| The water and nitrogen fertilizer are two essential and interacted factors in the growth and development of rice.By studying the combine mechanism of water and nitrogen between different irrigation methods and nitrogen management,we explored the best water and nitrogen combine management technology to achieve the synergistic effects of water and fertilizer,which is of great significance for water-saving and high-efficiency cultivation of Japonica rice in cold region.two Japonica rice(DN425 and SJ6)were selected as test materials.The experiment set 3 irrigation methods(W1,Normal irrigation;W2,Mild wetting-drying alternate irrigation;W3,Severe wetting-drying alternate irrigation)and 3 nitrogen application model(The ratio of basal fertilizer,tillering fertilizer,panicle fertilizer and grain fertilizer were 6:3:1:0(N1),5:3:1:1(N2),4:3:2:1(N3))at the same nitrogen level.Studied the effect of different coupling mechanism of water and nitrogen on growth characteristics,root activity,photosynthetic characteristics,dry matter accumulation,transport and distribution,spikelet formation mechanism,grain filling characteristics and root shoot ratio of Japonica rice in cold region,to reveal the law of yield formation of Japonica rice in cold region under the coupling of different irrigation methods and nitrogen fertilizers,To clarify the regulatory effects of irrigation methods and nitrogen fertilizer management on the yield formation of Japonica rice in cold region.Determine the best irrigation method and nitrogen fertilizer management,to provide the theoretical basis and technical support for efficient water-saving cultivation of japonica rice in cold regions.The main results of this experiment are as follows:1.The result indicated that the maximum tiller number,the number of final tillers,plant height and leaf area index were influenced by different irrigation methods and nitrogen application.Compared to W1,the tillering peak,final tiller number,plant height and leaf area index of Japonica rice in cold region decreased in W2 and W3 treatments,and the decreasing amplitude of the number of tillers,the number of final tillers,plant height and leaf area index of DN425 was less than that of SJ6;The maximum number of final tillers,plant height and leaf area index were the highest when each irrigation method was coupled with N2 treatment.2.The result indicated that the root activity of Japonica rice in cold region were affected by different irrigation methods and nitrogen application.Compared to W1,W2 treatment significantly improved the root activity,and the root activity decreased significantly under the W3 treatment.Under the different irrigation methods,there was difference in root activity between different nitrogen treatments during Japonica rice growth.3.Different irrigation methods and nitrogen fertilizer management significantly had influence on chlorophyll content of the functional leaves.The chlorophyll content of DN425 was decreased with the decrease of soil water potential before heading,and then chlorophyll content increased and decreased after heading.while SJ6 decreased.Under different irrigation methods,the chlorophyll content of functional leaves of Japonica rice decreased before heading with increase the ratio of postponed N application to the total N rate,and increased after heading stage with increase the ratio of postponed N application to the total N rate.Chlorophyll a/b value decreased when irrigation method and nitrogen operation changed.Pn increased first and then decreased and Tr?Gs?Ci decreased in DN425 with the decrease of soil water potential,while Pn,Tr,Gs and Ci of SJ6 decreased.Pn was higher in DN425 under W2N2 treatment,whlie Pn was higher in SJ6 under W2N2 treatment.4.Different irrigation methods and nitrogen fertilizer management had influence on the dry matter accumulation and translocation.Compared to W1,there was no significant difference between accumulation and output of plant dry matter of DN425 under W2 treatment,and the accumulation and output of root dry matter of DN425 decreased significantly under W3 treatment,the accumulation and output of root dry matter of SJ6 decreased significantly with the decrease of soil water potential,while the dry matter transport rate and contribution rate of two varieties were enhanced in W2 and W3 treatment.Under all irrigation methods,dry matter accumulation and transport capacity were higher in two varieties with N2 application,N2 was the best nitrogen application.5.Different irrigation methods and nitrogen fertilizer management significantly had influence on grain leaf ratio of rice.There was no difference between W1 and W2 in grain leaf ratio of DN425,and they all significantly higher than W3;grain leaf ratio was significantly decreased of SJ6 with soil water potential decreased.Grain leaf ratio in N2 was significantly higher than other nitrogen application under W1 and W2 treatment,the differences between N2 and N3 treatment were not significant under W3 treatment,but all significantly higher than N1 treatment.6.Different irrigation methods and nitrogen fertilizer management had influence on the growth of glume.The pollen fertility of Japonica rice in cold region decreased significantly with the decrease of soil water potential(There was no significant difference between W1 and W2 treatment in DN425);the change rates of the number of spikelet differentiation of two varieties were small with the decrease of soil water potential,while the number of spikelet degradation and degradation rate increased significantly,the sensitivity of the second branch spikelet to soil water potential was significantly higher than that of the first branch spikelet.There was no significant difference in the pollen fertility of two varieties by nitrogen application under the treatment of W1 and W2,Under the W3 treatment,increase the ratio of postponed N application to the total N rate The fertility of pollen grains rises first and then drops,and the pollen fertility of Dong nong 425 was significantly higher than SJ6.Under all irrigation methods,the number of spikelet differentiation increased and the retrograded spikelets and the rate of spikelet degradation decreased with the increase ratio of postponed N application to the total N rate.7.Different irrigation methods and nitrogen fertilizer management significantly had influence on yield of rice.The yield of two rice variety decreased gradually,with the decrease of soil water potential.Under all irrigation methods,the yield of rice was showed N2>N3>N1.Compared to W1,the reduction of yield in W2 treatment was mainly caused by the decrease of the number of effective spikes and the number of spikes.while the coupling of N2 treatment can maintain the number of grains and improve the root vitality and photosynthetic characteristics of plant population,thus improved the seed setting rate and 1000-grain weight,The decrease of the yield of W2N2 was smaller,W2N2 is the best way of water and nitrogen coupling.SJ6 was too sensitive to water to decrease yield components when there was slight water stress,resulting in significant reduction in production.Therefore,W1N2 treatment was the best water and nitrogen coupling. |
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