Abstract: Irrigation is one of the most important measures to regulate plant nitrogen metabolism in winter wheat (Triticum aestivum L.). However, excessive irrigation will cause the decline of nitrogen use efficiency and water use efficiency instead of higher yield and better quality. To determine the effects of irrigation amount on the uptake, distribution, use efficiency of nitrogen, the consumption and use efficiency of water as well as grain yield and quality, we experimented with wheat cultivars, Jimai 20 and Taishan 23 in 2004–2005 (in clay-soil field) and 2006–2007 (in sandy-soil field) wheat growth seasons. In the 2004–2005 growth season in which total rainfall was 196.10 mm, the irrigation treatments were 0 (no irrigation), 180 mm (irrigated 3 times at pre-sowing, jointing, and anthesis stages), 240 mm (irrigated 4 times at pre-sowing, pre-wintering, jointing, and anthesis stages), and 300 mm (irrigated 5 times at pre-sowing, pre-wintering, jointing, anthesis, and grain filling stages), respectively. In the 2006–2007 growth season in which total rainfall was 171.30 mm, the irrigation treatments were 0 (no irrigation), 120 mm (irrigated 2 times at pre-sowing and jointing stages), 180 mm (irrigated 3 times at pre-sowing, jointing, and anthesis stages), and 240 mm (irrigated 4 times at pre-sowing, pre-wintering, jointing, and anthesis stages), respectively. The amount of irrigation was 60 mm each time in both growth seasons. The two cultivars showed similar results in both growth seasons. In the 2004–2005 growth season, nitrogen uptake efficiency and nitrogen accumulation in grain in no irrigation treatment were lower than those in irrigation treatments, and resulted in lower grain yield and nitrogen fertilizer productive efficiency, but the nitrogen distribution proportion in grain at maturity and nitrogen use efficiency were higher in no irrigation treatment. Water use efficiency of two cultivars decreased with the increase of irrigation amount. Before jointing stage, the nitrogen uptake intensity in the treatment of irrigation with 180 mm water was significantly (P<0.05) higher than that of the other two irrigation treatments, but turned converse after jointing stage. The accumulation amount and uptake efficiency of nitrogen in plant had no significant differences among the 3 irrigation treatments at maturity. In Jimai 20, the irrigation treatment with water amount of 240 mm showed more favorable for nitrogen accumulation and distribution in grain, and the nitrogen fertilizer productive efficiency and use efficiency, grain yield (9 159.30 kg ha^-1) were significantly (P<0.05) higher than the other 2 irrigation treatments. But for integrated consideration of nitrogen uptake and accumulation, grain yield and quality, as well as water consumption and use efficiency, the treatment of irrigated 180 mm water was also recommended. In Taishan 23, the nitrogen accumulation amount and distribution proportion in grain at maturity, nitrogen use efficiency, nitrogen fertilizer productive efficiency, and grain quality had no significant difference among the 3 irrigation treatments, indicating that the cultivar was not as sensitive to irrigations as Jimai 20; but the higher grain yields of 9 682.65 and 9 698.55 kg ha^-1 (with water consumptions of 468.54 and 532.35 mm accordingly) were obtained under irrigated treatments with water amounts of 180 and 240 mm, respectively. In the 2006–2007 growth season, the highest grain yields (6 651.23 and 6 942.49 kg ha^-1) of Jimai 20 and Taishan 23 were obtained under the 240 mm irrigation with water consumptions of 490.88 and 474.88 mm, respectively. Our results implied that proper irrigation can increase grain yield, nitrogen use efficiency, and water use efficiency, and improve grain quality; higher grain yield is not resulted from higher amount of irrigation and water consumption. We suggest the following water regimes of Jimai 20 and Taishan 23 in wheat production: irrigating 3 or 4 times at pre-sowing, pre-wintering, jointing, and anthesis stages with water amount of 180–240 mm, and the irrigation at pre-wintering can be ignored based on rainfall and soil water content.

Key words: Irrigation amount, Wheat, Nitrogen uptake, distribution and use, Water consumption amount and water use efficiency, Grain yield and quality