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ARS Home » Southeast Area » Mississippi State, Mississippi » Crop Science Research Laboratory » Genetics and Sustainable Agriculture Research » Research » Publications at this Location » Publication #316568
Title: Effects of soil water holding capacity on evapotranspiration and irrigation scheduling

Author
item Feng, Gary
item Sui, Ruixiu
item Read, John
item ZHANG, BANGBANG - China Agricultural University
item Jenkins, Johnie

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The USDA Natural Resources Conservation Service (NRCS), through the National Cooperative Soil Survey, developed three soil geographic databases that are appropriate for acquiring soil information at the national, regional, and local scales. These relational databases include the National Soil Geographic (NATSGO) database, the State Soil Geographic (STATSGO) database, and the Soil Survey Geographic (SSURGO) database. The NATSGO database is used primarily for appraisal and monitoring of resources at the national scale of 1:5,000,000. The STATSGO database was designed for a regional scale of 1:250,000 across the contiguous United States. The SSURGO database provides finer-resolution information and was designed primarily for managing and inventorying resources at the farm to county scales ranging from 1:12,000 to 1:63,360. STATSGO database contains general soils information, but data available in STATSGO cannot be readily extracted nor parameterized to support regional environmental quality modeling. As such, each user must individually and repeatedly process data in STATSGO to obtain necessary soil properties. Therefore, we developed a comprehensive database, the Western States Soil Database (WSSD), for use in modeling regional soil and water resources and environmental quality across eight western states. It was successively used by a grid-based SMOKE-MM5-CMAQ-WEPS hybrid model. Results are acceptable as SSURGO database was used by WEPS model to estimate soil erodibility for a county at large scale. Then we tried to utilize SSURGO database for irrigation management at field scale. Soil physical and hydraulic properties in SSURGO database were evaluated at field scale in the west Delta and east Blackland Prairie of Mississippi. Forty soil samples from the top 0-15 cm at grid cell of 50 x 50 m were taken in a 7 ha field located in Delta. Difference in clay content between measured and SSURGO values ranged from 19 to 74%, while difference in silt content ranged from 30 to 55% for 80% of soil samples. Soil samples of three soil types, Vaiden silt clay, Okolona silt clay and Demopolis loam, were taken in the Blackland Prairie. Available Water Content (AWC, cm cm-1) was measured in comparison with SSURGO and soil texture based values for irrigation scheduling. Since both Vaiden and Demopolis are silt clay, their soil texture based AWC is 0.12, while Demopolis loam is 0.16. Only a range of AWC is provided in SSURGO database which is 0.1-0.15 for Vaiden soil all the way down to 100 cm depth, 0.2-0.22 at 0-18 cm and 0.18-0.2 at 18-100 cm depth for Okolona soil, 0.1-0.17 at 0-23 cm and 0.03-0.06 at 23-100 cm depth for Demopolis soil. In contrast, measured AWC value is 0.23 at 0-15 cm and 0.21 at 15-100 cm depth for Vaiden soil, 0.14 at 0-18 cm and 0.11 at 18-100 cm depth for Okolona soil, 0.18 at 0-23 cm and 0.14 at 23-100 cm depth for Demopolis soil. Certain percentage (i.e., 50%) of AWC in rooting zone is often taken as irrigation trigger point which is called Management Allowable Depletion (MAD). Selection or measurement of AWC can greatly affect when and how much an irrigation should be applied. As an example of Demopolis soil, on-site measured AWC could trigger an irrigation 10 more days earlier than AWC from other data sources for soybean in Mid or late July, 2014. Twenty mm difference in irrigation amount for replenishing soil profile was found among those trigger criteria. In comparison of measured values to the commonly used soil textured based AWC, 13 days difference in irrigation timing and 60-70 mm difference in maximum root zone was calculated. Compared measured AWC with SSURGO values, differences of 18 days in irrigation timing and 60 mm in irrigation amount were calculated. It suggests that AWC as a critical value for determining irrigation timing and amount should be measured on-site, soil texture based AWC and SSURGO datab