Font Size: a A A

Research On The Mitigation Technology Of Watermelon Continuous Cropping Obstacles And Its Mechanism

Posted on:2017-01-23Degree:DoctorType:Dissertation
Country:ChinaCandidate:R P YangFull Text:PDF
GTID:1223330485980803Subject:Vegetable science
Abstract/Summary:PDF Full Text Request
Watermelon in our country has high economic benefit, but the continuous cropping obstacle seriously affects the sustainable development of watermelon production. How to solve the problem of continuous cropping obstacle has become a worldwide problem. The essence of watermelon continuous cropping obstacle is soil properties changed due to watermelon continuous cultivation. A large number of studies have shown that, crop rotation, organic fertilizer application and high temperature and stuffy tent can relieve watermelon continuous cropping obstacle. But few people have study on the mechanism of change to ease the continuous cropping obstacle in soil system. Based on this, our experiment, of which take garlic as rotation crop, cow dung and crop stalks as the organic fertilizer, conducted with field experiment and indoor analysis, and researched on watermelon growth, the effects of fusarium wilt, soil physical and chemical properties, biological characters, and bacterial community diversities. Try to explore its mechanism of watermelon continuous cropping obstacle relaxation effect, and provide theoretical basis for the application of various measure in production. The main results are as follows.1. We had three successive years of watermelon cultivation experiment in field to study their effects on watermelon growth and soil properties through garlic rotation and cattle manure application, respectively. The results show that, plants grow significantly weaken after continuous cropping watermelon, and implementation of garlic rotation and the cattle manure can alleviate this kind of phenomenon to promote plant growth and increase output. At the end of the test, garlic rotation and cattle manure make watermelon yield increased by 67% and 67%, and blight disease incidence reduced by 38% and 50%, respectively. And the combination of garlic rotation and cattle manure application could increase yield by 138% and reduce blight disease incidence by 57%. This shows that the combined of the two measures have superposition effect. Further study found that garlic rotation and cattle manure application significantly increased the number of bacteria and actinomycetes, reduced the number of fungi, meanwhile, increase the ratio of bacterial and fungal community. Both garlic rotation and cattle manure application were significantly increased the enzymes activity(protease, urease, catalase, invertase, polyphenol oxidase, and alkaline phosphatase), reduced the total phenol content, promote the release of soil nutrient(available nitrogen, available phosphorus, available potassium and organic matter) in the soil to improve the continuous cropping soil fertility. In short, may be garlic rotation is more advantageous to reduce the incidence of blight for increasing in the numbers of bacteria and the reduction of fungi in the soil. While cattle manure has contributed more to increase the soil enzyme activity, which is conducive to overall improvement in the quality of soil, thus increasing watermelon yield.2. We have studied the influence on succession watermelon growth and soil characteristics with the short-term flooding of high temperature and stuffy tent technology in the greenhouse summer fallow period. Results indicate that short-term flooding with high temperature increased watermelon plant height by 29%, reduced blight disease incidence by 48%, and increased watermelon yield by 57%. This may mainly due to short-term flooding high temperature and stuffy tent significantly reduce the soil bulk density, the accumulation of various nutrient content, the salt content, the total phenol content, fungi number and increase the number of bacteria and actinomycetes significantly. The correlation analysis of watermelon growth and soil characteristics showed that, plant incidence and soil bacteria has significant negative correlation and significantly positively related with the total phenol content, but is not related with fungi and actinomyces quantity. Watermelon yield and salinity have negatively correlated and positively correlated with the number of bacteria and actinomycetes. In consequence, may be the influence on the bacterial colonies of short-term flooded of high temperature and stuffy tent has a more important role in reducing the incidence of plant and increase the yield.3. We have studied the influence on blight incidence, growth of watermelon seedlings, and fusarium oxysporum using plant allelopathy after putting different straw decomposing(garlic, garden chrysanthemum, marigold, celery, wheat and clover) in watermelon continuous cropping soil. It turned out that different decomposing increased watermelon seeds radicle taproot length and the number of lateral roots, improved the root-shoot ratio of seedling dry weight, and reduced the watermelon seedling blight disease index. Their allelopathic effects analysis show that different straw decomposing promoted the growth of watermelon fusarium oxysporum hyphae, significantly reduced the mycelial biomass, and in different degrees of inhibition of spore germination. Allelopathy to enzyme activity of fusarium oxysporum bacterium liquid(amylase, protease, pectinase and cellulase) related to crop types. But garlic has allelopathic inhibition to the four kinds of enzyme activity. Therefore, different straw decomposing restrain the growth of the pathogen may not be a direct inhibitory effect but by increasing the activity of microbial metabolism.4. We have analyzed the influence of different straw decomposing on watermelon continuous cropping soil characteristics. And the results show that different straw decomposing significantly increased the continuous cropping soil microorganism amount, promote the proportion of bacteria in total microorganisms; each of the decomposing improved the soil enzyme activity in different level. Among of those garlic has the highest activity of protease, dehydrogenase and alkaline phosphatase, wheat has the highest urease activity, and clover has the highest soil invertase activity. Decomposing of different straw significantly increased the release of continuous cropping soil nutrient. The content of available nitrogen and available phosphorus has an increasing trend with the decomposing and the extension of time. The content of available potassium raised and then reduced. Organic matter content is not related to decay time. The soil salt content increased according to the nutrient release. Soil p H value was related to crop species. Further analysis of the allelopathic effect demonstrates that the bacteria and actinomycetes in different decomposing is promoting effect. While fungus content and p H value in garlic and marigold are allelopathic inhibition. So, the role of different straw decomposing to watermelon fusarium wilt may be the result of group work of soil microbial community. The more abundance of the structure and the higher of the diversity of soil microbial community, the stronger of the ability against pathogenic bacteria.5. In order to further explore the interaction relationship between plants and microorganisms, we studied soil bacterial community diversity and abundance with different straw decay, using Illumia Hi Seq high-throughput sequencing platform V4 area augmentation of 16 s r DNA sequencing technology. Results indicate that, different straw decomposing products affect the content of advantage bacterium group of bacteria in the soil on the level of phylum(the relative abundance of top 10). The advantage bacterium groups in different straw decomposing products are proteobacteria, firmicutes and bacteroidetes. While the advantage bacterium groups in control are acidobacteria, gemmatimonadetes, planctomycetes, verrucomicrobia, crenarchaeota, actinobacteria, and chloroflexi. A further statistical differences of species number in each level demonstrated that, such as the level of phylum, garlic and marigold have 10 phylum more than the control, crowndaisy chrysanthemum and celery has 8 and 6 more than the control, respectively. While wheat and clover have 7 and 6 phylum more than the control, respectively. So, different straw decomposing products produced antagonism to pathogenic bacteria by increasing the relative abundance of bacteria and species diversity, improving the ratio of beneficial bacteria in the soil, and reducing relative contents of harmful bacteria in the soil.
Keywords/Search Tags:watermelon, continuous cropping obstacle, mitigation technology, soil properties, Fusarium wilt, bacterial diversity, high-throughput sequencing
PDF Full Text Request
Related items