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Study on Monitoring Points’ Layout and Spatial Variability of Soil Moisture in Automatic Drip Irrigation with Plastic Mulch in Cotton Field

Author: LiFangSong
Tutor: LeiXiaoYun
School: Xinjiang Agricultural University
Course: Agricultural Soil and Water Engineering
Keywords: Cotton Drip irrigation under mulch Soil moisture Spatial variability Monitoring points
CLC: S152.7
Type: Master's thesis
Year: 2011
Downloads: 97
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Abstract

Compared with surface irrigation, drip irrigation with plastic mulch in cotton field is an advanced irrigation technique.The advantages of that can be specified as following:a.consume less water; b. drain off soil salt; c.save land and workforce; d. adopt the technique of fertigation which can save the cotton from later recession by full fertilization; e. raise cotton quality; f.lessen production cost.But restricted by water shortages and increasing labour cost, this technique is inevitably developed towards automation and artificial intelligence.However, the realization of automation and artificial intelligence require some basic research work,for example:monitoring and forecast of soil moisture etc.As the spatial variability of soil moisture objectively exists, it seems very important to strengthen the academic research on spatial distribution of soil moisture variability and the rational layout of monitoring points in automatic drip irrigation under membrance in cotton field.Recently, some researches on spatial variability of soil moisture in surface irrigation and sprinkling irrigation were conducted while few of them were under membrance. In terms of different crop, different agrotype and different weather conditions, the specific under membrance drip irrigation patterns is also different.Advanced wireless sensor network information technology has already been applied in farmland information monitoring management by abroad developed countries. On the contrary, in China, soil moisture monitoring by large scale depends on remote sensing technique while artificial fixed-point measurement is a basic method in small scale.There are few systematic researches were done on the rational layout of monitoring points of soil moisture by moderate scale.For that reason, this paper analyzed the layout of monitoring points and spatial variability of soil moisture in automatic drip irrigation under membrance in cotton field using statistic and Geoinformational methods via some softwares such as SPSS 17.0,Arcgis9.3. The main conclutions on the spatial variability of soil moisture and the layout of monitoring points are as follows: 1. The spatial variability of soil moisture are moderate or weak in arid sandy loam conditions; As the depths increases.soil moisture and the mean value of variation coefficient both have an obvious increasing trend.This indicates that soil moisture variability are strengthening as depth increment;2. Soil moisture exist spatial autocorrelation when the depth range from 11.2m to 32.2m, and the variograms can met a spherecial model with a good fitting degree. The ratio of nugget variance to sill variance vary between 25% and 75% which represents moderate spatial autocorrelation.3. The distribution of soil moisture in seedling stage is of a little complexity, and it tends to be equally distributed at later stage.4. The monitoring points should be laid in a distance of 0-0.475m from drip irrigation belt in the cotton cultivation mode of four cotton lines under a plastic mulch with one drip irrigation belt fixed in the center (25 cm+45 cm+ 25 cm+40 cm)5. The combination of the classical statistics and geostatistics is a good way of study to reduce monitoring points numbers.Especially the application of area percentage statistics of soil moisture isogram, by which we can obtain the worst and arid area. We can decorate monitoring points in such area that can help us reduce the number of monitoring points.6. It is best to put the monitoring instrument at the depth of 20-40 cm in order to reduce the effect of human activities; It is appropriate to locate them at the depth of 10-30 cm to monitor soil moisture in seedling stage; If we want to monitor soil moisture in long time period, it’s good to put the monitoring instrument at the depth of 30-40 cm.

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CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil physics > Soil moisture
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