Abstract. Biochar is purported to provide agricultural benefits when added to the soil, through changes in soil water hydraulic conductivity (K_sat), and increased nutrient retention through chemical or physical means. Despite increased interest and investigation, there remains uncertainty regarding the ability of biochar to deliver these agronomic benefits due to differences in biochar feedstock, production method, production temperature and soil texture. In this project, a suite of experiments was carried out using biochars of diverse feedstocks and production temperatures, in order to determine the biochar parameters which may optimize agricultural benefits. Sorption experiments were performed with seven distinct biochars to determine sorption efficiencies for ammonium and nitrate. Only one biochar effectively retained nitrate, while all biochars bound ammonium. The three biochars with the highest binding capacities (produced from almond shell at 500 and 800 °C (AS500 and AS800) and softwood at 500 °C (SW500)) were chosen for column experiments. Biochars were amended to a sandy loam and a silt loam at 0 and 2 % (w/w) and saturated hydraulic conductivity (K_sat) was measured. Biochars reduced K_sat in both soils by 64–80 %, with the exception of AS800, which increased K_sat by 98 % in the silt loam. Breakthrough curves for nitrate and ammonium, as well as leachate nutrient concentration, were also measured in the sandy loam columns. All biochars significantly decreased the quantity of ammonium in the leachate, by 22 to 78 %, and slowed its movement through the soil profile. Ammonium retention was linked to high cation exchange capacity and a high oxygen to carbon ratio, indicating that the primary control of ammonium retention in biochar-amended soils is the chemical affinity between biochar surfaces and ammonium. Biochars had little to no effect on the timing of nitrate release, and only SW500 decreased total quantity, by 27 to 36 %. The ability of biochar to retain nitrate may be linked to high surface area, suggesting a physical entrapment rather than a chemical binding. Together, this work sheds new light on the combined chemical and physical means by which biochar may alter soils to impact nutrient leaching and hydraulic conductivity for agricultural production.

中文翻译：

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生物炭改变了两种农业土壤中的水力传导率并抑制了养分的淋溶

摘要。据称，生物炭添加到土壤中后，会通过改变土壤水的水力传导率（K _sat），并通过化学或物理手段增加养分的保留。尽管有越来越多的兴趣和研究，由于生物炭原料，生产方法，生产温度和土壤质地的差异，生物炭传递这些农艺效益的能力仍存在不确定性。在该项目中，使用各种原料和生产温度的生物炭进行了一系列实验，以确定可以优化农业效益的生物炭参数。用七个不同的生物炭进行吸附实验，以确定铵和硝酸盐的吸附效率。只有一种生物炭有效保留了硝酸盐，而所有生物炭均结合了铵。三种具有最高结合能力的生物炭（在500和800°C下由杏仁壳（AS500和AS800）和在500°C下由软木制成（SW500））被选择用于色谱柱实验。将生物炭修改为0和​​2％（w / w）的沙质壤土和粉质壤土以及饱和水力传导率（K_sat）进行了测量。生物炭减少ķ_坐在在两种土壤由64-80％，与AS800的异常，这增加ķ_饱和在粉壤土中增加了98％。在沙质壤土柱中还测量了硝酸盐和铵盐的突破曲线，以及渗滤液中的养分浓度。所有生物炭均显着减少了渗滤液中铵的含量，降低了22％至78％，并减缓了其在土壤剖面中的移动。铵的保留与高的阳离子交换能力和高的氧碳比有关，表明在生物炭改良过的土壤中铵保留的主要控制是生物炭表面和铵之间的化学亲和力。生物炭对硝酸盐释放的时间几乎没有影响，只有SW500减少了总量，降低了27％至36％。生物炭保留硝酸盐的能力可能与高表面积有关，表明存在物理捕获而不是化学结合。一起，