Effects Of Different Substrate Ratios And Nutrient Concentrations On Physiology And Growth Of Sequoia Sempervirens Container Seedlings

Different substrate ratios of container seedlings will affect the growth environment and nutrient supply of plant roots.The purpose of the present study is to get the optimal substrate ratios and the dynamic changes in nutrient concentrations of the substrates.It is essential to foster healthy container seedlings and fertilization management.Peat,green waste compost,soil and perlite were used as mixed substrate materials to study the effects of different substrate ratios on growth and physiology of 1.5-year-old Sequoia sempervirens container seedlings.The optimal substrate ratio of S.sempervirens container seedlings was obtained by L₉（4³）orthogonal design and was finally evaluated by principal component analysis.The concentrations of total nitrogen（N）,total phosphorus（P）,and total potassium（K）in different substrates and in S.sempervirens leaves were measured during the growing season.The growth and other physiological parameters were determined in parallel.The main results are as follows:（1）The volume ratios of nine group of different substrates were 1（Peat:Green waste compost:Soil:Perlite=5:1.5:0.5:3）;2（Peat:Green waste compost:Soil:Perlite=6:1:0.5:2）;3（Peat:Green waste compost:Soil:Perlite=4:1:1.5:3）;4（Peat:Green waste compost:Soil:Perlite=5:1:1:1）;5（Peat:Green waste compost:Soil:Perlite=6:0.5:1:3）;6（Peat:Green waste compost:Soil:Perlite=4:0.5:0.5:1）;7（Peat:Green waste compost:Soil:Perlite=6:1.5:1.5:1）;8（Peat:Green waste compost:Soil:Perlite=4:1.5:1:2）;9（Peat:Green waste compost:Soil:Perlite=5:0.5:1.5:2）.（2）There were significant differences in plant height,ground diameter,nutrient concentrations in substrates and leaves,physical and chemical characteristics among nine group of substrates.Green waste compost markedly increased the growth of S.sempervirens.（3）The principal component analysis was used with substrate bulk density,total porosity,water-holding porosity,aeration porosity,EC value,pH value,gas-water ratio,total nitrogen concentration,total phosphorus concentration,total potassium concentration and leaf total nitrogen concentration,total phosphorus concentration,total potassium concentration,total height increment and ground diameter increment as factors to evaluate the optimum substrate ratio of S.sempervirens container seedlings.The optimum ratio of the four substrate components of Peat:Green waste compost:Soil:Perlite was 4:1.5:1:2 for S.sempervirens container seedlings.（4）There were significant temporal changes in nutrients of different substrates and leaves with a similar trend.The total N and total P concentrations in the leaves of S.sempervirens grown in different substrates increased from March to May.The average increase in total N concentration was 22.1%and 156.2%in total P concentration.But the total K concentration decreased by 11.5%.From May to July,the concentrations of total N and total P showed a downward trend,with an average decrease in total N concentration of 13.2%and total P concentration of 16.1%.However,the total K concentration didn’t alter compared with the last measurement.From July to September,the total N and total P concentrations averagely decreased by 7.7%and by 33.3%,respectively.The total K concentration increased slightly by 7.9%.（5）According to stoichiometry,N:P was less than 14 in leaves of S.sempervirens which indicated that the growth was mainly limited by N.（6）There was some correlation in total phosphorus concentration between substrates and leaves of S.sempervirens.There was no significant correlation total nitrogen and total potassium concentrations between substrates and leaves of S.sempervirens,indicating that the nutrient changes were not parallel.（7）The photosynthetic parameters and chlorophyll concentrations of S.Sempervirens leaves in different substrates didn’t show similar trend during the growing season,but changes in the soluble protein concentration of S.Sempervirens leaves grown in different substrates during the growing season were consistent.The soluble protein concentrations in each substrate were the highest during July and August,ranging from 7.98¹2.64 mg g^-1.The highest soluble protein concentration occurred in the group 8 and the lowest occurred in group 7.The soluble protein concentrations decreased rapidly from August to September,averaging 60.4%.The soluble protein concentration in group 1 decreased by 73.9%and decreased by 40.7%in group 9.The volume ratio of Peat:Green waste compost:Soil:Perlite=4:1.5:1:2 was the optimal substrate ratio for S.sempervirens container seedlings.During the rapid growth period of S.sempervirens,enough N and P fertilizer is necessary.At the end of growing season,it would be better to add some K fertilizer to S.sempervirens container seedlings.