| In view of the problems of present machine early planting,middle control,the late weak spikes,in order to determine effects of seedling-raising on rice under the condition of reducing nitrogen in whole growing period and seedling-raising on rice under the condition of reducing nitrogen in partial,an experiment was carried out which use Zhongjiazao 17 as the early rice,Wuyou 308 as the late rice,to study the yield,yield components and nitrogen use efficiency of mechanical transplanted double-cropping rice,in this study there have three different densities and five different nitrogen application rates.The main findings are as follows:Treatment(early rice N12D4 and late rice N13D3),which could achieve the effect of increasing nitrogen and nitrogen fertilization.Moderate seedling-increase and nitrogen-decrease can be obtained with conventional nitrogen treatment(early rice N12D4,late rice N13D3)considerable yield.In the early rice,the nitrogen application level was N14,and late rice N15,whether it is increased or reduced the number of seedlings per hole,can not increase the yield,on the contrary there is the trend of cutting;in the early rice nitrogen level N8,late rice for the N9,whether it is increased or reduced the number of seedlings per hole,Nitrogen use efficiency is significantly improved,but due to too much nitrogen reduction,yield has significantly reduced.Moderate seedling and nitrogen can improve the quality of rice.Compared with conventional nitrogen seedling(early rice N12D4,late rice N13D3),seedling nitrogen treatment(early rice N10D5,late rice N11D4),although the amount of nitrogen applied decreased,the increase in the number of seedlings per well to ensure that the rice population sufficient effective panicle number,Leaf area index,increased seed setting rate and medium and late dry matter accumulation,and then enhanced the photosynthetic potential,which was beneficial to the yield and yield of rice.Moderate seedling reduction nitrogen can increase nitrogen use efficiency.Compared with conventional nitrogen application,the nitrogen uptake and utilization rates of early rice(N10D5)and early rice(N10D4)were not significantly different from those of the control.In all nitrogen treatments,The nitrogen partial productivity of nitrogen and nitrogen treatment was the highest,and the suitable agronomic efficiency was the highest.Under the condition of all 20% nitrogen reduction,the nitrogen application rate(N2:40: 10: 30)was the most favorable.Compared N2 、N3、N4,N3 had the highest number of tillers,but the final spike rate was the lowest,and the ineffective tillers caused the decrease of the number of spikelets per panicle and seed setting rate,and finally affect the yield;N4 had the lowest tiller number,it is due to no tillering fertilizer is not conducive tothe occurrence of tillers,and the seed number per panicle,seed setting rate and 1000-grain weight were significantly lower;N2 treatment can ensure adequate number of tillers at the same time,but also improve late spike rate,grains per spike and seed set,the most beneficial to rice yield.Under the condition of all 20% nitrogen reduction,the nitrogen application rate(N2:40: 10: 30)has the highest nitrogen use efficiency.The nitrogen use efficiency increased with the decrease of nitrogen application rate and increased with the increase of nitrogen application rate.Compared N2 、N3、N4,N2D6 had the highest nitrogen uptake and utilization efficiency and nitrogen partial productivity,and there was no significant difference between nitrogen agronomic efficiency and maximum value.N3 due to the use of high proportion of tillering fertilizer,resulting in inefficient tiller too much,spike rate decreased,thereby reducing the nitrogen absorption and utilization efficiency.N4 basal fertilizer is too much,and machine-transplanted rice can not afford early,slow seedling period of long-term characteristics,excessive basal fertilizer because crops can not be timely absorption and loss,thus reducing the nitrogen use efficiency. |
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