玉米秸秆还田对土壤地力及固碳能力的影响

为探明农产品化肥减量后土壤养分的变化,促进玉米秸秆还田,提升土壤肥力,从2019年开始在黑龙江省大庆市所属4个牧场连续3年进行玉米秸秆还田试验,期间随机选取31处采样点分别进行3次抽样,分析土壤样品中pH、碱解氮、有效磷、速效钾、有机质、有机碳和水溶性盐等指标,以此判断玉米秸秆还田对土壤地力和固碳能力的影响。结果表明,长期玉米秸秆还田土壤中有机质含量由21.2 g·kg^(-1)增长至23.6 g·kg^(-1);秸秆还田土壤中有效磷的含量平均增长约144.0%,而未还田土壤中有效磷含量的平均增长约138%;碱解氮含量由166.50 mg·kg^(-1)增长至194.50 mg·kg^(-1),且2022年与2021年测定的碱解氮含量差异显著。可见秸秆还田后土壤固碳能力增加,肥力增强,而pH一直维持在7.92~8.23。因此,合理运用玉米秸秆还田可改善土壤耕作环境,减少土壤中盐分聚集,提高土壤对有机碳的固定效果,调节土壤的酸碱稳定性,对东北土壤生产力的可持续发展具有重要意义。

活性腐殖质作为地力监测指标的应用意义

以稻田多熟制多点定位试验为材料,比较了土壤腐殖质分组法与活性腐殖质法(即NaOH—Na_4P_2O_7一次提取法)在表征土壤肥力变化上的应用价值,最后肯定了一次提取法在地力定位监测上的实用意义。

云和县标准农田建设现状和质量提升措施

云和县山多地少,耕地资源匮乏,加强以标准农田建设为主要内容的耕地质量提升工作具有重要的现实意义。本文通过对云和县标准农田建设状况的调查,分析云和县标准农田建设中存在的问题,提出了提升云和县标准农田质量的对策和措施,为稳固和发展粮食生产提供参考。

Ultimate end bearing capacity of rock-socketed pile based on generalized nonlinear unified strength criterion

In order to study the mechanism of bearing behavior at the tip of a pile embedded in rock, the generalized nonlinear unified strength criterion and slip line principle for resolving the differential equation systems which govern the stress field were applied to derive the ultimate end beating capacity based on some reasonable hypothesis and failure plane model. Both numerical simulation and test results were compared with the theoretic solution. The results show good consistency with each other and verify the validity of the present approach. The depth effect with respective to embedment ratio and other influence factors like geological strength index, intermediate principal stress, overburden factor, and damage on end bearing capacity were discussed in the analytical solution. The results show that the proposed yield criterion can be much better for investigating the ultimate end bearing performance of rock-socketed pile. The end bearing capacity increases with embedment ratio and the increasing degree is influenced intensely by the above parameters. Furthermore, ignoring intermediate stress effect would underestimate the strength properties of the rock material and lead to a very conservative estimation value.

Zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel

In order to investigate zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel, a new mechanical model subjected to dynamic unloading under hydrostatic pressure condition is proposed. The total elastic stress-field distributions is determined using the elastodynamic equation. The effects of unloading rate and dynamic mechanical parameters of isotropic deep rock masses on the zonal disintegration phenomenon of the surrounding rock masses around a deep spherical tunnel as well as the total elastic stress field distributions are considered. The number and size of fractured and non-fractured zones are determined by using the Hoek-Brown criterion. Numerical computation is carried out. It is found from numerical results that the number of fractured zones increases with increasing the disturbance coefficient, in-situ stress, unloading time and unloading rate, and it decreases with increasing parameter geological strength index, the strength parameter and the uniaxial compressive strength of intact rock.

Estimating Field Source Parameters of Gravity Change in North China Based on the Euler Deconvolution Method

Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theoretical model to get the best estimates of parameters. Gravity field change caused by the depth and distribution in North China is calculated by back analysis. The results show the structural index that equals 1 is suitable for inversion of the gravity variation data. The inversion results indicate that the depths of anomaly field sources are spread over the Hetao fault. The research method of this paper can be used in the quantitative study on the field source and may shed new light on the interpretations of gravity change, and also provide quantitative basis for earthquake prediction index criterions based on the gravity change.

Research Methodology for Tourism Destination Resilience and Analysis of Its Spatiotemporal Dynamics in the Post-epidemic Period

As the COVID-19 pandemic continues to spread, the global tourism industry is facing enormous challenges. There is an urgent need to explore an effective path for tourism to recover and revitalize. With the normalization of the epidemic, tourism destinations will pay more attention to the prevention, warning, and coping strategies of the epidemic, and this focus will also be evident in the study of tourism destination resilience in the post-epidemic period. Some studies on the epidemic and the resilience of tourism are currently underway, but few of them are integrated with research on the resilience of tourism destinations in the post-epidemic period, although no systematic research ideas or methods have been found. Based on resilience theory, this paper summarizes the general research ideas and develops an epidemic resilience model suitable for urban tourism destinations. The present study also proposes a set of research methods based on the index system to analyze the resilience and its spatiotemporal dynamic characteristics of tourism destinations in the post-epidemic period. The methodology can be divided into three stages: Firstly, construct the conceptual model and evaluation system for tourism destination resilience;Secondly, select case sites for empirical analysis, measure the resilience of tourism destinations, and analyze the characteristics of spatiotemporal differences and subsequent factors of influence;And finally, establish an adaptive management mechanism for tourism destinations to use in response to the epidemic and in guiding the formulation of post-epidemic recovery policies.

Soil Fertility Indices of Citrus Orchard Land Along Topographic Gradients in the Three Gorges Area of China

In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been undertaken to reduce soil and water losses from slope land used for citrus production, information on the effects of management practices on soil fertility indices is either limited or nonexistent. This study was conducted to compare the effects of 10 years of various management practices, citrus intercropped with white clover (WC), citrus mulched with straw (SM), citrus intercropped with contour hedgerows (CH), citrus orchard land with impermeable membrane (IM), and citrus intercropped with wheat (Triticum aestivum) and peanut (Arachris hypogaea) (WP), as treatments on soil fertility indices with that of the conventional citrus management (CM). Results showed that the soil organic carbon, total and available nitrogen, available potassium, and water-stable aggregate (> 0.25 mm) contents at the 0–5 cm depth were higher for the WC and SM treatments than the CM treatment. There was also spatial variation in soil fertility along slopes of the WC and SM treatments. The soil total and available nitrogen, phosphorus, and potassium, and water-stable aggregate (> 0.25 mm) contents at both the 0–5 and 5–20 cm depths were higher for the CH and IM treatments than the CM treatment. The average soil available nitrogen and available potassium contents were higher for the WP treatment than the CM treatment, but the WP treatment had little effect on the soil organic carbon, total nitrogen, and water-stable aggregate (> 0.25 mm) contents. These suggested that white clover intercropping and straw mulching were the most effective approaches to improve soil fertility in citrus orchard land of the Three Gorges area.