Decreasing of methanogenic activity in paddy fields via lowering ponding water temperature: A modeling investigation

Methane (CH₄) is a potent greenhouse gas and the huge CH₄ fluxes emitted from paddy fields can prejudice the eco-compatibility of rice cultivation. CH₄ production in submerged rice crops is known to be highly influenced by water temperature. Hence, lowering ponding water temperature (LPWT) could be an option to mitigate CH₄ emissions from paddy environments when it is possible either to irrigate with slightly colder water or to increase ponding water depth. However, paddy soil is a complex environment in which many processes are simultaneously influenced by temperature, leading to a difficult prediction of LPWT effects. For this reason, LPWT efficiency is here theoretically investigated with a one-dimensional process-based model that simulates the vertical and temporal dynamics of water temperature in soil and the fate of chemical compounds that influence CH₄ emissions. The model is validated with literature measured data of CH₄ emissions from a paddy field under time-variable temperature regime. Based on modeling results, LPWT appears promising since the simulated reduction of CH₄ emissions reaches about −12% and −49% for an LPWT equal to −5 °C during the ripening stage only (last 30 days of growing season, when rice is less sensitive to temperature variations) and −2 °C over the whole growing season, respectively. LPWT affects CH₄ emissions either directly (decreasing methanogenic activity), indirectly (decreasing activity of bacteria using alternative electron acceptors), or both. The encouraging results provide the theoretical ground for further laboratory and field studies aimed to investigate the LPWT feasibility in paddy environments.     

利用生态循环农业综合治理农业污染——以嘉兴市海盐县为例

总结发展生态循环农业的意义,分析了海盐县农业污染现状,并提出利用生态循环农业治理农业污染的措施与对策。     

美国农业保护性耕作技术的启示

为了学习与引进先进的保护性耕作技术,阐述了美国保护性耕作的起源,说明了传统耕作给农业生产带来的毁灭性的打击,并通过以免耕为主的保护性耕作的论述,进一步说明了黑龙江省耕作制度改革的必要性。同时通过美国先进耕作制度的论述,提出了黑龙江省发展保护性耕作制度的必要性和具体措施。     

农业院校高等数学教学存在的问题及其解决

根据农业院校高等数学教学体会进行了系统总结和思考,并对当前农业院校高等数学教学遇到的问题提出了改进建议。     

"互联网+"在休闲观光农业中的应用

2015年越来越多的行业运用"互联网+"为行业创造更多的价值,笔者基于休闲观光农业的现状,从服务形式、游客参与度、营销方式、文化内涵、评价体系方面分析了休闲观光农业行业发展和营销推广中存在的问题,提出利用"互联网+"的技术和手段解决这些问题的方法和措施。     

热带农业科技国际合作项目评价体系初探

从国际科技合作项目的特点出发,探讨提出热带农业科技国际合作项目评价体系的雏形,并对评价体系的项目前评价、项目中评价及项目后评价3个阶段的评价指标加以充实,为热带农业科技国际合作项目的科学、规范管理提供参考依据。     

高职数字图书馆个性化信息推荐服务研究

介绍了高职数字图书馆个性化信息服务的含义、服务模式、服务方式、重要性及存在的问题,提出了高职数字图书馆开展个性化信息服务的措施。     

贵州省农业社会化服务体系发展现状与对策研究

农业社会化服务体系越发达，就代表着农业现代化发展的程度越高。贵州省属于典型的山区农业省份，农业经济发展水平相对落后，为推进贵州的农业现代化发展，首先需要完善农业社会化服务体系建设。介绍了贵州省农业社会化服务体系建设的发展现状，包括农业技术推广服务、农产品流通服务、农村金融服务、农产品质量安全监管服务、农村信息服务等，并阐述了几种典型的模式，针对贵州农业社会化服务体系建设过程中存在的问题，提出发展对策。     

Enhancing pedotransfer functions with environmental data for estimating bulk density and effective cation exchange capacity in a data‐sparse situation

Soil bulk density (BD) and effective cation exchange capacity (ECEC) are among the most important soil properties required for crop growth and environmental management. This study aimed to explore the combination of soil and environmental data in developing pedotransfer functions (PTFs) for BD and ECEC. Multiple linear regression (MLR) and random forest model (RFM) were employed in developing PTFs using three different data sets: soil data (PTF‐1), environmental data (PTF‐2) and the combination of soil and environmental data (PTF‐3). In developing the PTFs, three depth increments were also considered: all depth, topsoil (<0.40 m) and subsoil (>0.40 m). Results showed that PTF‐3 (R²; 0.29–0.69) outperformed both PTF‐1 (R²; 0.11–0.18) and PTF‐2 (R²; 0.22–0.59) in BD estimation. However, for ECEC estimation, PTF‐3 (R²; 0.61–0.86) performed comparably as PTF‐1 (R²; 0.58–0.76) with both PTFs out‐performing PTF‐2 (R²; 0.30–0.71). Also, grouping of data into different soil depth increments improves the estimation of BD with PTFs (especially PTF‐2 and PTF‐3) performing better at subsoils than topsoils. Generally, the most important predictors of BD are sand, silt, elevation, rainfall, temperature for estimation at topsoil while EVI, elevation, temperature and clay are the most important BD predictors in the subsoil. Also, clay, sand, pH, rainfall and SOC are the most important predictors of ECEC in the topsoil while pH, sand, clay, temperature and rainfall are the most important predictors of ECEC in the subsoil. Findings are important for overcoming the challenges of building national soil databases for large‐scale modelling in most data‐sparse countries, especially in the sub‐Saharan Africa (SSA).     

Can additional N fertiliser ameliorate the elevated CO2‐induced depression in grain and tissue N concentrations of wheat on a high soil N background?

Elevated CO₂ stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO₂ Enrichment facility in a low‐rainfall cropping system on high soil N. Crops were grown with and without addition of 50–60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO₂ increased yield and biomass (on average by 25%) and decreased biomass [N] (3%–9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO₂. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO₂. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO₂, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply.