Chapter 11 Calcium, Magnesium, Sulphur and their Fertilizer
钙镁硫等都是作物生长发育所必需的营养元素，他们对作物生长发育及新陈代谢的作用也是其他营养元素所不能代替的。农业生产上施用含钙镁硫的石灰石膏等，除供给作物所必需的营养钙镁硫外，还有改良土壤的作用。
[目的与要求]
1 学习掌握植物体内钙镁硫的含量、功能、吸收和利用
2 学习掌握钙镁硫的种类、性质和合理施用技术
[重点]
1 植物对钙的营养功能和石灰肥料
2 硫的吸收与代谢
[难点]
硫的吸收与代谢
[课堂组织]
讲述、生活实例和多媒体教具结合
[教学内容]
11.1 Calcium and lime Fertilizer
11.1.1 Content and Distribution of Ca in Plants
0.1~5% of dry weight. Most calcium is located at cell wall, and a few at vacuole.
Dicotyledonous > Monocotyledon; Shoots > Roots; Stems and Leaves (older) > Fruit, Grains.
11.1.2 Nutrition Function of Calcium
11.1.2.1 Cell Wall Stabilization
There are an abundance of binding sites for Ca+ in the cell wall.In the storage tissues of apple fruits, the cell wall-bound fraction of Ca+ can make up as much as 90 % of the total.
11.1.3 Response of Plants to Ca Deficiency
图11－1白菜：干烧心
图11－2小麦：幼叶变形，失绿 图11－3白菜：缘腐病
缺素症状：
（1）植株矮小，茎、根的生长点出现凋萎或坏死；
（2）幼叶变形，叶缘呈不规则的锯齿状；
（3）叶尖相互粘边呈弯钩状，新叶抽出困难；
（4）早衰，结实少或不结实；
（5）常伴随铝、铁、锰的毒害。
过量：
可能导致或加重硼、铁、锌、锰的缺乏。
11.1.4 Lime Fertilizer
Calcium is the fifth most abundant element in earth’s crust (approximately 3.64%) .Calcium occurs as divalent cation (Ca2+) in the solution and on the exchange site of soil colloids. The amount of exchangeable is at least 100 times the amount of Ca2+ in the soil solution.
11.1.4.1 Indirect Role of Lime Fertilizer
11.1.4.1.1 Neutralize soil acid and eliminate the toxicity of Al, Fe, Mn
Liming will create a suitable environment for plants growth on acid soils.
11.1.4.1.2 Improve soil physical properties
The exchange Ca2+ is particular importance for soil structure:Ca2+ promotes the coagulation of soil colloids and thus improves soil structure, the stability of soil particle, and assort with the relationships among water, fertilizer, air and heat.It thus appears that liming is primarily a means of improving soil structure and pH.
11.1.4.1.3 Improve beneficial bacteria activation in soils and increase available nutrients
Adaptable pH for microorganisms:消化细菌：6.5-7.5; 氨化细菌: 6.5-7.5; 自生固氮菌: 6.5-7.8; 嫌气性固氮菌: 6.9-7.3;根瘤菌: 6.0-7.0; 纤维分解细菌: 6.8-7.5
11.1.4.1.4 Alleviate the destroy of disease, insect pests and weeds
Liming inhibits disease taking place;
Stronger alkaline lime can directly kill pathogen, insect egg and weed seed
11.1.4.2 Lime Fertilizer sorts and properties
11.1.4.2.1 Lime fertilizer sorts
（1） Raw lime (生石灰)
（2） Slaked lime or lime hydrate (熟石灰)
（3） Lime carbonate (碳酸石灰)
（4） Industry waste residue containing lime From Iron and Steel waste residue
（5） Other chemical fertilizer containing Ca
Raw lime
（1）主要成分是CaO (96-99%)；
（2）呈强碱性；
（3）可在短期内矫正土壤酸度，还有杀虫、灭草和土壤消毒的作用。
（4）用量不能过多，否则引起局部土壤过碱
Slaked lime or lime hydrate
（1）主要成分是Ca(OH)2 ，含CaO 70%
（2）呈强碱性，中和土壤酸性能力比生石灰弱。
Lime carbonate
（1）主要成分为CaCO3；
（2）中和土壤酸性的作用比较缓和，后效较长。
11.1.4.2.2 Application of lime fertilizer
（1）Calculating the application quantity
1）测定土壤酸度
一定浓度CaCl2溶液浸提，标准Ca(OH)2滴定
2）石灰用量的计算
施用时，石灰与土壤不易混合均匀，为避免局部过量，实际施用量只占测定值的一半。
假如：滴定100g土样酸度需1.5mmol Ca(OH)2，则每亩地施用石灰量为：
1.5÷100×74 ÷ 1000×150000×1/2 = 83.25 kg/亩
（2）影响石灰施用量的因素
1）作物种类：茶树耐酸，不需施石灰；水稻、烟草等中等耐酸，施适量石灰；大麦耐酸较差，重视施用石灰。
2）土壤性质
3）石灰的种类与性质
4）施用石灰的目的与方法
表11－1 Application of lime at the first year in acid soil (kg/mu)
Soil reaction clay loam sand
Stronger acidic (pH 4.5-5.0) 150 100 50-70
Acidic (pH 5.0-6.0) 75-125 50-75 25-50
Weak acidic (pH 6.0) 50 25-50 25
（3） 石灰的施用
1）可作基肥、追肥，不宜作种肥；
2）不宜连续大量施用；
3）不能与铵态氮肥和腐熟有机肥料混合施用；
4）注意均匀施用。
11.2 Magnesium and Magnesium Fertilizer
11.2.1 Content and Distribution of Mg in Plants
Content in plants: 0.05~0.7%
Distribution:
Legumes > Cereals (2~3 times)； Seed > stem, leaf >root
11.2.2 Nutrition Function of magnesium
11.2.2.1 Chlorophyll Synthesis and Cellular pH Control
A major function of Mg2+ is its role as the central atom of the chlorophyll molecule.
11.2.2. Protein Synthesis 2
Mg also has an essential function as a bridging element for the aggregation of ribosome subunits, a process that is necessary for protein synthesis.Mg is also required for polymerases and hence for the formation of RNA in the nucleus.
In leaf cells at least 25% of the total protein is localized in chloroplasts. Which explains why a deficiency of Mg particularly affects the size, structure, and function of chloroplast.
Table 11－2 Effect of Magnesium Deficiency on Fully Expanded Oat Leaves
Percentage of
Ma total Ma
Ma Chlorophyll content bound to
Supply (mg/g dry wt) (mg/g dry wt) chlorophyll
+Mg2+ 10.4 5.1 10
-Mg2+ 4.5 1.0 24
Lower chlorophyll contents in Mg-deficiency leaves are caused by inhibited protein synthesis rather than a lack of Mg2+.
11.2.2.3 Enzyme Activation and Energy Transfer
There is a long list of enzyme reactions which require or are promoted by Mg2+:
（1）phosphatases and ATPase;
（2）RuBP carboxylase;
（3）fructose-1, 6-diphosphatase
The substrate for most ATPases is Mg.ATP
11.2.3 Response of Plants to Mg Deficiency
Mg deficiency symptoms differ between plants although some general characteristics are apparent:
（1）Mg2+ is mobile in plants and deficiency always begins in the older leaves, then move to the younger leaves.
（2）Interveinal yellowing or Chlorosis occurs and in extreme cases the areas become necrotic.
（3）With cereals, the base of the leaf first shows small dark green spots, and becomes more chlorotic and striped. Necrosis occurs particularly at the tips of leaf.
图11－4油菜缺镁 图11－5 烟叶缺
图11－6葡萄缺镁 图11－7菜豆缺镁
缺素症状：
（1）在中下部叶片有较明显的症状
（2）叶色褪淡，脉间失绿，呈清晰的绿色网状脉纹
（3）单子叶植物叶脉上有间断串珠状绿色斑块，双子叶植物叶片上有紫红色斑块。
11.2.4 Magnesium Fertilizer
11.2.4.1 含镁肥料的种类、性质与施用
水溶性镁肥：硫酸镁、硝酸镁
微水溶性镁肥：白云石、蛇纹石、磷酸镁
施用镁肥效果较好的作物有：花生、紫云英、马铃薯、烟草。
11.2.4.2 含镁肥料的施用
可作基肥(1-1.5 kg Mg/亩)、追肥和根外追肥(MgSO4•7H2O 1-2%).
酸性土、高度淋溶的土壤、沼择土、砂质土上施用效果比较显著。
11.3 Sulfur and Sulfur Fertilizer
11.3.1 Content and Distribution of sulfur in Plants
Content: 0.1~0.5%
Cruciferaes > legume> cereal
Distribution: major located in leaves before flowering; transfer to other organs after mature.
Two major forms of sulfur in plants:
（1）Inorganic: SO42-;
（2）Organic: sulfur-containing amino acid
Sulfur taken by plants first satisfies the demand of organic sulfur synthesis. Superfluous sulfur is stored at vacuole.
11.3.2 Assimilation of sulfur
11.3.3 Nutrition Function of sulfur
11.3.3.1 protein synthesis
S is a constituent of cysteine and methionine and hence of proteins. S is a structural constituent of these compound (R1-C-S-C-R2) or acts as a functional group (R-SH) directly involved in metabolic reactions.
The formation of a disulfide bond between two adjacent cysteine residues in polypeptide chains is of fundamental importance for the tertiary structure。
The disulfide bond may form a permanent (covalent) cross-link between polypeptide chains or a reversible dipeptide bridge.Studying it will be useful to provide cellular resistance to dehydration (caused by drought and heat) and frost damage.
11.3.3.2 Transfer Electron
11.3.4 Response of Plants to Sulfur Deficiency
Inhibition of protein synthesis during sulfur deficiency leads to chlorosis, just as it does during N deficiency.
Unlike N, however, S deficiency symptom occurs first in younger, most recently formed leaves: a light green or a light yellow or yellow, and plants are rigid, brittle and the stems remain thin.
图11-8菜豆缺硫：新叶开始黄化 图11－9番茄缺硫
图11－10芹菜缺硫 图11－11 玉米缺硫
缺素症状：
（1） 植株发僵，新叶失绿黄化
（2） 双子叶植物较老的叶片出现紫红色斑块
（3） 开花和成熟期推迟，结实率低，籽粒不饱满。
11.3.5 Sulfur Fertilizer
（1）Gypsum, CaSO4·2H2O: 18.6% S;
（2）Magnesium sulfate, MgSO4·7H2O, : 13% S
（3）Potassium magnesium sulfate, K2SO4·2MgSO4: 22%S
（4）Sulfur-coated urea: 10-20% S
（5）Single superphosphate (13.9% S as gypsum; only 1% S in triple superphosphate)
（6）Ammonium sulfate, (NH4)2SO4：24% S
（7）Elemental sulfur, S (100% S ): oxidized to sulfuric acid by microorganisms; used also as acidifying agent
（8）Ammonium thiosulfate (ATS), (NH4)2S2O3, ：26% S, 12% N
Also Al2(SO4)3, and FeSO4, used as acidifying agents
11.3.5.1含硫肥料的种类与性质
1）Raw gypsum (生石膏, 普通石膏)
主要成分CaSO4•2H2O, 微溶于水; 含 CaSO4•2H2O>>55%, CaO 20.7-21.9%, S 18.6%
2) Slaked gypsum (熟石膏)
由生石膏加热脱水而成. 主要成分CaSO4•1/2H2O, 含 S 20.7%
3) Gypsum containing phosphate (含磷石膏)
主要成分CaSO4•2H2O, 含 CaSO4•2H2O 64%, S 11.9% , P2O5 ,0.7-4.6%
4)Sulfur(硫磺)
主要成分S, 含 S 95-99%
11.3.5.2 石膏、硫磺的作用
1) 供给作物硫、钙营养
2) 改良碱土
Na2CO3 + CaSO4 → Na2SO4 + CaCO3
NaHCO3 + CaSO4 → Na2SO4 + Ca(HCO3)2
[Colloid] + CaSO4 → [Colloid]Ca + Na2SO4
3) 改善作物营养条件
11.3.5.3 硫肥的施用
11.3.5.3.1 确定施用硫肥应考虑的因素
1）土壤条件
土壤全硫与有效硫: 土壤含硫0.01-0.05%, 平均为0.85%, 主要存在于有机质中,有机硫占土壤全硫的70-90%.
土壤pH ：酸性土壤中，铁、铝氧化物对SO4-的吸附能力较强，随pH的升高吸附下降。故酸性土壤上施用石灰，有效硫量增加。
土壤通气：土壤通气良好，硫以SO4-形式存在，排水不良的沤田中，SO4-被还原成H2S
2）作物种类
油菜、甘蓝、花生、大豆等对缺硫比较敏感，施用硫肥有较好的反应。结球甘蓝、花椰菜、大葱等需要大量的硫。
3）其它硫源
灌溉水
大气
11.3.5.3.2 Sulfur Fertilizer technique
1）以提供硫素营养为目的的石膏施用技术
石膏可作基肥、追肥和种肥；旱地作基肥一般每亩用量为15-25kg， 撒施后翻耕入土。
2）以改良土壤为目的的石膏施用技术
施用石膏必须与排灌工程相结合；重碱地采用全层施用法，在雨前或灌水前均匀施于地面，并翻耕入土，使之与土混匀，与土壤中的交换性钠起交换作用，形成Na2CO4。
[思考题]
1.钙在植物体内的生理功能及其缺素症状。
2.钙、镁、硫被吸收的形态与方式。
3.石灰肥料的主要种类。
4.施用石灰肥料对土壤与植物有何影响。
5.镁、硫在植物体内的主要生理功能及其缺素症状。