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71.
锌对增强玉米耐涝抗渍的作用及其机理初探 总被引:2,自引:0,他引:2
在缺锌的砂姜黑土上研究锌对玉米增产效应的田间试验中发现,在严重渍涝高温时,锌有显著的增强玉米耐涝抗渍的作用。其机理与锌能明显降低植株体内氮磷含量,提高钾素含量,从而增强玉米的抗渍涝与高温的能力有关。统计结果表明,玉米秸杆中氮磷含量占整株氮磷含量的百分数与死亡率呈显著的正相关,而秸杆中的含钾量与死亡率呈一定的负相关。 相似文献
72.
George A. Griffiths 《Journal of the American Water Resources Association》1982,18(4):575-584
ABSTRACT: Specific annual suspended sediment yields and their standard deviations are presented for 47 basins of North Island, New Zealand. Most of the variance in yields is explained by catchment mean rainfall. Rivers with similar flow range have similar suspended sediment concentration ratings, independent of differing watershed lithology and regolith, except for six basins having an abundance of soft fine sediments. Prediction equations for yield and its standard deviation are derived for four essentially arbitrary regions. AU feature rainfall as the independent variable. Differences between regions may owe to variations in intensity, frequency, and duration patterns of storms and, in one area, to bed material size as well. The temporal distribution of annual yields from a basin m be modeled by a two-parameter lognormal function: the prediction equations above may be used to evaluate this function at a site for which suspended sediment data are unavailable. 相似文献
73.
74.
蔬菜施不同肥料对产量和土壤肥力的贡献 总被引:8,自引:2,他引:8
为控制施肥对蔬菜和土壤的负面影响,充分利用施肥对土壤肥力的保护功能,探讨蔬菜合理的有机肥施用量,在不同质地土壤上,田间试验小白菜、苦瓜、豇豆三种蔬菜施不同量有机肥,收获时测定其产量、品质及试验前后的土壤有机质质量分数。结果表明,(1)在施适量无机NPK的条件下,每造蔬菜的有机肥(禽畜粪便,下同)施用量,砂土上小白菜为4500kg/hm^2、苦瓜和豇豆为3000kg/hm^2;在壤土上,小白菜和苦瓜均宜施3000kg/hm^2,豇豆则宜施4500kg/hm^2;在粘土上,小白菜每造只宜施1500~3000kg/hm^2的有机肥。(2)有机肥必须与无机肥合理配合施用,才能获得最佳的产量和品质效果。(3)施有机肥3000-4500kg/hm^2 适量无机肥可使土壤有机质水平保持在种植蔬菜前的质量分数水平,该施肥量和方式不仅可使蔬菜高产、优质,还有利于保护土壤肥力。(4)对蔬菜产量的贡献,有机肥和化肥配合施用的处理对蔬菜产量的贡献最大,来自土壤的效应由小到大依次为有机肥和化肥配合施用→化肥→有机肥,进一步反映合理施肥有利于保护土壤肥力。 相似文献
75.
76.
浙江天台山茶树光合日变化及光响应 总被引:18,自引:1,他引:18
自然条件下使用LCA-4型便携式光合测定系统研究了栽培天天台山主峰华顶山的茶树连体叶片的光合日变化及光响应。结果表明:在初夏晴天,上年越冬叶片(下称二年生叶)的光合速率,表观量子效率,羧化效率和饱和光强比展叶红16d的一年生叶高,CO2补偿点和光补偿点比一年生叶低,两者的净光合速率日进程曲线均为“双峰”型,午间胞间CO2浓度上升表明,此时净光合速率下降主要受非气孔限制因素的影响。一年生叶蒸腾速率高于二年生叶,它们日进程曲线为单峰河,午间最高,而气孔阻力进间最低。不同时段作光响应和CO2响应试验表明,上午茶树的表观量子效率,饱和光强和羧化效率较高,光补偿点和CO2补偿点较低。图3表4参26 相似文献
77.
78.
We present a strategy for using an empirical forest growth model to reduce uncertainty in predictions made with a physiological process-based forest ecosystem model. The uncertainty reduction is carried out via Bayesian melding, in which information from prior knowledge and a deterministic computer model is conditioned on a likelihood function. We used predictions from an empirical forest growth model G-HAT in place of field observations of aboveground net primary productivity (ANPP) in a deciduous temperate forest ecosystem. Using Bayesian melding, priors for the inputs of the process-based forest ecosystem PnET-II were propagated through the model, and likelihoods for the PnET-II output ANPP were calculated using the G-HAT predictions. Posterior distributions for ANPP and many PnET-II inputs obtained using the G-HAT predictions largely matched posteriors obtained using field data. Since empirical growth models are often more readily available than extensive field data sets, the method represents a potential gain in efficiency for reducing the uncertainty of process-based model predictions when reliable empirical models are available but high-quality data are not. 相似文献
79.
Peggy?Gunkel Estelle?Roth Bernard?FabreEmail author 《Environmental Chemistry Letters》2003,1(1):92-97
Agricultural practices can lead to copper accumulation in soils and at high concentration it can become toxic for plants.
One common toxic effect of copper on plants is a decrease of crop yield. Here, we studied 1) the crop yield of maize grown
on plots of a soil intentionally enriched with copper sulphate and 2) the possible relationship between the copper concentration
in chemical soil fractions and the maize crop yield. Anthropogenic copper is mainly bound to manganese oxides, to iron oxides
and to the organic matter. Maize (Zea maize L.) was grown on outdoor experimental plots. The crop yield was evaluated for three development stages: the 6–10 leaf stage,
the female flowering stage and the maturity stage, 2, 4 and 6 years after the soil copper enrichment. Strong crop yield reductions,
proving a toxic effect of copper on maize growth were noted 2 years after the copper input at the maturity stage and 4 years
after the copper input at the 6–10 leaf stage. Variations in maize crop yield are described with linear multiple regression
equations including the variable copper content in soil, and other variables when needed such as soil pH, soil organic carbon
level and the climatic variables, the precipitation rate and the ambient temperature. The crop yield study at the 6–10 leaf
stage and at the female flowering stage does not provide significant regression equations, while the crop yield study at the
maturity stage does. Request variables for the models are the total copper content or the copper bound to the organic matter
and the meteorological data.
Electronic Publication 相似文献
80.
还田秸秆配施外源纤维素酶效应研究 总被引:3,自引:1,他引:3
为探求促进秸秆降解的新途径,采用室内培养法研究了外源纤维素酶对秸秆降解速率及土壤速效养分的影响。结果表明,整个培养期内,小麦秸秆,玉米秸秆加酶处理与不加酶处理降解率都存在极显著差异(p<0.01),到培养结束时小麦秸秆加酶处理降解率高出不加酶处理7.10%~11.86%,玉米秸秆高出8.01%~14.04%;整个培养期内,小麦秸秆,玉米秸秆加酶处理与不加酶处理间土壤速效氮、磷、钾含量都存在极显著差异(p<0.01),培养结束时,小麦秸秆最优处理速效氮、磷、钾含量高出对照4.15mg·kg-1,3.60mg·kg-1,32.35mg·kg-1,玉米秸秆高出6.50mg·kg-1,4.27mg·kg-1,47.97mg·kg-1。结果说明添加外源纤维素酶能够提高秸秆降解速率,促进秸秆养分矿化。 相似文献