AM真菌抑制连作障碍的研究进展

从连作障碍产生的原因入手,对连作导致土壤因子向不利于作物生长转变的8个方面的原因逐一进行了阐述,包括土壤养分失衡、土壤微生物结构变化、土壤化感物质富集、土壤pH变化、土壤酶活性变化、土壤盐渍化、土壤物理性状变化和土壤水分亏缺;提出AM真菌对连作障碍的抑制作用,并从AM真菌可以提高植物自身耐胁迫性以及直接改善连作土壤环境两方面进行论证,为解决连作障碍的研究提供新的方向。     

不同农业措施对草莓连作土壤微生物群落特征的影响

[目的]探讨不同农业措施对草莓连作土壤微生物区系、活性、功能多样性及酶活性的影响。[方法]通过田间小区试验,利用土壤酶学方法、微生物培养方法和Biolog微生物自动分析系统,分析了土壤微生物群落特征。[结果]与不施肥相比,莓-稻水旱轮作、米糠＋日晒和石灰氮均显著提高草莓连作土壤细菌所占比例、细菌/真菌、土壤微生物总数、AWCD、土壤脱氢酶活性、Shannon指数、Simp-son指数和Mcintosh指数;莓-稻水旱轮作和米糠＋日晒还能提高土壤脲酶活性。与习惯施肥相比,莓-稻水旱轮作、米糠＋日晒可显著提高草莓连作土壤AWCD、Mcintosh指数,莓-稻水旱轮作和米糠＋日晒分别显著提高土壤脲酶和脱氢酶的活性。主成分分析表明,莓-稻水旱轮作、米糠＋日晒和石灰氮条件下草莓连作土壤微生物群落碳源利用特征与习惯施肥及不施肥显著不同。[结论]莓-稻水旱轮作和米糠＋日晒是控制草莓连作土壤生物退化的有效农业措施。     

牙鲆连续两代减数分裂雌核发育家系的遗传特征

对牙鲆(Paralichthys olivaceus)减数分裂雌核发育二倍体(Meio-G1)再次诱导减数分裂雌核发育,获得连续两代雌核发育二倍体家系(Meio-G2),以Meio-G1亲本与1尾普通牙鲆雄鱼人工授精获得的家系作为对照组(control)。利用15个微卫星标记对3个家系进行遗传特征分析。结果显示,15个微卫星位点在Meio-G1、Meio-G2和对照组3个家系中,分别扩增到30、28、50个等位基因,平均等位基因数为2.0、1.9、3.3,平均观测杂合度(Ho)分别为0.875 3、0.774 2、0.908 3,平均纯合度分别为0.124 7、0.221 5、0.091 7。3个家系个体间的平均遗传相似系数分别为0.891 7、0.923 8、0.520 2,亲代与子代之间的平均相似系数分别为0.916 6、0.930 4、0.560 3。高重组率的Poli9-8tuf、Poli18tuf、Poli107tuf 3个位点在Meio-G1和Meio-G2中观测杂合度均为1.0,低重组率的Poli33tuf、Poli24MHFS两个位点在Meio-G1和Meio-G2中均全部纯合,观测杂合度为0。结果表明,Meio-G2的纯合度、个体间平均相似系数以及亲子之间的平均相似度均略高于Meio-G1,显著高于对照组家系,证明连续两代诱导减数分裂雌核发育,能提高鱼类纯合度和遗传相似度,具有固定母本遗传性状的作用。     

作物连做障碍中酚酸类物质的生物降解研究

为了有效解决作物连做障碍中酚酸类物质的危害问题,探索了黄孢原毛平革菌所分泌的胞外酶系对酚酸类物质香草酸、阿魏酸和对羟基苯甲酸的降解功能。选用黄孢原毛平革菌(P.chrysosporium)与香草酸、阿魏酸、对羟基苯甲酸等酚酸类物质共同培养3天后,用高效液相色谱技术检测其含量。结果表明,3种酚酸平均降解率分别为98.39%、97.88%和58.20%,其降解效果均达极其显著水平。该研究结果,将为今后在农业生产中有效利用该菌进行农作物连做障碍治理和改善土壤环境,提供了理论依据。     

不同经济发展水平地区耕地利用变化对比研究

基于中国农产品成本收益资料与中国农村统计年鉴等基础数据,选择浙江、河南和四川3个处于不同经济区位和发展水平下的典型省份,系统分析了3个地区1980—2007年的耕地利用方式、集约度及其内部结构以及耕地产出的变化情况。结果显示:在种植结构上,近年来粮食播种面积占总播种面积的比例降幅次序为浙江>河南>四川,浙江蔬菜瓜果占地比例增加,而其他2省粮食作物仍占主导地位;劳动集约度持续下降,下降幅度浙江>河南>四川,到2007年形成劳动集约度水平与三地经济发展水平呈反比的关系;机械投入表现为与经济发展水平的正比关系;但经济发达省份在种子、化肥和农药等增产性投入方面未表现出显著优势,其增加幅度次序为河南>浙江>四川;从耕地产出变化情况看,近年来耕地生产率的增长幅度显著低于劳动生产率,劳动生产率的快速提高在经济发达的浙江更为显著,说明经济发展水平越高地区的农户,在耕地利用中越重视追求劳动生产率最大化的目标。     

大蒜对日光温室黄瓜生长及土壤生物学特性的影响

利用盆栽试验研究大蒜干样还田后,对日光温室黄瓜生长及土壤生化特性的影响。结果表明:添加大蒜干样后,显著增加黄瓜植株的鲜重,且与添加量成正比;在黄瓜的整个生长期,增加了细菌和放线菌的数量。当结果期大蒜的添加量为3.0%时,减少了真菌和镰刀菌的数量,并提高了土壤B/F(细菌+放线菌/真菌)值,优化了土壤微生物区系;而随着黄瓜的生长,促进黄瓜幼苗期根际土壤多酚氧化酶、蔗糖酶、尿酶和过氧化氢酶的活性。当结果期大蒜添加量大于2.0%时,对4种土壤酶具有显著的促进作用,使土壤环境有利于黄瓜生长。     

长江中下游地区耕地复种指数变化特征与潜力分析

基于1979—2007年统计资料,对长江中下游六省一市耕地面积、农作物总播种面积、粮食播种面积和耕地复种指数的变化特征进行了分析,并采用最大复种指数与热量、水资源之间的定量化关系模型计算分析了该地区的复种指数理论潜力和可挖掘潜力。结果表明：2007年与1979年相比长江中下游地区耕地面积、农作物总播种面积、粮食播种面积和总产量减少,耕地复种指数下降。以研究区2007年的耕地复种指数为参照,该区耕地复种指数理论可挖掘潜力为108.37%,其中最大的是浙江为160.5%,其次是湖北、江西、上海,分别为130.7%,113.0%,110.6%,其余各地也较大。复种指数的下降,严重影响了粮食生产。如何挖掘本区耕地复种指数潜力,提高农业机械化水平,进行土地制度创新等措施值得借鉴。     

冬种黑麦草对6种水稻土重金属含量及晚稻不同器官重金属累积与分配的影响

研究双季稻区6种不同土壤类型冬季种植黑麦草对土壤重金属含量及其对晚稻不同器官重金属积累与分配的影响, 可为水稻质量安全生产和产地安全适宜性评价提供重要参考。本文以7年定位试验为基础, 研究了南方双季稻区冬季种植黑麦草对6种不同水稻土耕层土壤重金属Cd、Pd、Hg和As含量的变化及其对晚稻不同器官重金属积累与分配的影响。结果表明, 在6种不同土壤类型中, 灰泥田土壤Cd含量极显著高于其他土壤类型; 黄泥田土壤Pd含量极显著高于其他土壤类型; 土壤Hg含量以红黄泥田最高, 达0.029 mg kg^-1, 与其他土壤类型差异达极显著水平; 土壤As的含量以黄泥田最高, 为29.5 mg kg^-1, 极显著高于其他土壤类型。6种不同土壤类型晚稻植株Cd、Pb、As含量均为根>茎叶>糙米。在晚稻植株根系、茎叶和糙米的Cd含量以红黄泥田最高, 均极显著高于其他土壤类型; 植株根系Pb、As含量以黄泥田最高, 分别为33.0 mg kg^-1和119.5 mg kg^-1, 均极显著高于其他土壤类型; 河沙泥水稻植株茎叶的Hg、As含量均极显著高于其他土壤类型。说明黄泥田种植水稻有利于降低稻米中重金属含量, 改善稻米品质。     

Agronomic performance of no-tillage relay intercropping with maize under smallholder conditions in Central Brazil

In the context of conservation agriculture on small scale farms of the Brazilian Cerrado, we hypothesized that planting a cover crop in relay with a commercial crop improves the efficiency of use of available natural resources, increasing biomass for use as fodder without reducing the grain yield of the main crop. The objective of this study was to measure the performance of two intercropped systems in terms of total above-ground biomass production and maize (Zea mays) grain yield: pigeon pea (Cajanus cajan) and Brachiaria (Brachiaria ruziziensis) sown as cover crops in established maize under a no-tillage management. The cover crops were sown at two different dates and a comparison was made with the three crops sown as a sole crop at the early sowing date. The experiment was conducted during the 2007-2008 and 2008-2009 growing seasons. Maize grain yield was not reduced by the presence of the relay cover crops in comparison with maize as the sole crop, even when the cover crop was sown soon after maize emergence. In contrast, the production of above-ground biomass by the cover crop was significantly lower when grown with maize than it was when grown as a sole crop. In the intercropped systems, when sown early, the cover crop produced higher total biomass than when sown late. Total above-ground biomass production of maize intercropped with a cover crop was much higher than that of any of the crops sown alone: the total biomass (average of the two growing seasons) produced by maize and pigeon pea was more than double that of maize grown alone. The land equivalent ratio (LER) of maize grain yield and biomass production was higher than one whatever the intercropped system used. It was particularly high when maize was intercropped with early sown pigeon pea; grain yield LER and biomass LER reaching, respectively, 1.72 and 1.73 in 2007-2008 and 2.02 and 2.03 in 2008-2009. These high LER values provide evidence for the complementary and the high efficiency of use of available resources by the intercropped plants and thus the advantage of such systems to produce both maize grain and cover crop forage under the conditions of our study.     

Clover cover crops under-sown in winter wheat increase yield of subsequent spring barley—Effect of N dose and companion grass

Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha⁻¹) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha⁻¹ more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.