地膜覆盖对制种田玉米花期调节的研究

选用 6个玉米自交系 ,1998年先进行模拟盖膜试验 ,得出其回归关系 ^y =8- 0 8x。1999年根据模拟试验结果再进行制种田盖膜试验 ,结果表明 ,父母本抽雄抽丝期相差在 10d之内 ,可将父母本同期播种 ,选择正确的时间地膜覆盖晚熟亲本 ,可以起到调节花期的作用 ,从而保证制种产量的稳产高产 ,减弱外界环境的干扰。     

沟川地玉米氮磷有机肥适宜用量及施氮时期的研究

通过对沟川地玉米氮、磷、有机肥用量的定量研究,建立了中等以上肥力沟川地玉米产量形成的施肥数学模型及最佳施肥组合方案,并确定了沟川地玉米氮、磷、有机肥作用效应顺序：氮肥＞磷肥＞有机肥。氮肥使用时间上以“一底一追”,施足底肥,重施拔节肥效果最好。实施最佳施肥方案,公顷产量达１０４３１０ｋｇ,比习惯施肥增产３７８％。     

Antioxidant activity of phenolic compounds obtained by autohydrolysis of corn residues

This study aimed to evaluate the effect of autohydrolysis temperature of corn residues in the antioxidant activity of the phenolic compounds extracted from the liquid phase. The treatments were carried out at 160, 180, 190 and 200 °C for 30 min in a pressurized batch reactor. Two different methods for phenolic compounds extraction from the autohydrolysis liquors were investigated. For that purpose, solvent extraction with ethyl acetate and acidic precipitation were performed for phenolic compounds recovery. These methods have been compared in terms of extraction yield, physicochemical properties of obtained polyphenols (characterization by Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis and Gel Permeation Chromatography), total phenolic content, total antioxidant capacity and Trolox equivalent antioxidant capacity (TEAC) values, measured in DPPH (2,2-diphenyl-1-picrylhydrazyl) test system. The maximum phenolic contents ranged from 6.04 mg GAE/100 mg extract in acidic precipitated samples to 16.45 mg GAE/100 mg extract in ethyl acetate soluble fractions. The results indicated that the ethyl acetate fractions possessed the highest antioxidant activity, reaching after 30-60 min the same capacity reported for the reference synthetic antioxidants (Trolox).     

超声波/稀H_2SO_4预处理对玉米秸秆液体发酵产纤维素酶的影响

[目的]研究超声波强化稀H2SO4预处理对玉米秸秆液体发酵产纤维素酶的影响,探索超声波强化稀H2SO4预处理玉米的最优条件。[方法]利用正交试验法研究超声波强化稀H2SO4预处理玉米秸秆,并以预处理后的秸秆为唯一碳源进行发酵,测定胞外发酵液的纤维素酶活性。[结果]当酸浴时间3h、酸浓度3．5％、超声功率150w、超声时间5h时,胞外发酵液中的纤维素酶活性最高,分别为FPA15．82 U／ml、Cx39．9U／ml、β—Glu55．94U／ml。[结论]在该组合条件下,胞外产纤维素酶具有较高的稳定性。     

玉米茎秆多糖提取工艺优化

[目的]研究玉米茎秆多糖提取的最优条件,为玉米茎秆资源的深入开发利用提供试验依据。[方法]通过单因素和正交试验,以多糖得率为指标确定玉米茎秆多糖热水浸提的最优条件。[结果]确定提取时间、温度、料水比在玉米茎秆多糖提取中影响因素的大小顺序为:提取时间温度料水比。玉米茎秆多糖提取最佳工艺参数组合为:温度80℃,提取时间3 h,料水比1∶30 g/ml。[结论]热水浸提法提取玉米茎秆多糖效果较好,以蒽酮-硫酸法测定多糖提取率方法可行,结果稳定。     

Reducing atrazine leaching by integrating reduced herbicide use with mechanical weeding in corn (Zea mays)

Concern about the effects of pesticides on the environment and the desire to reduce purchased inputs are stimuli to reduce herbicide use. Field research was conducted for three growing seasons to compare the chemical contamination and effectiveness of three weed management practices. Weed control treatments included application of a herbicide mixture of 1.5 kg ai ha⁻¹ of atrazine plus 0.9 kg ai ha⁻¹ of pyridate, this mixture being broadcast alone or band-applied in combination with mechanical weeding, and mechanical weeding alone. The results show that it is possible to decrease the amount of atrazine residue in soil with the band-applied treatment. Such a method is very attractive because crop yields were not decreased, at least in the short run. However, we do not yet know the long-term efficiency of this method regarding groundwater quality, weed population dynamic and crop yield. Further work is therefore needed to assess the long-term impact of this weeding method.     

玉米黄色素的提取工艺研究

[目的]确定提取玉米黄色素的优化工艺,得到最基础的提取数据。[方法]通过考察提取温度、料液比和提取时间对玉米黄色素提取的影响研究玉米黄色素的提取方法。[结果]色素吸光度随着温度的升高而升高,但温度越高,溶剂的挥发性越大,故以55℃以下温度为浸提温度较适宜。料液比为1∶18时,吸光度最大。吸光度随着浸取时间的延长而升高,当浸取时间达4 h时,浸提液的吸光度升高缓慢,基本上趋于平稳。提取率的变化与吸光度的变化一致。[结论]溶剂法提取玉米黄色素的最佳工艺条件为:提取温度为55℃,料液比为1∶18,浸提时间为4 h。     

Winter cover cropping influence on nitrogen mineralization,presidedress soil nitrate test,and corn yields

The mineralization and availability of cover crop N to the succeeding crop are critical components in the management of soil N to reduce N leaching. The effects of several leguminous and non-leguminous cover crops on soil N availability, N mineralization potential, and corn (Zea mays L.) yield were examined. The cover crops had variable effects on soil N availability and corn yield and N uptake. Because of the rapid mineralization of the cover crops following incorporation, the inorganic N levels in the soil sampled in mid-May 1992 (4 weeks after incorporation of cover crops), rather than the potentially mineralizable N, rate constants, initial potential mineralization rate, or cumulative N mineralized over 14 weeks, correlated well with N concentrations, C:N ratios, or the N added in the cover crops. However, the inclusion of potentially mineralizable N with inorganic N in a multiple regression improved the variability in the corn yield and the N uptake accounted for. Since extensive mineralization had occurred before the 21 May sampling, the potentially mineralizable N was affected more by the soil organic N and C than by the N concentrations of the cover crops. The presidedress NO₃ ^--N test levels were well predicted by the inorganic and potentially mineralizable N (R ²=0.89, P<0.01), although the test levels were better in predicting corn yield and N uptake. If the available soil N test needs to be made earlier than recommended by the presidedress NO₃ ^--N test, both inorganic and potentially mineralizable N are needed to better predict the corn yield and N uptake in the soils.