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Zinc

Zinc is required by plants,亚博体育官网无法取款动物和人类。关于爱尔兰土壤锌含量的研究,最近才开始,in the past,看来作物缺锌不是问题。几年前,在泥炭地(Gallagher,1969年)但这发生在一个地方,在前一年曾为芹菜作物大量施肥磷。磷是植物营养中锌的拮抗剂,在世界上种植玉米等锌敏感作物的地区也是如此。this fact is well recognised.In the absence therefore of crop or animal disorders suggestive of zinc deficiency,the element received little attention.In 1984 however,reports on an unidentified disorder in cereals in Co.路德出现了,经过初步调查,zinc deficiency was identified as a possible causative factor.全面的实地试验证实了这一点(麦克·奈德)et al.,1986).

图1。Glaciation and Soil formation

爱尔兰土壤的锌状况
以上提到的谷物问题主要发生在山坡上相对多石的土壤上。and closer inspection of the area revealed that the soils coincided with morainic deposits associated with the Midlandian glaciation.These particular deposits form part of the (Kells) Re-advance Moraine (Fig.1)。认识到这一事实为寻找其他可能的低锌土壤区域提供了一种方向性的方法。

Examination (Mac Naeidheet al.,1987年),在全国范围内约500种土壤(0-10厘米深)中,发现了一些面积小且分散性较好的区域(图2)。最大的区域出现在Louth和North Meth。Some of the remaining areas are certainly associated with soils formed from glacial and fluvio-glaclal deposits and in this respect the comparison between Figs.1 and 2 is interesting.More intensive soil sampling will be necessary before the true extent of the association between low-Zn soils and fluvio-glacial deposits can be established.Such an investigation will inevitably be easier in those counties for which a soil survey has been completed.

Zinc availability in soils
石灰化降低了土壤中锌对植物的有效性。锌被土壤中的铁和锰矿物以及某些粘土矿物吸收。铁矿物的吸收强度随着pH值的升高而增加,这部分解释了其可用性的降低。

Under conditions of high soil moisture the availability of zinc is increased.通常充满空气的孔隙现在充满了水,导致缺氧。在这种还原条件下,锌结合矿物的稳定性变差。

潜在缺锌土壤的定义如下:

  1. 总锌含量低的酸浸沙土
  2. High-lime soils where Zn availability is decreased
  3. 泥炭土和一些被石灰岩覆盖的泥炭

爱尔兰土壤中锌的频率分布
根据对500个表土(0-10cm深)的分析,爱尔兰土壤中锌的频率分布如图10所示。二乙烯三胺五乙酸(DTPA)所用的萃取剂,是公认的。1 mg/kg及以下的值表示敏感作物缺乏。Approximately 15 percent of soils fall into the risk area.显然,更多的工作需要集中在耕种区,在那里谷物将成为轮作的一部分。

图2锌含量低的土壤图3 EDTA可提取锌的分布频率(mg/kg)

爱尔兰土壤中的锌

Zinc (Zn) is an essential element for plants,亚博体育官网无法取款动物和人类。It is a component of many enzymes and it functions as a specific activator in numerous biological reactions.

土壤中的锌

In igneous rocks zinc substitutes for both ferrous iron and for magnesium and therefore it occurs in greater quantities in the more basic rocks.典型分析如下:basalts 100 mg/kg,diorites and andesites (intermediate basicity) 70 mg/kg,and granites (acidic) 50 mg/kg.在沉积岩中,页岩比砂岩或石灰岩更丰富。90和20 mg/kg锌分别为典型含量。锌具有铜系性质,常被发现为硫化物闪锌矿(zns)。也可能以碳酸盐(znco)的形式出现。)例如.,in the mineral smithsonite.硫化物矿物中的锌比硅酸盐矿物中的锌更容易进入溶液中,并且在土壤形成过程中可能会被吸附到粘土上。铝的含水氧化物,铁和锰,and on to organic matter.Montmorillonite is capable of absorbing quite large amounts of zinc.

土壤中锌的浓度反映了特定土壤来源的母体成分。In world soils Zn concentrations range from 1.5 to 2000 mg/kg with a mean value of 59.8 mg/kg (Ure and Berrow,1982)。Zinc values for non-polluted Irish agricultural soils fall within the range 10-200 mg/kg,而EDTA可提取值一般在2-15 mg/kg范围内,平均值约为6.5 mg/kg。The distribution of EDTA extractable Zn values below 2.0 mg/kg in Irish soils are shown in Fig.3.此类数值必须被视为可疑值。在沙质土壤和粗纹理冰川沉积物中,锌含量本来就很低。Deficiency of Zn in susceptible crops can be anticipated on such soils.

影响锌有效性的几个因素
Zinc mainly occurs in soil on surfaces of clays,含水氧化物和有机物,而不是土壤溶液(护面et al.,1990) but is taken up by plants from soil solution.

pH

土壤锌对植物的有效性在高pH条件下比在酸性条件下要低,当土壤中存在游离碳酸钙时,锌尤其不可用。However,正如Williams(1977)所示,植物种类对土壤酸碱度的反应可能有所不同,他通过降低土壤酸碱度增加了红三叶草对锌的吸收,而不是在同一土壤上生长的燕麦对锌的吸收。

有机质

Lindsay (1972) concluded that soluble Zn-organic complexes resulting from reactions with organic acids,amino acids or fulvic acids could increase Zn availability and that insoluble Zn-organic complexes could increase Zn deficiency.

土壤微生物活性可以从相对不可用的来源释放锌,众所周知菌根植物比未受感染的植物能吸收更多的锌。

Phosphorus

The enhancement of Zn requirements by P has been produced in plants grown in sand and water culture experiments,P供应水平很高(帕克,1993).Lonergan and Webb (1993) stated that it is likely that "P enhanced Zn requirements" are an artefact of glasshouse trials and have little relevance in crop production.However,爱尔兰有报道称,在磷含量高的泥炭地上种植的洋葱缺锌。但在较低的P水平没有缺乏(Gallagher,1969).The levels of Zn in the peat were,毫无疑问,这种缺陷可能是由于对磷的反应引起的稀释效应的反映。


Nitrogen can cure or enhance Zn deficiencies.其中n是有限的,增加一项将促进增长;where Zn is adequate Zn concentrations in plants will increase.The addition of high levels of N where Zn is limited will reduce Zn concentrations and can be attributed to a dilution of Zn in the plant due to enhanced growth.

Zinc concentrations in Irish herbage

The Zn requirements of grazing 亚博体育官网无法取款animals are poorly understood and recent data suggest that requirements were formerly over-estimated (White,1993).A Zn value of 40 mg/kg has been proposed for the diets of calves and dairy cows (NRC,1988).The typical range for Zn in non-polluted Irish pasture is 20-60 mg/kg with a mean value of about 30 mg/kg,在约翰斯顿城堡分析了25%的牧草样品,低于25 mg/kg,罗杰斯建议的最低要求。et al.(1989)爱尔兰奶牛。爱尔兰种畜牧场土壤微量元素含量的研究et al.(1995)发现全国30%的牧草样品的值小于25 mg/kg:县为80%的CO样品。Tipperary had herbage Zn values of <25 mg/kg.

There appears to be little variation in levels of Zn in Irish pasture herbage over the grazing season,四月到十月。

Zinc deficiency in Ireland

Macnaeidhe和Fleming(1988)报道了在东北公司的一个地区,春季谷物对叶面喷施锌的反应。劳思。The soils where the response was obtained are formed from material deposited by the drumlin re-advance moraine.该国其他地区的土壤来源于冰川和河流冰川沉积物,也被认为锌含量低。Such areas have EDTA extractable values of <2.5 mg/kg Zn.