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Title: Simulation of over-winter soil water and soil temperature with SHAW and RZ-SHAW

Author
item LI, ZIZHONG - China Agricultural University
item Ma, Liwang
item Flerchinger, Gerald
item Ahuja, Lajpat
item WANG, HAO - China Agricultural University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2012
Publication Date: 8/17/2012
Citation: Li, Z., Ma, L., Flerchinger, G.N., Ahuja, L.R., Wang, H. 2012. Simulation of over-winter soil water and soil temperature with SHAW and RZ-SHAW. Soil Science Society of America Journal. 76:1548-1563.

Interpretive Summary: Correct simulation of over-winter condition is important for the growth of winter crops and for initial growth of spring crops. The objective of this study was to evaluate RZWQM, SHAW and their hybrid RZ-SHAW for simulations of soil water and soil temperature of a Siberian Wildrye grassland in winter. Total soil water content, liquid water content, soil temperature and the depths of the frost and thaw in the 0-60 cm soil profile were measured from 2005 to 2007. The results showed that the RZ-SHAW model provided similar or better simulation than the original SHAW model for total soil water content, liquid water content, soil temperature and the depths of the frost and thaw. Both RZ-SHAW and SHAW simulated the soil freezing process well, but were less accurate in simulating soil thawing processes. Pre-winter irrigation effects on total water and liquid water could only be simulated during the freezing period. RZWQM could be used to simulate total water content and soil temperature during the winter, but was unable to simulate soil freezing.

Technical Abstract: Correct simulation of over-winter condition is important for the growth of winter crops and for initial growth of spring crops. RZ-SHAW (RZWQM-SHAW) is a newly developed model by coupling the Root Zone Water Quality Model (RZWQM) and the Simultaneous Heat and Water (SHAW) model. The objective of this study was to evaluate RZ-SHAW for simulations of soil water and soil temperature of a Siberian Wildrye grassland in winter by comparing with the original SHAW model and the original RZWQM model. Two irrigation treatments were designed to study pre-winter irrigation effects on soil water status in the following spring in two winter seasons (2005-2006 and 2006-2007), with measurements of total soil water content, liquid water content, soil temperature and the depths of the frost and thaw in the 0-60 cm soil profile. Across the treatments and years, the average root mean square deviation (RMSD) for simulated total soil water content was 0.030 m3 m-3 by both RZ-SHAW and SHAW models, and that for liquid water content was 0.028 m3 m-3 for both models. Both models provided better simulation of total and liquid soil water contents without pre-winter irrigation than with pre-winter irrigation with average RMSD of 0.022 m3 m-3 vs. 0.037 m3 m-3 by RZ-SHAW and 0.024 m3 m-3 vs. 0.042 m3 m-3 by SHAW for total soil water, and with average RMSD of 0.022 m3 m-3 vs. 0.034 m3 m-3 by RZ-SHAW and 0.022 m3 m-3 vs. 0.039 m3 m-3 by SHAW for liquid water. On average, RZ-SHAW simulated better soil temperature with average RMSD of 2.2oC compared to that of 3.1 oC by SHAW. Both RZ-SHAW and SHAW simulated the soil freezing process well, but were less accurate in simulating the soil thawing processes.