为探讨不同微生物菌群对华北地区中度石油污染土壤的修复效果,在实验室模拟条件下分别进行优势外源石油降解菌群的筛选和优势菌群与植物联合修复试验.结果显示:4种外源石油降解菌群中,PDC-3菌群对中度石油污染土壤总石油烃(TPH,total petroleum hydrocarbons)去除率为84.07％,在各菌群中效果最优;该优势菌群与植物联合修复中度石油污染土壤比单独使用优势菌群修复可获得更好的效果,优势菌群与黑麦草联用及优势菌群与紫花苜蓿联用120 d TPH的去除率分别为91.58％和89.30％,修复后土壤中TPH含量均小于500 mg/kg;同时优势菌群与黑麦草联合修复在90 d即可去除89.32％的土壤TPH,相比选用紫花苜蓿可有效缩短修复周期;优势菌群对土壤TPH的去除起主要作用,其贡献率远高于土著微生物菌群或植物的贡献率;植物对土壤TPH去除的贡献率为4.09％～6.48％,且其作用主要发生在修复过程的中后期;优势菌群单独使用或与植物联合修复中度石油污染土壤120 d均可有效去除C10～C12及C22～C40石油烃组分,去除率为85.14％～100.00％;然而,C13～C21石油烃组分含量表现出阶段性的积累效应;除对土壤石油烃的去除作用外,使用优势菌群进行生物修复存在一定的调节土壤pH、增加土壤肥力,且有利于恢复修复后的土壤功能.
【Objectives】Zinc deficiency is very often happened in maize in saline fluvo- aquic soils in Hexi Oasis Area of Gansu Province,the high soil magnesium levels have been regarded as a major contributor to thisdeficiency. The inhibition effect of magnesium to zinc in saline fluvo- aquic soils in Hexi Oasis Area were discussed in this paper. 【Methods 】 A pot experiment was conducted with maize as materials. Exchangeable magnesium contents of 287. 3,349. 2,411. 6,487. 9 and 755. 2 mg / kg were obtained by irrigating different amount of Mg SO4 solution. The maize plants were harvested at 46 days,the biomass of above and under ground parts were dried and weighed,the Zn contents were measured. The second leaf under the interior leaf was used for the determination of active oxygen and some enzyme activities. 【Results 】1) More high and extremely high exchangeable Mg level in soil inhibits the growth of maize seedlings. When magnesia applied levels is 221 mg / kg,i. e. the exchangeable Mg content in soil is over 487. 9 mg / kg,the growth of maize is stressed,when the Mg2 +applied level is 515 mg / kg,i. e. the exchangeable Mg content in soil is over 755. 2 mg / kg,the plant height is markedly decreased by 14. 5%,showing symptoms of magnesia poison and zinc deficiency,such as withered leaf margins and partial white stripes on the leaves( P 0. 01). 2) With the increase of or exchangeable Mg levels,the dry weight in the of Mg2 +addition maize are reduced by 11. 9%- 38. 3% and 4. 6%- 11. 9% respectively. The reduction in stem weight is significantly higher than in roots. 3) Maize leaf chlorophyll contents are reduced by 9.4%-45. 9% with the increase of the Mg2 +addition. The Mg level of 515 mg / kg would lead to withered and yellow leaves. The blade superoxide dismutase( SOD),peroxidase( POD) and catalase( CAT) activities are increased at first and then reduced quickly,the peak value appears at the exchangeable Mg levels of 147,74 and 147 mg / kg respectively. When the dose reaches 515 mg / kg,the values are reduced by 49. 75%,48. 06% and 32. 21%respectively. The malondialdehyde( MDA) contents are increased consistently in the range of 20. 39%-183. 58%.4) The exchangeable Mg levels significantly inhibit the uptake of Zn. Compared with the CK,the zinc contents in above ground parts are reduced by 4. 05%- 57. 09%,the uptake reduced by 15. 41%- 73. 55%; the root zinc contents are reduced by 7. 55%-18. 99%,and the uptake reduced by 11. 62%- 37. 40%. The zinc content and absorption in stems / leaves are reduced more than in roots. High exchangeable Mg level would also lead to lower upward transfer of zinc. 5) Soil available zinc contents are significantly reduced with the increase of exchangeable Mg levels. When the Mg level reaches 515 mg / kg,i. e. the exchangeable Mg content in soil is over 755. 2 mg / kg,the available zinc content falls to 0. 47 mg / kg,which is below the critical value of zinc deficiency( DTPA- Zn 0.5 mg / kg).【Conclusions】Zinc deficiency of maize in saline fluvo- aquic soil in Hexi Oasis Area is closely related to soil magnesium content. The high levels of exchangeable Mg contents show significant restraining effects on the maize seedling growth and biomass,the leaf chlorophyll content and the activities of superoxide dismutase( SOD),peroxidase( POD) and catalase( CAT). Over high exchangeable Mg levels decrease the zinc absorption by maize seedlings,and the inhibition in stem / leaf is significantly higher than in root system,which inhibites the upward transfer of Zn from root to shoot. The available zinc content in soil will also be reduced,when the Mg level reaches515 mg / kg,the available zinc content is below the critical value of zinc deficiency.
叶绿素是作物进行光合作用合成有机物的主要色素,实时监测烤烟叶片叶绿素含量对跟踪烟株氮素营养状况和判别烟叶成熟度具有重要的指导作用.基于对烤烟叶片光谱特征的分析,以不同供氮水平下实测的烟叶高光谱数据及叶绿素相对含量(SPAD)为数据源,采用一阶导数(1st Der)、多元散射校正(MSC)、标准正态变量(SNV)和SG平滑(SG)对原始光谱数据进行预处理,先采用连续投影法(SPA)挑选出每个预处理条件下的特征波长,后将各特征波段下的光谱反射率作为模型的输入变量,利用反向传播神经网络(BPNN)、随机森林(RF)和支持向量机(SVM)3 种机器学习的方法分别构建烤烟叶片叶绿素含量估测模型.使用决定系数(R2)、均方根误差(RMSE)和平均绝对值误差(MAE)对每个机器学习模型的性能进行了评估和比较.结果表明:3 种机器学习方法训练出的模型相比较,RF模型的预测准确率最高;烤烟叶片原始光谱经MSC和SNV预处理后的光谱信息作为输入变量,经RF算法建模具有较高的精度和良好的预测能力,模型为MSC-SPA-RF(R2=0.96,RMSE=1.15,MAE=0.94)和SNV-SPA-RF(R2=0.96,RMSE=1.14,MAE=0.94).说明基于机器学习利用高光谱数据估算烤烟叶片叶绿素含量具有可行性,这为实时、精确地监控烤烟生长过程中叶片叶绿素含量变化状况以及合理科学的进行田间管理提供了一定的理论基础.
定量分析我国不同条件下紫云英配施化肥对水稻产量的影响,为紫云英配施化肥模式在稻田的推广应用提供科学依据.以单施化肥为对照,通过搜集整理已发表的田间试验数据,运用整合分析(Meta-analysis)的方法,明确紫云英配施化肥对水稻产量的综合效应,量化分析了水稻种植模式、化肥配施比例、紫云英翻压量、施肥量、土壤理化性状对紫云英配施化肥增产效应的影响.结果表明:与单施化肥相比,紫云英配施化肥显著提高了水稻产量,增产率为4.47％(95％CI,3.16％～5.77％),其中单季稻增产率为4.89％(95％CI,3.01％～6.76％),双季稻增产率为4.06％(95％CI,2.26％～5.87％).水稻增产率随化肥配施比例的增加呈逐渐上升趋势,当化肥配施比例≤0.4时,水稻减产4.58％(95％CI,-2.26％～-5.87％).水稻增产率随紫云英翻压量增加呈先上升后下降趋势,以紫云英翻压量为22500～37500 kg/hm2 时,增产率较高.稻田施氮量>180 kg/hm2、施磷量30～60 kg/hm2、施钾量60～120 kg/hm2 时,紫云英配施化肥的水稻增产率较高;土壤有机质含量<20 g/kg,土壤全氮含量<1.5 g/kg,土壤有效磷含量为10～20 mg/kg,土壤速效钾含量<50 mg/kg,土壤pH 6.5～7.5时,紫云英配施化肥的水稻增产率较高.综上所述,与单施化肥相比,紫云英配施化肥可显著提高水稻产量,且在土壤有机质、全氮含量较低,土壤pH偏中性条件下增产效果较好.紫云英配施化肥条件下,化肥减施20％～40％,紫云英翻压22500～37500 kg/hm2 仍能保证水稻增产.
紫色土分布区域降雨集中、土壤养分淋失严重,导致土壤肥力下降、根区养分供应不足、根系发育不良等问题,提升土壤养分的供应强度有利于优化根系空间分布格局和促进根系生长.将原料肥和有机物料混匀后,利用1400 kg/cm2 的强大压力将其压制成砖肥(BF),同时,设置原料肥和有机物料物理混合(CK)为对照.于关键生育期测定垄向截面不同土层深度和离烟株不同远近距离的格点位置的土壤电导率(EC)、不同直径的根系组成和根系生物量,采用Logistic模型、指数模型拟合根系空间分布关键参数和生物量累积关键参数,研究砖肥对烤烟根区电导率及根系生长的影响.结果表明:在烤烟根系主要分布区,即主根系半径12.5 cm处,深度2.5～12.5 cm的土壤剖面,BF处理的EC比CK高90.5～281.6 μS/cm;主根系半径17.5 cm处,深度2.5～17.5 cm的土壤剖面,BF的EC比CK高160.1～392.2 μS/cm.在主根系15～20 cm水平半径内,BF的根系重量比CK提高150％;分布在10～15 cm深度土层的根系重量提高了26.5％,并且土壤剖面10～20 cm之间的侧根伸展性更强、分布更广.移栽后75、90和105 d,BF的田间根系生物量分别比CK提高12.7、11.9和9.7 g/株,烟叶生物量分别比CK高24.5、13.6和17.1 g/株,根系和烟叶生物量最大累积速率分别比CK提高了43.5％和15.7％.对于淋失严重的土壤,施用砖肥可以提高养分供应强度、优化根系分布格局和促进烤烟生长发育.
