Chapter 9 Phosphorus and Phosphorus Fertilizer

[目的与要求]

1.掌握磷的营养功能及磷营养诊断；

2.掌握磷肥的种类及施用技术；

3.了解土壤和植物体中磷的含量、分布；

4.了解我国磷肥工业的发展历程。

[重点]

1.磷营养诊断的方法

2.提高磷肥利用率的途径

[难点]

磷的吸收、运转、同化机理及影响植物吸收磷的主要因素

[课堂组织]

讲述、讨论和多媒体教具结合

[教学内容]

9.1 Content and Distribution of Phosphorus  in Plant

In general, P content varies from 0.2~1.1% of dry weight.Organic P about 85% existing in  phospholipids, RNA, DNA; Inorganic P about 15% existing in phosphate  of Ca, Mg and K.

Species: oil crops > Legumes > Cereals

Organs: young > old， reproductive > vegetative， grains > leaves > roots > stems

Comparmtmentation of Pi:

Most inorganic P stored in vacuoles (90%)

Most organic P existing in cytoplasm(90%)

Inorganic P and  organic P can be inter-transferred.

Inorganic P content and  P nutrition status?

P distribution varies with growth center And reusable!! In P deficiency, roots remains most P; In suitable P, roots remains a few P.

9.2 Nutrition Function of Phosphorus

9.2.1 General

Unlike nitrate, phosphate is not reduced in plants but remains in its highest oxidized form.

Phosphate remains as:

（1）Inorganic phosphate (Pi);

（2）Simple phosphate ester (C-O-P);

（3）Energy-rich pyrophosphate bond

（4）Phosphate diester (C-P-C).

9.2.2 P as a Structural Element

（1）DNA and RNA

（2）Phosphatelipid of biomembrane

（3）Phytate （植素）

Phytates are salts  (Ca and Mg) of phytic acid (植酸）， which is hexainositol phosphoric acid （六磷酸肌醇）.

Phytates are store pool of P, which will be released when seeds germinate.

Phytic acid also has high affinity for zinc and iron.

9.2.3 Role in Energy Transfer

In actively metabolizing cells, energy-rich phosphates are characterized by extremely high rates of turnover.

9.2.4 Regulation Role of Inorganic P

Pi has various essential functions in the metabolic pool:

    ① A substrate or an end product (ATP           ADP + Pi);

    ② Controls some key enzyme reaction (磷酸果糖激酶)；

    ③ Carbohydrate synthesis and transport；

    ④ Nitrogen metabolism；

    ⑤ Fat acid metabolism。

图9-1   Pi对光合作用中蔗糖及淀粉形成的调节

9.2.5 Role in improving crop adaptation to stress

9.2.5.1  Resisting drought

磷脂亲水基团提高细胞结构的充水度和胶体的束水能力；

 增加原生质的粘性和弹性，提高了其对局部脱水的抵抗力。

9.2.5.2 Resisting cold

磷能促进各种合成过程，低温下细胞液小分子有机物(如可溶性糖)含量较高，结冰点降低。

9.2.5.3 Resisting salt

（1）无机磷酸盐能增加细胞液的缓冲能力，使原生质pH保持稳定；

                H2PO4-                  HPO4 2-

（2）H2PO4-  对Cl-  有拮抗作用，可减少作物对其吸收。

9.2.6 Effect of Phosphorus on crop yield and quality

1.Cereal crops

2.Fibre Crops

3.Sugar Crops

4.Fruits

9.3 Absorption and utilization of Phosphorus

9.3.1  Absorption

Plants can take up phosphorus at the solution with an extremely low p concentration.

P in xylem: 0.4 µmol/ml;

P in Soil solution:   0.0005~0.002 µmol/ml;

400 times

Active process!! 

Plants obtained P from the soil solution in the form of H2PO4- and HPO42- ion.Plants absorb P mainly by root hair, which are driven by the pump of H+ -ATP enzyme located in tonoplast!

H+ and H2PO4- are co-transported.

9.3.2  Utilization

P is re-useable, which can be transported easily upon or down .

9.3.3  Factors

（1）Crop characteristics

（2）P status in soil solution

（3）VAM

（4）Environmental factors

（5）Interaction among nutrients

9.4 Response of Plant to Phosphorus Deficiency or Excessive Phosphorus

9.4.1 Phosphorus deficiency symptom 

Plants suffering from P deficiency are retarded in growth and the shoot/root dry matter ratio is usually low.Generally the symptom of P deficiency apper in the older leaves which are often of a darkish green colour.the stem of many annual plants suffering from P deficiency exhibit a reddish coloration because of enhanced anthocyanim (花青苷） formation.

  

图 9-2  大麦缺磷：老叶尖端焦枯，    图 9-3  油菜缺磷：自左至右，依次为幼叶至老叶，

下部有些老叶片呈紫红色                   叶片从暗绿、暗紫发展至紫红色

 

图 9-4 油菜缺磷：左为施氮、磷、钾正常油菜，中为不施肥对照，右为缺磷油菜，

表现为生长停滞，生长量与对照相近

9.4.2 Excessive phosphorus symptom 

（1）营养生长期缩短，繁殖器官过早发育，成熟提早，不利高产；

（2）茎叶生长受到抑制，植株矮小，早衰，根茎比大，纤维素多，品质差；

（3）谷类作物无效分蘖和瘪粒增加；

（4）豆科作物茎杆蛋白质增加，籽粒中蛋白质含量减少。

 

图 9-5  黄瓜磷过剩                               图 9-6  茄子磷过剩

叶脉间出现白斑，与细菌性斑点相似            由下部叶片开始，直至整株叶片黄化，叶脉附近有明显黄化斑点

9.5 Phosphorus Fertilizer

9.5.1 Manufacture of Phosphate Fertilizer

目前，中国磷肥生产企业共有400多家，生产能力在6 万吨(以P2O5计)／年以上的磷肥企业仅有20多家。

中国的磷肥生产总能力约为1000万吨(折P2O5)，仅次于美国，但中国磷铵、重钙及硝酸磷肥等高浓度磷肥在磷肥总生产能力和产量中所占比例仅为40％。

9.5.2 Sorts of Phosphate Fertilizer

It is classified into three sorts depending on its solubility:

（1）Insoluble or difficultly soluble phosphatic fertilizer (难溶性磷肥)

（2）Water soluble phosphatic fertilizer (水溶性磷肥)

（3）Citrate acid soluble phosphatic fertilizer(枸溶性磷肥或弱酸性溶性磷肥)

9.5.2.1 Insoluble Phosphatic Fertilizer (难溶性磷肥)

Definition: phosphatic component is insoluble in water or weak acid,  and soluble in more acid only.

Major sorts：

    Ground rock phosphate (磷矿粉)

Ground bone (骨粉)

Properties:

主要成分为磷灰石 Ca10(PO4)6 . F2/(OH)2/Cl2，溶液呈中性或微碱性、难溶、不易吸潮。一般P2O5含量：10-25%，其中弱酸溶性P2O5为 1-5%。

Transform in soil:

    化学、生物化学作用下逐渐分解，改变原来状态：

Ca5(PO4)3.F + 4H+ → 5Ca2+ + 3HPO42- + HF

On acid soils (pH 5.5), rock phosphate application gave yield comparable with the superphosphate application.

Application conditions:

（1）矿物性质：矿物是否易分解

（2）矿物细度：90%通过100目筛孔（0.14mm）

（3）土壤条件： 酸性土壤 ，盐基饱和度小的土壤

（4）作物种类：

根系形态（发达，根毛多）；根系分泌物多；根系阳离子代换量大。

利用能力最强：油菜、萝卜、荞麦；

利用能力较强：豆科；

利用能力中等：玉米、马铃薯、芝麻

利用能力差：  小麦、水稻。

Application:

（1）Suitable for basal dressing, not Seed or top dressing;

（2）Broadcast and deep placement (撒施、深施)；

（3）Suitable acid soils ；

（4）Beneficial to treat with acidic、Physiological acidic or organic fertilizer together;

（5）Belong to low-releasing which is suitable for tree and economic forest.

9.5.2.2 Water Soluble Phosphatic Fertilizer (水溶性磷肥)

Definition: Major component is soluble in water. Such as:Superphosphate (过磷酸钙), Double superphosphate (重过磷酸钙), monoammonium phosphate(磷酸一氨 ), diammonium phosphate （磷酸二氨 ）.

Component of superphosphate：

（1）Major component: 是水溶性磷酸一钙（Ca(H2PO4)2.H2O）和难溶性的石膏（CaSO4.2H2O）；

      Available P2O5  12-18%，       CaSO4 50%，

      FeSO4 and Al2(SO4)3 2 -4%，   Free acid  3.5-5%

Properties superphosphate:

（1）Offwhite power, and acidic odor

（2）Acidic in water solution

（3）Hygroscopic：

Degeneration (退化作用)：吸湿后过磷酸钙中的硫酸铁、铝与磷酸一钙作用形成难溶性的磷酸铁、铝的过程。

    Preventing from moisture at storage period.

Transform in soil:

Inhomogeneous dissolution (异成分溶解):

Ca(H2PO4)2.H2O + H2O  →  CaHPO4  + H3PO4

Result:

（1）Decrease pH (1.5) at fertilization spot;

（2）High concentration of H3PO4 (10~20 mg/kg) will defuse around;

（3）Increase the concentration of Al3+, Ca2+, Fe2+ and so on.

Chemical fixation of superphosphate (过磷酸钙的化学固定):

    过磷酸钙施肥点有很强的酸性，可溶解土壤中、的铁、铝、钙、镁等成分，当阳离子达一定浓度后，就会产生相应的磷酸盐沉淀，是磷肥有效性降低的现象。

In acid soils:

2Fe(OH)3  + Ca(HPO4)2•H2O    →     2FePO4  + Ca(OH)2 + 5H2O    

2Al(OH)3                            2AlPO4

In calcareous or neutral soils:

2Ca(CO)2  + Ca(H2PO4)2      →        Ca3 (PO4)2   + CO2 + 2H2O    

Sorption fixation of superphosphate (磷的吸持固定):

    存在于土壤溶液中的磷酸或磷酸根离子会被土壤固相所吸附，磷酸根离子会进一步与土壤胶体上的某些成分（Fe、Al、Ca、Mg）结合形成难溶性的盐。

Application:

Principle：Pay attention to decrease contacting area with soil (decrease fixation) and increase the contacting opportunity with root system due to the reason of fixation easily and fairly immobilization

（1）Placed application (集中施用)：band or hole application (条施或穴施)

（2）Made in the form of granulated fertilizer

（3）Mixing Application with organic fertilizer (2~3 times)

（4）Foliar application

9.5.2.3 Citrate acid Soluble Phosphatic Fertilizer (枸溶性磷肥)

Calcium-manganese phosphate fertilizer（钙镁磷肥）。

Definition:

主要成分能溶于2%的柠檬酸铵溶液的磷肥，称枸溶性磷肥,又称水溶性磷肥

Component:

主要形态为非晶态的α-Ca3(PO4)2及CaSiO3、MgSiO3等.   P2O5: 14-20%。

Properties：

（1）Celadon or lark  pownder;

（2）Weak  alkaline in water solution（pH8-8.5）；

（3）Glass shining (玻璃光泽)；

（4）Nonhygroscopic and convenient for storage and application.

Transformation in soils

On acid soils, 在土壤酸作用下逐渐转化为水溶性的磷 

Ca3(PO4)2 + 2H+   →        Ca(H2PO4)2

On calcareous soils, 在土壤酸或根系分泌物作用下逐渐转化为水溶性的磷 

Ca3(PO4)2 + 2CO2 + 2H2O  →     2CaHPO4+Ca(HCO3)2

2CaHPO4 + 2CO2 + 2H2O    →     Ca(H2PO4)2 +Ca(HCO3)2

In calcareous soils, its effectiveness is lower than superphosphate. However, in acid soils, it will be comparable or over superphosphate.

Application

Pay attention to the characteristics of crops, soils, fertilizers and application methods so as to improve its effectiveness

1）作物

      用于喜钙作物：苕子、蚕豆、豌豆、绿肥

      用于喜硅作物：小麦、水稻

2）土壤

      土壤酸度与肥效密切相关：

      在缺钙的酸性红黄壤上效果好。既能补充磷、钙、镁、硅等，还能中和土壤酸度，降低土壤中铁、铝危害。

3）肥料细度

       在40-100目之间，随粒径变细，肥效增加。

4）施用方法：

（1）适于作基肥，深施；

（2）与有机肥堆沤，借助微生物提高肥效；

（3）绿肥作物多施磷肥；

（4）N、P、K配合施用。

9.6 Phosphorus in Soil

Concentration of P in the soil solution are extremely, and for unfertilized soils are generally below 0.3 mg P/L. weathering and leaching have taken place.

Concentration of P in the soil solution are extremely, and for unfertilized soils are generally below 0.3 mg P/L. weathering and leaching have taken place.

H2PO4-         →             HPO4 2-

Acid soil                         alkaline soil

Labile P is readily able to move into solution;Non-labile P is relatively insoluble or unavailable to plants.The release of non-labile P to labile P form takes place extremely slowly.

9.6.1 Soil organic phosphate

Between 20 and 80% of the total P in mineral soils is generally present in organic forms (organic-P).Losses of organic-P will take place when soil organic matter levels decline , as for instance in some cropping system.

9.6.2 Soil inorganic phosphate

Soil inorganic-P can occur in the following forms:

（1） Calcium phosphate

（2）Iron and aluminum phosphate

（3） Adsorbed phosphate

9.6.3 Fixation of fertilizer phosphate by soils

In many soils, a large proportion of the added phosphate reacts with the soil in ways which , in the short term at least, make the phosphate less soluble and less available to plants.

图9－7 Factors affecting phosphate fixation by soil PH

9.6.4 phosphate cycle

图9－8磷素循环图

9.7 Phosphorus Fertilizer Application

9.7.1 Utilization rate    

It is lowest among the chemical fertilizers, only 10-25%。Because:

    1）Very easily fixed in soils；

    2）Very low diffusing in soils

9.7.2 Pathway for improving effectiveness

9.7.2.1  根据土壤条件合理分配和施用磷肥

（1）优先分配于含磷低的土壤

    全磷量 ＜ 0.1%(P2O5)的土壤，施磷肥都有增产效果。

    我国土壤全磷为0.04-0.25%

有效磷含量（ P ） 10 mg/kg 为临界值， 我国耕地缺磷面积为10亿亩

（2）土壤pH明显影响磷肥有效性

    pH6.0-7.0时，磷肥肥效相对较高

    pH＜5.5或＞7.0时，磷肥肥效低，应改良土壤。

9.7.2.2 根据作物的需磷特性和轮作制度合理分配和施用

1）不同作物需磷程度不同；

    需磷多的作物有：都哦可作物，绿肥，甜菜，甘蔗，油菜，棉花，甘薯，马铃薯，瓜，果，桑，茶，等。

2）生育期

    作物需磷临界期一般在生育前期。早施! At or before sowing

3）水旱轮作中的磷肥施用

    “旱重水轻”

4）旱作轮作中的磷肥施用

    重施秋播作物，春播作物可酌情少施。

9.7.2.3 根据磷肥特性合理施用

（1）水溶性磷肥：

    适宜于各种作物、各种土壤，以中性和石灰性土壤更为适宜；

可作基肥、种肥、追肥及根外追肥，等；

(2)弱溶性磷肥：适宜在酸性土壤上作基肥；

（3）难溶性磷肥：

    酸性土壤上撒施作基肥；

    吸磷能力强的作物，如油菜、萝卜菜、荞麦和豆科植物。

9.7.2.4 氮、磷、钾和有机肥配合施用

氮磷比例一般为1:0.5。

[思考题]

1.磷对植物体的主要生理功能。

2.植物磷缺乏与过量的症状表现。

3.植物细吸收磷的主要形态有哪两种，它们与土壤pH有何关系？

4.磷肥的主要种类及其特点？

5.磷肥利用率低的主要原因是什么？如何提高磷肥的利用率？

6.水旱轮作中磷肥分配的原则是什么？为什么？

7.名词解释：枸溶性磷肥，过磷酸钙的退化作用，磷的化学固定