更新修剪对盛果末期苹果树体营养及品质的影响

在渭北黄土高原地区,以‘红富士’苹果为试材,以当地长放修剪为对照,探讨更新修剪对盛果末期苹果树体营养和果实品质、产量的影响。结果表明:更新修剪提高了叶片、枝条、果实、根系中的氮、磷、钾、钙含量,特别是枝条中的氮、磷、钾、钙含量得到极显著提高。更新修剪极显著提高了单果质量、产量及经济价值,显著提高了果形指数和有机酸含量,对果实着色面积、可溶性固形物、可溶性糖、维生素C、果实硬度无显著影响。表明渭北黄土高原应积极开展盛果末期苹果树的更新修剪。     

Converting from no-tillage to pre-seeding tillage: Influence on weeds, spring wheat grain yields and N, and soil quality

On the Canadian prairies there has been a steady increase in no-till seeding coupled with more frequent cropping, facilitated by the greater use of snow management to increase stored soil water. Although no-till seeding can gradually improve soil conservation and soil quality, it may also increase the incidence of grassy weed infestations and thus cause more frequent use of costly herbicides, such as glyphosate. Our objective was to determine if no-till producers experiencing grassy weed problems could introduce pre-seeding tillage for a few years to more economically control perennial weeds, without adversely affecting grain yield and quality, and soil quality. An experiment in which spring wheat (Triticum aestivum L.) was grown for 9 years with no-tillage management on an Orthic Brown Chernozem (Typic Haplobroll) with treatments involving snow management and N rate, placement and timing, was converted to a study of pre-seeding shallow (5–7.5 cm) tillage with a cultivator, versus no-tillage, by replacing the N timing treatment in the tenth year. The experiment was then continued for three more years, during which we assessed the effect of tillage on weed populations, grain yield and N content, and on soil quality. Soil quality was also assessed following one more year during which the entire study site was summerfallowed and subjected to four tillage operations. Weed populations generally were not affected by tillage or snow management treatments, but differed among N rate and placement treatments, though not in a way that could be easily interpreted. Tillage had no effect on yield or grain N content. It increased the erodible fraction of soil (dry sieving), but did not affect wet aggregate stability. Neither microbial biomass C, nor C and N mineralization were affected by the change in tillage method. We conclude that the judicious use of shallow pre-seeding tillage in an otherwise no-till cropping system can be tolerated to manage persistent grassy weed problems without deleteriously influencing soil quality, grain yield or protein.     

机械化生态沃土耕作模式提高土壤质量及作物产量

为了解决小麦玉米两作区连年翻耕造成的土壤养分、水分流失、土壤沙化以及长期不耕作不利于作物高产等问题,将翻耕、旋耕、深松等适当结合,建立一种械化生态沃土耕作模式,设置一定的周期,周期内对土壤进行适度的耕作,并与连年翻耕和连年免耕模式进行试验对比。试验结果表明:5 a周期内机械化生态沃土耕作模式可以显著提高各层土壤有机质含量,0~10 cm提高最大达0.2%;连年免耕在前3 a可以显著提高O~10 cm土壤有机质含量,后2 a有所减少;连年翻耕在前3a可以显著提高20~30 cm土壤有机质含量,后2a显著减少。土壤含水率表现为机械化生态沃土连年免耕连年翻耕,随着时间变化,差异越来越显著。0~10 cm土壤容重在5%水平上机械化生态沃土耕作模式和连年免耕显著低于连年翻耕。机械化生态沃土耕作模式下作物产量显著高于连年免耕和连年翻耕,2014年增产优势最明显.比连年翻耕小麦增产30.8%,玉米增产28.4%,比连年免耕小麦增产22.5%,玉米增产20.9%。     

影响笼养蛋鸡高产稳产的几个主要环境因素

高产稳产高效益是蛋鸡饲养的最终目的，而实现这些目标必须为蛋鸡创造良好的生态环境条件，且必须采取一系列维持蛋鸡生态平衡的措施。本文结合动物环境科学的理论与实践，提出了一些看法。     

Recent changes in the climatic yield potential of various crops in Europe

Recent changes in the simulated potential crop yield and biomass production caused by changes in the temperature and global radiation patterns are examined, using the Crop Growth Monitoring System. The investigated crops are winter wheat, spring barley, maize, winter rapeseed, potato, sugar beet, pulses and sunflower. The period considered is 1976-2005. The research was executed at NUTS2 level. Maize and sugar beet were the crops least affected by changing temperature and global radiation patterns. For the other crops the simulated potential yield remained stable in the majority of regions, while decreasing trends in simulated potential yields prevailed in the remaining regions. The changes appear in a geographical pattern. In Italy and southern central Europe, temperature and radiation change effects are more severe than elsewhere, in these areas potential crop yields of more than three crops significantly decreased. In the UK and some regions in northern Europe the yield potential of various crops increased.In a next step the national yield statistics were analyzed. For a large majority of the countries the yield increases of wheat, barley and to a lesser extent rapeseed are leveling off. Several explanations could be given, however, as the simulated yield potential for these crops decreased in various regions, the changing temperature and radiation patterns may also contribute to the diminishing yield increases or to the stagnation. In more than 50% of the investigated countries the maize, potato and sugar beet yields continue to increase. This can be attributed to improving production techniques, new crop varieties, sometimes in combination with an improving climatic potential. In some regions in northern Europe, yields continue to increase.     

Selenium in agriculture: a nutrient or contaminant for crops?

Selenium (Se) is an essential nutrient for animals, humans, and microorganisms, but its role in the plants needs further exploration. It is considered beneficial at low levels, but is toxic at higher levels, and there is a fine boundary between these concentrations. Generally, Se levels less than 1 mg kg^?1 have been found to be beneficial for the plants while higher levels cause toxicity in most of the agricultural crops. At low concentrations, Se can act as a plant growth regulator, antioxidant, anti-senescent, abiotic stress modulator, and defensive molecule against pathogens in plants. At higher concentrations, plants show various toxic symptoms, which include stunting of growth, chlorosis, withering, and drying of leaves, decreased protein synthesis premature and even death of the plant. The roles of selenium as enhancer and inhibitor of plant growth in various agricultural crops are discussed here with recent updates. Biofortification of some crops with Se using agronomic and genetic approaches is being explored to cultivate them in the regions having Se-deficiency in foods. Strategies of phytoremediation of Se in hyperaccumulators and transgenic plants overexpressing enzyme/proteins to increase Se tolerance are also described.     

稻田免耕大麦的高产机理及优化配套栽培技术

1987～1989采用播种量、有机肥和化肥氮、磷、钾用量的五因素五水平的二次回归通用旋转组合设计,通过除草剂效应,施肥技术与方法等的小区试验,并且设置了高产示范田。经电子计算机统计分析和选优,总结出亩产350kg左右的“中群体、壮个体、稳健生长”的免耕大麦优化高产配套技术方案,并建立了各麦区主要栽培措施的数学模型。     

水分对芒果叶片、产量及果实品质影响的研究进展

近年来由于环境变化加剧和水资源日益匮乏,干旱对世界范围内的作物生长带来了巨大的影响。综述近几年水分对芒果叶片、枝梢生理生化的影响及灌溉对芒果产量、单果重、可溶性固形物、可滴定酸等含量的影响。探讨水分对芒果生理及果实品质的研究,为以后芒果生产实践奠定一定基础。     

Future yield growth in field crops: what evidence exists?

Crop yields are an important determinant of C input into the soil and ultimately of soil organic carbon (SOC). Models to predict changes in SOC require crop yield and future yield growth information. In this review, yield trends for 11 major crops in the US for the period 1939–1994 are analyzed. Historical data are analyzed to detect evidence of a yield plateau. Yields are extrapolated to the year 2020 based on linear and exponential yield trends estimated in the paper. Forward-looking information on yield gaps, on the biological potential for future yield growth, and socio-economic determinants of yield growth is examined for evidence that yield growth may plateau in the near future. A linear model of yield growth indicates a compound annual rate of growth of between 0.7% and 1.3% per year for major US crops through 2020. Under an exponential model, growth rates could range up to 3% per year. This could lead to substantial increases in SOC if crop residues are retained. Biophysical limits, including those imposed by agronomic and tillage practices, do not appear to prevent rates of growth consistent with the linear model. How socioeconomic forces will affect future growth are subject to greater uncertainty.