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氮是肥料三要素之一,对柑桔来说,尤为重要。氮的施用量常与柑桔产量呈正相关。缺氮时,引起柑桔新梢停止生长,或枝梢短弱,老枝枯萎,老叶脱落,叶色变成淡绿黄色,光合作用减弱,容易形成“小老树”。其果实变小,应变淡红,成熟提早。产量降低,品质变劣。我省红壤丘陵上大多数桔园,土壤氮素缺乏,远远不能满足柑桔生长发育对氮素的需要,施氮能明显提高柑桔产量。然而目前施氮技术上存在不少问题,氮肥利用率较低,一般只有30～50％。造成这种浪费的主要原因,是施用不合理,方法不对,施氮没有和其它农技措施相结合。应当怎样提高氮肥的施用效率,夺取柑桔丰收呢?笔者认为应注意抓住以下几点。
Nitrogen is one of the three elements of fertilizer, especially for citrus. Nitrogen application rates are often positively correlated with citrus production. Nitrogen deficiency, causing citrus shoots to stop growing, or short branches and shoots, withered old branches, old leaves fall off, leaf color into a light green and yellow, weakened photosynthesis, easy to form “small tree.” Its fruit becomes smaller, strain red, mature earlier. Yield decreases, quality deteriorates. Most orange orchards in the red soil hills of our province are deficient in soil nitrogen, far from being able to meet the need of nitrogen for the growth and development of citrus. Nitrogen fertilizer can obviously increase the output of citrus. However, there are many problems in nitrogen application at present. Nitrogen utilization rate is low, generally only 30-50%. The main reason for this waste is the unreasonable application and the incorrect method. N application is not combined with other agricultural measures. How to improve the efficiency of nitrogen fertilizer, to seize the citrus harvest? I think we should pay attention to the following points.