Abstract The objectives of the current study were to investigate the effects of nitrogen (N), phosphorus (P), and potassium (K) application rates on yield and quality of citrus fruits, and soil nutrient availability. The experiment was carried out using 8-year-old ‘Navelina’ navel orange (Citrus sinensis L. Osbeck) trees in an acid yellow sandy soil over three consecutive growing years in Zigui County in the Three Gorges Reservoir Area. This experiment consisted of 14 treatments with three factors (N, P, and K) and four levels of each factor. N application doses were 0, 66, 132, and 198 kg hm−2; P application doses were 0, 16.5, 33.0, and 49.5 kg hm−2; K application doses were 0, 27, 54, and 81 kg hm−2. P application at 49.5 kg hm−2 increased the yield of citrus by 32.6 % attributed to the increase in fruit number rather than mean fruit weight. P application did not affect total soluble solids of fruits when compared with the treatment without P application. Soil receiving 198 kg hm-2 of N rate revealed the lowest soil pH, which likely increased the toxicity of aluminum and then reduced citrus yield compared with the treatment without N fertilization. N and P application did not affect available N and available P in soils compared with treatments without N and P applications, respectively. We speculate that the increased fruit yield response of citrus trees by P fertilization is possibly due to aluminum detoxification as a result of phosphate complex with aluminum ions.

中文翻译：

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三峡库区酸性土壤施磷提高柑橘类植物3年产量

摘要 本研究的目的是研究氮（N）、磷（P）和钾（K）的施用量对柑橘类水果产量和品质以及土壤养分有效性的影响。该试验是在三峡水库区秭归县连续三年生长的酸性黄沙土壤中使用8年生'Navelina'脐橙（Citrus sinensis L. Osbeck）树进行的。该实验包括 14 个处理，三个因子（N、P 和 K）和每个因子的四个水平。N 施用剂量为 0、66、132 和 198 kg hm-2；磷施用剂量为 0、16.5、33.0 和 49.5 kg hm-2；K 施用剂量为 0、27、54 和 81 kg hm-2。施磷 49.5 kg hm-2 使柑橘产量增加 32.6%，这归因于果实数量而非平均果实重量的增加。与不施磷的处理相比，施磷不影响果实的总可溶性固形物。接受 198 kg hm-2 氮肥的土壤显示出最低的土壤 pH 值，与不施氮肥的处理相比，这可能会增加铝的毒性，然后降低柑橘产量。与分别不施氮和施磷的处理相比，施氮和施磷不影响土壤中的速效氮和速效磷。我们推测，磷肥对柑橘树果实产量的增加响应可能是由于磷酸盐与铝离子复合导致铝解毒。与不施氮肥的处理相比，这可能会增加铝的毒性，然后降低柑橘产量。与分别不施氮和施磷的处理相比，施氮和施磷不影响土壤中的速效氮和速效磷。我们推测，磷肥对柑橘树果实产量的增加响应可能是由于磷酸盐与铝离子复合导致铝解毒。与不施氮肥的处理相比，这可能会增加铝的毒性，然后降低柑橘产量。与分别不施氮和施磷的处理相比，施氮和施磷不影响土壤中的速效氮和速效磷。我们推测，磷肥对柑橘树果实产量的增加响应可能是由于磷酸盐与铝离子复合导致铝解毒。