| High quality of seedlings is the basic premise and way to obtain high yield of mechanically transplanted rice.However,in actual production,the quality of seedlings is uneven,and weak seedlings still account for a large proportion,which seriously affects the consistency of the growth starting point of mechanical transplanting rice in the field.There have been some reports on the differences in the effects of different seedling qualities on the growth and yield of mechanically transplanted rice,but the differences in tillering characteristics,root growth,nitrogen absorption and utilization and yield formation of rice with different seedling qualities and their relationships are not clear.Therefore,this study designed the experiment of different application methods of tillering fertilizer,and carried out corresponding research to solve the above problems,with a view to clarifying the ways and physiological basis for strong seedlings to promote rice growth and increase yield,and how weak seedlings can make up for the inferior influence on rice growth and yield caused by weak seedling quality through reasonable tillering fertilizer operation,so as to provide data support and theoretical basis for different seedling qualities of mechanically transplanted rice to exert their yield potential as much as possible.The results are as follows:1.Effects on rice yield with different seedling qualities.1)The yield of strong seedlings was higher than that of weak seedlings,with an average increase of 26.47%;2)With the increase of tillering fertilizer application,the yield of strong and weak seedlings increased first and then decreased.The highest yield of strong seedlings was N3(base fertilizer+primary tillering fertilizer)and weak seedlings were N4(base fertilizer+secondary tillering fertilizer).It can be seen that on the basis of applying basic fertilizer,strong seedlings can get the maximum yield only by applying tillering fertilizer once,while weak seedlings need to be applied twice to achieve sufficient yield;3)No matter how much tillering fertilizer is applied to weak seedlings,the yield level of strong seedlings applying tillering fertilizer at one time can not be reached;4)By comprehensive correlation analysis and path analysis,the correlation and contribution between panicle number and yield are the largest.2.Effects on tillering characteristics of rice with different seedling qualities.1)The first tillering time is 7-12 days after planting,and 8-15 days after planting;The time of tillering termination is 37-44 d after planting for strong seedlings and 37-42 d;for weak seedlings.The duration of tillering is 25-37 d for strong seedlings and 22-34 d for weak seedlings.Adding tillering fertilizer is beneficial to promote tillering and delay the time of tillering termination.The leaf age of the first tillering is 5.82-6.80 for strong seedlings and 6.32-6.96 for weak seedlings;With the application of tillering fertilizer,the leaf age of the first tillering tends to be earlier;2)When tillering occurs for the first time,the average dry matter of each treatment plant is 18.58%higher than that of weak seedlings;Increasing tillering fertilizer is beneficial to promote the accumulation of dry matter in single stem of plants;3)During the first tillering,the average nitrogen content and SPAD value of strong seedlings were 11.22%and 4.49%higher than those of weak seedlings.With the application of tillering fertilizer,the nitrogen content and SPAD value of the first tillering plant gradually increased;4)The dry matter weight of a single stem and the nitrogen content of a plant during the first tillering are negatively correlated with the time of occurrence,that is,the greater the dry matter and nitrogen content of a single stem of a strong and weak seedling,the earlier the first tillering occurs;Increasing tillering fertilizer is beneficial to promote the accumulation of dry matter and the increase of nitrogen content in plants,thus promoting the occurrence of tillering;5)The dynamic trend of tillers of strong and weak seedlings is similar,and they all reach the peak seedlings at 40 days after planting.The strong seedlings are higher than the weak seedlings at all stages,the peak seedlings are 7.90%higher than the weak seedlings,and the panicle formation rate is 2.35 percentage points higher than the weak seedlings.Increasing the application of tillering fertilizer is beneficial to the increase of tillering,but the panicle forming rate shows a downward trend;6)Both strong and weak seedlings can tiller at the 3/09/0 leaf position,and there is little difference between them at the 4/0-6/0 leaf position,with the main difference at the 3/0 and 7/0-9/0 leaf positions.Strong seedlings can tiller with little tillering fertilizer,or the tillering rate is higher than that of weak seedlings.Adding tillering fertilizer is beneficial to increase the span of tillering leaves of strong and weak seedlings.The panicle formation rate of strong seedlings was significantly higher than that of weak seedlings,and the trend of tillering formation rate and tillering incidence rate at different leaf positions was similar.3.Effects on root morphological characters and nitrogen absorption of rice with different seedling qualities at tillering stage.The number,dry weight and longest root length of strong seedlings were significantly higher than those of weak seedlings,which were 25.64%,19.26%and 8.41%higher respectively.Increasing tillering fertilizer is beneficial to promote the occurrence and enrichment of adventitious roots,but it is not conducive to root elongation;The nitrogen content and nitrogen uptake of strong seedlings at tillering stage increased by 25.34%and 51.36%respectively.Adding tillering fertilizer is beneficial to the significant increase of these two indexes.4.Effects on nitrogen absorption and utilization of rice with different seedling qualities.1)The nitrogen content and nitrogen uptake of the whole plant in each treatment of strong seedlings were significantly higher than those of weak seedlings,and the tillering stage,heading stage and maturity stage increased by 5.93%,16.67%,15.46%,45.44%,11.81%and 32.83%respectively;The two indexes of increasing tillering fertilizer showed an increasing trend,and N5 treatment was the highest for strong and weak seedlings.2)The nitrogen grain production efficiency,nitrogen harvest index,nitrogen partial productivity and nitrogen utilization rate at the mature stage of strong seedlings were higher than those of weak seedlings,increasing by 1.97%,15.91%,36.08%and 16.33%respectively;These indexes of tillering fertilizer increased first and then decreased,and the maximum treatment of these indexes of strong and weak seedlings was different.5.Effect on leaf area coefficient of rice with different seedling qualities.The leaf area coefficients of strong seedlings at tillering stage and heading stage were significantly higher than those of weak seedlings,increasing by 18.41%and 9.78%respectively.With the application of tillering fertilizer,the leaf area coefficient of strong and weak seedlings showed an increasing trend at tillering stage,and the effective leaf area coefficient of strong and weak seedlings increased first and then decreased at heading stage.N3 treatment was the largest for strong seedlings and N4 treatment was the largest for weak seedlings. |
