Crop coefficient and ratio of transpiration to evapotranspiration of winter wheat and maize in a semi-humid region

Crop coefficient ( K c) is an important parameter for irrigation scheduling and water allocation. This study investigated and determined the crop coefficients and the ratio of transpiration to evapotranspiration ( T p /ET c) of winter wheat ( Triticum aestivum L.) and maize ( Zea Mays) based on lysi...

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Bibliographic Details
Published in:Agricultural water management 2003-04, Vol.59 (3), p.239-254
Main Authors: Kang, Shaozhong, Gu, Binjie, Du, Taisheng, Zhang, Jianhua
Format: Article
Language:English
Subjects:
Agricultural and forest climatology and meteorology. Irrigation. Drainage
Agricultural and forest meteorology
Agronomy. Soil science and plant productions
Biological and medical sciences
corn
Crop climate. Energy and radiation balances
Crop coefficient
crop production
developmental stages
equations
Evapotranspiration
Fundamental and applied biological sciences. Psychology
General agronomy. Plant production
humid zones
irrigated farming
irrigation management
Leaf area index
Maize ( Zea Mays)
mathematical models
measurement
seasonal variation
soil water content
sowing date
stomata
Transpiration
Triticum aestivum
water allocation
Wheat ( Triticum aestivum)
winter wheat
Zea mays
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Summary:Crop coefficient ( K c) is an important parameter for irrigation scheduling and water allocation. This study investigated and determined the crop coefficients and the ratio of transpiration to evapotranspiration ( T p /ET c) of winter wheat ( Triticum aestivum L.) and maize ( Zea Mays) based on lysimeter data for 10 years in a semi-arid region of northwest China (34°20′N, 108°24′E). Several relationships, K c and days after sowing (DAS), K c and leaf area index (LAI), and T p/ET c and LAI, were also analyzed. The average seasonal ET c for winter wheat and maize were 443.6 and 424.0 mm, respectively, compared to their reference crop evapotranspiration (ET 0), 483.9 and 407.7 mm, respectively, for their seasons. The seasonal transpiration accounted for 67.0 and 74.0% of their evapotranspiration for winter wheat and maize, respectively. The average, maximum and minimum seasonal K c were 0.92, 1.33 and 0.42, respectively, for winter wheat, and 1.04, 1.43 and 0.45, respectively, for the maize. The relationship between K c and DAS was fitted to a fifth-order polynomial equation with significant correlation coefficients, R 2=0.960 and 0.980, respectively, for wheat and maize. The maximum K c occurred at about 200 and 80 DAS for winter wheat and maize, respectively. K c and LAI showed a saturation relationship, R 2=0.861 and 0.952, respectively, for wheat and maize, and K c exceeded 1.0 when LAI was larger than 2.5 for both crops. The T p/ET c and LAI also showed saturation relationship, R 2=0.968 and 0.981, respectively, for wheat and maize. T p/ET c started from 0 at sowing, and reached to its maximum, near 0.9, at the middle growth stage or when LAI reached to about 3.0 for both crops. T p/ET c maintained at its maximum when LAI was larger than 3.0. These results should help the precise planning and efficient management of irrigation for these crops in this region.
ISSN:0378-3774
1873-2283
DOI:10.1016/S0378-3774(02)00150-6