| Vegetable cultivation in facility has become prevalent around the world because of its high economic benefit. However, the successive cultivation of same vegetable, high temperature and humidity, excessive application of fertilizer and water in facility cultivation has lead to decrease of soil quality, such as soil acidification, salinization and disease caused by pathogen, which has restricted the development of facility cultivation. Phytophthora blight, one of worldwide soilborne plant diseases, is caused by Phytophthora capsici, which has heavily attacked pepper production. A technical, economic and sustainable measure was urgently needed to control plant disease. According to this practical problem, soil waterflooding combining with wheat straw was carried out to prevent pepper blight in the field. The effects of soil waterflooding for different time combining with different amount of wheat straw on soil chemical and biological properties, the suppression of Phytophthora blight of pepper and the grain yield of pepper was studied to provide a theoretical basis and technical support for improving soil quality and the suppression of Phytophthora blight of pepper.This paper was aimed to study effects of soil waterflooding for different time combining with different amount of wheat straw on soil chemical and biological properties, the number of P. Capsici and the suppression of Phytophthora blight of pepper in greenhouse. The results showed that soil waterflooding combining with application of wheat straw affected soil chemical and biological properties. Soil waterflooding combining with application of wheat straw decreased soil Eh, the content of soil ammonium nitrogen, nitrate nitrogen, the diversity index of soil fungi and the population of soil fungi and actinobacteria, and increased the content of soil organic acids, total phenolic acids, organic matter, total nitrogen, total phosphorus, total potassium, the population and the diversity index of soil bacteria. Soil waterflooding or combining with application of wheat straw (0.25%, w/w) significantly reduced the population of P. capsici as compared with moisturing treatment at 10 days after waterflooding. And the population of P. capsici of soil waterflooding combining with application of wheat straw (0.5%; 0.25%, w/w) was more than conventional soil waterflooding treatment. The treatment of soil waterflooding combining with application of wheat straw had a high population of P. capsici, however, the disease incidence of Phytophthora blight of pepper was 0.00% at 14 days after waterflooding, which may be attributed to the effect of soil waterflooding combining with application of wheat straw on improving soil chemical and bilological properties and enhancing disease resistance of plants. Soil moisturing treatment combing with application of wheat straw significantly increased population of P. capsici and had higher disease incidence Phytophthora blight of pepper as compared with soil moisturing treatment, which may be attributed to that the degradation of straw in the soil provided nutrients for growth of P. capsici.The effect of soil waterflooding combining with different amount of wheat straw on the content of chemical matter in soil solution and the suppression of Phytophthora blight of pepper was studied in two kinds of soil. These results showed that soil waterflooding combining with application of wheat straw increased the content of ammonium nitrogen, nitrate nitrogen, organic acids, total phenolic content and DOC of soil solution for both two kinds of soil. And the content of ammonium nitrogen, nitrate nitrogen, organic acids, total phenolic content and DOC of soil solution of sandy soil were higher than those of clay soil. The content of ammonium nitrogen, nitrate nitrogen, organic acids, total phenolic content and DOC of soil solution in treatment of soil moisturing combining with application of wheat straw were lower thant those of the treatment of soil waterflooding combining with application of wheat straw. While waterflooding time was prolonged, the content of main chemical matter was increased in sandy soil, however, only the content of organic acids was increased and the content of ammonium nitrogen, nitrate nitrogen, total phenolic content and DOC was decreased in clay soil. The cracking ability of soil solution to spores of P. capsic in both kinds of soil were higher than 50%. The soil solution of two waterflooding treatments containing wheat straw (0.25%,0.75%) had highest cracking capacity against P. capsici among all treatments for both kinds of soil. The germinate rate of P. capsici of treatment soil waterflooding combining with application of wheat straw was higher than that of soil waterflooding treatment and soil moisturing treatment in caly soil, however, the germinate rate of P. capsici of treatment soil waterflooding combining with application of wheat straw was lower than that of soil waterflooding treatment and soil moisturing treatment in sandy soil. The content of soil available nutrient in clay soil was higher than that of sandy soil, however, the content of available nutrient of soil solution in clay soil was lower than that of sandy soil. The cracking capacity against P. capsici of soil solution in clay soil was higher than that of sandy soil, and the germination rate of P. capsici of treatments containing wheat straw (0.50%,0.75%) in clay soil was higher than that of sandy soil. So, it is speculated that there are other substances in soil solution affecting the cracking capacity and germiation rate.The effect of soil waterflooding combining with application of wheat straw on the release of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) was studied. The results showed that the release rate of CH4 of soil moisturing treatments was low, and soil waterflooding treatments increased the release rate of CH4. However, the soil waterflooding treatments increased the release rate of CH4 by 6 times than that of soil moisturing treatments at 14 days after soil waterflooding. The release rate of CO2 of soil waterflooding treatments containing wheat straw was lower than that of soil moisturing treatments containing wheat straw. And the release rate of CO2 increased as the amount of wheat straw increased. The release rate of N2O of soil waterflooding treatments containing wheat straw was significantly higher than that of soil moisturing treatments and soil waterflooding treatment.The effect of soil waterflooding combining with wheat straw on soil chemical properties, the growth of pepperand the suppression of Phytophthora blight of pepper was studied in field. The results indicated that soil waterflooding combining with wheat straw (400 kg-acres-1) decreased soil Eh, the content of ammonium and nitrate nitrogen, the population and diversity index of soi fungi, and increased the content of organic acids, total phenolic acids, soil organic matter, phosphorus, potassium, the population and diversity index of soil bacteria, which was consistent with the results under laboratory experiment. Soil waterflooding combining with wheat straw decreased the population of P. capsici by 19.0% and the disease incidence of Phytophthora blight of pepper by 59.0%, and increased the yield of pepper by 12.3% as compared with soil waterflooding treatment. The pot experiment using soils from field showed that the disease incidence of Phytophthora blight of pepper under soil waterflooding treatment and soil waterflooding combining with wheat straw treatment was 80% and 40%, respectively. Soil waterflooding combining with wheat straw promoted the growth of peppers, increased production and fruit quality, decreased the disease incidence of Phytophthora blight of pepper, improved the chemical and biological properties and microbial community structure of soil. These finding suggested that soil waterflooding combining with wheat straw is an effective means in regulating of soil characteristics controling soil borne diseases. |
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