Study On Cultivation Techniques Of Direct-Seeding Rapeseed (Brassica Napus L.) Interplanted In Rice Field

In recent years, since the area of double rice (including late matured rice) and light simplification cultivation of rice expanding constantly, rice maturity has delayed, making the competition between rice and rapeseed more prominent, winter fallow fields of Yangtze River are over a total of 6 million hm2. However, promoting rapeseed under sowed in rice field cultivation model can make rapeseed sowing earlier and ease the contradiction between crops for using the temperature and light resources effectively and increase cropping index, so it's an effective way to use the winter fallow fields of double cropping area in southern of China. At present, in Hubei, Jiangsu, Anhui, Jiangxi, Zhejiang and other provinces, the rapeseed under sowed in rice field cultivation model has been adopted universally, but the appropriate cultivation system has not been built in production, resulting a low and unstable yield. This research studied impacts of symbiosis time of rice and rapeseed and seeding quantity on germination rate, seeding survival rate, growth condition, physiology and biochemistry indicators, yield and quality of rapeseed which under sowed in rice field, then based on suitable symbiosis time of rice and rapeseed and seeding quantity, we used seed treatment to solve long hypocotyls, dead seedlings and other issues in order to provide the basis for promoting the cultivation technology. The main results are as follows:1. Under the cultivation model of rapeseed under sowed in rice field, symbiosis period and seeding quantity were the key factors to affect the density of rapeseed. The rapeseed undersowing rice was favorable for improving the density at the seedling stage, in terms of Wuhan pilot, the seedling density of rape was 545,000 ha-1 when symbiosis period was zero days (CK), but the density of rape was 1069,000 ha-1 when symbiosis period was 5 days, the density of rape was 1268,500 ha-1 when symbiosis period was 10 days, the density of rape was 1432,000 ha-1 when symbiosis period was 15 days. The rapeseed density decreased with delay of the growth period, and the decline of the density at the other growth stages increased with extension of symbiotic period. Symbiosis time and seeding quantity had significant effect on rapeseed density during each growth period of rapeseed; moreover, there was significant positive interaction effect on three leaf stage. The density at maturity period of two experiment locations reached maximum when symbiosis time was 10 days and the seeding quantity was 9.0 kg ha-1, the density of Wuhan pilot was 819,000 ha-1, and the density of Wuxue pilot was 840,000 ha-1.2. The symbiosis period and seeding quantity impact the growth and development status of each period. Compared with CK, the rapeseed under sowed in rice field cultivation model could increase height of plant, number of green leaves, leaf area index(LAI), weight of shoot, weight of root, length of crown, leaf chlorophyll content, sugar and nitrogen content in rape leaves at wintering stage. However, apart from LAI increased with seeding quantity increased, the other indictors were decreased with seeding quantity increased. Therefore, symbiosis period and seeding quantity affected yield component, yield per plant as well as plot yield. Compared with CK, the rapeseed undersowing rice cultivation model can significantly increase the rapeseed yield. In terms of the two pilots of Wuhan and Wuxue, average amplitude was 16.0% when symbiosis period was 5 days, it reached 39.1% when symbiosis 10 days, then it was 20.7% when symbiosis 15 days. And the two pilots all reach the high yield when symbiosis time was 10 days and the seeding quantity was 9.0 kg ha-1, the yield of Wuhan pilot was 2435 kg ha-1, the yield of Wuxue pilot was 2358 kg ha-1, and they were all higher than average yield of Hubei province in recent years.3. Under the cultivation model of rapeseed under sowed in rice field, Paclobutrazot (PP333) and long hypocotyl inhibitor (an agent for treating rape seed explored in this research) could inhibit long hypocotyl, improve seedling quality and increase production significantly. The appropriate concentration range of PP333 and long hypocotyl inhibitor soaking seed were 4ppm to lOppm and 80ppm to 200ppm respectively. But Paclobutrazot inhibited seed germination significantly; the inhibition rate up to 50% or more, and it also affected the uniformity of rape seedlings, the amplitude reached to 59.56%. However, long hypocotyl inhibitor had no significant inhibition to germination, and compared with CK, it had no impact on the uniformity of rapeseed seedlings; the amplitude is only 21.05%. Therefore, long hypocotyl inhibitor is better than Paclobutrazot. In the condition of seed completely immersed in long hypocotyl inhibitor solution, reducing Liquid-material ratio would not change the inhibit effect, and when the seed dried after soaking, the inhibit effect would maintain strong within 4 months.4. Under the cultivation model of rapeseed under sowed in rice field, when symbiosis period was 10 days, compared with CK, long hypocotyl inhibitor soaked seed could shorten the length of crown by 50% and increase the rate of seedling survival by 20%, so the density at maturity stage was higher than CK and the increasing degree was up to 19.3%. For the Huashuang5 planted in Wuhan from 2009 to 2010, when seeds treated with long hypocotyl inhibitor, the plant height, number of primary branches, number of pod per plant were higher than CK significantly, but number of seeds per pod and 1000-seeds weight decreased, so the difference of yield per plant at maturity stage were not significant. However, the density at maturity stage was significantly higher than that of CK, which led to a significant increase in actual production, and the increase degree was 22.6%. For Zhongshuang10, treated with line seedling inhibitor and planted in Wuxue, the actual production increased by 20.7% compared with CK.