Application and prospect of ultrasound in agriculture
Ultrasound refers to sound waves with frequencies higher than the upper limit of human hearing. Ultrasound is also widespread in nature, but human ears can't hear it. Ultrasonic waves can easily enter seawater, strata, human body and many solids and liquids, and can penetrate almost any substance. Therefore, compared with light wave and electromagnetic wave, ultrasonic wave has its unique ability in collecting information inside materials. More importantly, ultrasonic energy with higher audio frequency or intensity can be used to change some states of matter or have some important influence on the development and growth of living things. Combined with related research topics, this paper briefly reports some new applications and prospects of ultrasound in agriculture.
1 application of ultrasonic wave in agriculture
1. 1 Basic principles of ultrasonic treatment and processing.
Ultrasonic processing equipment is mainly composed of ultrasonic generator, transducer, ultrasonic concentrator and matching circuit between ultrasonic generator and transducer. As shown in figure 1, the ultrasonic generator generates certain high-frequency electric energy and supplies it to the ultrasonic transducer. The electrical energy is converted into mechanical energy by the ultrasonic transducer, and then the mechanical energy is amplified by the ultrasonic concentrator, so that the acoustic energy acts on the substance to be treated. The basic principle of ultrasonic treatment and machining is mainly to use the cavitation phenomenon of fluid dynamics. Ultrasonic cavitation refers to various dynamic manifestations of ultrasonic activated bubbles, which can be regular and gentle steady cavitation or very strong and short-lived transient cavitation. Transient cavitation bubbles contract adiabatically until the collapse moment, and the bubbles can present high temperature and high pressure of thousands of atmospheres, accompanied by powerful shock waves or jets. Because of its mechanical function, ultrasonic radiation can enhance particle movement and accelerate mass transfer in liquid medium, and also affect boundary layer, membrane, cell wall and vacuole. Ultrasonic cavitation can also destroy cells and denature enzymes. Some of the new applications of ultrasound in agriculture mentioned below are basically realized by following the above basic principles.
1.2 ultrasonic determination of lead in soil
Lead is an element harmful to human body. It is a constant element in soil analysis. When the suspension is directly injected into the soil to determine lead by flame atomic absorption spectrometry, the sampling characteristics are affected because of the large sampling amount of soil samples and the high viscosity of suspension emulsion, which is not easy to disperse evenly. The method of ultrasonic treatment of suspension before sampling can make the sampling go smoothly and make the suspension stable for a long time. The sensitization of sodium dodecyl sulfate (sDS) can improve the sensitivity of direct sampling suspension by flame atomic absorption spectrometry. This method is rapid, simple and accurate. It is suitable for the determination of lead in various soil samples.
1.3 Effect of Ultrasonic Treatment on Seed Germination Rate
Ultrasonic treatment can affect the germination rate of seeds, which is species-specific. It was found that higher seed germination rate could be obtained under mild ultrasonic treatment. When the ultrasonic treatment time exceeds the maximum, the mortality of seed embryos will increase and the germination ability of seeds will naturally decrease. Therefore, when discussing the effect of ultrasonic treatment on seed germination, different treatment conditions, such as the intensity and duration of ultrasonic treatment, will have different effects on seed germination, resulting in different results.
1.4 Effect of ultrasonic treatment on plant growth
Like other environmental pressures, ultrasound is also a kind of pressure. It has an important influence on the growth and development of plants. Ultrasonic treatment can affect the survival and growth of plants or some organs. The research on the influence of organ growth should focus on roots, and mild ultrasonic treatment can promote rooting. After ultrasonic treatment of plant cells, there is a consistent phenomenon, that is, mild treatment with low dose and short time can obviously accelerate and induce plant cell division, stimulate cell growth and accelerate protein synthesis of protoplasts; However, if the treatment time is prolonged and the treatment dose is increased, it will cause negative and irreversible effects. Ultrasonic treatment of fresh-keeping liquid can obviously increase the fresh weight of cut chrysanthemum, carnation and other plants, delay the days when the fresh weight begins to decline, increase the maximum flower stem and prolong the vase life. It can be seen that ultrasonic treatment with a certain frequency and intensity can strengthen some physiological and biochemical indexes of plants and promote their growth and development.
1.5 Effect of ultrasonic treatment on plant respiration
The study of plant respiration has always been a hot spot in plant physiology research, especially for crops, its respiration is directly related to yield, so its research has important theoretical and practical significance for the development of agriculture. The AlbuE study in 1975 found that the respiration intensity of annual plants (such as tomatoes and cucumbers) decreased after the vegetables were treated with low-frequency ultrasound (25kHz), while that of biennial plants (such as Chinese cabbage and onions) increased. It can be speculated that ultrasonic treatment of related crops can improve crop yield.
1.6 ultrasonic ploughing
Traditional plows need heavy machine traction, which not only compacts the deep soil, but also makes it unable to maintain moisture and nutrients; Moreover, the turned topsoil will be eroded by wind and rain. This is a big worry for many farmers. In addition, due to repeated ploughing, the roots of plants and rotten plants are turned out of the surface, and they will emit carbon dioxide gas. Jordan agricultural machinery engineer Nida? Abuhard invented the use of ultrasonic waves to loosen the soil. His experimental results show that scarification can reach a depth of 20 cm. This fully meets the loosening depth of general crops.
1.7 ultrasonic treatment of plant roots
Sugar is one of the main components in plants, and soluble sugar mainly refers to monosaccharide and oligosaccharide. Monosaccharide phosphoric acid is not high in plant cells, but it is the main intermediate product in the process of photosynthesis and respiration. It is extremely important in the metabolic process. After sound wave stimulation, the soluble sugar content in roots was about 29.6% higher than that in control group. Rich protein is the material basis for cells to carry out a series of physiological activities. After sound wave stimulation, the soluble protein in roots increased by 35.3%, and the high level of soluble protein content ensured the vigorous division and growth ability of cells. This shows that after sound wave stimulation, the root cells of plants divide vigorously and grow strongly.
1.8 ultrasonic disinfestation promotes silkworm egg hatching.
250W-CFS ultrasonic generator (produced by Zhongyuan Electronic Instrument Factory) is used to match the independent cleaning tank. 19.5 ~ 20.5 kHz, the chestnut with insects in the fruit is soaked in tap water in the cleaning tank, and the machine is turned on15min. After that, dry in water and keep it for two weeks. When the chestnut fruit was cut open, the larvae about 10mm long survived, and the larvae less than 6mm died. After prolonged treatment, the insect mortality was basically the same. In addition, some people have treated silkworm eggs with similar methods and equipment (about half a minute), and the direct result is that the incubation time of ant silkworms is basically the same: the tracking results show that the reeling rate of cocoons grown by adults under the same conditions is improved; There are also attempts to treat pests in fruits (such as apples and pears) with ultrasound, but after doing some small experiments under the conditions at that time, most of them failed.
2 Problems to be solved
The application of ultrasound in agriculture is an early research field, but it has not been popularized and is still in the exploration stage. In order to further develop its application value, efforts should be made in the following aspects:
2. 1 Theoretical research and improvement
The biological effect of ultrasound is not only related to the total dose of irradiated biological tissues, but also related to the distribution of irradiation dose in space and time. These relationships are different for different biological tissues. Due to many influencing factors, the repeatability of some experimental results obtained at present is not satisfactory, and the regularity remains to be explored, so there is still a lot of work to be done in this regard.
2.2 amplification problem
At present, although the biological effects produced by ultrasound have been applied in a few treatments, most of them belong to laboratory research, and there is still a lack of intermediate data for amplification to reflect the quantitative description of the process. At present, there is no standardized and quantitative scale, so a lot of and sufficient research work is needed in the biological effect and mechanism of ultrasonic stimulation, reaction kinetics and the amplification design of the reactor.
2.3 Synergy problem
Although ultrasound has great advantages in agricultural production, its influence on organisms is various, which depends on its frequency, intensity and action time. High intensity ultrasound will destroy cells and inactivate enzymes. Low intensity ultrasound can promote cell growth and improve enzyme activity, which makes the application of ultrasound in agriculture dual. Therefore, in order to make ultrasonic treatment of organisms more reasonable in theory, ultrasonic treatment should be combined with other treatment technologies, which is technically feasible and economically more reasonable.
3 the application prospect of ultrasound in agriculture
3. 1 The appearance of new high-efficiency frequency converter
Magnetostrictive material is a traditional ultrasonic transducer material. Because of its stable performance, high power capacity and good mechanical strength, it is still used in some special fields, but it also has some shortcomings such as low energy conversion efficiency, complex excitation circuit and difficult material processing. With the large-scale popularization and application of piezoelectric ceramic materials. In a period of time, magnetostrictive materials showed signs of being replaced by piezoelectric materials. However, with the emergence of some new magnetic materials, such as ferrite, rare earth giant magnetostrictive materials and ferrofluid transducer materials, magnetostrictive transducers have attracted people's attention. It can be predicted that with the improvement of material processing technology and the reduction of cost, some new magnetostrictive materials will be widely used in underwater acoustic and ultrasonic fields. At present, the working frequency of ultrasonic transducer has developed from the commonly used low frequency (20kHz) to a higher frequency (hundreds of kilohertz or even megahertz), and the working frequency of transducer has also developed from a single working frequency to multiple working frequencies. In addition, the successful development of new rare earth giant magnetostrictive materials has laid a solid foundation for the development of new magnetostrictive transducers. The successful development of these new high-efficiency transducers will certainly expand the application scope of ultrasonic technology.
3.2 The application of ultrasonic technology in agriculture will have new development and improvement.
The biological effect of ultrasound is not only related to the total dose of irradiated biological tissues, but also related to the distribution of irradiation dose in space and time. These relationships are different for different biological tissues. At the same time, ultrasound can also be combined with far-infrared radiation breeding and crop seed treatment technology for mutation, from which excellent mutant individuals can be selected and new varieties can be cultivated through a series of breeding procedures. This kind of experiment has been carried out abroad, and the effect is not bad; The application prospect and potential of ultrasound in the cultivation and production of medicinal materials are still great, which is of great practical significance for promoting the development of national medicinal materials production: ultrasound has also made some contributions to artificial precipitation enhancement in agriculture, forestry and animal husbandry. At present, the application of ultrasonic agriculture in China has not been cited.
Attract enough attention from relevant parties. However, many experiments have proved that the possibility and diversity of ultrasonic application in agriculture are great, and it has shown its power and broad prospects. According to the existing space test results at home and abroad. The author predicts. If the seeds treated by ultrasonic waves on the ground are taken into space to germinate and grow, it is likely that more magical results will appear. We can fully believe that before long, the new ultrasonic technology will play a unique role in serving China's socialist agricultural modernization and improving agricultural productivity.