1. Emphasize fertilizer, despise organic muck. Decreasing organic muck must induce increase fertilizer, to bring on scarcity of nutritious element,harden soil, affect growth, yield and fruit quality.

2. Incline phosphorus fertilizer. Five age trees usually have been irrigated Ca, Mg and P 4-5kg, barmy cattle dung and persulfates calcium 1-1.5kg everyone, ammonium bicarbonate mix calcium 1-1.5kg, ammonium dihydrogen phosphate 1-1.5kg per year, compound fertilizer over 2.5kg per year. These are including phosphorus of fertilizer; the total is 3.7 times for natural situation. The result is waste more phosphorus, at the same time, other nutrients are deficient, such as boron, manganese,zinc,and copper.

3. Excessive nitrogen fertilizer. Nitrogen fertilizer could accelerate chlorophyll to form, it makes grapefruit keep green. Some fruit growers have a mistake which leaves greener is better. Every tree has complex fertilizer 1-1.5kg in winter; fertilize urea 0.5kg in spring and abloom time; it is using urea, ammonium bicarbonate or high nitrogen of complex fertilizer when need to fertilize fixed-fruitage muck, enriched-fruitage muck, and grown-fruitage muck. It induced long tresses thin fruitages; in summer, the more nitrogen fertilizer, the more tresses; in fall, if you fertilize more nitrogen fertilizer, it will cause bud to polarize; while, over nitrogen would make grapefruits to absorb more calcium and magnesium, but it lacks potassium, phosphorus, manganese, and molybdenum.

4. Over use microelement. There are Magnesium, boron, zinc, manganese, and molybdenum whole necessary microelement of grapefruit. Lack any microelement will cause grown and fruit. Boron is important for fruitage. Lack it, bring on fruitage is small and abnormality, seedcase has tear stains, sarcocarp is dark black. Usually, only spurt 0.2% borax or 0.1% boric acid 2-3 times with out root in florescence and young fruitage. But separate fruit grower adopts 50g-100g by sprinkling way or irrigating way, even 250g. It make poisoning of boron badly, yellow-red leaves, until whole leaves fall off. Use over magnesium will result in lack calcium.