Study On Determination Method Of Optimum Specifications For Field Irrigation Experimental Plot

Irrigation experiment is a basic work to ensure the rational exploitation,efficient utilization,optimal allocation and scientific management of agricultural water resources.The results of irrigation experiment play an important role in the planning,design and management of irrigation engineering.However,as the layout of water-saving irrigation is inconsistent with test sites,the result is poor both in representation and comparability.Therefore,it is of great practical significance to get experimental data with a high precision and representation by scientifically and reasonably determining the optimum experimental plot area.In order to determine the optimum specification for experimental plot under the typical irrigation method in northern Henan,drip irrigation and surface irrigation of winter wheat,and surface irrigation of summer corn were taken as the research object.Then the influence of factors such as the spatial distribution of soil moisture,the border effects of crops and the lateral infiltration of soil moisture were considered to determine the optimum layout of experimental plot.The main conclusions are as follows:(1)The optimum specification for core areas under typical irrigation methods for winter wheat and summer maize were determined.The optimum plot area is 60-80 m~2 at the situation of 1level 1 replication for winter wheat on surface irrigation.It is feasible to set 2 replications with 40 m~2 per repetition or 3 replications with 20m~2 per repetition at the situation of 2 level with the difference between treatments more than 15%.When the difference between treatments is in 10-15%,2 replicates with each repeated 80 m~2 or 3replicates with each repeated 30m~2 can be set.The optimum experimental plot can be designed as a rectangle with a length-to-width ratio from 5:1 to 7:1 along the direction of water flow.For the drip irrigation experiment,the optimum plot area of the experimental plots at 1 level and 1replication is 60-80 m~2.When the experiment is at 2 levels and the difference between treatments is more than 15%,2 replicates with each repetition 80m~2 or 3 repetitions with each repetition 40m~2 can be set.When the difference between the treatments is in 10-15%,it can be set to 2 repetitions with each repeated 150m~2 or 3 repetition with each repeated 60m~2.The optimum experimental plot can be designed as a rectangle along the drip irrigation belt,and the ratio of length to width is from 4:1 to 5:1.The optimum plot area is 70-90m~2 at the situation of 1 level and 1 replication for summer maize on surface irrigation.It is possible to set 2 replications with 70 m~2 per repetition or 3 replications with 30m~2 per repetition at the situation of 2 levels when the difference between treatments is more than 15%,while 2 replications with 150 m~2 per repetition or 3 replications with 50 m~2 per repetition with difference between 10%and 15%.The optimum experimental plot can be set in a rectangular shape with a length-to-width ratio from 5:1 to 10:1 along the direction of water flow.As the number of experimental levels increases,the experiment area can be reduced accordingly.(2)The lateral infiltration range of winter wheat and summer corn with surface irrigation in typical soils of northern Henan Province was determined.After irrigation of winter wheat,lateral seepage of soil moisture in the ridge occurs in the soil layer of 0-60cm,affecting 60cm depth outside the ridge,and soil moisture within 60cm from the ridge.For summer maize,lateral water seepage in ridge occurs within 20-60cm soil layer,affecting 60cm of soil depth in outside of the ridge and 60cm from the ridge for horizontal direction.Thus,the plot interval should be greater than 60cm,or vertical plate buried should be placed at 60cm deep in the center line of the field ridge aiming to avoid the impact of lateral infiltration between treatments after irrigation.(3)The border effects of winter wheat and summer maize were analyzed.The border effects of plant height and leaf area mainly affect the jointing period of winter wheat and summer maize,and the impact range are both from side to 3 lines,while the yield are both to 2lines.(4)The optimum specifications for irrigation experimental plots were determined in North Henan.Based on the specification of core area in experimental plot,the border effect and the range of soil moisture lateral infiltration were considered to determine the optimum experimental plot.The optimum irrigation specification is the core area with a protection zone of 0.6m wide for winter wheat and 1.8m wide for summer maize.