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为了替代在作物播种前就决定施氮量的传统技术 ,提出了一种基于作物生长过程中根据作物及土壤状况来决定施肥量的氮肥管理系统。在作物刚发芽时 ,系统只供给少量的氮肥 ;在作物需要并能够吸收利用大量氮肥时 ,系统在最佳的时间和地点施加足量的氮肥。该文叙述了该系统中必不可少的两项技术 :作物需氮遥感测试技术和变量施肥技术。专门研究了利用多光谱图像传感器的遥感技术 ,发现多光谱图像与叶绿素含量之间有密切联系。这说明可利用多光谱图像传感器的测试结果来描述玉米需氮的状况。另外 ,还开发了一种由脉宽调节管 (PWM)、压力控制器、由电脑设定的喷嘴控制系统和基于含量分布图的应用软件组成的变量控制系统。这种变量控制系统包含 2 5个能各自单独调节流量的 18m覆盖宽的喷嘴。该文展示了该系统在伊利诺斯州和爱荷华州试验田中应用的研究结果。 1998年 ,在伊利诺斯州和爱荷华州 4块试验田中 ,玉米平均产量每公顷增长了 14 40 kg。 1999年 ,在爱荷华州的 6块试验田 ,玉米平均每公顷产量增长了 44 0 kg。
In order to replace the traditional technique of determining the amount of nitrogen applied before sowing, a nitrogen management system based on crop and soil conditions to determine the amount of fertilizer applied during crop growth was proposed. When the crop has just sprouted, the system supplies only a small amount of nitrogen fertilizer; when the crop needs and can absorb large amounts of nitrogen fertilizer, the system applies sufficient nitrogen fertilizer at the optimum time and place. This article describes the two technologies essential to the system: remote sensing of crop nitrogen demand and variable fertilization techniques. Specifically studying the use of multi-spectral image sensor remote sensing technology and found that there is a close relationship between multi-spectral images and chlorophyll content. This shows that the multispectral image sensor test results can be used to describe the status of nitrogen demand in maize. In addition, a variable control system consisting of PWM, pressure controller, nozzle control system set by computer and application software based on content distribution has also been developed. The variable-volume control system contains 25 nozzles with 18 m wide coverage that individually adjust the flow rate. This article shows the results of this system used in experimental fields in Illinois and Iowa. In 1998, the average yield of maize increased by 14 40 kg per hectare in four plots of plots in Illinois and Iowa. In 1999, in six Iowa experimental plots, the average yield of corn per hectare increased by 44 0 kg.