| In the context of agricultural supply-side structural reform and agricultural green development in parallel,rice production must not only improve yield and quality,but also improve nitrogen use efficiency and reduce fertilizer application,so as to improve rice production efficiency.It is obvious that only rice varieties with high quality,high yield and high nitrogen ues efficiency can adapt to this new production demand.In addition,with the transfer of rural labor force,labor-saving and cost-saving rice cultivation management has become one of the important characteristics of modern rice cultivation development.In rice production,quick-effective nitrogen fertilizer is widely used.In the process of rice production,multiple application of nitrogen fertilizer takes a lot of labor,and the fertilizer efficiency is low and often can not meet the requirements of systematic fertilizer for rice growth.In recent years,controlled release nitrogen fertilizer(CRNF)has developed rapidly.Compared with common chemical nitrogen fertilizer,CRNF optimized design can realize one-time base application in the whole growth period,greatly save labor and improve fertilizer utilization efficiency.In the southern of the lower Reaches of the Yangtze River,the distribution area of late japonica with long growth period is the most concentrated in China due to good hydrothermal temperature conditions.In this area,it is not only famous for high yield and large amount of fertilizer application,but also more urgent for late japonica rice with high quality,high yield and high nitrogen use efficiency and labor-saving and efficient fertilization technology due to economic development and labor shortage.Therefore,it is an urgent problem that how to screen late japonica rice with high quality,high yield and high nitrogen use efficiency and establish a formula suitable for one-time application of controlled release nitrogen fertilizer.Based on the above background,this study was based on area of the single cropping late-maturing Japonica rice in the southern of lower reaches of Yangtze River,62 late-maturing japonica rice varieties(lines)in this area were collected as materials,which were divided into soft rice and non-soft rice.In this study,the differences of rice yield,quality and nitrogen absorption and utilization efficiency among different rice varieties were systematically studied,and the characteristics of high quality,high nitrogen yield and high efficiency japonica rice varieties were comprehensively screened from 2017 to 2018,Then,one-time fertilization study of CRNF was carried out,in order to provide theoretical basis and technical support for improving quality,yield and efficiency of late japonica rice production in this region from 2018 to 2019.The main results are as follows:1.Screening of good quality,high yield and high nitrogen use yield late japonica varieties:There was no significant difference in yield and nitrogen use efficiency between soft rice and non-soft rice varieties of late-maturing japonica rice.There was little difference in processing quality between the two varieties,and the processing quality of all rice varieties was in line with the national quality grade 3 rice standard;The appearance quality of soft rice was significantly worse than that of non-soft rice,especially the chalkiness grain percentage and chalkiness degree were significantly higher than that of non-soft rice;The amylose content and protein content of soft rice varieties were significantly lower than those of non-soft rice varieties,and the gel consistency was longer,and the eating quality of rice was significantly higher than that of non-soft rice varieties;According to the actual distribution of rice taste value,yield and recovery nitrogen use rate of all japonica rice varieties in the range and combined with cluster analysis method,classification critical value of taste value(X)of non-soft rice type,level 1:X?60;level 2:60>X?55;level 3:55>X?50.classification critical value of taste value(X)of soft rice type and level 1:X?75;level 2:75>X?70;level 3:70>X?65.All japonica rice varieties were classified into high yield type:X?10.00t hm-2 and middle yield type:10.00t hm-2>X 9.25t hm-2.N recovery use efficiency(?40%)was high N use efficient cultivar.Rice with taste value up to level 1 rice type,yield up to high yield type and nitrogen use efficiency up to high nitrogen use efficiency type were taken as standards,ten rice cultivars with good taste value high yield and high nitrogen use efficiency(GHH)were screened.Among them,there are 4 non-soft rice types,which are Changnongjing 14-7,Wuyunjing23,Wuyunjing2917and Wuyunjing30.There are 6 types of soft rice,including jia 58,jia 67,Nanjing 46,Nanjing 5055,Su 2250,and SuXiangjing 100.2.Main characteristics of high quality,high yield and high nitrogen use efficiency of late japonica cultivars tested:(1)In terms of rice yield,compared with low cooking and eating quality,middle yield,middle nitrogen use efficiency(LMM)type,GHH of non-soft rice and soft rice varieties had no obvious advantage in material production in the early stage,but in the middle and late stage,especially from heading to maturity,GHH of non-soft rice and soft rice had higher leaf area index,which promoted material production and accumulation,and eventually led to higher yield.(2)In terms of rice quality,there was no significant difference in grain protein content between non-soft rice with GHH and non-soft rice with GHH,but the content of amylose in grain of non-soft rice with GHH was significantly lower,which resulted in higher taste value of non-soft rice with GHH.The amylose content of soft rice with GHH and soft rice with LMM were both low,however,the protein content of GHH soft rice is low,which led to the high taste value of GHH soft rice.(3)In addition,GHH rice not only absorbed more nitrogen and accumulated more nitrogen,but also had higher nitrogen use efficiency,regardless of non-soft rice or soft rice cultivars.3.A one-time application of controlled-release nitrogen fertilizer experiment was carried out on representative GHH soft rice varieties.combination of one of two short-acting CRNFs(release periods were 40 and 60 days)and one of three long-acting CRNFs(release periods were 80,100 and 120 days)to apply with the conventional urea(CU)as a one-time application of basal fertilizer.Six combinations of CRNFs were established based on their release periods:A1,40+80 days;A2,40+100 days;A3,40+120 days;B1,60+80 days;B2,60+100 days;and B3,60+120 days.CU applied split at basal,tillering and panicle differentiation stages,respectively as control(CK).Results showed that,the A2(combination of 40 days release period+100 days release period to apply with the urea)treatment achieved the same yield as that of CK,and yield of the B2(combination of 60 days release period+100 days release period to apply with the urea)treatment exceeded the yield of CK.Short-acting CRNF in CRNF treatment and long-acting CRNF with partial nitrogen release in early stage provided nitrogen needed before the critical leaf age of effective tillering for late japonica rice,which could promote the occurrence of effective tillering,The peak of N release from the long-acting CRNF of the A2 and B2 treatments was about 50 days after transplanting,which met the N demand of late japonica rice during the panicle initiation stage.After heading,rice grown under the A2 and B2 treatments likely absorbed the part of small and appropriate amount of nitrogen from the CRNF,which could improve seed setting rate eventually.Therefore,the yield of A2 and B2 treatments is higher.4.Milling quality,appearance quality,milled rice starch content and taste value of rice in CRNF treatments were significantly higher than CK.In contrast,protein,gliadin,and glutenin contents and hardness of rice in the CRNF treatments were lower than CK.The higher protein content of rice in the CK resulted in higher gelatinization temperature and harder rice,which may explain why the eating and cooking qualities of rice in the CK were lower than those of rice in the CRNF treatment.5.Results of the similarities and differences in nitrogen accumulation and utilization among the different treatments was mainly due to the different controlled-release periods of the CRNF.The peak of N release from the long-acting CRNF of the A2 and B2 treatments was about 50 days after transplanting,which met the N demand of late japonica rice during the panicle initiation stage and led to the highest N accumulation after heading.Compared with B2 treatment.A2 treatment had a shorter controlled release period of short-acting CRNF.In the early stage of rice growth,there was less nitrogen accumulation at jointing stage and no outstanding performance from jointing to heading stage.As a result,A2 treatment only had the same amount of nitrogen accumulation from heading to maturity stage as CK.which was significantly lower than B2 treatment.In this study,recovery N use efficiency,physiological N use efficiency and agronomic N use efficiency of A2 and B2 treatments were higher than those of CK.In conclusion,there was no significant difference in yield and nitrogen use efficiency between soft rice and non-soft rice among late maturing japonica rice,but there were significant genotypes difference in rice quality in the southern of the Lower Yangtze River.For non-soft rice,cultivars with large biomass,high leaf area index,more grains per spike and low amylose content were selected,for soft rice,rice varieties with high leaf area index,high dry matter accumulation and low protein content can be selected in the middle and late stage,which is an effective way to realize synergistic improvement of rice yield,rice quality and nitrogen ues efficiency in this region.A 40-day short-acting CRNF combined with a 100-day long-acting CRNF(A2 treatment)achieved the same yield and higher N use efficiency attained from rice supplied with CU in the CK.The 60-day short-acting CRNF combined with the 100-day longacting CRNF(B2 treatment)achieved greater yield and higher N use efficiency than that attained in the CK.Compared with those of the CK,rice grown under all the CRNF treatments achieved higher milling quality,appearance quality,starch content and taste value.Additionally,rice grown in all the CRNF treatments produced lower protein contents.These results demonstrate that the A2 and B2 treatments can achieve the simultaneous improvement of yield,quality and N use efficiency of rice. |
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