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81.
《植物养料与土壤学杂志》2017,180(4):430-435
According to the German Soil Taxonomy, the formation of cemented horizons in Podzols is restricted to the precipitation of iron oxides. However, in iron‐poor sandy substrates, also illuviation of only organic compounds can form cemented horizons with penetration resistances of up to 14 kg cm−2. We present a reproducible field test for classifying pedogenic cementation in Podzols and suggest considering cemented horizons (Bmh and Bhm) in the upcoming edition of the Guidelines for Soil Mapping. 相似文献
82.
福克212是目前南安市主要种植的优质马铃薯新品种,2011年通过福建省农作物品种审定,具有丰产、熟期早、优质和抗病等特点。主要介绍了福克212在南安市种植表现,总结出其高产栽培技术,为冬种马铃薯生产提供参考。 相似文献
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康氏粉蚧每年在东宁县发生2代,其越冬卵孵化与5月份平均气温有相关性,平均温度越高卵孵化时期越早越集中,化学防治的关键时期是越冬卵孵化盛期,由于其体表被有蜡质,只有采取综合防治措施才能取得较好的防治效果. 相似文献
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87.
M. Hühn 《Journal of Agronomy and Crop Science》1998,181(4):249-255
A general approach to determine the effect of accuracy of sowing technique on yield per area
Caused by nonperfect seed placement accuracy of sowing machines as well as by many other abiotic and biotic factors the resulting plant stands exhibit nonregular plant distributions. Based on several simplifying assumptions a stochastic approach provides a quantitative determination of the effects of accuracy of sowing technique on yield per area. In this approach, two random variables are assigned to each individual plant: single plant yield E and single plant area A, which is calculated in this paper by the construction and quadrature of the so-called Thiessen-polygons. The yield per area F is calculated as the expectation of the ratio E/A. By assuming a deterministic mathematical relationship between E and A, the calculation of F reduces to the calculation of the expectation of a function of only one random variable A. A simple approximation with sufficient accuracy for many applications only depends on the mean and on the variance of the areas of the individual plants. For demonstration purposes, the theoretical approaches and results have been finally applied to three data sets for drilled seeds of winter oilseed rape (plant density: 60 plants/m2 and distance between rows: 10 cm). These data sets exhibit different accuracies of the longitudinal distributions within rows which have been quantitatively measured by the coefficient of variation for the distances between plants within rows: Yield depression increases with an increasing variability of plant distances within rows. 相似文献
Caused by nonperfect seed placement accuracy of sowing machines as well as by many other abiotic and biotic factors the resulting plant stands exhibit nonregular plant distributions. Based on several simplifying assumptions a stochastic approach provides a quantitative determination of the effects of accuracy of sowing technique on yield per area. In this approach, two random variables are assigned to each individual plant: single plant yield E and single plant area A, which is calculated in this paper by the construction and quadrature of the so-called Thiessen-polygons. The yield per area F is calculated as the expectation of the ratio E/A. By assuming a deterministic mathematical relationship between E and A, the calculation of F reduces to the calculation of the expectation of a function of only one random variable A. A simple approximation with sufficient accuracy for many applications only depends on the mean and on the variance of the areas of the individual plants. For demonstration purposes, the theoretical approaches and results have been finally applied to three data sets for drilled seeds of winter oilseed rape (plant density: 60 plants/m
88.
金光杏梅品种表现及优质高产栽培技术研究 总被引:1,自引:0,他引:1
金光杏梅是河南省新乡市农业局从杏与李的自然杂交后代中选出的优良变异类型,具有较高的栽培推广价值,1999年通过省级鉴定。介绍了金光杏梅的品种表现,从选择壮苗、高标准建园,分季、分批采用不同方法高接,加强土肥水管理,精细整形修剪,合理调整结果量,综合防治病虫害等方面提出了一套优质高产栽培技术规程。 相似文献
89.
详细阐述了听力训练在高职学生的英语学习中的重要作用以及高职学生在英语听力训练中存在的问题及采用的对策与方法。 相似文献
90.
多媒体数据库关键技术的探讨 总被引:1,自引:0,他引:1
随着多媒体技术和网络技术的飞速发展,以及多媒体信息的日益丰富,多媒体数据库技术已成为当前研究的热点.本文介绍了多媒体数据库的特点,探讨了多媒体数据库中的若干关键技术,并给出了一个多媒体数据库的简单实例. 相似文献