Study On Nutrient Absorption Of Early Maturing Rapeseed Varieties In Three-ripe Areas Of South China

It is an inevitable measure to increase the planting area of rape and increase the yield of rape by using the winter idle fields and winter light-temperature resources of double-cropping rice area in south China to develop the three-ripe winter rape system,which is of great significance to increase the self-sufficiency rate of edible oil in China.In order to solve the problem of crops in rotation system of rape planting in three-ripe areas of south China,a number of early winter rape varieties have been cultivated in recent years by breeders,however,the nutrient absorption regulation of these early maturing varieties has not been studied in depth,which restricts the green and efficient production of three-ripened rape and the full production potential of early maturing winter varieties.Therefore,in this study,two early maturing winter rape varieties and two conventional maturity winter rape varieties are used as experiment materials.Through continuous field trials for two years,the differences in regularity of dry matter accumulation and nutrient uptake between early maturity and conventional maturity winter rape varieties are investigated,which provide a basis for the scientific fertilization of rape in rice-rice(ratooning rice)-oil rotation.The main results are as follows:1.The results of studies on rape dry matter accumulation and nutrient absorption showed that there was no significant difference in yield between the two mature varieties tested,the harvest index of one early maturing variety was significantly higher than that of conventional maturity varieties in 2017-2018,and the harvest index of two early maturing varieties was significantly higher than that of conventional maturity varieties in 2018-2019(hereinafter referred to as 17-18 year and 18-19 year).The net increment in dry matter of two mature varieties was the greatest during the flowering stage or silique stage(differences between varieties and annual),the sum of the net increment in dry matter in these two periods accounted for more than 60% of the total dry matter accumulation,among them,two early maturing varieties accounted for 79.9%-80.0% in 17-18 year and 68.2%-69.1% in18-19 year,two conventional maturity varieties accounts for 61.0%-64.6% in 17-18 year and58.6%-60.0% in 18-19 year,that was,the percentage of dry matter accumulation in early maturing varieties was significantly higher than that in conventional maturity varieties in late growth period.The net increment of nitrogen was the largest in the flowering stage of early maturing varieties and in the seedling stage of conventional maturity varieties,the ratio of net increment to the total accumulation for nitrogen,early maturing varieties in the flowering stage were 46.8%-47.7% in 17-18 year and 33.7%-41.9% in 18-19 year,conventional maturity varieties in the seeding stage were 48.6%-73.9% in 17-18 year and 53.4%-56.7% in18-19 year.In the period with the highest net increment for phosphorus,early maturing varieties were mainly in the silique stage(only one variety was in the flowering stage in17-18 year),and conventional maturity varieties were in the flowering stage,the proportion of net phosphorus increment during the silique stage in early maturing varieties was24.0%-47.5%(17-18 year)and 31.7%-39.3%(18-19 year),and that in conventional maturity varieties was 13.8%-0.9%(17-18 year)and 14.2%-26.0%(18-19 year),which in early maturing varieties was significantly higher than that in conventional maturity varieties.The net increment of potassium both varieties was the largest in the flowering stage,but early maturing varieties in the second high accumulation period were in the silique stage or the bolting stage and conventional maturity varieties were in the seedling stage,indicating that the potassium accumulation of early maturing varieties was also lagging behind.In short,the accumulation of dry matter and nutrients in early maturing varieties were mainly concentrated during the flowering stage-the silique stage,and there was a lag phenomenon in early maturing varieties.2.The results of studies on organ dry matter accumulation and nutrient absorption showed that the highest period of leaf dry matter and nutrient accumulation for two mature varieties was the seedling stage,but the ratio of net increment to the total accumulation of early maturing varieties was lower than that of conventional maturity varieties in that period,while net increment after the seedling stage was opposite;With the second high period of nitrogen and potassium accumulation,the early maturing varieties was in the flowering stage、the conventional maturity varieties was in the bolting stage,and both varieties in that period of phosphorus accumulation were in the bolting stage,but the net increment ratio of early maturing varieties was significantly higher than that of conventional maturity varieties.For the net increment of dry matter and nutrient in the stem,the highest period of two mature varieties was the flowering stage,while the second high period for the net increment of dry matter,early maturing varieties was in the silique stage,conventional maturity varieties was in the bolting stage,for the net increment of nutrient,two mature varieties were both in the bolting stage or the seedling stage.The largest period of dry matter net increment in the root of early maturing varieties was the flowering stage,and that of conventional maturity varieties was the seedling stage or the flowering stage.Early maturing varieties was significantly lagged behind conventional maturity varieties for nutrient accumulation in the root,both mature varieties had the largest net nitrogen increment at the seedling stage,but their proportion of early maturing varieties was lower than that of conventional maturity varieties,while the proportion of early maturing varieties was higher than that of conventional maturity varieties in the bolting stage and the flowering stage,the net increment of phosphorus and potassium in early maturing varieties were the largest during the bolting or flowering stage(the two varieties were different),it was the largest at the seedling stage for conventional maturity varieties.The ratio of dry matter and nutrient net increment of reproductive organs,the early maturing varieties was higher than that of conventional maturity varieties in the silique stag,the early maturing varieties was lower than that of conventional maturity varieties in the flowering stage.In short,there was a lag in the accumulation of dry matter and nutrients in each organ of early maturing varieties compared with that of conventional maturity varieties.