Double cropping wheat and corn in a sub-humid region of China
1994
Zixi, Z. | Stewart, B.A. | Fu, X.
Double cropping wheat (Triticum aestivum L.) and corn (Zea mays L.) is common in sub-humid regions of north China. This study was conducted to evaluate the system without irrigation. During the 5-year study period, annual rainfall averaged 638 mm with 387 mm occurring in July, August and September. Water stress often occurred from mid-April to the end of the wheat growing season in early June, and sometimes extended to the early part of the corn season that begins immediately after wheat harvest and ends in mid-September. Wheat and corn grain yields increased as a linear function of evapotranspiration. Average grain yield was 5.2 Mg ha-1 for wheat and 5.1 Mg ha-1 for corn, with water-use efficiencies, expressed as grain yield per unit of water consumed, of 1.48 and 1.94 kg m-3, respectively. Average precipitation values for the 5-year study period closely paralleled long-term averages, and a probability analysis indicates that yields obtained in the study may be representative of what can be expected over a long period. Therefore, double cropping wheat and corn in this region of China appears highly feasible and results in more than 95% of the precipitation being utilized by evapotranspiration during the growing seasons. Soil water content fluctuates periodically during the year. Phase lags and amplitude decrease with soil depth. One-half of the water utilized by wheat, 175 mm, was furnished by rainfall during the growing season, and the other half was obtained from soil water stored at the time of seeding in mid-October. In contrast, soil water increased during the corn growing season in which rainfall was 384 mm, and evapotranspiration was 263 mm.
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