Master of Science in Biological and Agricultural Engineering (MSBAE)


Biological and Agricultural Engineering

Document Type



In the state of Louisiana surface irrigation is widely used due to the low start-up cost, typically high rainfall, and soil conditions. Irrigation scheduling is an important practice to achieve water use efficiency in agriculture. The objectives of this study were to compare three different methods to determine crop evapotranspiration (ETc) for soybeans in addition to, evaluate a computer based irrigation scheduling program using real scale fields. Weather variables, soil moisture and irrigation water use collected during the summer months of 2005 and 2006 at a production agriculture farm in northeast Louisiana were studied. The ETc estimates obtained using atmometers (ETgage); a weather station approach; an evapotranspiration algorithm from the computer based Arkansas Irrigation Scheduler (AIS). Three weeks of continuous ETc values showed that the atmometer and the weather station methods estimated similar values. The AIS method estimated lower values than the other two methods. The higher estimates by the weather station compared to the AIS are related to higher ETo values throughout the analyzed period. Similar estimation by the atmometer and the weather station methods suggest that these approaches were more suitable than the AIS method for estimating ETc at Angelina Plantation. The AIS proved to be a good scheduling tool that accurately predicts the crop’s irrigation needs. However, the results obtained at Angelina Plantation suggest that the farmer or irrigator programs the irrigation events modified by on-farm requirements. The AIS monitored the Maximum Allowable Depletion (MAD). Higher MAD values at the end of the crop cycle reduced the number of irrigations per field but increased the water use. Non-standard procedures implemented in leveled basins suggested a negative impact in the field drainage and made the irrigation process more labor intensive. Extra care is necessary to avoid waterlogging with level basins.



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Release the entire work immediately for access worldwide.

Committee Chair

Daniel L Thomas



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Engineering Commons