| Wheat is the main grain crop of dry land agriculture system, how to improve its yield andquality becomes a hot issue, which has attracted great concern of the society. Two crucialfactors that restrict agricultural production in dry land are deficiencies of water and nutrient.These two factors should be controlled to achieve the aim of high yields, high quality, andhigh efficiency. Changing the plant physiological activity and growth and developmentprocess by using the plant growth regulator, and then enhance utilization effect on nutrientand the environment adaptability, to cause the change of crop production towards the goal ofexpectations, and increase crop yield and improve the quality of agricultural products, whichis called crop chemical control technology. A large number of domestic and internationalresearches confirmed the effect of various plant growth regulators on wheat growth, but theapplication of plant growth regulator was restricted to the regulation of a certain growth stage.The formation of crop growth and development, yield and quality has apparently phasic andcontinuity, which means the metabolic and growth characteristics of plant at different growthstages were different, so the means and purpose of physiological regulation should also bedifferent; in the mean time, the continuity of crop nutrition decided growth characteristics andmetabolic processes of the crops at a certain stage, so it is difficult to increase the yield andimprove the crop quality. Therefore, to improve water and nutrient use efficiency, differentphysiological regulatory measures should be conducted at different stages of crop growth, andcoordinate the relationship between environment and crop growth. In addition, how tocombined chemical control and nutrition regulation effectively, is also a problem for thefurther study.This study was regarding two breeds of winter wheat-Xiaoyan22and Xiaoyan6as thestudy subjects, investigated at different level of nitrogen (N) application, the effect of PP333soaking seed and spraying PP333and6-BA at different wheat growth stages on the growthand yield, the uptake of N, P, K and water use efficiency, as well as NO3-N accumulation insoil profile, which aims to provide the effective control measures, corresponding theoreticalfoundation and technical basis of improving wheat yield to the. The main conclusions were as follows:(1) The change regularities of accumulation of NO3-N in different depths were almostthe same in the different nitrogen treatments. The accumulation of nitrogen was highest in the20-40cm depth, and decreased as the depth increased. NO3-N accumulations in the soil profilewere not significantly different in the N120and N0treatments. But the accumulation ofnitrogen was significantly higher in the N240treatment than that in the N0and N120treatments. This result suggested that excessive application of N was the main reason of theincrease of NO3-N accumulation in the subsoil.(2) At different growing stage of winter wheat, under different nitrogen levels, the useof growth regulators at different growth stages all raised dry matter accumulation of Xiaoyan6and Xiaoyan22in different organs, promoted nitrogen accumulation, which showed thetrend as BA> PP333> W, and increased nitrogen uptake efficiency (NAE). In the mean time,it also promoted P, K absorption of winter wheat at different growing stages, and thecumulative trend of organ was BA> PP333> W, and the differences between the differentnitrogen level were also significant, which showed the trend as Xiaoyan6, N240> N120> N0,and Xiaoyan22, N120> N240> N0. The difference of Water use efficiency varied amongvarieties, and application of growth regulator increased the water use efficiency of twovarieties.(3) There were interaction among the different varieties, nitrogen fertilizer and regulatorto water use efficiency of wheat. These two varieties of water use efficiencies were different.The water use efficiency of Xiaoyan6was highest at240kg N/hm~2level after using theregulators, and while the water use efficiency of Xiaoyan22was highest at120kg N/hm~2level. Among different nitrogen rates, soil nitrogen use efficiency, nitrogen contribution rateand nitrogen harvest index was significantly different. The utilization rate of nitrogen wassignificantly higher in the N240treatment than that in the N120treatment, which meansdescription of nitrogen increased to a certain quantity, the utilization rate of nitrogendecreased as the amount of nitrogen use increased after the nitrogen application reached at acertain amount. Reasonable application of nitrogen fertilizer is to one of the effective ways toimprove the utilization rate of nitrogen.(4) We studied the effect of combined application of Paclobutrazol and6-BA atdifferent nitrogen levels on the growth and yield of Xiaoyan6and Xiaoyan No.22. The resultsshowed that, wheat after soaking seed by Paclobutrazol significantly increased tillers per plant,and in the elongation stage, spraying PP333can significantly decreased plant height. Usinggrowth regulator increased the area and relative chlorophyll content of leaves (SPAD value) atall the growth stages, and especially in the early filling stage of6-BA significantly increased SPAD values of mature leaves, showing the effect of retarding the senescence of leaves andextending functional period of leaves. The use of PP333and6-BA significantly increasedwheat yield at different stages, and wheat yield increased by601.2kg/hm~2by using PP333and6-BA than the water treatment, which was significant; the main reason of the grainincrease was the increase of grain number per spike and1000-seed weight. Thus, using PP333and6-BA complexes effectively controled the growth of wheat and increased the yield at thedifferent growing stages. |
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