不同形态氮素及铵硝比例对咖啡氮吸收和生长的影响

为提高咖啡氮肥肥料有效性,采用溶液培养的方法,研究NH_4~+和NO_3~-2种不同形态氮吸收速率、5种铵硝比例(10∶0、7∶3、5∶5、3∶7、0∶10)对咖啡生长及其氮素利用的影响。结果表明,不同形态氮素对咖啡的生长影响差异显著,铵硝混合营养下咖啡的生长明显优于单一形态氮素处理。在单一形态氮素条件下,咖啡对NH4+的最大吸收速率大于对NO3-的最大吸收速率;当2种形态氮素同时存在时,铵态氮会抑制硝态氮的吸收,硝态氮促进铵态氮的吸收;铵态氮促进地上部分生长,但浓度过高反而抑制地上部分生长;硝态氮的增加有利于根系的生长,但抑制了咖啡地上部分的生长。因此,在咖啡苗期,铵硝比例控制在7∶3~3∶7有利于咖啡生长。

Effects of Different Nitrogen Forms and NH4+-N/NO3--N Ratios on the Nitrogen Uptake and the Growth of Coffee

In order to im prove the nitrogen fertilizer effectiveness of coffee, a solution culture is employed to investigate the influence of NH4+-N, NO3--N on nitrogen uptake and five proportions (ratios between nitrate and ammonium is 10∶0、 7∶3、 5∶5、 3∶7、 0∶10, respectively) on coffee growth and nitrogen using. The results showed that the effects of different forms of N on the growth of coffee are significant; coffee grows obviously better with both N forms supplies than with single form of N. Using solution contains a single form of N, the maximum uptake rate of NH4+is higher than that of NO3-. When both NH4+ and NO3-are existed, the NO3-uptake is largely inhibited by NH4+, while the NH4+ uptake is promoted by NO3-. NH4+can promote the growth of the above ground parts, but when the concentration of NH4+ is too high, it can inhibit the chlorophyll content and the growth of the above ground parts. When the NO3-/NH4+ratio is increasing in culture solution, the root growth can be improved, but the growth of the above ground parts is inhibited. Therefore, in the coffee seedling stage, the NH4+-N/NO3--N ratio can be controlled in the range of 7∶3~3∶7.