Effects of row spacing and seeding rate on radiation use efficiency and grain yield of wheat

This study investigated the effects of row spacing (RS) and sowing rate (SR) on vegetative growth, radiation use efficiency (RUE) and grain yield of winter wheat. A field experiment was carried out in 2007 2008 at the Yucheng Comprehensive Experimental Station of Chinese Academy of Sciences, which is located in the North China Plain. The experiment included 9 treatments consisting of 3 row spacings and 3 sowing rates. The row spacings were 20 cm, 25 cm and 30 cm whereas the sowing rate were 6 kg·667m 2, 9 kg·667m^-2 and 12 kg·667m^-2. The treatments were laid out in a randomized complete block design with three replicates. Plots were 6 m long and 8 m wide and border rows were excluded from sampling to eliminate edge effects. Plant stem density, leaf area index were determined at seedling, jointing, booting, flowering, filling, milky-ripe and harvest stages, grain yield and yield compliments were determined at harvest stage. The intercepted radiation was measured from reviving to maturity stage. The results showed that row spacing had greater effect on winter wheat growth than sowing rate. Furthermore, there was no significant interaction between row spacing and sowing rate. The change trend in plant stem density varied within row spacing and was constant within sowing rates. Although the most tillers per plant was under row spacing of 20 cm, the spike rate of tillers was the least. The change in leaf area index (LAI) was the same as that in plant stem density. However, leaf area duration (LAD) increased with both widening row spacing from 20 cm to 30 cm and increasing sowing rate from 6 kg·667m^-2 to 12 kg·667m^-2. Grain yield and radiation use efficiency (RUE) increased significantly with widening row spacing under the same sowing rate, which was strongly correlated with stem density. Average grain yield increased by 81.62 g·m^-2 and 162.53 g·m^-2 as row spacing increased from 20 cm to 25 cm and 30 cm. Meanwhile average RUE increased by 0.18% and 0.35% as row spacing increased from 20 cm to 25 cm and 30 cm. Sowing rate slightly affected grain yield and RUE. Moreover, there was no obvious interaction effect of row spacing by sowing rate on grain yield and RUE. The results indicated that row spacing generally had a greater effect on wheat vegetative growth, grain yield and RUE than sowing rate. It was therefore strongly suggested to change from the conventional row spacing of 15 20 cm to the more efficient row spacing of 25 30 cm of wheat production and good field conditions in the North China Plain. Sowing rate also increased appropriately on the basis over conventional rates, which increased grain yield and RUE of wheat.