Ecosystem water use efficiency in an irrigated cropland in the North China Plain

• Published in: Journal of hydrology (Amsterdam) Vol. 374; no. 3; pp. 329 - 337
• Main Authors: Tong, Xiao-Juan, Li, Jun, Yu, Qiang, Qin, Zhong
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.08.2009; [Amsterdam; New York]: Elsevier; Elsevier
• Subjects: agricultural land; agroecosystems; corn; crop rotation; crops; diurnal variation; Earth sciences; Earth, ocean, space; Exact sciences and technology; Hydrology; Hydrology. Hydrogeology; irrigated farming; Leaf area index; seasonal variation; Solar radiation; Summer maize; Triticum; Triticum aestivum; Water use efficiency; Water vapor deficit; Winter wheat; Zea mays; China; Far East; Asia; China, People's Rep., North China Plain; Summer maize; Water use efficiency; Water vapor deficit; Solar radiation; Leaf area index; Winter wheat; efficiency; rotation; solar radiation; covariance; air; evapotranspiration; agriculture; surface water; diurnal variations; irrigation; correlation; water vapor; ecosystems; plains; partial pressure; water resource management; temperature; seasonal variations
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2009.06.030

The eddy covariance technique and the cuvette method were used to investigate water use efficiency in an irrigated winter wheat ( Triticum asetivum L.)/summer maize ( Zea mays L.) rotation system in the North China Plain. The results show that ecosystem water use efficiency (WUE e) changed diurnally and seasonally. Daily maximal WUE e appeared in the morning. WUE e generally peaked in late April in wheat field and in late July/early August in maize field. From 2003 to 2006, seasonal mean WUE e was 6.7–7.4 mg CO 2 g −1 H 2O for wheat and 8.4–12.1 mg CO 2 g −1 H 2O for maize. WUE e was much lower than canopy water use efficiency (WUE c) under small leaf area index (LAI) but very close to WUE c under large LAI. With the increase in LAI, WUE e enlarged rapidly under low LAI but slowly when LAI was higher than one. WUE e was greater on the cloudy days than on the sunny days. Under the same solar radiation, WUE e was higher in the morning than in the afternoon. The ratio of internal to ambient CO 2 partial pressure ( C i/ C a) decreased significantly with the increase in photosynthetically active radiation (PAR) when PAR was lower than the critical values (around 500 and 1000 μmol m −2 s −1 for wheat and maize, respectively). Beyond critical PAR, C i/ C a was approximately constant at 0.69 for wheat and 0.42 for maize. Therefore, when LAI and solar radiation was large enough, WUE e has negative correlation with vapor pressure deficit in both of irrigated wheat and maize fields.