Optimizing Reductive Soil Disinfestation And Suppression Effect On Weed Germination

In recent years, the facility agriculture has been developed rapidly in our country because of its high multiple-cropping index and high yield. However, high-intensity crop production, irrational fertilization and irrigation mode have resulted in serious issues, soil degradation, secondary salinization and soil-borne diseases, etc. which have become the urgent problems to be solved in facility agriculture. Reductive soil disinfestation ?RSD? can significantly kill thesoil-borne pathogens in a short period of time by adding the easily decomposable organic materials to the soil, flooding and film mulching. Meanwhile, RSD can also improve the soil properties and restore the soil conditions to a status which benefit the crop growth. Hence, on the basis of fully understand the impact of RSD in improving degraded farmland soil,clarifying the most suitable dosage of water and organic materials,it can promote the popularization and application of RSD. On the basis of previous studies, this paper mainly studied the most suitable application rate of water and organic materials of RSD in field conditions and the suppressed effect of RSD on weeds.Firstly, soils, which continuous cropping artemisia selengensis and induced cropping obstacles, collected from Bagua Island were used to study the effects of RSD on soil-borne pathogens suppression and soil properties improvement under different water contents and straw additions by using molecular biology techniques and plate count method. The results showed that 60% water holding capacity?WHC?+5 g kg^-1 maize straw can improve the soil physical and chemical properties effectively. The soil pH and NH4+-N concentration were significantly enhanced while the NO3--N and SO₄^2- concentration were significantly reduced when compare to the control. Thus, 60% WHC combined with 5 g kg^-1 maize straw is enough to solve the issue of soil secondary salinization,being more economical and convenient than current RSD practices with flooding and adding large amounts of organic materials.But, 60% WHC RSD treatments can't effectively suppress the proliferation of pathogens in the soil, and even promote the growth of pathogens. While 100% WHC RSD treatments could suppress over 90% of Fusarium oxysporum, Phytophthora and Pythium, 100% WHC combined with 10 g kg^-1 maize straw could suppress 96% of Fusarium oxysporum.Secondly, soils which degraded seriously on the account of continuous rotation broccoli, collected from Longtan were used to study the inhibitory effect of RSD treatments on weeds in lab conditions through microscopic examination and germinating induction. Field experiment was also carried out in vegetable fields at Chunjiang Town of Changzhou to study the suppressing effect of RSD treatments on weeds. Pure weed seeds were collected to study the effects of harmful substances on the seed germination, such as organic acids, Fe²⁺ and Mn²⁺,which were generated during the process of RSD treatments, and ultimately clarified the suppressing mechanism of weed germination by RSD. The results showed that the germination of weeds was significantly suppressed by RSD treatments and the weed density in soil was also decreased. The weeds number was increased after fertilization, but it was still significantly lower than the untreated control. The field experiment further validates this result. After planting celery, weeds in the soil was still significantly suppressed and the germination rate was very low because of the RSD treatments.Through the study of the mechanism of RSD on weed suppression, the germination rate of weed seeds that treated with harmful substances was suppressed in different degrees. Acetic acid and butyric acid are the main contributors to the weed suppression. The germinations of weed seeds that treated with 0.66% acetic acid and 0.176% butyric acid were almost completely suppressed.In summary, RSD treatments not only kill soil-borne pathogens and repair the degraded soil, but also suppress the growth of weeds significantly. Therefore, RSD can reduce the using of herbicide and human input in weed control. 60% WHC combined with 5 g kg^-1 maize straw can improve soil properties effectively. For the soil with severe soil-borne diseases, 100% WHC combined with 10 g kg^-1 maize straw can be used as a universal condition in field conditions, which can significantly suppress the pathogen at the minimum adding amount of water and straw.