滴灌均匀性对土壤水分传感器埋设位置的影响

合理选择土壤水分传感器埋设位置以减少监测点密度和成本,是基于无线传感器网络制定灌溉处方图亟待解决的一个关键问题。该研究基于土壤含水率时间稳定性原理,将直接代表平均土壤含水率的点位用于土壤水分传感器布设位置点的选取,在水平方向分布均匀,垂直剖面土壤颗粒组成变异程度随土层深度增加的粉壤土田块内分析了低、中、高灌水均匀系数(分别为0.6、0.8和0.97)对春玉米主要根系层土壤含水率空间分布均匀性和时间稳定性的影响。结果表明,春玉米生育期内,随灌水均匀系数降低,土壤含水率空间分布均匀度降低,但低、中、高灌水均匀系数处理的土壤含水率均匀系数均大于0.81;低、中、高灌水均匀系数处理的平均Spearman秩相关系数均达到了显著水平(P0.05),但土壤含水率空间分布结构相似性随灌水均匀度的增加而减小;对高灌水均匀系数处理,0~0.2、0.2~0.4、0.4~0.6、0.6~0.8 m土层直接代表平均土壤含水率的测点比例分别为83%、78%、53%和86%。随灌水均匀系数降低,各土层直接代表平均土壤含水率的测点数量减少,说明土壤水分传感器随机布设引起的测量误差将随滴灌灌水均匀度的减小而增大。

Influence of drip irrigation uniformity on buried position of soil moisture sensor

Abstract: Prior to adopting the wireless sensor network system to schedule the irrigation, one of the key problems needing to be resolved is developing the placement criteria for soil moisture sensors to decrease the measurement density and investment. In this study, the temporal stability of soil water content was used to guide the sensors to be placed in the positions directly representing the plot-average soil water content. The influences of drip irrigation uniformity on spatial distribution uniformity and temporal stability of soil water content were also investigated to analyze the choosing probability of buried locations for soil moisture sensors with different drip irrigation uniformity. This field study was conducted at the experimental station of China Institute of Water Resources and Hydropower Research in Daxing District, Beijing City in 2011 and 2012. During the growing season of spring maize, the effective rainfall was 356 and 381 mm in 2011 and 2012, respectively, and irrigation was applied 4 times in each year. The low, medium and high drip irrigation uniformity, corresponding to the Christiansen uniformity coefficient (Cu) of 0.60, 0.80 and 0.97, respectively, were used in the irrigation of the spring maize. The low and medium Cu values were obtained by randomly assembling segments of drip tubes with 5 different nominal discharge values (1.05, 1.4, 1.65, 2.3, and 2.6 L/h at 0.1 MPa) along the entire length of the line. A temporal stability analysis of soil water content was conducted by regularly measuring soil water contents at 54 locations in the ?eld during the growing season of maize. Results indicated that the uniformity coefficient of soil water content was bigger than 0.81 in all treatments and it decreased with the decreasing of drip irrigation uniformity. The average Spearman''s rank correlation coefficient was significant at the probability level of 0.05 in all treatments, while the structure similarity of soil water content distribution decreased with the increasing of irrigation uniformity. The soil water content in all measurement points has great temporal stability within and between experimental years. In the high drip irrigation uniformity treatment, the percentage of positions directly representing the mean soil water content was 83%, 78%, 53%, and 86% in layer of 0-0.2, >0.2-0.4, >0.4-0.6, and >0.6-0.8 m, respectively, and it decreased with the decreasing of drip irrigation uniformity. The experimental results demonstrated that the buried locations for soil moisture sensors can be determined only through one-year study, and its choosing probability is lowered with the decreasing of drip irrigation uniformity.