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Nitrate nitrogen losses through subsurface drainage and crop yield are determined by multiple climatic and management variables. The combined and interactive effects of these variables, however, are poorly understood. Our objective is to predict crop yield, nitrate concentration, drainage volume, and nitrate loss in subsurface drainage from a corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation as a function of rainfall amount, soybean yield for the year before the corn-soybean sequence being evaluated, N source, N rate, and timing of N application in northeastern Iowa, U.S.A. Ten years of data (1994-2003) from a long-term study near Nashua, Iowa were used to develop multivariate polynomial regression equations describing these variables. The regression equations described over 87, 85, 94, 76, and 95% of variation in soybean yield, corn yield, subsurface drainage, nitrate concentration, and nitrate loss in subsurface drainage, respectively. A two-year rotation under average soil, average climatic conditions, and 125 kg N/ha application was predicted to loose 29, 37, 36, and 30 kg N/ha in subsurface drainage for early-spring swine manure, fall-applied swine manure, early-spring UAN fertilizer, and late-spring split UAN fertilizer (urea ammonium nitrate), respectively. Predicted corn yields were 10.0 and 9.7 Mg/ha for the swine manure and UAN sources applied at 125 kg N/ha. Timing of application (i.e., fall or spring) did not significantly affect corn yield. These results confirm other research suggesting that manure application can result in less nitrate leaching than UAN (e.g., 29 vs. 36 kg N/ha), and that spring application reduces nitrate leaching compared to fall application (e.g., 29 vs. 37 kg N/ha). The regression equations improve our understanding of nitrate leaching; offer a simple method to quantify potential N losses from Midwestern corn-soybean rotations under the climate, soil, and management conditions of the Nashua field experiment; and are a step toward development of easy to use N management tools. 相似文献
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Twenty nine germplasm lines of Chenopodium quinoa and two of Chenopodium berlandieri subsp. nuttalliae were evaluated for 12 morphological and 7 quality traits for two test seasons. The 19 traits were analyzed for cluster and
principal component analysis. The first four PCs contributed 78.70 % of the variability among the germplasm lines. The first
PC accounted for 39.5% of the variation and had inflorescence/plant, plant height and stem diameter as the traits with largest
coefficients, all with positive sign. The characters with greatest positive weight on PC2 were days to maturity (0.309), inflorescence length (0.260) and branches/plant. All the germplasm lines were grouped into
six clusters based on average linkage method. Cluster III had high values for seed yield and most of the quality traits but
showed a small seed size. The dendrogram separated the two lines of C. berlandieri subsp. nuttalliae from the quinoa lines. 相似文献
35.
分析了现代农业推广的主要模式,对农业推广的主要方法进行了研究.在此基础上归纳总结了农业推广中技术与农民各自的特点. 相似文献
36.
The present research is focused on the application of hyperspectral images for the supervision of quality deterioration in ready to use leafy spinach during storage (Spinacia oleracea). Two sets of samples of packed leafy spinach were considered: (a) a first set of samples was stored at 20 °C (E-20) in order to accelerate the degradation process, and these samples were measured the day of reception in the laboratory and after 2 days of storage; (b) a second set of samples was kept at 10 °C (E-10), and the measurements were taken throughout storage, beginning the day of reception and repeating the acquisition of Images 3, 6 and 9 days later. Twenty leaves per test were analyzed. Hyperspectral images were acquired with a push-broom CCD camera equipped with a spectrograph VNIR (400–1000 nm). Calibration set of spectra was extracted from E-20 samples, containing three classes of degradation: class A (optimal quality), class B and class C (maximum deterioration). Reference average spectra were defined for each class. Three models, computed on the calibration set, with a decreasing degree of complexity were compared, according to their ability for segregating leaves at different quality stages (fresh, with incipient and non-visible symptoms of degradation, and degraded): spectral angle mapper distance (SAM), partial least squares discriminant analysis models (PLS-DA), and a non linear index (Leafy Vegetable Evolution, LEVE) combining five wavelengths were included among the previously selected by CovSel procedure. In sets E-10 and E-20, artificial images of the membership degree according to the distance of each pixel to the reference classes, were computed assigning each pixel to the closest reference class. The three methods were able to show the degradation of the leaves with storage time. 相似文献
37.
贵州烤烟常规化学成分与中性香气物质的相关分析 总被引:2,自引:0,他引:2
为了摸清贵州烟叶原料质量,提高其可用性,以贵州4个烤烟产区的33个烟叶样品为材料,采用多变量统计分析方法对其常规化学成分与中性香气物质含量的相关性进行分析。结果表明:贵州烤烟常规化学成分在不同地区间存在广泛的差异,但还原糖含量在地区间稳定性较好;常规化学成分和众多香气成分都存在密切相关,其相关系数达到极显著或显著水平;常规化学成分与中性香气物质之间的第Ⅰ典型相关系数(0.911**)达极显著水平,共得到6个与典型变量相关显著的性状,分别为烟碱、钾、美拉德反应产物、芳香族氨酸降解产物含量、糖碱比和氮碱比。 相似文献
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39.
云南施甸烟区植烟土壤肥力综合评价 总被引:1,自引:0,他引:1
利用模糊数学原理和多元统计方法对云南施甸县烤烟种植区的肥力状况进行了分析与综合评价,结果表明:土壤平均pH值较高,为7.13,宜植烟土壤占总数的56.86%;有机质平均含量为31.08 g/kg,宜植烟土壤占总数的71.57%;碱解氮、速效磷、速效钾、有效硼、有效锌、水溶性氯平均含量分别为107.23、21.56、251.81、0.46、1.79、16.65 mg/kg,交换性镁的平均含量为1.04 cmol/kg。全县土壤肥力综合指标值存在较大差异,变幅为0.302~0.831,平均为0.600,变异系数为19.00%,其中Ⅰ、Ⅱ、Ⅲ、Ⅳ级土壤分别占总数的22.55%、40.20%、28.43%、8.82%,水长、由旺、万兴烟区的Ⅰ、Ⅱ、Ⅲ级土壤比例合计均达100%,甸阳的最低,为80%。施甸县烤烟种植区的土壤肥力综合指标值较高,但不同地块的养分含量差异较大,应适量施用有机肥、微量元素肥料。 相似文献
40.
采用自行设计的调查问卷对浙江省20多家医疗卫生单位的科技人员对查新咨询信息的利用情况及其影响因素进行了调查,采用多因素非条件Logistic回归分析法分析了查新咨询信息利用的影响因素,提出了提高查新咨询信息利用水平的对策。 相似文献