Study On Water And Fertilizer Requirement Of Populus×Euramericana Cv."74/76" Seedlings

Populus×euramericana cv."74/76" is an ideal tree species with the characteristics of short rotation,fast growth,excellent quality and anti-disease.With the spreading of Populus×euramericana cv."74/76",higher-standard management measure and more saplings are required.However,there is no scientific management model of Populus×euramericana cv. "74/76" at present,especially few research on precise irrigation based on water use and nutrients requirement of the sapling.In provinces of Beijing,most suitable for the growth of Populus×euramericana cv. "74/76",the trias of the water use and nutrition dynamics for the different age of saplings were studied about growth rhythem,photosynthetic characteristic,nutrition dynamics.The pot weighting,heat balance Dynamax packaged sap flow measuring system and automatic weather recording system,were employed to analyse the relationships of water use with test meteorological factors.The results showed that:(1) The logistic model can reflect on the most significant level the relation of the element content(C,N,P,K) and the growing time(T)and the effective accumulated temperature(K),and the relation of the root collar diameter,shoot height,total leaves area and the growing time(T)and the effective accumulated temperature(K) respectively,of which the correlation is significant and all the correlation coefficients are higher than 0.95.Based on the equation,they can be divided into three periods.(2) The net photosynthetic rate for seasonal variations shows two peaks,which are in early August and in the end of September.The second peak is caused by the cool weather.(3) There is a significant positive correlation between average daily water use and root collar diameter,shoot height,leave areas.The analyse of partial correlation showed that the root collar diameter and the photosynthetically effective radiation were always the dominant factor affecting the average daily water use for Populus×euramericana cv."74/76" I_1-0 and Populus×euramericana cv."74/76" I_1(2)-0.The partial correlation analyse of the effect on SFD by meteorological factors showed different order among sunny days,clondy days and rainy days.Tested by regressive coefficient,the regressive equation showed most significant level between SFD and meteorological factors.(4) Soil evaporation accounted for a high percentage of evapotranspiration during major growth season,especially more than 95%in April and May,so how to reduce soil evaporation is a major breakthrough in water-saving.In September water use accounts for 43%～47%of total water use in major growth season,and also accounting for 27%～31%of the total evaportransperation.Measures to control water and fertilizer were taken to promote sapling lignification and improve the quality of saplings in mid-September,so the trial of reducing the water use in September,is a major breakthrough in water-saving.(5) Nutrients concentrations in the I_1-0 of Populus×euramericana cv."74/76" in a growing season,is N 9.15712 g,P 0.882676 g,K5.351916 g,respectively.And nutrients concentrations in the I_1(2)-0 of Populus×euramericana cv."74/76" in a growing season,is N 7.462 g,P 0.745 g,K4.198 g,respectively.