Addition of biochar to soil has been shown to reduce nitrogen (N) leaching in pot experiments, but direct field measurements are scarce, and data is lacking especially from colder, boreal conditions. We studied the effect of soil organic amendments on nitrate (NO₃^-) and ammonium (NH₄⁺) leaching using the resin bag method, by placing the bags containing ion-exchange resins under the plough layer. We compared N leaching under five different treatments at the Päästösäästö project site (Soilfood Oy) in Parainen, south-western Finland: non-fertilized control, fertilized control, and three different organic amendments: spruce biochar, willow biochar and nutrient fiber. During the 2017 growing season, resin bags were changed monthly between the end of May and beginning of September, extracted with 1 M NaCl, and analyzed for inorganic N. The daily leaching rate of NO₃^- was greatest at the beginning of the growing season, right after fertilization. Ammonium leaching was generally lower, and independent of the time since fertilization. The spruce biochar reduced cumulative NO₃^- leaching by 68% compared to the fertilized control. The NH₄⁺ leaching in the organic amendment treatments did not statistically significantly differ from the fertilized control in pairwise comparisons. In October 2017, after harvesting, the resin bags were placed under soil columns again, and left in the soil over winter to accumulate N leached during the plant-free period. Cumulative NO₃^- leaching during winter was consistent with the corresponding summer results, and average leaching decreased in the order: willow biochar > fertilized control > nutrient fiber > non-fertilized control > spruce biochar. Thus, we show here, for the first time in a field study from boreal conditions that spruce biochar soil application decreased nitrate leaching, while increasing its retention in the surface layer of the biochar-amended soil.

在盆栽试验中，向土壤中添加生物炭可减少氮（N）的浸出，但缺乏直接的野外测量，尤其是在寒冷，寒冷的气候条件下，缺乏数据。我们研究了硝酸盐（NO的土壤有机添加物的效果₃ ^- ）和铵（NH ₄ ⁺）使用树脂袋方法浸出，方法是将装有离子交换树脂的袋放在犁层下。我们比较了芬兰西南部Parainen的Päästösäästö项目站点（Soilfood Oy）在五种不同处理方式下的氮淋失：非施肥控制，施肥控制和三种不同的有机改良剂：云杉生物炭，柳树生物炭和营养纤维。在2017年的生长季节中，树脂袋在5月底至9月初之间每月更换一次，用1 M NaCl提取并分析无机氮.NO ₃的每日浸出率^-在生长季节开始时最大，受精后立即进行。铵的浸出通常较低，并且与施肥后的时间无关。云杉生物炭减少了累积NO₃ ^- 68％浸出相比受精控制。在成对比较中，有机修饰处理中的NH ₄ ⁺浸出与受精对照在统计学上没有显着差异。2017年10月，收获后，将树脂袋再次置于土壤柱下，并在冬季留在土壤中，以积累无植物时期淋溶的氮。累计NO ₃ ^-冬季的淋​​溶与相应的夏季结果一致，平均淋溶的顺序为：柳树生物炭>受精对照>营养纤维>非施肥对照>云杉生物炭。因此，在这里，我们首次在野外研究中从云杉生物炭土壤施用的野外条件中减少了硝酸盐的淋失，同时增加了其在生物炭改良过的土壤表层中的滞留率。