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51.
研究了田间原位条件下,棉田滴灌不同施氮量下氮肥在土壤中的空间分布与作物吸收后残留规律。结果表明硝酸盐在水平方向和垂直方向具有明显的空间变异。同一氮肥用量下,以滴头为中心,硝酸盐在水平方向分布顺序为0 cm<10 cm<20 cm<40 cm<30 cm,在水平方向上硝酸盐随水移动且可以扩散到离湿润锋后部,垂直方向硝酸盐变化顺序为0-20 cm>20-40 cm>40-60 cm,为浅层累积型。无论水平方向还是垂直方向,氮肥用量对硝酸盐分布均有显著性影响。收获后,残留硝酸盐分布在点源水平距离5-40 cm,垂直距离0-60 cm土体内,残留硝酸盐累积量随氮肥用量的增加而增加。这些结果说明土壤硝酸盐存在明显空间变异,施肥显著增加了其浓度和残留量,同时可能会淋洗出根层,造成养分利用率下降和环境污染。因此,适宜的氮肥用量是控制硝酸盐向深层移动和累积的主要措施。 相似文献
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53.
[目的]研究微胚乳超高油玉米籽粒胚乳消减和油分积累规律。[方法]以高油玉米115为对照,研究2种微胚乳超高油玉米籽粒的胚、胚乳、种皮及相应油分的积累规律。[结果]微胚乳超高油玉米在籽粒发育过程中胚乳干重在发育的第27 d达最大,第37 d消减基本结束;胚的重量一直增加,种子成熟时和胚乳的重量相当;整粒干重第32 d达最大。3个玉米品种授粉后的种皮干重一直增加,第32 d基本稳定,整粒油分37 d前一直增加,之后趋于稳定。微胚乳超高油玉米胚乳的油分在17~27 d增加较慢,27~37 d增加迅速,37 d到成熟期下降,比高油115的高很多;胚的油分在17~27 d增加,27 d到成熟期略下降。高油玉米115胚和胚乳的重量一直增加,胚乳的油分一直很低,胚的油分在17~27 d增加。[结论]该研究为微胚乳超高油玉米的籽粒胚乳消减机理研究提供了参考。 相似文献
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55.
本文研究了晋中盆地麦收后直播特早熟夏玉米单交种冀承单 3号 ,在不同时期追施氮肥处理的干物质积累与分配动态。结果表明 :不同时期追肥处理不影响特早熟夏玉米茎、叶、叶鞘、雌穗及地上部干物质积累的动态趋势 ,但对特早熟夏玉米干物质积累与分配的效应则表现出一定差异 ,到成熟期 ,大喇叭口期追肥处理地上部及雌穗干物质积累较拔节期追肥处理高 4 12g/株及 0 97g/株 ,且前者经济系数为 0 42 ,后者则为 0 4,表明大喇叭口期追施氮肥不仅有利于后期干物质积累且有利于干物质向子粒的转移 相似文献
56.
Adequate K, Mg and Ca supply is important to develop well-structured and functional cell walls and membranes in fruit, and insufficient levels or imbalances of these minerals are known to be involved in various postharvest disorders. Microclimatic variation exists in the ‘Nules Clementine’ mandarin tree canopy and results in lower photosynthetically active radiation (PAR) levels and temperature as well as a higher humidity inside the tree canopy. The aim of this experiment was to determine the impact of this variation in microclimate on accumulation patterns of K, Ca and Mg in the flavedo of the fruit rind during stages II and III of fruit development. Fruit mass, dimensions, rind colour development and mineral composition of the flavedo were measured to describe the condition of fruit borne on the outside and inside of the tree's canopy. The data revealed that canopy position influenced mineral nutrient accumulation patterns in the flavedo. Outside fruit flavedo accumulated significantly higher concentrations of Ca and Mg in all three seasons (2005–2007). In contrast, inside fruit flavedo (shaded fruit) accumulated significantly higher levels of K compared with outside fruit flavedo. The accumulation of K and Ca differed from that of kiwifruit and apple in that Ca concentration increased and K decreased towards maturity. These results suggest that xylem, as in citrus leaves, is the main vasculature supply conduit to the citrus fruit flavedo for mineral nutrients. The reduction of transpiration potential by lower temperatures and higher humidity inside the canopy could be responsible for the reduced accumulation of Ca and Mg. The high K concentration of inside fruit flavedo is suggested to be a stress response, due to the low light levels, to maintain osmotic potential in the shaded rind tissue, and this imbalance could possibly lead to a reduction in rind condition, which manifests through rind breakdown symptom development. 相似文献
57.
58.
用δ~(13)C法研究黑土添加有机物料后有机碳的变化规律 总被引：1，自引：0，他引：1
通过室内短期培养实验,利用δ13C的方法研究了外源有机物料分解过程中黑土有机碳的变化规律。结果表明:黑土中添加有机物料后,土壤有机碳的数量明显增加。在有机物料分解过程中,随着培养时间的延长,土壤有机碳的总量在逐渐下降,总的变化趋势是先快后慢,渐趋平缓,到培养结束(30天),有机物料在土壤中净残留率小于50%。黑土有机碳的δ13C值受进入土壤中有机物料的种类所影响,从数量上土壤有机碳的δ13C值可以反映土壤中不同来源有机碳的变化。在小麦秸秆分解过程中,新进入黑土中的有机碳转化较快,而土壤中固有的有机碳转化较慢,添加有机物料可以增加土壤中有机碳的固定。 相似文献
59.
人工模拟大气CO2 浓度倍增和土壤干旱对植物体内S含量积累及分配的影响研究结果表明 ,高CO2 浓度和土壤干旱均使冬小麦不同部位含S量增加 ,而使大豆籽粒中S含量减少 ;干旱虽使小麦籽粒S含量增加 ,但却使小麦籽粒减产幅度大于S含量增幅。干旱对大豆的影响大于小麦 ,干旱减少大豆S含量 ,且降低大豆产量。高CO2 浓度和土壤干旱对毛乌素 3种牧草优势种茎和叶S含量的影响较复杂 ,但干旱使茎和叶生物量降幅远大于S含量变化。高CO2 浓度和土壤干旱使植物固定S总量下降 ,表现为负效应。 相似文献
60.
Background River and lake sediments constitute complex and difficult analytical samples. On the other hand, sediments play a fundamental
role in the distribution of toxic compounds in aquatic systems and in the evaluation of the current state and the course of
changes taking place in the environment.
Among elements present in the environment in trace concentrations, but having well-elaborated toxic properties, one of most
dangerous is arsenic. The element occurs in the environment in several chemical forms, predominant are inorganic forms of
As(V) and As(III), and methylated forms such as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA).
Objectives Reported herein are experiments, which were undertaken with the aim of examining the dynamics of arsenic sorption in sediments
and its dependence on speciation of the element and the pH in the environment. Simultaneously, influence of organic matter
content and chemical composition of the sediments on As sorption, were investigated.
Methods Sediment samples (upper 10 cm layer) were collected from three sites located in the vicinity of Cracow:
Using XRD and IR methods, mineral composition of sediments was analysed. Concentrations of iron, manganese, aluminium and
arsenic as well as organic matter content in solid samples were analysed.
Sorption experiment 100 g of dry sediment sample was placed in a 400 ml volume glass beaker. 300 ml of arsenic containing solution was poured
into the beaker. Every 30 min (total experiment time span equalled 7 to 7.5 hours), 0.5 ml of the suspension’ (the beaker
content was constantly mixed) was collected and centrifuged, and the concentration of arsenic was determined in the supernatant.
In the series of experiments, solution contained about 0.05 μg/ml of arsenic in organic (DMAA) and inorganic forms, at different
pH values — 3, 5, 7 and 9.
Results and Discussion Examined sediments of Vistula river and Dobczyce Lake were characterised by relatively high concentrations of arsenic, iron,
manganese and aluminium.Rudawa river. At pH 3, the concentration of inorganic As in solution decreased from an initial value of 0.049 μg/ml to 0.012 μg/ml in
7.5 hours time. The same decreasing tendency was found at pH 5 (initial value 0.046 μg/ml, after 7.5 hours - 0.015 μg/ml).
Less distinct sorption effects were noted at pH 7 and 9.
Vistula river. At all pH values, a very significant decrease of inorganic As concentration up to 80% of the initial value, as well as a
short time of achieving an equilibrium state (1 – 2.5 hours), was found.
Dobczyce lake. Inorganic As was distinctly accumulated in sediments at pH 3 (decrease of As concentration in solution from 0.052 to 0.007
μg/ml after 7.5 hours of the experiment) and at pH 5. At pH 7, about 40% of As was accumulated in sediments (solution As concentration
decrease from 0.050 to 0.030). Only 20% of As adsorbed on sediments at pH 9.Very weak accumulation of organic form of As (DMAA)
was found in all examined sediments at pH 3 and 5. At higher pH values no sorption was registered.
Conclusions The following facts were established:
Recommendations The presented method of analysis of As sorption in sediments and results visualization (based on a newly defined coefficient)
provides a useful tool for the characterization of sorptive properties of sediments and may be used for other compounds as
well. Crucial, functional information — how much of a given element may be accumulated in sediments at a certain pH — is obtained
without digestion of the sediment sample, in an experiment taking less than one day. 相似文献
| • | Rudawa river — 37 km long river, flowing mainly through the suburban area; |
| • | Vistula river — heavily contaminated, main Polish river; |
| • | Dobczyce reservoir — artificial reservoir on Raba river, total capacity of 125,000,000 m3, supplying about 60% of drinking water to the city of Cracow. |
| • | inorganic form of arsenic was effectively accumulated in all analysed sediments; |
| • | inorganic As sorption in sediments strongly depended on pH — for sediments of Rudawa river and Dobczyce lake, the highest sorption was found at pH 3, and a decrease of accumulated As was noted with an increase of pH (at pH 9, the lowest amount of As was immobilised in sediments); in the case of Vistula river sediments, a reverse tendency was found; |
| • | organic form of arsenic (DMAA) was accumulated only at pH 3 in all sediments and less significantly at pH 5 (Vistula river sediments); no sorption of that form of As was found in the other sediment samples; |
| • | state of equilibrium (no change in inorganic As concentration in liquid medium) was achieved in 1 hour for Vistula river sediments, after about 2 hours for Rudawa river and after about 4 hours for Dobczyce lake sediments. |