Influence of tillage and crop residue on soil physical properties and yields of rice and wheat under shallow water table conditions

An experiment was conducted to evaluate the effects of tillage and residue incorporation on soil properties and yields of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) in rotation for 4 years on a silty clay loam of an Aquic Hapludoll with natural water table fluctuating between 0.05 and 0.97 m depth The rice experiment was laid out in split plot design with four levels of tillage, viz. conventional puddling (CP), puddling by four passes of rotavator (PR), reduced puddling by two passes of rotavator (ReP), and direct seeding without puddling (DSWP) and two levels of residue, viz. residue incorporation (RI) and residue removal (RR) in four replications. The treatments for wheat were zero tillage (ZT) and conventional tillage (CT) with RI and RR superimposed over the plots of rice. Tillage for rice increased puddling index and bulk density (BD) over the years. The increase was significantly higher in CP and PR than in ReP. In wheat season, BD was higher under ZT than under CT but the differences were not significant. Puddling decreased saturated hydraulic conductivity with time, which became significantly lower in CP and PR in the fourth year than in ReP in the first year. Infiltration rate (IR) also decreased with time and was lowest in CP and PR. In wheat season, IR was at par under ZT and CT. Rice yield in PR was maximum and at par with that in ReP. But wheat yield was lowest in PR and highest in DSWP, and was at par in DSWP and ReP. Thus, rice yields were optimum under ReP, in which changes in soil properties were least, and wheat yields were optimum both under ZT and CT in the DSWP and ReP plots of rice under shallow water table conditions of the silty clay loam.     

Monitoring of subaqueous depots with active barrier systems for contaminated dredged material using dialysis samplers and DGT probes

Background, Aims and Scope  Disposal of dredged material in subaqueous depots is increasingly considered an economic and ecologically sound option in managing contaminated dredged material. The concept of subaqueous disposals capped with active barrier systems has been developed to minimize this risk of contaminant release. As such a depot represents a permanent installation within a sensitive ecosystem, it requires a thorough monitoring concept. It is the goal of this work to develop such a concept regarding general considerations and results of laboratory and field investigations. Methods  In addition to the state-of-the-art techniques developed for other under-water constructions, this monitoring concept is developed with particular respect to the chemical isolation of the dredged material from the overlying water body. It comprises the use of seepage meters, dialysis samplers, and DGT gel probes for determining the migration of selected target solutes. The capability of the dialysis samplers is demonstrated by comparing field results with model calculations. The appropriateness of DGT probes to assess the impact of humic substances on trace metal speciation and on copper toxicity is demonstrated with the aid of laboratory experiments. Results and Discussion  The experimental results show that, by using dialysis samplers, the temporal changes in concentration-depth-profiles of heavy metals in the pore solution can be monitored. Additionally, the application of DGT probes facilitates the in situ detection of labile species of a metal in the presence of dissolved humic substances, which serves to reflect its toxicity. Conclusions. Three subsequent monitoring phases are distinguished on the basis of both general considerations and the findings from field results: A hydraulic phase that is characterized by compaction and pore water expulsion, a geochemical phase in which the demobilization of pollutants can occur due to substantial changes in the physico-chemical conditions (pH, EH), and a steady-state-phase where pore water flow and geochemical conditions are approaching their minimum. Recommendations and Outlook  The monitoring concept suggested here provides a versatile tool to assess the chemical isolation of subaqueous sediment depots and other contaminated sediment sites. This is of great importance as subaqueous disposal is increasingly considered a future management strategy as space for upland disposal is limited and treatment, in general, proves to be too costly.     

几种保护性耕作措施在黄土高原旱作农田的实践

自2001年起,甘肃农业大学的研究者在甘肃省定西市安定区李家堡镇布设了不同保护性耕作措施下春小麦→豌豆和豌豆→春小麦轮作系统的定位试验,以研究免耕不覆盖(NT)、传统耕作秸秆还田(TS)、免耕秸秆覆盖(NTS)、传统耕作地膜覆盖(TP)和免耕地膜覆盖(NTP)等保护性耕作措施在黄土高原旱作农田生态系统中的效应。本文就近10年依托该试验获取的相关研究结果进行综述,重点阐述特定土壤、气候、农作制度下土壤理化性状、土壤微生物及其酶活性、土壤温室气体排放、作物生理生态等对上述几种保护性耕作措施的响应。初步得到免耕秸秆覆盖措施有助于形成良好的土壤结构、减少土壤侵蚀、改善土壤持水特性、提高土壤养分利用效率、改善土壤微生物区系、增强作物光合效能、增加作物产量等结论,对筛选出当地适宜的耕作模式、改善区域土壤质量、促进农业可持续发展有重要意义。在此基础上,提出目前该项研究存在的问题和今后重点关注的方向:1)保护性耕作土壤碳循环机理;2)覆盖方式的创新;3)温室气体排放测量方法的改进与完善。     

传统稻鱼系统生产力提升对稻田水体环境的影响

如何在提升传统农业系统生产力的同时又不破坏其内涵、还对环境不产生负面影响,是一个受到研究者持续性关注的挑战性课题。本研究以具有1 200年历史的全球重要农业文化遗产稻鱼系统为例,研究稻鱼系统鱼的放养密度对生产力和环境的影响,探讨能够显著提升稻鱼系统生产力且又不破坏其传统性(产品优质、环境友好)的途径。研究表明,传统稻鱼系统(RF)(田鱼目标产量375 kg.hm 2)与水稻单作系统(RM)水体的化学需氧量(COD)、总氮(TN)、总磷(TP)及铵态氮(NH4+-N)含量均没有显著性差异。随着田鱼养殖密度提高(鱼产量由750 kg.hm 2提高到3 000 kg.hm 2)和饲料投入的相应增加,稻鱼系统的生产力和经济产出大幅度提高(稻鱼系统的净经济收入增加25.2%~101.4%),但稻鱼系统(RF)水体的COD值及TN、TP和NH4+-N含量均呈现增加的趋势,尤其是当鱼目标产量增至3 000 kg.hm 2时,水体TP含量和COD值显著提高,面源污染风险增加。分析还表明,鱼放养目标产量为2 250 kg.hm 2时,稻鱼系统经济效益最佳,此时净经济收入比传统稻鱼系统增加55.9%,并且不会对水体环境质量产生负面影响。     

再生稻根干物质量及根系活力与产量的相关性研究

对不同施N水平、不同品种再生稻根干物质量及根系活力与产量的相关性研究结果表明 ,再生稻头季稻产量与根系干物质量及根系活力密切相关 ;再生稻再生分蘖的生长发育依赖于头季稻残留的根系 ,再生季稻穗数及产量与头季稻成熟期和再生季稻齐穗期的根系机能呈极显著线性正相关 ,并与芽肥施用量呈抛物线形相关     

农业生态旅游地综合评价指标体系的研究

研究提出农业生态旅游地评价原则与评价方法 ,建立了包括旅游资源、农业与生态环境和社会经济条件 3个子系统的综合评价指标体系 ,并利用该指标体系综合评价了泰山农业生态旅游开发实验区     

履带式稻(麦)联合收割机液压——机械式行走系统的研究

液压行走系统因其结构简单、操纵方便、转向灵活等特点已广泛在联合收割机中采用。该文分析了液压一机械式联合收割机行走系统的工作过程，并以某联合收割机为例，对液压行走系统的配置方案、液压元件的选型、液压系统主要参数的确定、液压系统的性能验算和实测等方面进行了研究。研究结果表明，此液压行走系统的设计是合理的、可行的，完全可以满足联收机实际使用条件和较恶劣的工况。这为我国联合收割机液压行走系统的设计和配置提供重要的参考价值。     

施氮和灌溉管理下作物产量和土壤生化性质

氮和水对作物生长非常重要,研究施氮和灌溉管理下作物产量、土壤性质以及它们的关系对我国农业科学有重要意义。本文以中国科学院封丘农业生态试验站为平台,研究了施氮(每季施氮150 kg·hm?2、190 kg·hm?2、230 kg·hm?2、270 kg·hm?2,以不施氮为对照)和灌溉(灌溉量达到0~20 cm、0~40 cm、0~60 cm土壤的田间持水量,以雨养为对照)管理下小麦-玉米轮作系统作物产量和土壤生化性质,以及它们之间的关系。研究结果表明,150~270 kg·hm?2施氮量对2008年、2009年玉米产量和2009年、2010年小麦产量无显著影响;灌溉对2010年玉米产量无显著影响,而2008年、2009年玉米产量随灌溉量增大而增加。尽管2008—2011年小麦产量随灌溉量变化趋势不一致,但与雨养相比灌溉提升了小麦产量。施氮在不同程度上提升了土壤全氮和速效氮含量、脱氢酶和脲酶活性、微生物生物量碳、基本呼吸和硝化势,稍微降低了土壤pH并大幅降低了速效磷含量(降幅48.7%~51.6%);灌溉提升了土壤全氮含量和脱氢酶活性,降低了全钾含量、脲酶活性、基本呼吸、硝化势。多元回归分析显示,某些土壤生化性质(全氮、溶解性有机碳、速效磷含量及微生物生物量碳氮、呼吸熵、硝化势)与2009年、2010年玉米产量很好地线性拟合。综上,土壤生化性质因施氮和灌溉发生不同程度的分异,因施氮和灌溉而分异的土壤生化性质能部分地鉴定作物产量。本研究方法可为产量主导因子的筛选及产量估算模型的建立提供一定参考依据。     

县级测土配方施肥指标体系建立研究—以江苏省江都市水稻为例

以江苏省江都市水稻为例,基于地力差减法预测氮肥用量、 养分丰缺指标法预测磷钾肥用量,构建县域测土配方施肥指标体系,研究分析20052011年测土配方施肥田间试验示范。结果表明,当种植水稻预测目标产量为6825~9270 kg/hm2（平均为8145 kg/hm2）,氮肥推荐用量为146.42~57.4 kg/hm2（平均为207.5~ kg/hm2）。磷钾肥施用标准: 当有效磷含量高于21 mg/kg,不推荐施用磷肥;当有效磷含量在17~21 mg/kg时,推荐施磷（P2O5）量为40.5 kg/hm2;当有效磷含量在10~17 mg/kg时,推荐施磷（P2O5）量为 48 kg/hm2;当有效磷含量低于10 mg/kg 时,推荐施磷（P2O5）量为64.5 kg/hm2。当速效钾含量高于140 mg/kg,不推荐施用钾肥;当速效钾含量在115~140 mg/kg时,推荐施钾（K2O）量为 22.5 kg/hm2;当速效钾含量在60~115 mg/kg时,推荐施钾（K2O）量为40.5 kg/hm2;当速效钾含量低于60 mg/kg 时,推荐施钾（K2O）量为 82.5 kg/hm2。同时对施肥指标体系建立进行校验分析,结果表明基于试验建立施肥指标体系是可行的,从而为构建县域测土配方施肥指标体系提供了方法,达到因土施肥的目的。     

球根海棠离体培养的形态发生研究

 球根海棠外植体可在同一条件下同时诱导不定芽和胚状体, 经间接途径和直接途径的体细胞胚胎发生频率均很高, 体细胞胚为单细胞起源或多细胞起源。以再生嫩叶为继代中间体, 在较高温度(28 ℃) 下诱导, 可建立高效扩繁体系。纵切芽丛继代形成大量愈伤组织, 愈伤组织继代半年后几乎完全丧失分化能力, 发生激素驯化作用, 而且愈伤组织细胞染色体数目已发生广泛变异。