More than 10% of Peruvian sugarcane is irrigated with ‘filter cake water’ (FCW). No responses to applied N have been reported on these soils. This study evaluated N gains and losses in sugarcane crops (H32-8560 cultivar) irrigated with FCW. Input of N via irrigation water corresponded to 101 kg N/ha. The inorganic N (representing 1% of total N) initially present in the soil prior to planting corresponded to 161 kg N/ha and the mineralized N from total N which becomes available during the growing season to 161 kg N/ha. The N by the aerial part of the plant was 272 kg N/ha; 75% of this amount was removed during harvest (204 kg N/ha), and the remainder (25%) was lost by pre-harvest burning (68 kg N/ha). Nitrogen within the stubbles, rhizomes and roots corresponded to 92 kg N/ha. The total input of N into the soil was estimated to be 423 kg N/ha and extractable N to 364 kg/N ha. The balance was in favor of N gains, with an average gain of 59 kg N/ha. This N-balance explains why results from numerous field experiments have demonstrated that there is no response to N fertilization in fields irrigated with FCW.

中文翻译：

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“滤饼水”灌溉甘蔗的氮循环

秘鲁10％以上的甘蔗用“滤饼水”（FCW）灌溉。在这些土壤上未报告对施用氮的反应。本研究评估了FCW灌溉的甘蔗作物（H32-8560品种）的氮素损失。通过灌溉水输入的氮量相当​​于101千克氮/公顷。种植前最初存在于土壤中的无机氮（占总氮的1％）相当于161 kg N / ha，而在生长季节可利用的总N中的矿化N达到161 kg N / ha。植物地上部分的氮为272 kg N / ha；收获期间除去了其中的75％（204千克氮/公顷），其余（25％）因收获前燃烧而损失（68千克氮/公顷）。残茬，根茎和根中的氮含量相当于92 kg N / ha。估计土壤中氮的总输入量为423 kg N / ha，可提取的N为364 kg / N ha。其余部分有利于增加氮肥，平均增重59千克氮/公顷。这种氮平衡解释了为什么大量田间试验的结果表明，在FCW灌溉的田间对氮肥没有反应。