Bacterial leaf blight in rice is a significant disease, and understanding the effects of straw burning on pathogens and antibiotic resistance genes (ARGs) in paddy fields is crucial. Soil and rice stubble samples were collected from bacterial leaf blight outbreak areas in Ningbo City of Zhejiang Province, and these samples were subjected to high-throughput metagenomic sequencing to investigate the effects of straw burning. The results indicated that the relative abundance of pathogens in the rice stubble was significantly higher than that in the soil. After straw burning, except for the significant increase in available potassium content, there were no significant changes in the other physicochemical properties of the soil. Overall, there were no significant differences in pathogen community diversity after straw burning, but straw burning led to a sharp decrease in the relative abundance of Xanthomonas oryzae in the rice stubble. The relative abundances of ARGs in the soil and rice stubble increased after straw burning, but there were no significant differences compared with those before straw burning (P＞0.05), while the relative abundance of mobile genetic elements (MGEs) in the rice stubble decreased significantly after straw burning (P＜0.05). The proportion of positively correlated links in the coexisting networks of pathogens-ARGs decreased after straw burning. Mantel analysis revealed that the water content (r=0.642, p＜0.01), pH value (r=0.582, p＜0.05), total organic carbon content (r=0.325, p＜0.05), total nitrogen content (r=0.570, p＜0.01), and available phosphorus content (r=0.311, p＜0.05) were closely related to the soil ARG subtypes; the dissolved organic carbon (DOC) content (r=0.275, p＜0.05) and available potassium content (r=0.312, p＜0.05) were correlated with the ARG subtypes, and the DOC content (r=0.201, p＜0.05) significantly affected the pathogen community structure in the rice stubble. In summary, straw burning can reduce the relative abundance of X. oryzae in the rice stubble, which suggests that it may be a viable option for preventing and controlling rice bacterial leaf blight; moreover, a reduction in the positive correlation ratio of pathogens-ARGs and in the relative abundance of MGEs after straw burning may inhibit the formation of potentially resistant pathogens. However, given the complexity of soil biological compound pollution, the effects of straw burning on pathogens and ARGs in paddy fields need to be further explored by long-term location experiments.

In the highly acidic soil pilot area contaminated by cadmium (Cd) in Yongkang City of Zhejiang Province, we screened low-Cd-accumulating rice cultivars and soil passivators in the field and performed the combined effect tests for two consecutive years to explore the safe utilization technology model suitable for local Cd-polluted paddy fields. The results showed that ‘Xiushui 519’ (XS519), ‘Zhenuo 106’ (ZN106), ‘Zhongzheyou 1’ (ZZY1H) and ‘Zhongjia 8’ (ZJ8H) could be recommended as low-Cd-accumulating rice cultivars suitable for local planting. Among them, ‘Xiushui 519’ had the lowest and most stable Cd accumulation ability, and the average bioconcentration factors (BCFs) of Cd in the rice grains in the two years were 0.090 and 0.159, respectively; in the screening tests of passivators, the improvement effect of lime (L) on soil pH was significant. Lime, iron-modified biochar (FeC) and calcium-magnesia phosphate fertilizer (CaMgP) could reduce soil available Cd contents to a certain extent (passivation rates were 14.8%, 7.1% and 6.9%, respectively). In addition, 1 800 kg/hm² iron-modified biochar and 2 400 kg/hm² soil conditioner had better effects on reducing the Cd content in the rice grains of ‘Zhongjia 8’, which decreased by 32.2% and 29.0%, respectively, after application. According to the results of the combination tests of the low-Cd-accumulating cultivars and passivators, both the application of 2 250 kg/hm² iron-modified biochar and 2 250 kg/hm² soil conditioner increased obviously the soil pH values at the tillering stage and filling stage, the soil conditioner of which had a better improvement effect. The Cd contents in the rice grains of ‘Xiushui 519’ and ‘Zhenuo 106’ were extremely significant correlations with the soil pH values (5.19-5.61) at the mature stage. Within the range of soil pH values involved in the test, except for the combination of ‘Xiushui 519’ and the 1 500 kg/hm² soil conditioner, the Cd content in the rice grains increased with increasing application amount of passivators. Therefore, planting ‘Xiushui 519’ (a low-Cd cultivar) directly is the best choice for the safe utilization of Cd-contaminated paddy fields in this area, which is both economical and convenient.

To understand the community structure composition and dynamic change characteristics of human pathogenic bacteria (HPB) in soils after manure application, laboratory cultivation experiments were conducted on agricultural soils with long-term application of chicken manure, pig manure, or chemical fertilizer in five regions of Hangzhou, Jiaxing, Quzhou, Jinhua, and Longyou in Zhejiang Province, and the community compositions of the soil bacteria and HPB were analyzed by high-throughput sequencing and sequence alignment methods. The results showed that a total of 75 HPB were detected in 160 soil samples and two manure samples, and the dominant HPB were Bacillus_megaterium_QM_B1551 (24.2%) and Clostridium_beijerinckii_NCIMB_8052 (23.1%). The Shannon indexes of bacteria and HPB in the soils decreased after the application of pig manure, while the diversities of bacteria and HPB in the soils with the application of chicken manure or chemical fertilizer had no significant changes. The results of the principal coordinate analysis showed that there was a significant difference in the bacterial community composition of soils between the manure treatment and the unfertilized control, especially in the pig manure treatment (P＜0.001); 22.7% of all HPB were shared among the soil samples; and the relative abundance of most HPB in the soils treated with manure was higher than that in the unfertilized control, and it decreased continuously with the extension of cultivation time. The results of the variance partitioning analysis showed that soil physicochemical properties, bacterial communities, and their interactions were important factors contributing to the variation of HPB in the soils. In summary, the HPB variation characteristics in soils treated with manure are influenced mainly by manure types, soil types, soil physicochemical properties, and inherent bacterial communities.

Non-flooding plastic film mulching cultivation (PM) for rice is a comprehensive and innovative technology that utilizes plastic film covering as the core to achieve water-saving rice production. However, after mulching with plastic film, nitrogen (N) fertilizer can only be applied once as a basal fertilizer before transplanting, which will lead to excessive vegetative growth at the early stage and potential N deficiency at the late growth stage, thereby limiting the high yield of rice. Polymer coated urea (CR) is a controlled release N fertilizer that has become one of the best management measures for improving crop yield and N use efficiency under a traditional flooding cultivation (TF) pattern, but it has not been evaluated in a long-term positioning test under the PM pattern. In this study, taking the high-yielding and medium-maturing indica hybrid rice cultivar ‘Liangyoupeijiu’ as a test material, the effects of applying CR and urea (UR) on rice yield, N use efficiency and soil nutrient contents were compared under the PM and TF patterns. The results showed that, compared with applying UR, applying CR under the TF and PM patterns improved the N use efficiency by 9.2% and 15.4%, respectively (P＜0.05), and increased the rice yield by 8.6% and 15.0%, respectively (P＜0.05). Compared with the TF pattern, the PM pattern accelerated the decomposition of soil organic matter and reduced the contents of total N and alkali-hydrolyzable N in the soil. Compared with applying UR, applying CR under the PM pattern alleviated the decrease of the total N and alkali-hydrolyzable N contents in the soil and increased the economic benefits by 16.8%. In summary, applying CR is an effective way to solve the problem of N deficiency at the late growth stage of rice under the PM pattern.