| In order to clarify the root quality characteristics of super hybrid rice continuous yield increase,this experiment adopts two kinds of tillage measures: deep tillage(25～30cm)and shallow tillage(10～15cm),and selects the representative varieties of super hybrid rice from the first to the fifth stage.Liangyou Peijiu,Y Liangyou No.1,Y Liangyou No.2,Y Liangyou 900 and a new generation of test varieties Chaoyou 1000(renamed Xiangliangyou 900 through the national trial in2017)were used as materials to study the differences in root structure.What’s more,different nitrogen fertilizer application rates were manipulated to study the response of super hybrid rice roots to nitrogen fertilizer with different yield potentials.This study provides theoretical basis for large-area balanced high-yield cultivation and super rice breeding practice.The results were as follows:1.The root index of super hybrid rice showed some changes in different soil layers(0-15 cm,15-30 cm,30-45cm).The root length,root surface area and root number were all higher in 0-15 cm soil,and the root average diameter and root projection area were lower.The root volume and root projection area were the highest in 15-30 cm soil,and other indexes were average.In the 30-45 cm soil,the root average diameter was the largest,and other indicators were lower than the average.Compared with shallow tillage,the root length value of each variety under deep tillage was 25% higher than that of shallow tillage.The root surface area,root projection area,root volume,root number and other indicators were more than 10%higher than shallow tillage;The roots of different soil layers were compared.The0-15 cm deep tillage was lower than the shallow tillage 6.78%,the 15-30 cm deep tillage exceeded the shallow tillage 11.56%,and the 30-45 cm exceeded the shallow tillage 35%.After comprehensive comparison of roots,study found that Xiangliangyou 900 was the best,followed by Y Liangyou 900,and Liangyoupeijiu was the worst;analyses concluded that deep tillage can improve the soil structure of the paddy field in the long-term flooding conditions,enhance soil permeability and water retention,and provide more favorable root growth environmental conditions than shallow tillage.2.With the increase of nitrogen application rate,the root indexes of the roots of the first to fifth super hybrid rice showed a trend of increasing first and then decreasing,and the lowest nitrogen N0 was the lowest,reaching the highest under N14 or N20,then gradually in N26 and N30.Lowering,deep tillage root index was better than shallow tillage.Under different root layers,the root index of 0-15 cm soil did not increase significantly with the increase of nitrogen application rate,while the root system of 15-30 cm and 30-45 cm soil layer increased significantly with the nitrogen application rate.The roots reached the highest index(root length,root dry weight,number of roots,root volume)under N14,and the nitrogen content of each variety decreased after N20 treatment.The optimum nitrogen application rate of different super rice varieties was slightly different.Liangyoupeijiu performed best at N10 level,while other varieties had the best index under N14 conditions.The root indexes of Xiangliangyou 900 and Y Liangyou 900 with higher yield potential were significantly higher than those of the first three varieties under N26 and N30 conditions,showing a certain high nitrogen adaptability.3.With the promotion of the growth period,the root layer of each soil layer of the fifth stage super rice showed a certain level of changes in different soil layers.The root index of 0-15 cm showed the trend of increasing first and then decreasing,and at the heading and flowering stage.The index reached its peak during the growth period;the root index of 15-30 cm as a whole maintained a high root activity after the tillering period;the root index of the 30-45 cm root index was stable during the heading and flowering period.The root index reached the peak after the heading and flowering period,and then began to decrease.However,the root indexes of Xiangliangyou 900 and Y Liangyou 900 did not decrease significantly.On the contrary,the lower layer(30-45cm)had a certain increase in root system,while the other three varieties showed a significant downward trend;the roots of Xiangliangyou 900 and Y Liangyou 900 showed more lasting vigor than other varieties,and the slowing of root senescence was an important indicator for maintaining high yield of super rice.Research on the variety of high-yield records should be inextricably linked.4.In summary,using the CI-600 root monitoring system,the root morphological changes of the five-stage super hybrid rice within deep and shallow tillage and different nitrogen application rates were analyzed in Xinyang area.Results showed that super rice root was mainly distributed in the soil range of 0～35cm,and the overall morphological indexes of roots reached the peak in the 0～35cm soil layer.The root quality of the roots in the 15-30 cm and 30-45 cm roots after the heading and flowering period may be of critical importance to the yield potential improvement of the super hybrid rice.The roots of each variety showed the best under N14,indicating that the yield and root quality could be synergistically increased between 210 kg/hm2 and 300kg/hm2.Compared with the tillage method,the root indexes of the fifth-stage super hybrid rice were higher in deep tillage than those in shallow tillage.Combined with deep and shallow tillage as well as nitrogen application rates,this study indicates that the appropriate increase of deep tillage and nitrogen application has a certain effect on the growth of middle and lower roots.Under the conditions of this experiment,the five-stage super rice variety reached the optimal root growth under the deep tillage N14 nitrogen treatment.Follow-up observation of the two varieties,Xiangliangyou900 and Y Liangyou 900,will be continued in following trials in this region. |
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