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排序方式： 共有3092条查询结果，搜索用时 36 毫秒
1.
Ruirui Zhang Andrew J Hewitt Liping Chen Longlong Li Qing Tang 《Pest management science》2023,79(11):4123-4131
The application of pesticides is not simply delivering chemicals to the target area. It also involves considering the negative aspects and developing strategies to deal with them during the application process, to ensure the maximization of pesticides use efficiency and the maintenance of the ecosystem. Unmanned aerial vehicle (UAV) sprayers demonstrate unique advantages compared to traditional ground sprayers, particularly in terms of maneuverability and labor intensity reduction, showed great potential for chemical application in pest control. It is undeniable that there exist challenges in the practice of UAV spraying, such as higher potential risks of pesticide drift or pathogen transmission, uncertainty canopy deposition for different crops, and unexpected leaf breakage induced by downwash flow. Maximizing the utilization of downwash flow while avoiding lateral air movement outside the intended target crop area is a major issue for chemical application with UAV sprayers, particularly in light of the increasingly apparent consensus on the need for enhanced environmental protection during the chemical application process. It must be considered that the operation strategy in different scenarios and for different crop targets is not the same, unique requirements should be given on nozzle atomization, flight parameters, adjuvants and aircraft types in specific working situations. In future, the implementation of spray drift prediction, technical procedures development, and other solutions aimed at reducing pesticide drift and improving deposition quality, is expected to promote the adoption of UAV sprayers by more farmers. © 2023 Society of Chemical Industry. 相似文献
2.
《Agricultural Water Management》2002,56(2):143-151
The study uses the concepts of marginal water use efficiency (MWUE), and elasticity of water production (EWP) to reveal the dynamic interrelations of crop yield (Y), seasonal evapotranspiration (ET), and water use efficiency (WUE) based on the functional relation of an ET production function (ETPF). When the ETPF is linear, the changing trend of WUE with ET is directly affected by the intercept of the function, and the EWP will be numerically equivalent to a yield response factor (KY) when ET reaches maximum ET (ETm). When the ETPF is quadratic, the ET needed to maximise WUE is less than the ET for maximum yield (Ym), and the ET value that occurs at maximum WUE equals the arithmetic square root of the ratio of the intercept of the function to the coefficient of function quadratic term. The interrelationships of Y, ET, and WUE are demonstrated using a quadratic ETPF developed for maize from data obtained in a field experiment. 相似文献
3.
Jing?Guo Xingxing?Li Zhenhong?LiEmail authorView author&#;s OrcID profile Leyin?Hu Guijun?Yang Chunjiang?Zhao David?Fairbairn David?Watson Maorong?Ge 《Precision Agriculture》2018,19(5):895-911
The main objective of this research was to examine the feasibility of Multi-GNSS precise point positioning (PPP) in precision agriculture (PA) through a series of experiments with different working modes (i.e. stationary and moving) under different observation conditions (e.g. open sky, with buildings or with canopy). For the stationary test carried out in open space in the UK, the positioning accuracy achieved was 13.9 mm in one dimension by a PPP approach, and the repeatability of positioning results was improved from 19.0 to 6.0 mm by using Multi-GNSS with respect to GPS only. For the moving test carried out in similar location in the UK, almost the same performance was achieved by GPS-only and by Multi-GNSS PPP. However, for a moving experiment carried out in China with obstruction conditions, Multi-GNSS improved the accuracy of baseline length from 126.0 to 35.0 mm and the repeatability from 110.0 mm to 49.0 mm, The results suggested that the addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing improved the positioning repeatability, while a positioning accuracy was achieved at about 20 mm level in the horizontal direction with an improvement against the GPS-only PPP results. In space-constrained and harsh environments (e.g. farms surrounded with dense trees), the availability and reliability of precise positioning decreased dramatically for the GPS-only PPP results, but limited impacts were observed for Multi-GNSS PPP. In addition, compared to real time kinematic (RTK) GNSS, which is currently most commonly used for high precision PA applications, similar accuracy has been achieved by PPP. In contrast to RTK GNSS, PPP can provide high accuracy positioning with higher flexibility and potentially lower capital and running costs. Hence, PPP might be a great opportunity for agriculture to meet the high accuracy requirements of PA in the near future. 相似文献
4.
Yuting Cai Shifeng Cao Zhenfeng Yang Yonghua Zheng 《Postharvest Biology and Technology》2011,59(3):324-326
This study investigated the regulation of ascorbate acid (AsA) and glutathione metabolism and chilling tolerance by methyl jamonate (MeJA) in loquat fruit. The results showed that application of MeJA to loquat fruit inhibited the incidence of chilling injury manifested as internal browning (IB) and increased AsA and reduced glutathione (GSH) contents due to the inhibition of ascorbate oxidase activity and enhancement of monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase activities. Meanwhile, MeJA also enhanced activities of ascorbate peroxidase, glutathione peroxidase and glutathione-S-transferase. Our results suggested that MeJA can regulate the ascorbate and glutathione metabolism and has important roles in alleviating oxidative damage and enhancing chilling tolerance in loquat fruit. 相似文献
5.
The effects of Phomopsis longanae Chi infection on browning development and disease incidence in relation to energy status in pericarp of harvested longan fruit were investigated. Longan fruit were inoculated for 5 min with P. longanae at 104 spores mL−1, while fruit dipped in sterile deionized water were used as control. These fruits were stored at (28 ± 1) °C and 90% relative humidity for up to five days. The results showed that the browning index, disease incidence, cellular membrane permeability and AMP content increased but the contents of ATP and ADP, and energy charge decreased in pericarp of longan fruit infected by P. longanae. It was suggested that P. longanae infection caused energy deficiency in longan fruit, possibly resulting in accelerated senescence and decreased resistance to pathogen, and thus promoted browning development and disease occurrence. 相似文献
6.
Nowadays agricultural practices are based in the use of N fertilizers which can lead to environmental N losses. These losses can occur as nitrous oxide (N2O) emissions as result of the microbial processes of nitrification and denitrification. N2O together with carbon dioxide (CO2) and methane (CH4) are the strongest greenhouse gases (GHG) associated with agricultural soils. Nitrification inhibitors (NI) have been developed with the aim of decreasing fertilizer-induced N losses and increasing N efficiency. One of the most popular NI is the 3,4-dimethylpyrazol phosphate (DMPP) which have proven to be an advisable strategy to mitigate GHG emissions while maintaining crops yield. A new NI, 3,4-dimethylpyrazole succinic (DMPSA), has been developed. The objective of this study was to compare the impact of the new nitrification inhibitor DMPSA on greenhouse gases emissions, wheat yield and grain protein with respect to DMPP. For this purpose a field-experiment was carried out for two years. Fertilizer dose, with and without NIs, was 180 kg N ha−1 applied as ammonium sulphate (AS) split in two applications of 60 kg N ha−1 and 120 kg N ha−1, respectively. A single application of 180 kg N ha−1 of AS with NIs was also made. An unfertilized treatment was also included. The new nitrification inhibitor DMPSA reduces N2O emissions up to levels of the unfertilized control treatment maintaining the yield and its components. The DMPSA shows the same behavior as DMPP in relation to N2O fluxes, as well as wheat yield and quality. In spite of applying a double dose of N at stem elongation than at tillering, N2O losses from that period are lower than at tillering as a consequence of the influence of soil water content and temperature reducing the N2O/N2 ratio by denitrification. NI efficiency in reducing N2O losses is determined by the magnitude of the losses from the AS treatment. 相似文献
7.
Exposure of mature ‘Fallglo’ tangerine fruit to blue light with a photon fluence rate 40 μmol m−2 s−1 reduced symptom development of blue mold (Penicillium italicum), green mold (Penicillium digitatum), and stem end rot (Phomopsis citri) postharvest decays. Direct exposure to blue light was required to reduce decay caused by Penicillium. Blue light (40 μmol m−2 s−1) reduced in vitro fungal growth of P. italicum and P. citri. The growth of P. digitatum was more tolerant to blue light, however, the activity of fungal polygalacturonase was reduced by blue light at the intensity of 40 μmol m−2 s−1. Gas chromatography–mass spectrometry analysis identified 29 chemical constituents in flavedo oil; blue light induced only octanal accumulation. Application of octanal suppressed growth of P. italicum, P. digitatum, and P. citri in vitro. Treatment of fruit with octanal at 5 mM or 50 mM suppressed symptom development caused by Penicillium and P. citri, but discolored the peel. Inhibition of postharvest decays by blue light may be due to a combination of inhibition of fungal growth and induction of defensive responses in the host. 相似文献
8.
Strawberry fruit have a very short shelf-life and senescent period due to their high degree of perishability and infection caused by several pathogens that can rapidly reduce fruit quality. The aim of this study was to determine the efficacy of carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC) and composites with chitosan (CH) coatings on the shelf-life and overall quality of strawberry fruit. Strawberry fruit dipped for 2 min in solutions of CMC (1%), HPMC (1%), CMC (1%) + CH (1%) and HPMC (1%) + CH (1%) were stored at 11 ± 1 °C, 70–75% RH, while the uncoated fruit served as controls. Fruit coated with edible coatings showed significant delays in the change of weight loss, decay percentage, titratable acidity (TA), pH, total soluble solids (TSS) and ascorbic acid content as compared to uncoated control fruit. In addition, the edible coatings had a positive effect on maintaining higher concentrations of total phenolics and total anthocyanins, which decreased in control fruit due to over-ripening and senescence processes. Compared to the controls, all the coatings had positive effects on the inhibition of cell wall degrading enzymes and among all the tested coatings, CMC + CH and HPMC + CH was superior in inhibiting enzyme activity. These findings suggest that the use of CMC 1% + CH 1% and HPMC 1% + CH 1% coatings are useful for extending the shelf-life and maintaing quality of strawberry fruit. 相似文献
9.
Maternal inheritance of sugars and acids in peach fruit were investigated during two successive years using reciprocal populations derived from ‘low acid’ (LA) flat peach ‘Zaolupan’ and non-LA round peach ‘Zaoxing’. The reciprocal populations segregated into LA round, LA flat, non-LA round and non-LA flat-fruited offspring. Generally, the reciprocal populations had similar range and mean values of sugar and acid. Mean values were to different degree lower than or similar to mid-parental values. Maternal inheritance did not show significant effects on sugars and acids. Broad sense heritability of sugars and acids was high, ranging from 0.61 to 0.90. The correlations among sugars and acids were studied, and positive correlations were always found between glucose and fructose, and quinate and shikimate. Generally, mean glucose, fructose, sorbitol, quinate and shikimate contents did not show significant difference among LA round, LA flat, non-LA round and non-LA flat-fruited progenies. Mean sucrose and total sugar contents of flat-fruited progenies tended to be higher than round-fruited progenies, while mean malate, citrate and total acid contents did not significantly differ with fruit shape (round vs. flat). 相似文献
10.
《Forest Ecology and Management》1998,112(3):203-211
Genetic control of germination parameters and the effects of accelerated aging in mountain hemlock (Tsuga mertensiana [Bong.] Carr.) seeds were investigated using standard germination tests and simulated aging, respectively. Germination parameters were studied on seeds collected from individual trees from two natural populations (Sooke and San Juan) located on southern Vancouver Island, BC. Strong genetic control was confirmed by the high heritability estimates that ranged from 0.35 to 0.82 (stratified) and from 0.58 to 0.73 (unstratified) for Sooke and from 0.30 to 0.85 (stratified) and from 0.45 to 0.84 (unstratified) for San Juan. Simulated aging was conducted on eight seedlots collected from natural stands representing the species distribution in British Columbia. Stratified and unstratified seeds were aged at 100% RH and 37.5°C for 0 to 21 days at 3-day intervals. Seed aging accounted for the majority of variation which ranged from 97.61% to 99.86% of the total variation observed. Gradual loss of seed viability was observed over the aging treatments with a total loss of viability after aging for 12 days. Differential losses in viability among seedlots were maximum after aging for 6 days. Results are discussed in terms of the impact of long-term storage and the reliance on seed banks for ex-situ conservation of this species. 相似文献