| Phosphorus is one of the essential elements of plant growth and development,however,the lack of available phosphorus in red soil of southern China has become an important limited factor in agroforestry production.Although the application rate of phosphate fertilizer has a significant effect on the increase of agricultural and forestry plants,the application of phosphate fertilizer is easy to be fixed,which resulted in very low efficiency of fertilizer use.Moreover,excessive application of phosphate fertilizer can easily lead to the loss of nutrient such as leaching and surface run off huge economic and ecological hazards.Therefore,there is an important significance on how to ensure the plant productivity,improve the putilization efficiency and reduce pollution.Compared with the fertilization of soil plant roots,foliar fertilization can directly spray the nutrients to the plant foliage,and smear to the stem,branches,flowers,fruit and other organ surfaces,which can be quickly absorbed by plants.In addition,in the middle and later,the nutrient of growth plants uptake caused by the under development of root or the decrease of root activity often leads to the deficiency syndrome,and the foliar fertilization can supplement the nutrient element.Visibly,foliar fertilizer can be effective to a certain extent,and eased a reality problem of the current soil phosphorus supply.Chinese fir[Cunninghamia lanceolata(Lamb.)Hook.]with fast growth,high amount of material,wood buniform structure,etc,which is an important fast-growing timber species peculiar in southern China.In recent years,with the rapid expansion of the area of Chinese fir afforestation,more and more continuous planting in the same forest land,and insufficient soil content of available phosphorus has led to a decline that a number of successive planting of Chinese fir plantation.Moreover,with the price of Chinese fir trail,the density of Chinese fir plantation is increasing,which resulted in early closure of Chinese fir plantation,combined with insufficient soil for phosphorus,and considerable competition for resources such as water and fertilizer among trees.At present,there are some reports on the competition of soil phosphorus in the adjacent Chinese fir soil,but there is little report on whether the foliar fertilization can effectively alleviate the phosphorus nutrient competition intensity among the fir plants of the low phosphorus environment,and this is precisely key problems of how to maintain long-term productivity of high-yield Chinese fir.In view of the plant crown size is to determine the plant on their space resource utilization efficiency of a biological characteristics,especially for foliar fertilization absorption has a significant impact.In this study,selected two Chinese fir clones with different crowns(narrow crown type and broad crown type),which were widely used in the production of Yangkou Forest Farm in Fujian.Based on the laboratory simulation.The control individual plant we constructed "narrow-narrow"type,"wide-wide" type,"narrow-wide" type of different crown combinations of the adjacent strains of competition,and dealed with,the roots of phosphorus,not phosphorus,foliar fertilization treatment respectively.Through the determination of different phosphorus supply and different competition patterns of Chinese fir growth index,morphological indicators,physiological indicators,comparison of different crowns of Chinese fir in different treatment periods changes in biomass,plant photosynthesis,root morphology and differences in phosphorus use efficiency.The effects of foliar fertilization on the competition of the adjacent plants were studied under different phosphorus supply conditions.The effects of foliar fertilization on the narrow crown and broad crown Chinese fir clones were studied.In order to reveal the difference of the adaptation strategy of different crown Chinese fir on the foliar fertilization under the condition of competition,it was clarified whether the effect of foliar fertilization on the competition of Chinese fir clones was obviously,which aims to provide scientific basis for rational fertilization and long-term productivity of Chinese fir in southern low-phosphorus environment.The main findings are as follows:(1)The effect of foliar application of phosphorus on the variation of phosphorus nutrition in the "narrow-narrow" crown competition model was as follows:Compared with the root phosphorus and not phosphorus treatment,the root length,surface area,diameter and volume of the roots were rapidly increased in the early stage of the experiment,but the root morphological index was the most obvious in the middle stage of the experiment.From the roots,stems and leaves of different vegetative organs of phosphorus content point of view,there was no significant difference in phosphorus content in the roots of Chinese fir under phosphorus treatment(p>0.05);To the late test,the foliar application of phosphorus content in the roots of Chinese fir was significantly higher than that of the other two treatments(p<0.05).At this time,the foliar application content was significantly higher than that of not phosphorus treatment,but the difference was not obvious with the application of phosphorus at the root,and the difference of phosphorus content was not obvious.During the whole experiment period,the foliar application content could promote the accumulation of root biomass,which was significantly larger than the other two treatments,and significantly improved the root/shoot ratio at the end of the experiment.This may be related to the maximum fluorescence yield of the larger leaves of the foliar application content of the narrow crown Chinese fir at the later stage.On the whole,foliar phosphorus significantly improved the narrow crown type Chinese fir seedling ground diameter growth,the growth of seeding also has a certain role in promoting.(2)The effect of foliar application of phosphorus on the variation of phosphorus nutrition in the "wide-wide" crown competition model was as follows:Compared with the roots for phosphorus and without phosphorus treatment,the foliar phosphorus at the beginning of the experiment,which promoted the root length and volume of the rapid growth of indicators,but the surface area and diameter is not obvious.In the middle of the experiment phosphorus,in addition to diameter indicators of proliferation is not obvious,the other root morphological indicators of the most obvious proliferation,at the end of the experiment,all root morphological indexes were the most obvious.From the roots,stems and leaves of different vegetative organs of phosphorus content.There was no significant difference in phosphorus content in the roots of Chinese fir at the beginning and the middle of the experiment(p>0.05).At the later stage of the experiment,foliar phosphorus content in the roots of Chinese fir was higher than that of the other two treatments and the content of stem and phosphorus in leaves was significantly lower than that in roots(p<0.05),but there was no significant difference in leaf phosphorus content between different treatments(p>0.05).But the phosphorus content in leaves of late foliar application was higher than that of non-phosphorus treatment.During the whole experiment period,the foliar application content could promote the accumulation of root biomass,which was significantly larger than the other two treatments,and significantly improved the root/shoot ratio at the end of the experiment.But the maximum fluorescence yield was relatively low at the late stage of the foliar phosphorus application.On the whole,foliar phosphorus significantly improved the wide crown type Chinese fir seedling ground diameter growth,the growth of seeding also has a certain role in promoting.(3)The effect of foliar application of phosphorus on the variation of phosphorus nutrition in the "wide-narrow" crown competition model was as follows:Compared with the roots for phosphorus and phosphorus treatment,the narrow-crowned Chinese fir seedlings,the early roots of phosphorus to promote root length,surface area,diameter and volume and other morphological indicators of rapid proliferation,and wide-crowned Chinese fir seedlings in the foliar application of phosphorus treatment tends to obviously significant increase.From the roots,stems and leaves of different vegetative organs of phosphorus content point of view.There was no significant difference between phosphorus content in the roots and non-phosphorus of Chinese fir(p>0.05),and the contents of non-phosphorus were the lowest in the first and middle stages of the experiment.The late of foliar phosphorus content of the narrow crown was the lowest and the wide crown was highest.At this time both of the stem phosphorus content is relatively low,but the leaf phosphorus content are the highest.During the whole experiment period,the foliar application of phosphorus promoted the accumulation of root biomass of narrow-crowned and broad-crowned Chinese fir seedlings,and the values were significantly higher than those of the other two treatments,and the root/shoot ratio was significantly improved in the later stage of the experiment.The maximum photochemical efficiency of the narrow crown was significantly higher than that of the other two treatments(p<0.05),while the wide crown type was lower in the later stage of the experiment.In total,foliar application of phosphorus significantly increased in the growth of wide-crowned Chinese fir seedlings,whichalso has a specific role in promoting.(4)In summary,the phosphorus application on the foliage is similar to that of the root,which alleviates the alleviation of the phosphorus nutrient competition intensity of the Chinese fir roots.In the early stage,application for root growth of Chinese fir seedings under foliar application of phosphorus and phosphorus are good.In the middle of the competition,the root system of Chinese fir seedlings was the best under the condition of foliar phosphorus application.With the extension of the competition time of the adjacent plants,the root growth of Chinese fir was significantly higher than that of foliar phosphorus and root application in the later stage.The phosphorus deficiency could promote the proliferation of Chinese fir roots and enhance its ability to develop phosphorus,while the phosphorus and phosphorus on the leaves to effectively alleviate the phenomenon of phosphorus.On the other hand,the photosynthetic parameters,such as maximum fluorescence yield and maximum photochemical efficiency,were significantly higher than those of wide-crowned Chinese fir at the later stage of the experiment.But the content of root phosphorus in root system was significantly larger than that in narrow crown.Visibly,the response strategies of different crown Chinese fir clones to the vegetative competition of the adjacent plants were different.This is an adaptive mechanism for the different crown types of Cunninghamia lanceolata to the competition stress,and provides scientific theory and practice basis for the selection of Chinese fir plantation. |
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