| Abstract:Nutrient management technologies about no-tillage, fertilizer application and straw-returning, which are three crucial procedures in simplified cultivation of rapeseed, were studied by this research. The purpose was to supply some suggestions for establishing a technological system about simplified cultivation of rapeseed. The main results showed as follows.1 Compared with conventional tillage treatment, no-tillage had two adverse effects on rapeseed growth:firstly, no-tillage was in favor of weed development, the N, P2O5, and K2O nutrient rates absorbed by weeds in no-tillage treatment were respectively 1.9 times,2.4 times and 2.5 times as many as conventional treatment. This result indicated that competitive ability of nutrients of weeds in no-tillage treatment was obviously stronger than conventional tillage treatment; secondly, the soil density of no-tillage was significantly higher than conventional tillage, which were bad for root and shoot growth of rapeseed. So some measures must be taked to control these two adverse effects. To the former, straw-mulching was a good method to restrict the weed growth; while to the latter, nutrient rates should be increased.2 A pot experiment was carried out to determine the effects of different N management modes on rapeseed yield and N use efficiency, N leaching as well as N balance. The results showed that both rapeseed yield and N uptake and utilization increased with N fertilizer split application. N fertilizer divided into three times to apply was the best N fertilizer management mode to increase rapeseed yield and N use efficiency. The risk of N leaching was increased evidently when all N fertilizer applied as base. Compared with N fertilizer split application treatments, the total N leaching rates of all N fertilizer applied as base treatment increased averagely by 22.6%. The research about N balance showed that decreasing basal N rates and increasing top-dressing N rates could increase N uptake and utilization and decrease apparently loss rates of N fertilizer. In conclusion, N fertilizer applied before sowing and at the beginning of bud, respectively, was the best N fertilizer management mode, which can meet the require of simplified cultivation, also can guarantee the effect of fertilizer application. 3 Field experiment was conducted to study effect of different N fertilizer applied ratio of base and topdressing on dry matter accumulation, N uptake and yield of rapeseed. Five kinds of ratio were included in this experiment, which were 3:7 (T1),4:6 (T2),5:5 (T3),6:4 (T4) and 7:3 (T5), respectively. The results showed that with basal N fertilizer rates increasing, dry matter accumulated rates of rapeseed changed like a quadratic curve at seedling, bud and pod period of rapeseed growth. T3 treatment was highest in five treatments all the time. The variational tendence of N uptake was same as dry matter accumulation. Yield of T3 treatment was the highest in five treatments, while T1 treatment was the lowest. The result of main quality of rapeseed showed that with topdressing rates increasing, protein content also gradually increased, while the oil content were highest when ratio of base and topdressing were 5:5 and 6:4. The results above indicated that 5:5 was the best ratio when N fertilizer splited two times to apply.4 Field experiment was conducted to study effect of different basal fertilizer applied period on dry matter accumulation, nutrition uptake and yield of rapeseed. The purpose was to resolve the problem of nutrient loss due to basal fertilizer applied at surface of soil in no-tillage. The results showed that when basal fertilizer applied at the same time with rapeseed transplanting, dry matter accumulated rates, nutrient uptake rates and yield of rapeseed were all obviously higher than the treatments whose basal fertilizer applied before rice harvesting, which indicated that throughout method of changing basal fertilizer applied period to resolved the problem of nutrient loss was not reasonable.5 Effect of different basal fertilizer applied depth on rapeseed emergence, growth and yield were studied throughout combining pot experiment with field experiment. The pot experiment results showed that basal fertilizer applied too shallow (2 cm and 4 cm) inhibited the emergence and growth at seedling period of rapeseed seriously. With fertilizer applied depth increasing, the inhibition becomed smaller and smaller. There were some differences in research results between field experiment and pot experiment. No matter what depth the basal fertilizer applied, there was no inhibition putting up in growth of rapeseed. When basal fertilizer applied at 4 cm and 6 cm depth, rapeseed growed well in whole growth period. Among five fertilizer applied depth treatments, yield of 4 cm treatment was highest, while 2 cm treatment was lowest, the yield of former increased by 16.8% compared to latter. In conclusion,4 cm was the best basal fertilizer applied depth.6 Straw-returning research consisted with a pot experiment and a field experiment. The results of the pot experiment showed that both mulching straw and ploughing straw under soil could inhibit the emergence of rapeseed, but the inhibition from the former was more serious than the latter. The effect of straw-mulching on growth of rapeseed at seedling period was very limited, but ploughing straw under soil can restrain the growth of rapeseed at seedling period very much. The results of the field experiment indicated that compared with CK treatment, soil water content heightened. And in different depth of soil, variation of temperature on the same day inclined to moderation with straw mulching. These two beneficial effects could improve signficantly condition of rapeseed growth and nutrient uptake. Compared with no straw-muching treatment, straw mulching could increased significantly rapeseed yield, average increasing rate was 18.1%, but there were few differences in rapeseed yield among treatments of different straw-mulching rates. In conclusion,7500 kg/hm2 was the best straw-mulching rates. When strawing-mulching rates reached to 7500 kg/hm2, the sowing rates should increase 1.2-1.3 times basing on conventional rates.
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