Effect of sowing date on dry matter accumulation and yield of maize in hilly regions of Sichuan Province, China

The main maize varieties (‘Zhenghong 505’ and ‘Chengdan 30’) were sowed at 5 dates with 15-day intervals from March 26^th to May 25^th in hilly regions of Central Sichuan Basin to investigate the effects of different sowing dates on the dry matter accumulation and yield of maize. The study also aimed at providing the theoretical basis for the selection of appropriate sowing date of maize in the hilly regions of Central Sichuan Basin. The results showed that with delayed sowing date, the growth period (especially the period from seeding to spinning) shortened, dry matter accumulation and its contribution to yield decreased after spinning and harvest index decreased. However, early sowing increased dry matter accumulation after flowering. Yield formation in late sowing needed more allocation and transport of accumulated photosynthate before flowering. The yield of ‘Zhenghong 505’ maize variety decreased with delayed sowing date, while, the yield of ‘Chengdan30’ slightly increased firstly and then decreasing with delayed sowing. There was no significant reduction in yield of early summer maize ‘Chengdan30’ sown on May 10 and spring maize sown on April 10. However, compared with spring maize, yield of summer ‘Chengdan30’ maize sown on May 25 decreased due to shortened growth period, low dry matter accumulation and low harvest index. For early spring sowing, yield of ‘Zhenghong 505’ maize variety was generally higher than that of ‘Chengdan 30’ maize variety. For summer maize, however, yield of ‘Chengdan 30’ maize variety was higher than that of ‘Zhenghong 505’ maize variety. This suggested that ‘Chengdan 30’ maize variety had a stronger vigor under summer sowing than ‘Zhenghong 505’ maize. Sowing date had greater effect on dry matter accumulation, yield and yield components of ‘Zhenghong 505’ maize than on ‘Chengdan 30’ maize. This indicated that a close attention should be paid to sowing date in maize cultivation. In the hilly regions of Central Sichuan Basin, the suitable sowing date range of spring maize was relatively wide, implying that the production obstacle was rather the contradiction between farming system and mechanized production. More attention should be paid to summer sowing in terms of selection of crop variety and sowing date, which should end by mid-April or early May.