Effect of direct-seeding methods on physiological characteristics and grain yield of rice and its cost analysis

Abstract: Little is known about the differences on yield performance, population development, physiological characteristics, cost and economic benefit among different direct-seeding methods of rice. Three direct-seeding methods, manual direct-seeding on dry land (MaDD), manual direct-seeding on wet land (MaDW), and mechanical direct-seeding on wet land (MeDD), were applied. The experiments were conducted using conventional rice, Wuyunjing 23, to investigate the yield and its components, nitrogen use efficiency, number of tillers and productive tillers, dry matter accumulation of shoot and root, leaf photosynthetic rate, root oxidation activity, leaf area index and duration, crop growth rate and cost. The results showed that, compared with MaDD, MeDD and MaDW increased the grain yield by 11.9% and 6.3% and agronomic N use efficiency by 10.1% and 4.9%, respectively. From the yield components analysis, the increase in grain yield was mainly attributed to the increase in panicles per unit area. Compared with MaDD, MeDD significantly increased the number of tillers at heading and maturity stage and productive tillers. Except mid tillering stage, the shoot dry matter weight under MeDD and MaDW was greater than that under MaDD during whole growth period. The shoot dry matter weight under MeDD was greater than that under MaDW at maturity stage. Similar to shoot dry weight, root dry weight performed the same change trend during whole growth period. The ratio of root to shoot under MaDD was the greatest at mid tillering stage. There was no difference on the ratio of root to shoot among the 3 direct-seeding methods except mid tillering stage. Compared with MaDD, MeDD significantly increased the leaf photosynthetic rate and root oxidation activity of rice at heading and maturity stage. At mid tillering stage, there was no difference on leaf area index among 3 direct-seeding methods. Leaf area index under MeDD and MaDW was greater than that under MaDD at middle and late growth stage. Leaf area index under MeDD was greater than that under MaDW at maturity stage. At early growth stage (from sowing to panicle initiation stage), there was no difference on leaf area duration among 3 direct-seeding methods. Leaf area duration under MeDD and MaDW was greater than that under MaDD at middle and late growth stage (from panicle initiation to maturity stage). Leaf area duration under MeDD was greater than that under MaDW at grain filling stage. The crop growth rate showed the similar change trend as leaf area index. MeDD cost the minimum, 3 540 Yuan per hectare in total, which included 1 350 Yuan soil preparation cost, 450 Yuan sowing cost, 1 140 Yuan herbicide and employee cost and 600 Yuan manual weeding and employee cost. Production value and total cost were 24 624 and 14 115 Yuan per hectare under MeDD, respectively. Economic benefit, 10 509 Yuan per hectare under MeDD, was higher than that of MaDD and MaDW. The results suggested that MeDD significantly increased productive tillers and dry matter accumulation from heading to maturity stage, and number of tillers, leaf area index and duration, crop growth rate, leaf photosynthetic rate and root oxidation activity at middle and late growth stage of rice. MeDD also decreased total cost and increased economic benefit because of its high efficiency and low cost in mechanical operation and low weeding cost. In conclusion, MeDD improves leaf photosynthetic performance and enhances aboveground population reasonable growth and underground root activity, and achieves higher grain yield and economic benefits.