Soil NO₃^– affects microbial processes, plant productivity, and environmental N losses. However, the ability to measure soil NO₃^– is limited by labor-intensive sampling and laboratory analyses. Hence, temporal variation in soil solution NO₃^– concentration is poorly understood. We evaluated a new potentiometric sensor that continuously measures soil solution NO₃^– concentration with unprecedented specificity due to a novel membrane that serves as a barrier to interfering anions. First, we compared sensor and salt extraction-based measurements of soil NO₃^– in well-controlled laboratory conditions. Second, using 60 d of in situ soil NO₃^– measurements every 10 s, we quantified temporal variation and the effect of sampling frequency on field estimations of mean daily NO₃^– concentration both within and across days. In the laboratory, sensors measured soil NO₃^– concentration without significant difference from theoretical adjusted soil NO₃^– concentration or conventional salt extraction-based methods. In the field, the sensors demonstrated no within-day pattern in soil NO₃^– concentration, although individual measurements within a day differed by as much as 20% from the daily mean. Across days, when soil solution NO₃^– was dynamic (early spring) and sampling frequency was >5 d, estimates of mean daily NO₃^– concentration were >20% from the actual mean daily concentration. In situ soil sensors offer potential to improve fundamental and applied sciences. However, in most situations, sensors will measure soil properties in a different manner than conventional salt-extract soil sampling-based approaches. Research will be required to interpret sensor measurements and optimize sensor deployment.

中文翻译：

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连续原位土壤硝酸盐传感器：跨时间高分辨率测量的重要性以及与基于盐提取的方法的比较

土壤 NO ₃ ^–影响微生物过程、植物生产力和环境氮损失。然而，能够将测量土壤NO ₃ ^-是通过劳动密集型采样和实验室分析的限制。因此，对土壤溶液 NO ₃ ^-浓度的时间变化知之甚少。我们评估了一种新型电位传感器，该传感器连续测量土壤溶液 NO ₃ ^-浓度，由于一种新型膜可作为干扰阴离子的屏障，因此具有前所未有的特异性。首先，我们比较了NO土壤的基于提取传感器和盐测量₃ ^-在良好控制的实验室条件下。二、原位土壤NO ₃使用60 d^–每 10 秒测量一次，我们量化了时间变化和采样频率对现场估计的平均每日 NO ₃ ^–日内和日间浓度的影响。在实验室中，传感器测量的土壤 NO ₃ ^-浓度与理论调整的土壤 NO ₃ ^-浓度或基于传统盐提取的方法没有显着差异。在该领域中，传感器没有表现出日内图案在土壤中NO ₃ ^-的浓度，虽然从每日平均多达20％差异在一天之内各个测量。几天后，当土壤溶液 NO ₃ ^–是动态的（早春），采样频率 > 5 天，平均每日 NO ₃ ^-浓度的估计值与实际平均每日浓度相比 > 20%。原位土壤传感器为改进基础科学和应用科学提供了潜力。然而，在大多数情况下，传感器将以不同于传统盐提取土壤采样方法的方式测量土壤特性。需要研究来解释传感器测量值并优化传感器部署。