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Antenna PVC pipe Irrigation Scheduling


The weighted average of the soil water content was used for irrigation scheduling. The weighted average measured by the sensors at 48 hours after the soil was saturated was used as the sensor-measured field capacity (FC). Irrigation was triggered when the soil water content (SWC) dropped close to the level of approximately plant available water (PAW) of 50 percent (see fig. 3). The plant available water is calculated as follows: PAW = 100 × [(Sensor- measured SWC) – (SWC at wilt point)] / (FC – SWC at wilt point).


Caution: This requires understanding the soil FC, PAW and soil water level to trigger irrigation events for different crops.


Figure 3. Irrigation events scheduled in cotton based on sensor-measured soil water content.


Cable between antenna & logger


Figure 2. Bendable antenna mount (left) and soil moisture sensing device with a bendable antenna mount installed in a soybean field for irrigation scheduling (right).


Spring


Base


0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05


15 cm 30 cm 61 cm Weighted avg.


0.00 5/26/13 6/15/13 7/5/13 7/25/13 8/14/13 9/3/13 9/23/13 10/13/13 11/2/13 Time


Disclaimer. Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U. S. Department of Agriculture and does not imply approval of the product to the exclusion of others that may be available.


Ruixiu Sui, PhD, is a research agricultural engineer and lead scientist at the United


States Department of Agriculture, Agricultural Research Service, Crop Production Systems


Research Unit at Stoneville, Mississippi. He holds three patents and has published 150 refereed journal articles and conference papers.


irrigationtoday.org 17


Soil water content {m3


/m3


}


Bendable antenna mount


Soil moisture measurement device installed in field


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