Effects Of Soil Compaction Stress On Apple Growth

Soil compaction is an indicator measuring the degree of soil compaction,and it has a direct relationship to other properties such as soil bulk dentisity.Soil compaction, high density is one of stress factors which is prevalent in China's current production of fruit trees.Effcets of different soil compaction on apple plant growth,soil microbial and soil enzymatic activities were studied in the experiment, aim to enrich pomology physiological theory of adverse circumstances and provide theoretical basis for soil improvement.Pot culture experiment was conducted to study the effects of soil compaction with different soil bulk dentisity(SBD,1.25 g·cm-3,1.40 g·cm-3and 1.55 g·cm-3) on apple tree growth, biological yield,chlorophyll fluorescence parameters,root growth and root activities of apple seedling.Though field experiments,difference of plant grow characteristic and biological yield of gala apple grafted on two rootstock(Malus hupehensis and Malus sieversii) growing under different SBD for two years were investigated.Interaction effects of soil compaction and water stress was researched preliminarily.In order to understand the reason that siol compaction affects apple growth, variation of microbiol number and soil enzymatic activities of different SBD were investigated preliminarily.Malus hupehensis ,Malus prunifolia and gala appale growth index and biological yield declineded at different degrees under soil compaction.Thougt the analyze of chlorophyll fluorescence parameters,we found out that conversion of light energy function of plant leaves dicreased under 1.55 g·cm-3SBD.The increase of Superoxide anion radical and Hydrogen peroxide content induced the rise activity of antioxidant enzymes,but the rise degree of reactive oxygen species (ROS) was bigger than the rise activity of antioxidant enzymes,so ROS did harm to cell membrane,which resulted in the increase of permeability of the membrane and lipid peroxidation, and which performanced in remarkable increasing of REC and MDA content of leaves.Through observation of root form and activity of Malus prunifolia seedling on different date,root of Malus prunifolia seedling under 1.55 g·cm-3SBD growed slowly,root number and activity decreased.The difference between 1.25 and 1.40 g·cm-3treatment were not significant. However, in the case of continuous drought, a certain extent soil compaction was conducive to soil moisture maintaining, injury of drought stress on plant was less than low soil bulk density.The impact of soil compaction on apple plant grafted different rootstock were different.Soil microbiol and soil enzymatic activities also were affected by the variation of soil compaction,Moderate compaction was favorable for soil microbiol number increase, especially for bacteria.With soil compaction increase,the activity of urease and dehydrogenase dropped, alkalescence phoshatase and invertase activity both were highest in 1.40 g·cm-3SBD, catalase enhanced with the soil compaction increasing.On the whole,soil compaction is not conducive to the growth of apple and the increase of biological yield.However, in the case of continuing drought compacted soil can maintain more water than loose soil. In the event of soil compaction change,apple plant morphology, physiological,biochemical functions,as well as the bulk density of soil,soil microbiol and soil enzymatic activities will produce adaptive response and adjustment.