An Improved Frequency Domain Technique for Determining Soil Water Content

For many years a soil water content sensor with low cost, reliability and sufficient accuracy has been desirable. Thus, an improved measurement method based on the frequency domain (FD) principle for determining soil water content was considered. Unlike other measurement principles, a new measurable index, η, which was independent of the output impedance and the amplitude of the oscillator while relying on the electrical impedance of a multi-pin probe, was pro- posed. Moreover, a model for processing the impedance of the multi-pin soil probe was developed, and several important electrical parameters for establishing their operating ranges applicable to this probe were evaluated. In order to confirm the theoretical analysis, an experiment was conducted with a 4-pin probe. Using the developed model, the relationship between the proposed index η and soil volumetric water content was shown to be linear (R2 = 0.9921). Thus, as the measurable index, η seemed satisfactory.

棉花自动化滴灌灌水频次对土壤墒情及产量的影响

为研究棉花自动化滴灌灌水频次对土壤墒情及产量的影响,于2019-2020年在新疆昌吉农业园区现代化灌溉示范区,对棉花自动化滴灌在相同灌溉定额(W=4800 m^(3)/hm^(2))、施肥量(尿素300 kg/hm^(2),二胺234.67 kg/hm^(2),硫酸钾117.33 kg/hm^(2))及其他农艺管理措施与大田保持一致时,试验设置4个处理,分别对各处理3个重复进行灌水频次试验研究。结果表明:灌水频次处理(T1:12次、T2:10次、T3:8次、T4:6次)时棉花籽棉产量分别为5751.72、5434.22、5353.71、5261.89 kg/hm^(2),水分利用效率为1.20、1.13、1.20、1.10 kg/m^(3),其0~40 cm深度平均土壤含水率为23.84%~34.51%、21.45%~32.97%、19.52%~32.67%、16.94%~32.37%;在气候、土壤、田间及管理措施等条件相同的情况下,推荐棉花生育期内灌水次数12次、灌水周期6 d作为棉花自动化滴灌灌水频频次和灌水周期。