Interannual water vapor and energy exchange in an irrigated maize-based agroecosystem

• Published in: Agricultural and forest meteorology 2008-03, Vol.148 (3), p.417-427
• Main Authors: Suyker, Andrew E., Verma, Shashi B.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agricultural and forest meteorology; agroecosystems; Agronomy. Soil science and plant productions; Biological and medical sciences; canopy; Canopy conductance; corn; Energy exchange; energy transfer; Evapotranspiration; Fundamental and applied biological sciences. Psychology; gas exchange; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Glycine max; growing season; irrigated farming; leaf area index; leaf conductance; Maize; nitrogen content; no-tillage; Soybean; soybeans; species differences; Water balance and requirements. Evapotranspiration; water vapor; Zea mays
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2007.10.005

In this paper, we present results from 4 years (May 2001–May 2005) of water and energy flux measurements made in a no-till, irrigated maize–soybean rotation system in eastern Nebraska, USA. The peak green leaf area index (LAI) reached 6.0 and 5.5 in maize (2001 and 2003, respectively) and 5.7 and 4.4 in soybean (2002 and 2004, respectively). The dependence of evapotranspiration (ET) on leaf area was consistent with previous studies. There was a nearly linear relationship between the daily ET/ET o (where ET o is the reference evapotranspiration over a grass reference crop) and LAI until a threshold LAI (between 3 and 4). Above this threshold LAI, the ET/ET o was virtually independent of LAI. The cumulative growing season (planting to harvest) evapotranspiration was 544 and 578 mm for maize, and 474 and 430 mm for soybean. The interannual variability in the growing season ET totals correlated very well with the number of days when the LAI was greater than 3. The non-growing season period (harvest to subsequent planting) contributed between 20 and 25% of the annual ET totals for both crops. The maximum canopy surface conductance ( G smax) was 29 mm s −1 for maize in both years, 41 mm s −1 for soybean in 2002 (peak LAI = 5.7) and 36 mm s −1 for soybean in 2004 (peak LAI = 4.4). The variability in G smax was largely explained by the leaf nitrogen concentration, consistent with the literature.