Radiation use efficiency and yield of winter wheat under deficit irrigation in North Chin

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Water stress is a frequent and critical limit to wheat (<I>Triticum aestivum</I> L.) production in North China. It has been shown that photosynthetic active radiation (PAR) is closely related to crop production. An experiment was conducted to investigate the effects of deficit irrigation and winter wheat varieties on the PAR capture ration, PAR utilization and grain yield. Field experiments involved Jimai 20 (J; high yield variety) and Lainong 0153 (L; dryland variety) with non-irrigation and irrigated at jointing stage. The results showed that whether irrigated at jointing stage or not, there was no significant difference between J and L with respect to the amount of PAR intercepted by the winter wheat canopies. However, significant differences were observed between the varieties with respect to the amount of PAR intercepted by plants that were 60–80 cm above the ground surface. This result was mainly caused by the changes in the vertical distributions of leaf area index (LAI). As a result, the effects of the varieties and deficit irrigation on the radiation use efficiency (RUE) and grain yield of winter wheat were due to the vertical distribution of PAR in the winter wheat canopies. During the late growing season of winter wheat, irrespective of the irrigation regime, the RUE and grain yield of J were significantly (LSD, <I>P</I> < 0.05) higher than those of L. These results suggest that a combination of deficit irrigation and a suitable winter wheat variety should be applied in North China.