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一、序言植物的含钾量通常比其他任何营养元素(除氮素外)都多。每公顷吸收利用的钾量可从50至200公斤K以上,视作物种类和产量而有不同。由于大多数土壤不能满足作物连续种植的需要,所以往往需要施用钾肥。一般作物的含钙量比钾要低些,其需要量通常在20—150公斤Ca/公顷之间。可是由于大多数土壤或者本来就含有较多的钙,或者因施用石灰而供给丰富的钙,因此钙素养分的缺乏是不常见的。一般作物吸收的镁比较少,每公顷多在10公斤以下到25公斤Mg左右。缺镁的情形偶尔是有的,特别在砂质土壤上,或在那些与钾和(可能)钙比起来镁的
I. Preface Plants contain more potassium than any other nutrient (except nitrogen). The amount of potassium absorbed per hectare may range from 50 to 200 kg K or more, depending on the crop species and yield. Potassium fertilization is often required because most soils do not meet the needs of continuous cropping. The general crop calcium content is lower than potassium, its demand is usually between 20-150 kg Ca / ha. However, the lack of calcium nutrients is uncommon since most soils either inherently contain more calcium or are rich in calcium due to the application of lime. The general crop absorption of magnesium is relatively small, more than 10 kg per hectare to about 25 kg Mg. Magnesium deficiency occurs occasionally, especially on sandy soils, or in those that are more magnesium than (and possibly) calcium