测定叶片氮素含量是诊断茶树氮素状况的一项重要方法。本文利用盆栽试验,通过不同的供氮水平,研究了利用叶绿素仪（SPAD-502）进行茶树氮素营养快速诊断的适用性。结果表明,茶树新梢产量与氮素用量、成熟叶氮素含量之间呈线性加平台的反应关系,成熟叶的SPAD值与其全氮含量呈显著线性正相关,并与茶树产量存在着比较明显的关系拐点,初步显示SPAD可以较好地表征茶树的氮素营养状况,有可能作为快速诊断方法用于指导茶树施肥,但是还需要通过大田试验进行进一步验证。本文还探讨了测定位点、叶位、天气状况、田间原位或离体测定方式、表面清洗以及样本量等因素对SPAD测试精度的影响。
Determination of nitrogen concentrations in tissues is an important diagnostic means for N status of plants. A pot experiment with tea plants applied with different amounts of N fertilizer was carried out to evaluate the usefulness of SPAD-502 as a diagnostic tool. The results showed that the yield of young shoots and N concentration of mature leaves responded to N application rates with a pattern of an initial linear increase before a platform was reached. There was a significantly positive linear relationship between the SPAD reading and total N concentration of mature leaves. The similar pattern of an initial linear increase followed by a platform was observed for the relationship between SPAD reading and the yield. These results suggested that the N status of tea plants may be characterized by the measurement of SPAD reading of mature leaves and the SPAD is a potentially useful rapid diagnostic tool in N fertilization recommendation. However, this needs further validation from field experiments. Those factors which may influence the precision of SPAD measurement, such as the point of test on a leaf, selection of leaves from twig (position), weather condition, in situ or in vitro analysis, surface cleaning and the number of leaves for a composite sample were also investigated.
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