1、第五章 植物的钾素营养与钾肥第一节植物的钾营养表5-1 主要农作物中钾的含量（彭克明，1987）二）调节气孔的运动 钾离子通过在气孔的保卫细胞和相邻的叶肉细胞中的流动来调节气孔开闭。表5-2 气孔张、闭时，蚕豆叶片表皮组织保卫细胞内各种离子的浓度三）提高酶活性 钾是生物体中很多酶的活化剂。植物体中约有60多种酶需要在K+离子的参与下才能充分活化。这些酶包括合成酶、氧化还原酶和转移酶类等。其活化特点是需要较高的K+浓度（4080mM），而其它离子在该浓度时对植物就会产生毒害。一般植物细胞的钾浓度为150mM。 1）合成酶类：乙酰辅酶A、NAD合成酶、谷胱甘肽合成酶、淀粉合成酶、苹果酸合成酶等 2
2、）氧化还原酶：甘油酸脱氢酶、苹果酸脱氢酶、琥珀酸脱氢酶等 3）转移酶类：丙酮酸激酶、6-磷酸果糖激酶 其它：ATP酶等 辅酶酶蛋白全酶KK4、增加光合作用 钾离子进入细胞质，有利于维持叶绿体膜两边的电势差，从而保证光合作用顺利进行。增加光呼吸、减少暗呼吸。表5-5 钾对同化、光呼吸和暗呼吸的影响（People，1979）表5-8钾对小麦籽粒中ABA含量、灌浆期和粒重的影响（Haeder，1981）表5-12 钾对于抑制病虫害发生的作用（引自Perrenoud）表5-13水稻细胞木质化程度与施钾是关系三、作物的缺钾症状 第三节土壤中的钾及其有效性表5-13一般矿物的含钾量表5-14矿物钾对作物的
3、有效性（J.K.Plunner，1918）二、土壤中钾的转化云母/伊利石长石蛭石中间产物高岭石云母（ 10%）水化云母（6 8%）伊利石（4 6%）过渡性矿物（ 3%）蛭石或蒙脱石（ 2% ）土壤中钾的循环三、影响土壤中钾的有效性因素MgCaKKaaARe钾的活度系数第三节 钾肥的性质与施用表5-15 草木灰的成分（%）第四节钾肥的合理施用表5-16土壤速效钾水平与钾素营养水平（刘芷宇等，1980）Effect on plant vigour and healthIn the absence of satisfactory potash supply, plants will be poor
4、and stunted, especially in dry seasons. Physiological stress will be more damaging if potash nutrition is limiting - frost damage will be more severe, waterlogged areas will take longer to recover and plants will wilt earlier and remain flaccid for longer under drought conditions.Crops will be more
5、susceptible to disease and pests especially where nitrogen and potash availability are imbalanced. This will result in weaker, sappier growth which will contain a higher concentration of soluble N compounds and simple carbohydrates providing a readily available food source and attractive focus for p
6、athogens. Thinner cell walls with less mechanical resistance to predators may also result from potassium shortage. A review of over 1000 cereal trials found that where potash levels were low and out of balance with N supply, application of potash reduced disease and bacterial infections in over 70%
7、of cases.Effect of potash on straw strengthPotash enhances the development of strong cell walls and therefore stiffer straw. Lodging is affected by obvious factors such as variety, N rate and weather, but low potash levels also increase the risk of lodged crops with the associated loss of yield and
8、quality. The effect can be as dramatic as a growth regulator in some circumstances as illustrated in the photograph below.Deficient KSatisfactory KLow yieldFull yieldInefficient N responseFull N responseIncreased risk N lossMinimum N lossReduced 1000 grain/specific weightFull 1000 grain & specific w
9、eightReduced grain ripening periodMaximum grain ripening periodLower grain number/earFull grain number/earPoorer grain sampleNormal grain sampleWeaker strawNormal straw strength for varietyIncreased lodging riskLodging risk normal for varietyIncreased susceptibility to droughtNormal drought resistan
10、ceIncreased disease susceptibilityNormal disease susceptibilitySpecial casesSand soilsIt is not economic to increase soil K beyond 100 mg/l on these soils because of their very low capacity to hold nutrients. Improvement can be achieved by many years dressing with FYM. Nutrients should be applied li
11、ttle and often on these soils.Loamy sandsIt is not economic to increase soil K beyond 150 mg/l on these soils because of their low capacity to hold nutrients. Improvement can be achieved by many years dressing with FYM.K releasing clay soilsSome clay soils can release potash over many years. Normal
12、potash rates can be reduced by 50 kg/ha and omitted completely at index 3. See PDA leaflet19.High pH soilsIt is sometimes suggested that calcareous soils may have a different requirement for phosphate and potash. The principles of response and the recommendations given above are applicable to these
13、soils. However for the shallower chalk/limestone soils there can be greater risk of loss of potash, even though they have a higher clay content than sandy soils, because of their depth and the high proportion of stone in topsoil (both these factors restricting the volume of soil for nutrient provisi
14、on) Target fertility in these cases must be adjusted as with other low retentive soils. Calcareous soils with pH typically over 7.5 and high organic matter (puffy chalk soils) may lock-up a higher proportion of applied potash than other soils, so that low index levels may take longer to improve. But this does not alter the amount of nutrient required to achieve full yield.Manures
