Dynamic Change Of Bulk Density,Compactness And Water Content Of Cinnamon Soiland Its Effects On Maize Growth

As one of the main zonal soils in Liaoning,Liaoning cinnamon soil owns the abundant land resource and light and heat resource,on which we can plant food crops widely such as maize.But due to the greater precipitation variability,frequent droughts,and due to the long-term rotary tillage,decreasing of organic content that lack of which result in deterioration of soil physical property such as plough layer gets thinner,plow pan gets shallower,soil hardening,soil bulk density increasing and so on,all the questions that restricts the growth of maize have already drawn people's widespread attention.While the systematic and quantitative researches on the influence soil physical property will have on the corn growth during the different growth periods and the sound plowing layer structure still lacks.In this paper,the dynamic changes of soil bulk density,compactness and water content,their relationship and the effects of three of them on the growth of maize were studied by using the root box.And by improving the physical properties to promote the growth of corn.The study results can provide the theoretic evidence for establishing the evaluation index system of the cinnamon soil reasonable plowing layer and technology of choosing the reasonable plough layer structure.The study conclusions are as follows:(1)For different plowing depths,soil bulk density gets bigger as the growth period gets closer and the depth increases.The soil bulk density between 0?25cm is mainly influenced by the plowing depth,plowing 25 cm can decrease the 15?25 cm soil bulk density signally.The growth of maize root during the jointing stage and the soil water content is more than 23%during the filling stage result that the soil bulk density shows a descending tendency.(2)In the maize growth period,the soil compactness of different plowing depths is mainly influenced by the soil water content.The influence of tillage to soil compactness is bigger than the influence of water content between the 0?25 cm but is smaller than the soil water content between the 25?45 cm.Plowing 25 cm can decrease the soil compactness between 15?25 cm signally,especially at the corn jointing and tasseling stage,which is less 7.5?12.5 cm than the maximum of soil compactness treated by rotary tillage.(3)Both adding organic fertilizer and mulching film can decrease the soil bulk density and compactness of each period and each soil layer,and the changing of the soil bulk density and compactness is minimum and most stable with the treatment of mulching film,the average amplitude of variation of soil bulk density is 0.11 g·cm-3,which is at least less 0.04 g·cm-3 than the amplitude of variation with non-mulching film treatment;the average amplitude of variation of compactness is 0.064 MPa,which is at least less 0.05 MPa than the amplitude of variation with non-mulching film treatment.(4)When the growth of crop can not be influenced,by studying the influence of different soil water content and soil bulk density to the compactness,we concluded that both soil bulk density and water content have an influence on the compactness,the relationship expression isP=0.0307?-0.5229?6.9739(P is compactness,0 is water content,p is soil bulk density)When the water content is less than 5%,the influence of soil bulk density to soil compactness is bigger than water content;When unit weight is higher than 1.3 g·cm-3.the influence of water content to soil compactness is bigger than soil bulk density;and when soil bulk density is higher than 1·3 g·cm-3 or the water content is less than 5%,the soil compactness is greater than or equal to 2 MPa,which will restrict the root to grow.(5)When the growth of crop can be influenced,by the relationship between the soil compactness,water content and soil bulk density,the nether exponential equations can be got:Plowing 15 cm:Plough layer 0?15 cm P=0.042740(-1.049)?20.79 R2=0.9201Substratum 15?45 cm P=0.019860(-1 328)?21.77 R2=0.6547Plowing 25 cm:Plough layer 0?25 cm P=0.09702?(-1 523)?18.73 R2=0.8652Substratum 25?45 cm P=1.605?(-2.593)?19.54 R2=0.8134The goodness of fit are all over 0.65,the above equations can fit the relationship between the soil compactness and water content and soil bulk density under the different plowing depths and tillage measures in cinnamon soil area quantitatively.Compared with the equations we have got before,the moisture changing process is the main factor that lead to the difference between the two.(6)Plowing 25 cm,the total length and total surface of roots between 0?15 cm soil layer have no difference with the treatment of rotary tillage,the soil layer between 15?25 cm is higher than rotary tillage signally;All the plant height,stem diameter and the chlorophyll content are better when the plowing depth is 25 cm,which means plowing 25 cm is good for growth of corn root and aboveground part of maize between 15?25 cm.Three improvement measures all can both promote the growth of root and the aboveground part of maize,which mainly manifesting as film mulching>organic fertilizer with straw>straw.(7)The soil compactness mainly influence the growth of root between 15?25 cm.The soil compactness increases to 2 MPa at the tasseling stage,the rate of growth of root total length and root total surface slow down signally,tuber gets more thick.When the soil compactness reaches 2 MPa,the soil bulk density reaches 1.4 g·cm-3,the growth of maize root is restricted badly;and the soil compactness increasing will influence the rate of maize growth signally,which mainly manifest as the growth of plant height and stem diameter slow down,the increasing of chlorophyll content slow down.(8)Different plowing depth,different maize yield,the yield of plowing 25 cm increases than the yield of rotary tillage signally,which proves that the deep plowing can boost the yield of maize.All the improvement measures(straw,organic fertilizer and film mulching)make contributions to yield,other measures besides adding straw contribute to boost the yield extremely,but the transaction is not outstanding.(9)Path analysis proving that the influence the soil physical property make to yield can be mainly manifested as soil compactness>water content>bulk density/total porosity.The problem of water is easy to loss after plowing should be paid attention to during the maize growth period except the seeding time;the great influence of soil compactness to yield is manifested at other times,so the changing of soil compactness should be attached importance to,especially in the arid seasons,more attention should be paid to avoid the maize being threatened by not only the moisture but also the compactness.Overall all,the problems such as climate with less rain,signal tillage method and so on in the Liaoxi cinnamon soil area can result in increasing the bulk density and soil compactness.By studying the tillage measures,the temporal and spatial variation and the influence factors to figure out the factors that influence the soil compactness and the mathematical models that influence the factor relations,and to explore the influence the soil compactness have on the maize growth of the aboveground part and underground part with different tillage measures,then provide the theoretical evidence for establishing the cinnamon soil reasonable plough layer evaluation index system and choosing the reasonable plough layer structure technology.