Abstract:
Abstract: The objective of this research was to improve the accuracy and representativeness of the experimental plot date by determining the optimum plot area and the replication number for the wheat drip irrigation. The heterogeneity of soil moisture in experimental plots was provided by Smith heterogeneity index. The relationship between the plot area and the repetition number of the wheat drip experimental plot was measured by Hatheway method. The effect of shape on the accuracy of experimental data was determined by studying the soil moisture heterogeneity index in the horizontal direction of drip tape and the vertical direction of drip tape in experimental plot. The results showed,when the plot area was increased, the variance of soil water in the field was reduced and the relationship between them was in power function . For the plot form 1 m2 to 50-100 m2, the variance decreased significantly. The full irrigation treatment variance was decreased by 0.79-0.84, and the deficit irrigation treatment variance was reduced by 0.79-0.84. For the plot more than 100m2, the increase of plot area had a limited effect on the variance reduction. To determine the optimum size of the experimental plot you need take the factors as below into consideration, as the number of treatments increased, the real difference between treatments decreased, and the required size for the experimental increased. When the size of the plot increased to a certain value, improving the identification ability of test difference by increasing the area of experimental plot was limited and adding the repetition number to improve the distinguishing ability of the difference between treatments was necessary. For 50-100 m2 of experimental plots, when the repetition was increased, the experimental accuracy could be improved with the same area to distinguish the smaller real difference between treatments. By increasing the number of repeats from 2 to 3, the differences of soil moisture between the treatments could be detected which increased from 23.2%-26.5% to 13.1%-15.0%. The recognition ability of the real difference among the treatments could be significantly improved. Hatheway method was used to calculate the optimal experimental plot of the full and deficit irrigation treatment. Due to its larger coefficient variation of soil moisture and heterogeneity index, the deficit irrigation treatment required larger testing area. In order to facilitate the layout of the field experiment, the unified standard of the plot was set up with the optimum specification of deficit irrigation treatment. When the experiment was divided into full and deficit irrigation treatment, the testing plot should be 3 replicates, and the size of each repeat plot should be 50 m2.When the irrigation experiment was divided into three treatments, the experiment layout should be 3 replicates, and the size of each replicate plot was 100 m2. For the experimental plot shape, according to the relationship between the variance of field block and the size of experimental plot, the Power function was fitted by whether the length is greater than the width to calculate the soil moisture heterogeneity index in horizontal the direction of drip tape and the vertical direction of drip tape. About the difference between two directions, the heterogeneity index of deficit irrigation treatment was greater than that of full irrigation treatment. The heterogeneity index in the horizontal direction of drip tape was greater than that in the vertical direction of drop tape. Therefore, the result of rectangular area arranged along the direction of the drip tape was more accurate (smaller deviation) than other shapes. The rectangular experimental plot with aspect ratio between 1:1 and 5:1 could balance the variability of both directions and made the experimental plot more representative. This paper provided a scientific basis for determining the specifications of drip irrigation experimental plot and the theoretical support for the standardization of irrigation experimental layout.