圆形喷灌机泵注式施肥装置设计与田间试验

圆形喷灌机水肥一体化作业时对喷洒肥液均匀性有较高要求,需要采用比例施肥装置,确保注入喷灌机的肥液流量保持恒定。为此设计了基于柱塞式注肥泵的泵注式施肥装置,并以注射喷嘴的孔口直径、安装位置以及注肥泵的电源频率为变量,进行了圆形喷灌机应用泵注式施肥装置的喷灌施肥均匀性试验。结果表明,圆形喷灌机停止状态下,注肥泵电源频率50 Hz运行时,3种注射喷嘴孔口直径和3种安装位置的组合工况下喷灌施肥的均匀系数CU为99.00%~99.65%,变异系数CV为0.46%~1.37%,其中当注射喷嘴孔口直径为2.5 mm、安装在进水管水平段位置的工况时获得的喷灌施肥均匀性最佳。圆形喷灌机行走状态下,测得单列雨量筒喷灌施肥均匀系数C*UH为88.77%~90.66%,表明圆形喷灌机采用泵注式施肥装置能够获得较高的喷灌施肥均匀性。此外,通过对比注肥泵电源频率在50 Hz和46 Hz时的喷灌施肥均匀性,发现喷头喷洒肥液的电导率总平均值与电源频率之间具有显著的正相关性,表明改变注肥泵的电源频率是圆形喷灌机实现高均匀度变量喷灌施肥的一种有效途径。

Design and Field Experiment on Fertilizer Injection Device in Center Pivot Irrigation System

As the center pivot irrigation system requires high fertigation uniformity, a kind of proportional fertilizing device was adopted in order to make the injection flux of fertilizer solution stable. A fertilizer injection device with plunger pump was designed. Based on the orifice size and installation location of injection check valve, and power frequency of plunger pump, field experiments on a center pivot irrigation system with fertilizer injection device were carried out to evaluate fertigation uniformity. The results indicated that when the center pivot irrigation system stopped and the plunger pump worked with power frequency of 50Hz, the Christiansen uniformity coefficient CU and variation coefficient CV of fertigation ranged from 99.00% to 99.65% and from 0.46% to 1.37% respectively under the combination of three orifice diameters and three installation locations. The maximum CU could be obtained by using the injection check valve with the orifice diameter of 2.5mm and the installation positioned at the horizontal inlet pipe. And when the center pivot irrigation system ran, the Heermann-Hein uniformity coefficient of fertigation C*UH with single line catch cans ranged from 88.77% to 90.66%, which indicated that the center pivot irrigation system can obtain high fertigation uniformity with the fertilizer injection device. In addition, the fertigation uniformity was compared with plunger pump working at power frequency and non power frequency of 46Hz. It was found that the average electrical conductivity of fertilizer solution had a significant positive correlation with the power frequency. Thus, changing the power frequency of plunger pump can provide an effective way to achieve high uniformity of variable rate fertigation for the center pivot irrigation system.