Abstract: Improving radiation use efficiency (RUE) of the canopy is necessary to increase wheat (Triticum aestivum) production.  Tridimensional uniform sowing (U) technology has previously been used to construct a uniformly distributed population structure that increases RUE.  In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE.  This study was done during 2014–2016 in the Shunyi District, Beijing, China.  The soil type was sandy loam.  Wheat was grown in two sowing patterns: (1) tridimensional uniform sowing (U); (2) conventional drilling (D).  Four planting densities were used: 1.8, 2.7, 3.6, and 4.5 million plants ha^–1.  Several indices were measured to compare the wheat canopies: photosynthetic active radiation intercepted by the canopy (IPAR), leaf area index (LAI), leaf mass per unit area (LMA), canopy extinction coefficient (K), and RUE.  In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D.  LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns.  IPAR and LAI increased with increasing density under the same sowing pattern.  However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha^–1 treatments was not significant for both sowing patterns.  Therefore, LAI within the same planting density was not affected by sowing pattern.  RUE was the largest for the U mode with a planting density of 3.6 million plants ha^–1 treatment.  For the D sowing pattern, the lowest planting density (1.8 million plants ha^–1) resulted in the highest yield.  Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha^–1 treatment, but the highest RUE and highest yield were observed under this condition.  For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha^–1.  These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns.  The effect of sowing pattern×planting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant (P<0.05).  Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE (r=0.880, P<0.01), LMA (r=0.613, P<0.05), and spike number (r=0.624, P<0.05).  These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha^–1, can effectively increase light interception and utilization and unit leaf area.  This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number (P<0.05), kernel number, grain weight, and an overall increase in yield.

Key words: tridimensional uniform sowing ,  extinction coefficient ,  leaf area index ,  leaf mass per unit area ,  wheat