基于土壤水分空间变异的变量灌溉作物产量及节水效果

提高整个田块作物生长指标和产量的均匀性是实施变量灌溉水分管理的目标之一。该研究基于土壤可利用水量(available water holding capacity,AWC)将试验区划分为4个水分管理区,利用相同的灌水控制指标(0.45AWC)进行分区变量灌溉水分管理;作为对照,基于最小AWC区的土壤水分进行均一灌溉水分管理。对比变量灌溉和均一灌溉条件下冬小麦、夏玉米生长指标(株高、叶面积指数、地上部分干物质质量)、叶片相对叶绿素含量、产量及其均匀性,分析AWC对作物生长和产量的影响。结果表明,与均一灌溉相比,夏玉米变量灌溉节水14.1%,冬小麦灌水量相同。与均一灌溉相比,变量灌溉对冬小麦、夏玉米生长指标、叶片相对叶绿素含量和产量的影响均未达到显著水平,而不同AWC管理区之间作物生长指标和产量的差异均达到了显著水平。为获得更高的作物产量,建议不同AWC管理区内采用不同的灌水控制指标。研究可为大型喷灌机变量灌溉水分管理决策提供依据。

Yields and water-saving effects of crops as affected by variable rate irrigation management based on soil water spatial variation

Abstract: Improving the uniformity of crop growth parameters and yield across the field is one of the objectives in utilizing the variable rate irrigation (VRI) technology. To improve the water management level of VRI, the crop growth parameters, including plant height, leaf area index (LAI), aboveground dry matter, leave relative chlorophyll content (SPAD), yield, and their spatial uniformity were compared between VRI and uniform rate irrigation (URI) managements, and the influences of soil available water holding capacity (AWC) on crop growth parameters and yield were also analyzed. This study was conducted at the experimental station of China Agricultural University in Zhuozhou, Hebei Province (39.45°N and 115.85°E) in 2014. This site belongs to the Taihang mountain alluvial flood plain and experiences a warm and semi-humid monsoon climate with an annual mean temperature of 11.6°C and an annual mean precipitation of 563.3 mm. One quadrant of the center-pivot controlled area (1.64 hm2) was used in the experiment. The main soil types were loam and sandy loam, and both the coefficients of variation for sand and clay percentiles increased with depth in the site. During the growing seasons of winter wheat and summer maize, the seasonal rainfall for winter wheat (61.2 mm) was substantially lower than the long-term average, while it (311.6 mm) was ample for summer maize. According to the relationships between field capacity, wilting point, and clay, silt, and sand percentiles measured from the upper 0.6 m of the profile, the experimental area was delineated into 4 management zones with AWC varying from 152.2 mm to 161.4 mm for zone 1, from 161.4 mm to 170.9 mm for zone 2, from 170.9 mm to 185.1 mm for zone 3, and from 185.1 to 204.7 mm for zone 4. Each zone was then equally divided into 2 sub-zones to represent the VRI and URI treatments. Each VRI treatment was individually managed with an equal irrigation trigger point of 0.45AWC. For the URI treatments, irrigation was triggered when soil water content in the management zone having minimum AWC values (zone 1) depleted to 0.45AWC. The soil water content was measured with Trime access tubes and Decagon soil moisture sensors. A center-pivot irrigation machine that had been modified to enable to apply variable rate in different plots was used to implement the experiments. The results indicated that the soil water content was different among management zones with different AWC values, and the difference increased during the growing season of winter wheat as the less rainfall than that for summer maize. Correspondently, the total irrigation amount was same for winter wheat between URI and VRI treatments, while it was 14.1% lower for summer maize than that for the URI treatment since the frequent precipitation decreased the dependence on irrigation. Compared with URI management, there was minor effect of VRI management on spatial uniformity of winter wheat and summer maize; the variation coefficient values for all parameters of winter wheat increased from 0.02 to 0.04, while it decreased by 0.05 and 0.02 for aboveground dry matter and yield of summer maize, respectively. No significant influences of VRI management on crop growth parameters and yield were detected, while their differences were significant among the management zones. The experimental results suggested that the management zones with different AWC should be managed individually with different irrigation trigger points to improve the uniformity of crop growth and to maximize the crop yield.