Abstract
Tea (Camellia sinensis L.) plants have an optimal pH range of 4.5–6.0, and prefer ammonium (NH4+) over nitrate (NO3−); strong soil acidification and nitrification are thus detrimental to their growth. Application of NH4+ -based fertilizers can enhance nitrification and produce H+ that can inhibit nitrification. However, how soil acidification and nitrification are interactively affected by different NH4+-based fertilizers in tea plantations remains unclear. The objective of this research was to evaluate the effect of the application of different forms and rates of NH4+ -based fertilizers on pH, net nitrification rates, and N2O and NO emissions in an acidic tea plantation soil. We conducted a 35-day aerobic incubation experiment using ammonium sulphate, urea and ammonium bicarbonate applied at 0, 100 or 200 mg N kg−1soil. Urea and ammonium bicarbonate significantly increased both soil pH andnet nitrification rates, while ammonium sulphate did not affect soil pH but reduced net nitrification rates mainly due to the acidic nature of the fertilizer. We found that the effect of different NH4+-based nitrogen on soil nitrification depended on the impact of the fertilizers on soil pH, and nitrification played an important role in NO emissions, but not in N2O emissions. Overall, urea andammonium bicarbonate application decoupled crop N preference and the form of Navailable in spite of increasing soil pH. We thus recommend the co-application of urease and nitrification inhibitors when urea is used as a fertilizer and nitrification inhibitors when ammonium bicarbonate is used as a fertilizer in tea plantations.
【以下为百度翻译，仅供参考】茶树（Camellia sinensis L.）的最适pH值范围为4.5-6.0，与硝酸盐（NO3-）相比，更喜欢铵（NH4+）；但是强烈的土壤酸化和硝化作用并不利于茶树生长。施用NH4+基肥料能促进硝化作用，产生抑制硝化作用的H+。然而，不同NH4+基肥料对茶园土壤酸化和硝化作用的交互影响尚不清楚。本研究旨在探讨不同形态和施用量的NH4+肥料对酸性茶园土壤pH值、净硝化速率、N2O和NO排放的影响。我们用硫酸铵、尿素和碳酸氢铵在0、100或200 mg Nkg−1土壤上进行了35天的好氧培养试验。尿素和碳酸氢铵显着提高了土壤pH值和净硝化速率，而硫酸铵对土壤pH值没有影响，但降低了净硝化速率，主要是由于肥料的酸性。研究发现，不同NH4+基氮对土壤硝化作用的影响取决于肥料对土壤pH值的影响，硝化作用对NO排放起重要作用，但对N2O排放没有影响。总的来说，尽管土壤pH值升高，尿素和碳酸氢铵的施用使作物对氮的偏好和氮的有效形式脱钩。因此，我们建议在茶园中使用尿素作为肥料时，同时施用脲酶和硝化抑制剂，而当碳酸氢铵用作肥料时，则应同时施用硝化抑制剂。
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