Effects Of Different Nitrogen Fertilizers On Growth And Development Of Three Varieties Of Chinese Prickly Ash Saplings

Chinese prickly ash is a deciduous shrub or small tree of Zanthoxylum in Rutaceae.It is an important spice,oil and medicinal economic tree species in China,and its planting area and yield rank first in the world.The supply of nitrogen is related to the transformation of various substances and energy in plants,affecting the growth and development of plants.In order to promote the high-quality development of prickly ash industry,fertilization management has become more and more important.However,there are few studies on the application of nitrogen fertilizer in Chinese prickly ash,and the effects of different nitrogen fertilizers on the growth and development of Chinese prickly ash have not been reported.Therefore,in this study,the two-year-old Chinese prickly ash saplings of the three main varieties of‘Jinkuiyichuanhong’,‘Tengjiao’and‘Jiuyeqing’,were used as the research objects for pot experiment.Three kinds of nitrogen fertilizers such as sodium nitrate(NaNO3),ammonium bicarbonate(NH4HCO3)and urea(CH4N2O)and three levels of low(L),medium(M)and high(H)(the amount of pure N applied in the whole year was 1 g/plant,2 g/plant and 3 g/plant,respectively)were set up in ten treatments(numbered NL,NM,NH,AL,AM,AH,UL,UM,UH),with no fertilization CK as the control group.The effects of different nitrogen fertilizers on the growth,photosynthesis and physiological and biochemical characteristics of Chinese prickly ash saplings were comprehensively evaluated,in order to screen out the most suitable nitrogen fertilizer type and application amount for each variety of Chinese prickly ash saplings.The main results are as follows:(1)Compared with sodium nitrate and ammonium bicarbonate,urea significantly promoted the morphological growth of Chinese prickly ash,and there were significant differences among different concentrations(P<0.05).The three nitrogen fertilizers significantly increased the plant height increment and ground diameter increment of’Jinkui’,reaching the maximum in UM and UL,respectively,which were significantly higher than CK by 333.46%and 167.54%,and significantly higher than‘Jiuyeqing’.The high level of urea(UM)was more conducive to the growth of the root of ’Jinkui’,and promoted the biomass accumulation of the organs.(2)The effect of nitrogen fertilizer on photosynthesis of different varieties of Chinese prickly ash has certain difference.A high level of ammonium bicarbonate(AH)was most conducive to promoting the accumulation of chlorophyll in‘Jinkui’and significantly increasing Pn(Net photosynthetic rate).All three nitrogen fertilizers reduced Pn,Gs(Stomatal conductance)and Tr(Transpiration rate),and the inhibitory effects of sodium nitrate(NL～NH)and urea(UL～UH)were stronger.(3)Urea and sodium nitrate are more conducive to enhancing the resistance of Chinese prickly ash.High levels of urea(UH)significantly reduced the leaf relative conductivity of ’Jinkui’,and sodium nitrate(NL,NH)was beneficial to the accumulation of soluble sugar in ’Jinkui’.The minimum value of leaf relative conductivity appeared in UL,which was 56.16%lower than that of AM.(4)The distribution of nutrient elements nitrogen,phosphorus and potassium in roots,stems and leaves of prickly ash saplings has different characteristics.The high level of ammonium bicarbonate(AH)had a stronger effect on the absorption of nitrogen by’Jinkui’,and the total nitrogen content of each organ under this treatment was significantly higher than that of CK.The application of nitrogen fertilizer significantly increased the absorption of phosphorus in the roots and stems of ’Jinkui’,and the maximum total phosphorus content appeared in NM and AH,respectively.Urea was beneficial to promote the accumulation of nitrogen in the roots and stems of Tengjiao’.The total nitrogen content of UH was the highest,which was 26.36%and 59.63%higher than that of CK,respectively.The effect of sodium nitrate(NL～NH)on total nitrogen in leaves of Tengjiao’ was ’low promotion and high inhibition’.Ammonium bicarbonate and urea had a ’low promotion and high inhibition’ effect on the total phosphorus content in the roots of ’Tengjiao’,and the value of medium nitrogen level(AM,UM)was the highest under the same nitrogen fertilizer.Sodium nitrate(NM,NH)inhibited the absorption of potassium in the stems of ’Tengjiao’,but NH significantly promoted the absorption of potassium in leaves.The highest total nitrogen content in the roots and stems of ’Jiuyeqing’ was NL and AH,which were significantly higher than CK by 70.07%and 51.24%,respectively.Urea(UL～UH)is more conducive to the absorption of phosphorus in the stem of ’Jiuyeqing’;sodium nitrate(NL～NH)promoted the absorption of phosphorus in the leaves of’Jiuyeqing’,and the higher the level,the better the effect.(5)According to the growth indexes,the principal component analysis method was used for comprehensive evaluation.The results showed that the application of nitrogen fertilizer could promote the growth and development of Chinese prickly ash.Among them,the most suitable nitrogen fertilizer treatment for the growth of ’Jinkui’ was AH(ammonium bicarbonate,3 g/plant).The best nitrogen fertilizer treatment for ’Tengjiao’and ’Jiuyeqing’ was UH(urea,3 g/plant).