模拟稻田中氮磷的变化特征及其降污潜力分析

为研究稻田中氮磷的变化特征和降污潜力,采用室外微区模拟稻田春耕施肥耕整试验,在3、6cm和9cm等3个不同蓄水深度处理（分别表示为t-3、t-6、t-9）条件下,对稻田氮磷含量变化的动态特征及降污潜力进行了探讨。田面水氮磷质量浓度变化与土壤中氮磷的流失密切相关。土壤扰动、基肥（缓释肥）的释放、硝化-反硝化作用、悬浮颗粒物（SS）的物理沉降等综合因素的影响,是导致田面水氮磷质量浓度变化呈先升后降趋势的主要原因。在蓄水处理后1周内,各处理的田面水氮磷质量浓度大小顺序为：Ct-3〉Ct-6〉Ct-9,总氮（TN）、总磷（TP）质量浓度与蓄水深度呈显著的负相关（Y=-33.97x＋133.4,R2=0.999和y=-0.115x＋0.61,R2=0.994）。春耕插秧时,因水分管理要求,需要立即排水,相对于蓄水3cm的常规水分管理,若能蓄水9cm后再排放,可减少排放总氮45.57%~86.88%、总磷33.02%~62.79%;若蓄水6cm再排放,可减少排放总氮35.76%~72.13%、总磷9.88%~50%。但考虑到＂浅水活苗＂之实际,以人工蓄水5~6cm较为适宜。另外,在蓄水5~6cm的前提下,于第5d或第7d排水,减排降污效果显著;第5d排水,相比第3d排水,可减少排放总氮21.22%~55.41%、总磷67.67%~83.70%。从稻田春耕生产实际要求和降污效能综合考虑,选择6cm的蓄水深度并在第5d排水,是提高稻田减排降污潜力的农艺措施之一。     

不同耕作制度对南方稻田甲烷排放的影响

以南方稻田温室气体甲烷排放为研究对象,选取冬季休闲和种植绿肥作物紫云英(AstragalussinicusL.)两种主要模式,在早稻(OryzasativaL.)移栽之前进行旋耕和翻耕两种处理,以全年休闲为空白对照,利用静态箱法测定甲烷排放通量。结果表明,甲烷排放在水稻抽穗期达到极大值,至收获甲烷排放呈减少趋势,以无稻全年休闲区甲烷排放通量最低,在抽穗至收获阶段平均排放速率为3.43mg·m-2·h-1,冬闲及冬季种植紫云英处理分别比无稻休闲区排放通量高114.3%和420.3%;甲烷浓度具有强烈的空间异质性,地表以上50cm空间内,早稻抽穗至成熟阶段甲烷浓度是大气甲烷浓度的35.2倍;稻田甲烷高浓度低排放速率以及低浓度高排放速率现象表明,甲烷排放速率与其浓度之间具有非一致性。     

中国保护性耕作净碳汇的时空分异特征及其驱动力

在碳达峰碳中和背景下,探讨中国保护性耕作的净碳汇效应对于减缓全球气候变暖和实现国家“双碳”目标具有重要现实意义。该研究以保护性耕作技术的固碳排碳效应为切入点,从土壤固碳、生物固碳和温室气体排放三个层面测度2000—2019年中国各省保护性耕作的净碳汇效应,在此基础上运用探索性空间数据分析法揭示其时空格局特征,并采用地理探测器方法从农业资源、社会经济和自然环境三个维度探究影响中国保护性耕作净碳汇空间分异的驱动力。实证结果显示：①中国保护性耕作净碳汇在研究时期内呈逐年增加态势,但不同区域和不同措施的净碳汇及增幅存在差异。其中,中部地区净碳汇及增幅最大,西部地区和东部地区次之,东北地区位居最后;秸秆还田措施的净碳汇及增幅均大于免耕措施。②中国保护性耕作净碳汇在空间上呈北高南低、西高东低的分布格局,且表现出“东西差异缩小、南北差异扩大”的演变特征,同时呈正的空间相关关系且冷热点分区明显,即空间分异特征显著;③因子探测结果表明农业机械化水平、经济发展水平、保护性耕作推广强度和日照对中国保护性耕作净碳汇空间分异的驱动力度较大;交互探测结果显示双因子交互作用的解释力度均强于单因子作用,在技术推广前期“保护性耕作推广强度+其他因子”的交互作用凸显,后期“经济发展水平+其他因子”和“受教育程度+其他因子”的交互作用逐渐显现。研究结论旨在为优化保护性耕作技术的推广政策和实现国家“双碳”目标提供参考依据。     

农田固碳措施对温室气体减排影响的研究进展

农田是CO2,CH4和N2O三种温室气体的重要排放源,在全球范围内农业生产活动贡献了约14%的人为温室气体排放量,以及58%的人为非CO2排放,不合理的农田管理措施强化了农田温室气体排放源特征,弱化了农田固碳作用。土壤碳库作为地球生态系统中最活跃的碳库之一,同时也是温室气体的重要源/汇。研究表明通过采取合理的农田管理措施,既可起到增加土壤碳库、减少温室气体排放的目的,又能提高土壤质量。农田土壤碳库除受温度、降水和植被类型的影响外,还在很大程度上受施肥量、肥料类型、秸秆还田量、耕作措施和灌溉等农田管理措施的影响。本文通过总结保护性耕作/免耕,秸秆还田,氮肥管理,水分管理,农学及土地利用变化等农田管理措施,探寻增强农田土壤固碳作用,减少农田温室气体排放的合理途径。农田碳库的稳定/增加,对于保证全球粮食安全与缓解气候变化趋势具有双重的积极意义。在我国许多有关土壤固碳与温室气体排放的研究尚不系统或仅限于短期研究,这也为正确评价各种固碳措施对温室气体排放的影响增加了不确定性。     

SURFACE WATER QUALITY IMPACTS OF TILLAGE PRACTICES UNDER LIQUID SWINE MANIJRE APPLICATION1

ABSTRACT: Field studies were conducted to investigate the effects of tillage practices on the saturated hydraulic conductivity, and quantity and quality of surface runoff water resulting from the application of the liquid swine manure as a fertilizer. As part of the study, infiltration experiments were conducted on silt-loam soil with no-tillage (NT) and disk tillage (DT) practices. Liquid swine manure was applied on test plots, and the rainfall was applied by the portable rainfall simulator. The infiltration data was analyzed for the saturated hydraulic conductivity (K8) and runoff volume determinations. The surface runoff water was analyzed for total N, total P, ammonia, and nitrate concentration determinations. The study indicated that the tillage had significant effects on K_s, and quantity and quality of runoff water. The K_s values of the NT plots were found to vary from 0.693 to 1.734 mm/min, with a mean of 1.494 mm/min, while they varied from 1.056 to 2.543 mm/min, with a mean of 2231 mm/mm in the DT plots. The total N, total P, ammonium nitrogen and nitrate nitrogen concentrations were lower in runoff generated from DT plots, compared to that from the NT plots. The chemical concentration levels were significantly different in runoff waters collected one-day after manure application than in those collected 40-days after the manure application. Study suggested that the DT practice must be preferred over the NT practice if liquid swine manure is used as the fertilizer. The study is further continued to assess the long-term impacts of swine manure application and tillage on the quantity and quality of surface runoff water.     

EVALUATION OF MANAGEMENT PRACTICES TO CONTROL AGRICULTURAL POLLUTANTS1

ABSTRACT: The objective of this study was to evaluate the effectiveness of various land-use practices upon the production of nonpoint source pollutants from small agricultural watersheds in Northern Virginia. Pollutant production at each watershed was determined by individual monitoring stations. Data analysis consisted of a determination of the site specific pollutant yield for similar watersheds subjected to differing crop management approaches. These collected data were then compared to those generated by a parametric, event model developed for this investigation. This synthetic data base was used to eliminate or reduce errors resulting from monitoring site differences and to extend the collected data for additional comparisons.     

旋流除砂系统排砂管路改造与优化运行

针对南方某污水处理厂旋流除砂系统由于设计及设备选型不合理,造成排砂管路反复堵塞,使系统长期处于\"瘫痪\"状态,通过水力学分析结合实际运行工况提出改进措施,并对系统除砂性能进行测试,依据测试结果提出沉砂池优化运行方案。结果表明,旋流除砂系统排砂管路高度应满足气提扬程要求,经改造后,系统未发生堵塞现象,优化运行后的系统出砂量由平均240 kg/d增加到300 kg/d,且出砂中粒径小于0.3 mm砂粒所占比例由40%提高至78%,砂粒表面的附着有机物含量由前期的10%下降到4%。     

新型旋流-扰流絮凝反应工艺的试验研究

本在对絮凝理论分析的基础上,设计了几种不同扰流形式的旋流扰流絮凝反应器。通过试验对其絮凝效果进行了分析和比较,找出了比较合理的絮凝器结构。这对于研制开发新型絮凝反应器,发挥新型絮凝剂的效能,提高出水水质,保证供水安全具有十分重要的现实意义。     

耕作深度调控秸秆还田对农田土壤呼吸的影响

秸秆还田和耕作深度处理是影响农田土壤呼吸最重要的农业管理措施之一,但二者交互作用影响农田土壤呼吸的机制尚不清楚.基于此,针对中国的旱地农田生态系统,利用已发表的116篇研究论文,借助Meta分析技术,探究秸秆还田和耕作深度处理及其二者交互作用对农田土壤呼吸的影响及其调控因素,为农田生态系统实现\"碳中和\"提供重要的数据支撑和理论依据.结果表明,免耕导致土壤呼吸减少了 8.3％,而浅耕和深耕处理对土壤呼吸的影响不显著,但对土壤呼吸的增加量仍呈现出深耕＞浅耕＞免耕的趋势.虽然,浅耕和深耕对土壤呼吸和土壤有机碳(SOC)的影响均相对较小,但是免耕导致土壤呼吸减少了 8.3％的同时却又导致SOC增加了 7.05％,因此实施免耕措施对农田土壤固碳减排具有重要意义.此外,耕作深度会显著调控秸秆还田对土壤呼吸的影响,且土壤呼吸的增加量呈现出深耕秸秆还田＞浅耕秸秆还田＞免耕秸秆还田的趋势,整体平均增加了14.51％.秸秆还田后不同深度耕作处理下土壤呼吸的增加量与土壤容重、农作物产量、土壤有机碳、以及土壤温度和水分的改变量密切相关,且对土壤呼吸增加量的贡献呈现出土壤容重＞农作物产量＞土壤有机碳＞土壤水分＞土壤温度的趋势.虽然SOC在深耕秸秆还田、浅耕秸秆还田和免耕秸秆还田处理下分别增加了 29.32％、10.12％和23.94％,但是土壤呼吸在深耕秸秆还田和浅耕秸秆还田处理分别增加了 29.32％和18.92％,而在免耕秸秆还田处理下仅增加1.2％.所以,免耕秸秆还田也有利于农田土壤固碳减排.因此,在中国的旱地农田生态系统中,耕作深度会调控秸秆还田对土壤呼吸的影响程度,而这种调控主要与土壤理化性质有关,尤其与土壤容重关系最为紧密,且免耕和免耕秸秆还田均是有利于农田土壤固碳减排的重要农业管理措施.     

Effects of Alternative Cotton Agriculture on Avian and Arthropod Populations

Abstract:  Among the major agricultural crops in the southeastern United States, cotton ( Gossypium hirsutum L.) generally provides the least suitable habitat for most early successional songbirds. Newer cropping approaches, such as use of conservation tillage and stripcover cropping, offer hope for improving the ecological value of cotton fields. We examined the effects of clover stripcover cropping with conservation tillage versus conventionally grown cotton with either conventional or conservation tillage on avian and arthropod species composition and field use in east-central Georgia. Stripcover fields had higher bird densities and biomass and higher relative abundance of arthropods than both conservation tillage and conventional fields. During migration and breeding periods, total bird densities on stripcover fields were 2–6 times and 7–20 times greater than on conservation and conventional fields, respectively. Abundance and biomass for epigeal arthropods were also greatest on stripcover fields during much of the breeding season. Although the clover treatment attracted the highest avian and arthropod densities, conservation fields still provided more wildlife and agronomic benefits than conventional management. Our findings suggest that both conservation tillage and stripcropping systems will improve conditions for birds in cotton, with stripcropped fields providing superior habitat. The reduction of inputs possible with the clover system could allow farmers to lower costs associated with conventional cotton production by $282–317/ha. This reduction of input, coupled with similar or possibly increased yield over conventional systems makes stripcover cropping not only a good choice for reducing negative impacts on wildlife and surrounding ecosystems, but also an economically desirable one.