Abstract. A new soil nitrate monitoring system that was installed in a cultivated field enabled us, for the first time, to control the nitrate concentration across the soil profile. The monitoring system was installed in a full-scale agricultural greenhouse setup that was used for growing a bell pepper crop. Continuous measurements of soil nitrate concentrations were performed across the soil profile of two plots: (a) an adjusted fertigation plot, in which the fertigation regime was frequently adjusted according to the dynamic variations in soil nitrate concentration, and (b) a control plot, in which the fertigation was managed according to a predetermined fertigation schedule that is standard practice for the area. The results enabled an hourly resolution in tracking the dynamic soil nitrate concentration variations in response to daily fertigation and crop demand. Nitrate–nitrogen (N–NO3) concentrations in and below the root zone, under the control plot, reached very high levels of ∼ 180 ppm throughout the entire season. Obviously, this concentration reflects excessive fertigation, which is far beyond the plant demand, entailing severe groundwater pollution potential. On the other hand, frequent adjustments of the fertigation regime, which were carried out under the adjusted fertigation plot, enabled control of the soil nitrate concentration around the desired concentration threshold. This enabled a substantial reduction of 38 % in fertilizer application while maintaining maximum crop yield and quality. Throughout this experiment, decision-making on the fertigation adjustments was done manually based on visual inspections of the soil's reactions to changes in the fertigation regime. Nevertheless, it is obvious that an algorithm that continuously processes the soil nitrate concentration across the soil profile and provides direct fertigation commands could act as a “fertistat” that sets the soil nutrients at a desired optimal level. Consequently, it is concluded that fertigation that is based on continuous monitoring of the soil nitrate concentration may ensure nutrient application that accounts for plant demand, improves agricultural profitability, minimizes nitrate down-leaching and significantly reduces water resource pollution.

中文翻译：

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使用在线土壤硝酸盐数据优化施肥


摘要。安装在耕地中的新型土壤硝酸盐监测系统使我们首次能够控制整个土壤剖面的硝酸盐浓度。该监测系统安装在一个用于种植甜椒作物的全尺寸农业温室中。对两个地块的土壤剖面进行了土壤硝酸盐浓度的连续测量：(a) 调整灌溉施肥地块，其中根据土壤硝酸盐浓度的动态变化经常调整灌溉施肥方案，以及 (b) 对照地块，其中灌溉施肥是根据预定的灌溉施肥时间表进行管理的，这是该地区的标准做法。结果使得能够以每小时的分辨率跟踪动态土壤硝酸盐浓度变化，以响应日常灌溉施肥和作物需求。在整个季节，对照地块下根区及其下方的硝酸盐-氮 (N-NO3) 浓度达到非常高的水平 ∼ 180 ppm。显然，这种浓度反映了过度的灌溉施肥，远远超出了植物的需求，带来了严重的地下水污染潜力。另一方面，在调整后的灌溉施肥小区下进行灌溉施肥制度的频繁调整，可以将土壤硝酸盐浓度控制在所需的浓度阈值附近。这使得化肥施用量大幅减少了 38%，同时保持了作物的最高产量和质量。在整个实验中，灌溉施肥调整的决策是根据土壤对施肥灌溉制度变化的反应的目视检查手动完成的。 然而，很明显，连续处理整个土壤剖面的土壤硝酸盐浓度并提供直接灌溉施肥命令的算法可以充当“施肥调节器”，将土壤养分设置在所需的最佳水平。因此，得出的结论是，基于连续监测土壤硝酸盐浓度的灌溉施肥可以确保养分的施用满足植物需求，提高农业盈利能力，最大限度地减少硝酸盐下淋并显着减少水资源污染。