/L) of oxytetracycline, 50 mg/L Zn²⁺ inhibited oxytetracycline degradation, while 50 mg/L Cu²⁺ inhibited oxytetracycline degradation in medium with higher concentration (200 mg/L) of oxytetracycline. DJ1 strain had high tolerance to tetracycline antibiotics and chloramphenicol, the tolerating concentrations to both were above 700 mg/L. DJ1 strain could grow on the plate of binary cross medium with antibiotics and heavy metals of Cu²⁺ and Zn²⁺, showing dual resistance to antibiotics and heavy metals.

DJ1 strain has high tolerance to tetracycline antibiotics, chloramphenicol, Cu²⁺ and Zn²⁺. It can efficiently degrade oxytetracycline and can be used to control antibiotic contamination in the environment.

To study the effects of drip fertigation on soil active organic carbon content and methane (CH₄) emission flux in sugarcane field, and investigate the relationship between soil methane emission flux and soil active organic carbon content.

The field experiment with different irrigation and fertilization treatments under drip irrigation was conducted in Nanning Irrigation Experimental Station from March to December in 2018. Four fertilization levels were designed: Conventional fertilization (F₁₀₀, N 250 kg·hm⁻², P₂O₅ 150 kg·hm⁻², K₂O 200 kg·hm⁻²), incremental fertilization 1 (F₁₁₀, 10% increase based on F₁₀₀), incremental fertilization 2 (F₁₂₀, 20% increase on the basis of F₁₀₀), and reducing fertilization (F₉₀, 10% reduction based on F₁₀₀). Two drip irrigation levels were set: W₁₈₀ (180 m³·hm⁻²) and W₃₀₀ (300 m³·hm⁻²). Soil CH₄ emission flux and active organic carbon contents at different growth stages of sugarcane were measured using conventional method, and the relationships between soil CH₄ emission flux and active organic carbon contents in sugarcane field were analyzed by Pearson method.

At tillering stage, W₃₀₀F₁₂₀ treatment increased soil soluble organic carbon (DOC) content by 156% compared with W₃₀₀F₁₀₀ but had lower CH₄ emission flux in soil than the other treatments. At maturing stage, W₃₀₀F₁₂₀ treatment increased soil DOC content and microbial biomass carbon (MBC) by 114% and 49.6% compared with W₃₀₀F₁₀₀, respectively. CH₄ emission flux in sugarcane field was only positively correlated with soil DOC content, with the correlation coefficient of 0.38.

Soil DOC content significantly affects CH₄ emission flux in sugarcane field. W₃₀₀F₁₂₀ treatment can increase soil soluble organic carbon content in sugarcane field at tillering and maturing stages, and reduce soil CH₄ emission in sugarcane field at tillering stage.

To solve the problems of high cost, high labor intensity and low production efficiency in pepper planting, seeding and transplanting, an air-suction type precision direct seeding machine for pepper was developed considering pepper planting pattern and agronomic requirements in south area.

The machine consists of a main frame, a copying mechanism, a fan, a transmission system, a derailleur, an air-suction seed device, a ditching device and a pressing device, which can complete the ditching, seeding, soil covering and pressing operations at one time. The seed metering machine uses the principle of taking seeds by negative pressure and discharging seeds by breaking pressure. According to the seeding requirements and physical characteristics of pepper seeds, the size of seeding plate, the number and size of seeding holes were determined. Sowing precision and quantity requirements were ensured. The seeding part is connected with the main frame by a parallel four-bar copying mechanism, so as to realize the ground copying of the seeding monomer and ensure the ditching and seeding depth.

Field test results showed that the average qualified rate of 1−3 grains/hole was 91.16%, the average leakage seeding rate was 0.18%, and the average repeat seeding rate was 8.66%. In tests of different hole distances, qualified rates for different hole distances were above 89%, the repeat rate was below 4.85%, the leakage seeding rate were below 11%, the coefficients of variations of the hole distances were below 23.77%, and the qualified rate of seeding depth was 86%.

The working performance of the whole machine meets the requirements for pepper planting. This research can provide a reference for the research and development of precision vegetable seeders.