添加秸秆对不同有机含量土壤酸度及缓冲性能的影响

通过向低（LSOM）、中（MSOM）、高（HSOM）及去除（RSOM）有机质土壤中添加玉米秸秆进行室内培养试验，研究秸秆添加量对不同有机质含量土壤酸度及缓冲性能的影响。结果表明，在15℃恒温培养150天后，土壤pH、交换性盐基离子、CEC和盐基饱和度的含量均随着秸秆添加量的增加而上升，交换性H⁺、交换性Al³⁺含量均随着秸秆添加量的增加而降低；其中，秸秆添加量为10~15 g/kg时，LSOM处理中土壤pH增幅、交换性Al³⁺及交换性H⁺含量减幅最大；秸秆添加量为15~20 g/kg时，在MSOM和HSOM处理中土壤pH增幅及土壤交换性Al³⁺、交换性H⁺含量减幅最大；且HSOM处理添加秸秆后对降低土壤酸度效果最好。土壤中添加秸秆后可明显提高土壤酸碱缓冲能力，且土壤对加碱侧表现出的缓冲区间比酸侧明显；土壤的缓冲容量随秸秆添加量增加而升高，且HSOM处理对酸碱缓冲能力 > MSOM处理 > LSOM处理 > RSOM处理。     

塔里木河上游棉区不同类型盐土阳离子交换量分布特征及影响因素

【目的】研究塔里木河上游棉区不同类型盐土CEC的分布状况及影响因素。 了解不同类型盐土土壤特性及肥力状况,为新疆南疆干旱区盐土改良利用提供理论依据。【方法】以阿拉尔绿洲草甸盐土(MeS)、沼泽盐土(MaS)、残余盐土(ReS)、洪积盐土(PrS)、棕漠林盐土(DeS)5种典型盐土为对象,研究该流域不同类型盐土阳离子交换量(CEC)的剖面分布规律,分析盐土CEC的影响因素,并利用灰色关联法对盐土CEC与土壤理化性质之间的关系进行了量化。【结果】该区盐土CEC在2.02～25.54 cmol/kg,平均值为12.39 cmol/kg,CEC随剖面深度的变化规律各类型盐土有所不同,不同类型盐土CEC大小依次为MeS> ReS > DeS > PrS > MaS。粘粒是干旱区盐土CEC的主要来源;pH、CaCO₃、盐基总量(TEB)和碱化度(BSP)与盐土CEC呈极显著正相关,是盐土CEC的主要影响因素,其中CaCO₃对盐土CEC的贡献不容忽视;盐土有机质(SOM)含量极低,对盐土CEC未表现出显著性影响;交换性钙饱和度(CaSP)、交换性镁饱和度(MgSP)及交换性钾饱和度(KSP)对盐土CEC有显著的抑制作用。【结论】塔里木河上游棉区不同类型盐土CEC有显著差异,不同类型盐土保肥、供肥及缓冲性能不同。pH、CaCO₃、TEB和ESP是CEC主要贡献因子,SOM对盐土CEC无显著的影响。     

Towards the sustainable intensification of agriculture—a systems approach to policy formulation

The sustainable intensification of agriculture involves providing sufficient food and other ecosystem services without going beyond the limits of the earth’s system. Here a project management approach is suggested to help guide agricultural policy to deliver these objectives. The first step is to agree measurable outcomes, integrating formal policy goals with the often much less formal and much more diverse goals of individual farmers. The second step is to assess current performance. Ideally, this will involve the use of farm-scale metrics that can feed into process models that address social and environmental domains as well as production issues that can be benchmarked and upscaled to landscape and country. Some policy goals can be delivered by supporting ad hoc interventions, while others require the redesign of the farming system. A pipeline of research, knowledge and capacity building is needed to ensure the continuous increase in farm performance. System models can help prioritise policy interventions. Formal optimization of land use is only appropriate if the policy goals are clear, and the constraints understood. In practice, the best approach may depend on the scale of action that is required, and on the amount of resource and infrastructure available to generate, implement and manage policy.     

重组白细胞介素-2高效纯化方法建立

依次通过离子交换法、凝胶过滤法纯化重组白细胞介素-2(IL-2)粗品,利用SDS-PAGE电泳和hIL-2 Elisa kit检测纯化后重组IL-2的纯度和浓度。结果表明,纯化后的重组IL-2纯度和浓度高。本纯化方法简单、稳定、纯化效果好,可为重组IL-2的生产工艺提供技术支持和依据。     

Productive performance of juvenile freshwater prawns Macrobrachium rosenbergii in biofloc system

The aim of this study was to compare two rearing systems for freshwater prawn Macrobrachium rosenbergii: one with use of a recirculating aquaculture system with biofilters (RAS) and another with use of microbial flocs (F). Thirty postlarvae of freshwater prawn with an initial average weight of 0.13 ± 0.05 g were randomly stocked in six experimental units with 0.20 m² and volume of 50 L. The experiment lasted thirty days. Dissolved oxygen, temperature and pH were monitored daily; ammonia concentration was determined three times per week; nitrite concentration, alkalinity and hardness were measured weekly. For the formation of microbial floc, molasses was used to keep the ammonia concentrations within safe levels for prawn farming. The variables of water quality remained within the suitable range for the production of the species, except for ammonia concentrations at the F treatment, which exceeded the safe levels. At the end of the experiment, the following parameters were evaluated: survival, specific growth rate, weight gain and feed conversion rate. Differences were found only in feed conversion rate with better values on RAS treatment. The microorganisms present in the RAS and F treatment were also evaluated. The densities of rotifers, amoebas and total bacteria were higher at the F treatment although the same organisms were found at the RAS treatment. The results of this study showed the possibility of rearing M. rosenbergii in biofloc system technology.     

SiO2纳米颗粒对黄瓜“新唐山秋瓜”幼苗根系 解剖结构和气体交换的影响

硅是地壳内含量第二丰富的元素。近年来,人们开始探索硅的纳米材料在农业领域的运用。为更好地将二氧化硅纳米颗粒应用于园艺植物生产,以黄瓜栽培品种新唐山秋瓜(Cucumissativuscv."QiuguaofNew Tangshan")为材料,采用盆栽的方式研究不同施入量下(0、5、10和20m L)浓度为30%的二氧化硅溶液对黄瓜根系解剖结构、根毛形成、黄瓜叶片光合色素含量、叶绿素荧光参数以及气体交换的影响。结果表明,二氧化硅纳米颗粒对黄瓜的根系解剖结构并没有显著的影响,但对根毛形成的影响较大,在每盆20m L二氧化硅溶液条件下的根毛密度最高。施入不同量的二氧化硅溶液对黄瓜叶片光合色素含量均有提高但并不明显,且在较低施入浓度下,光合作用机制得到一定的提高。黄瓜叶片的净光合速率随着二氧化硅施入量的增加逐渐增加,但施入量对蒸腾速率的影响不明显。综上,二氧化硅纳米颗粒通过促进根毛形成以及提高净光合速率能够提高植物的生长机理,进而促进植物生长和产量的提高,将其运用于农业生产及园艺作物生产上具有广阔前景。     

荒漠草原不同时间尺度下垫面水分消耗与气象植被因子的关系

利用大型称重式蒸渗仪2012—2018年连续观测数据，系统解析了希拉穆仁荒漠草原植物生长季（4—10月）不同时间尺度蒸散发（ET)与气象植被因子之间的关系。研究表明：（1）小时、日和月尺度上，始终与ET保持高度相关的气象植被因子包括风速（P<0.01）、空气温度（P<0.01）和降水量（P<0.01）；（2）结合不同时间尺度主控因子，利用多元回归定量表征了小时、日、月尺度的下垫面ET变化特征，经验方程决定系数分别为0.94（P<0.01）、0.42（P<0.01）、0.82（P<0.01），小时和月尺度上的经验方程可较好地反映希拉穆仁荒漠草原下垫面耗水特征；（3）ET与降水差值显示，2012—2018年希拉穆仁荒漠草原植物生长季（4—10月）水汽交换以下垫面水分消耗为主，8月份发生干旱事件的概率最大。     

The effect of nearly closed RAS on the feed intake and growth of Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus) and European eel (Anguilla anguilla)

One of the challenges that Recirculating Aquaculture Systems (RAS) are still facing is the risk that in RAS fish grow less than in flow-through systems due to the accumulation of substances originating from feed, fish or bacteria associated with the water re-use. The present study investigated whether RAS with high and low accumulation levels of these substances affect feed intake and growth of Nile tilapia Oreochromis niloticus, African catfish Clarias gariepinus, and European eel Anguilla Anguilla. One-hundred and twenty individuals of each species were used (start body weights: Nile tilapia 264.8 ± 8.3 g; African catfish 253.2 ± 2.1 g and European eel 66.6 ± 1.3 g). For a period of 39 days, growth and feed intake were compared between high and low accumulation RAS. HIGH accumulation RAS was designed for maximal accumulation of substances in the water by operating the system at nearly-closed conditions (30 L/kg feed/d), using mature biofilters and high feed loads; and (2) LOW accumulation RAS was designed to be a proxy for flow-through systems by operating at high water exchange rates (1500 L/kg feed/d), new biofilters and low feed load. HIGH accumulation RAS induced a reduction in feed intake (42%) and growth (83%) of Nile tilapia, as compared to systems that are a proxy for flow-through conditions. This effect was not observed in European eel and African catfish. The cause of this reduced feed intake and growth rate of Nile tilapia is still unclear and should be addressed in further studies.