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Science and Technology， Wenchuan 623000， China; 2. Aba Prefecture Lumber Inspection Station， Wenchuan 623000， China
Abstract In the arid valley of the upper reaches of the Minjiang river， combined application tests of nitrogenous and phosphorus fertilizers were conducted to the 1yearold seedlings of Pinus radiate to investigate the appropriate amount of fertilization， so as to provide bases of fertilization management of young P. radiate in the arid valley. Different combined application amounts of nitrogenous and phosphorus were studied based on the randomized blocks design. The results showed that in comparing 3 treatment groups with the control， the first and second treatments significantly increased the ground diameter and height of P. radiate， while the third treatment merely significantly increased the ground diameter. Under the conditions of this study， the recommended fertilization amount was 30 g of urea and 150 g of calcium superphosphate per plant for the oneyearold P. radiate.
Key words Nitrogenous and phosphorus fertilizers; Combined fertilization; Pinus radiata; Growth; Influence
Pinus radiata is a coniferous evergreen tree native to California， USA， which can grow as high as 30 m. It has dominant trunks with small crowns， and it has strong branching capacity with developed root systems， making it have strong adaptability， resistances to arid and barren， excellent fastgrowing and highyielding performance， good material quality， short rotation period （30a）， and high economic returns[1]. P. radiata was introduced by Aba Autonomous Prefecture Forestry Institute of Science and Technology in 1989， and at present， there is an area of almost 2 000hm2 of experimental demonstration forests planted in the arid valley of the upper reaches of Minjiang River[2].
This study was aimed to study the effects of different application rates of nitrogenous and phosphorus fertilizers on the growth of an 1yearold P. radiata， and to screen out suitable application rates of nitrogenous and phosphorus fertilizers， so as to improve the growth of P. radiata and provide bases for the fastgrowing， highquality and efficient production of P. radiata in arid valley of the upper reaches of Minjiang River.
Test Area Overview
The test area was located in Puxi valley mouth of Lixian County， Zagunaohe River Basin， the first tributary of the upper reaches of Minjiang River. Belonging to the center of arid valley， the area had an average annual temperature of 11.8 ℃， average annual precipitation of 543.4 mm， and average annual evaporation of 1 800 mm. Going from the west to the north， the slope was 40° with an elevation of 1 800 m. The soil was hilly cinnamon soil with granular structure， good aeration， strong permeability， poor water retention and severe drought. The soil pH was 8.34， which was alkaline， and the gravel content was 43.1%. The soil had strong skeleton grains， low organic matter content， and the basic physical and chemical properties of the soil were as shown in Table 1. The main ground cover was Gramineae plants， and the shrubs were Sophora davidii， Bauhinia purpurea， Convolvulus tragacanthoides， Astragalus glabra， Daphnia chrysantha and other semishrubs， with the coverage of 20%-40%. And there was no litter layer nor humus layer. Materials and Methods
Test materials
The test object was a 1yearold plantation of P. radiata. The test nitrogenous fertilizer was urea[CO（NH2）2]with pure N content of 46%， and the phosphorus fertilizer was superphosphate[Ca （H2PO4） H2O]with 15% of P2O5.
Test design
（1） Test treatment： the 1 factor with 3 levels design was used to carry out the fertilization test 2[3]（Table 2）.
（2） Field test method： there were 100 plants for each treatment with 3 repetitions， and randomized block method was used for field arrangement.
Test method
（1） Test plot setting： the tests were laid out in the plots with the same plant growth of P. radiata and site conditions， especially the plots in the same repetition.
（2） Fertilizer application time and method： the fertilizers were applied on April 15， 2015， which were applied in the way of circular fertilization， that is， the fertilizers were sprayed to the semicircular ditches which were about 15-20 cm deep dug at about30 cm from the uphill direction of young trees to the dry base， and then the ditches were reclaimed with soil.
（3） Growth observation： the tree height and ground diameter of the fertilized tree species were measured for the first time from April 10 to 12， 2015 （before fertilization test）， and then in every October of the following years （after the forest stopped growing）， the tree height and ground diameter were measured for 2 consecutive years.
Data processing and analysis
In this study， SPSS 20.0 （USA） was used for data analysis. Oneway ANOVA was used to reveal the effects of fertilization on plant height and ground diameter of P. radiata under different treatments. If the test results showed that fertilization had significant effects on plant height and ground diameter of P. radiata， Tukey test was used to conduct multiple comparisons， which was to test the significance of differences of each index among treatments （α= 0.05）. All data in the tables were in the form of average±standard deviation.
Results and Analysis
The results of oneway ANOVA showed that there was no significant difference in plant height and ground diameter between different treatments of P. radiata before fertilization （P>0.05） （Table 3）.
The effects of fertilization on plant height and ground diameter of P. radiata were as shown in Fig.1. Compared with the control （CK）， treatment 1， treatment 2 and treatment 3 significantly increased the ground diameter of P. radiata by 47.02%， 23.16% and 14.79% （P<0.05）， indicating that fertilization could significantly increase the ground diameter of P. radiata， and the increase in treatment 1 was the highest. Compared with CK， the plant height of P. radiata significantly increased by 8.69% and 7.33%in treatment 1 and 2 （P<0.05）， while that of treatment 3 increased by 3.49%， but not significantly （P>0.05）.
The same capital letters in the figure indicate that there is no significant difference among treatments （P>0.05）， whereas different capital letters indicate significant difference among treatments （P<0.05）.
The comparison on soil nutrient content before and after fertilization in November 2017 was shown in Table 4.
As shown Table 4， the fertilization after planting P. radiata made the soil pH decrease when compared with that before the fertilization， and the soil turned from alkalinity to slight alkalinity. Moreover， the soil organic matter content increased by 15.78%， the hydrolyzed N increased by 32.13%， the available P increased by 37.10%， the available K increased by 45.76%， the total N content increased by 113.62%， the total P content increased by 92.86%， and the total K content decreased by 7.07%. Therefore， planting P. radiata and fertilization can promote vegetation restoration， facilitate plant growth， increase soil ground cover and soil organic matter content， and improve soil fertility.
Conclusion
P. radiata is sensitive to fertilization， and the combined application of nitrogenous and phosphorus fertilizers can promote the growth and development of P. radiata. Compared with CK， treatment 1， treatment 2 and treatment 3 significantly increased the ground diameter of P. radiata by 47.02%， 23.16% and 14.79% （P<0.05）， indicating that fertilization could significantly increase the ground diameter of P. radiata， and the increase of treatment 1 was the highest. Compared with CK， treatment 1 and treatment 2 also significantly increased the plant height of P. radiata by 8.69% and 7.33% （P<0.05）， while that of treatment 3 increased by 3.49%， but not significantly （P>0.05）. Under the conditions of this study， the recommended fertilization amount is 30 g of urea and 150 g of calcium superphosphate per plant for the oneyearold P. radiate.
The combined application of nitrogenous and phosphorus fertilizers promotes the growth of plants. Moreover， it also increases the availablecontents of N， P and K， enhance the contents of total N and P， and promotes the transformation and utilization of the rich K resources in soil.
Agricultural Biotechnology2019
References
[1] WU ZX， LIU QL， HUANGQ， et al. Experiments with the introduction and cultivation of Pinus radiata D. Don in the upper reaches of the Minjiang River， Sichuan Province， China[J]. Journal of Sichuan Forestry Science and Technology， 2005， 26 （3）： 1-10.
[2] XIONG L， PENG XX， WANG ZL， et al. Effect of different sowing time on seedling growth of Pinus radiata[J]. Journal of Sichuan Forestry Science and Technology， 2012， 33 （6）： 54-55.
[3] LUO MF. Experiments design in forestry[M]. Beijing： China Agricultural Publishing House， 1991.
Editor： Na LI Proofreader： Xinxiu ZHU
Abstract In the arid valley of the upper reaches of the Minjiang river， combined application tests of nitrogenous and phosphorus fertilizers were conducted to the 1yearold seedlings of Pinus radiate to investigate the appropriate amount of fertilization， so as to provide bases of fertilization management of young P. radiate in the arid valley. Different combined application amounts of nitrogenous and phosphorus were studied based on the randomized blocks design. The results showed that in comparing 3 treatment groups with the control， the first and second treatments significantly increased the ground diameter and height of P. radiate， while the third treatment merely significantly increased the ground diameter. Under the conditions of this study， the recommended fertilization amount was 30 g of urea and 150 g of calcium superphosphate per plant for the oneyearold P. radiate.
Key words Nitrogenous and phosphorus fertilizers; Combined fertilization; Pinus radiata; Growth; Influence
Pinus radiata is a coniferous evergreen tree native to California， USA， which can grow as high as 30 m. It has dominant trunks with small crowns， and it has strong branching capacity with developed root systems， making it have strong adaptability， resistances to arid and barren， excellent fastgrowing and highyielding performance， good material quality， short rotation period （30a）， and high economic returns[1]. P. radiata was introduced by Aba Autonomous Prefecture Forestry Institute of Science and Technology in 1989， and at present， there is an area of almost 2 000hm2 of experimental demonstration forests planted in the arid valley of the upper reaches of Minjiang River[2].
This study was aimed to study the effects of different application rates of nitrogenous and phosphorus fertilizers on the growth of an 1yearold P. radiata， and to screen out suitable application rates of nitrogenous and phosphorus fertilizers， so as to improve the growth of P. radiata and provide bases for the fastgrowing， highquality and efficient production of P. radiata in arid valley of the upper reaches of Minjiang River.
Test Area Overview
The test area was located in Puxi valley mouth of Lixian County， Zagunaohe River Basin， the first tributary of the upper reaches of Minjiang River. Belonging to the center of arid valley， the area had an average annual temperature of 11.8 ℃， average annual precipitation of 543.4 mm， and average annual evaporation of 1 800 mm. Going from the west to the north， the slope was 40° with an elevation of 1 800 m. The soil was hilly cinnamon soil with granular structure， good aeration， strong permeability， poor water retention and severe drought. The soil pH was 8.34， which was alkaline， and the gravel content was 43.1%. The soil had strong skeleton grains， low organic matter content， and the basic physical and chemical properties of the soil were as shown in Table 1. The main ground cover was Gramineae plants， and the shrubs were Sophora davidii， Bauhinia purpurea， Convolvulus tragacanthoides， Astragalus glabra， Daphnia chrysantha and other semishrubs， with the coverage of 20%-40%. And there was no litter layer nor humus layer. Materials and Methods
Test materials
The test object was a 1yearold plantation of P. radiata. The test nitrogenous fertilizer was urea[CO（NH2）2]with pure N content of 46%， and the phosphorus fertilizer was superphosphate[Ca （H2PO4） H2O]with 15% of P2O5.
Test design
（1） Test treatment： the 1 factor with 3 levels design was used to carry out the fertilization test 2[3]（Table 2）.
（2） Field test method： there were 100 plants for each treatment with 3 repetitions， and randomized block method was used for field arrangement.
Test method
（1） Test plot setting： the tests were laid out in the plots with the same plant growth of P. radiata and site conditions， especially the plots in the same repetition.
（2） Fertilizer application time and method： the fertilizers were applied on April 15， 2015， which were applied in the way of circular fertilization， that is， the fertilizers were sprayed to the semicircular ditches which were about 15-20 cm deep dug at about30 cm from the uphill direction of young trees to the dry base， and then the ditches were reclaimed with soil.
（3） Growth observation： the tree height and ground diameter of the fertilized tree species were measured for the first time from April 10 to 12， 2015 （before fertilization test）， and then in every October of the following years （after the forest stopped growing）， the tree height and ground diameter were measured for 2 consecutive years.
Data processing and analysis
In this study， SPSS 20.0 （USA） was used for data analysis. Oneway ANOVA was used to reveal the effects of fertilization on plant height and ground diameter of P. radiata under different treatments. If the test results showed that fertilization had significant effects on plant height and ground diameter of P. radiata， Tukey test was used to conduct multiple comparisons， which was to test the significance of differences of each index among treatments （α= 0.05）. All data in the tables were in the form of average±standard deviation.
Results and Analysis
The results of oneway ANOVA showed that there was no significant difference in plant height and ground diameter between different treatments of P. radiata before fertilization （P>0.05） （Table 3）.
The effects of fertilization on plant height and ground diameter of P. radiata were as shown in Fig.1. Compared with the control （CK）， treatment 1， treatment 2 and treatment 3 significantly increased the ground diameter of P. radiata by 47.02%， 23.16% and 14.79% （P<0.05）， indicating that fertilization could significantly increase the ground diameter of P. radiata， and the increase in treatment 1 was the highest. Compared with CK， the plant height of P. radiata significantly increased by 8.69% and 7.33%in treatment 1 and 2 （P<0.05）， while that of treatment 3 increased by 3.49%， but not significantly （P>0.05）.
The same capital letters in the figure indicate that there is no significant difference among treatments （P>0.05）， whereas different capital letters indicate significant difference among treatments （P<0.05）.
The comparison on soil nutrient content before and after fertilization in November 2017 was shown in Table 4.
As shown Table 4， the fertilization after planting P. radiata made the soil pH decrease when compared with that before the fertilization， and the soil turned from alkalinity to slight alkalinity. Moreover， the soil organic matter content increased by 15.78%， the hydrolyzed N increased by 32.13%， the available P increased by 37.10%， the available K increased by 45.76%， the total N content increased by 113.62%， the total P content increased by 92.86%， and the total K content decreased by 7.07%. Therefore， planting P. radiata and fertilization can promote vegetation restoration， facilitate plant growth， increase soil ground cover and soil organic matter content， and improve soil fertility.
Conclusion
P. radiata is sensitive to fertilization， and the combined application of nitrogenous and phosphorus fertilizers can promote the growth and development of P. radiata. Compared with CK， treatment 1， treatment 2 and treatment 3 significantly increased the ground diameter of P. radiata by 47.02%， 23.16% and 14.79% （P<0.05）， indicating that fertilization could significantly increase the ground diameter of P. radiata， and the increase of treatment 1 was the highest. Compared with CK， treatment 1 and treatment 2 also significantly increased the plant height of P. radiata by 8.69% and 7.33% （P<0.05）， while that of treatment 3 increased by 3.49%， but not significantly （P>0.05）. Under the conditions of this study， the recommended fertilization amount is 30 g of urea and 150 g of calcium superphosphate per plant for the oneyearold P. radiate.
The combined application of nitrogenous and phosphorus fertilizers promotes the growth of plants. Moreover， it also increases the availablecontents of N， P and K， enhance the contents of total N and P， and promotes the transformation and utilization of the rich K resources in soil.
Agricultural Biotechnology2019
References
[1] WU ZX， LIU QL， HUANGQ， et al. Experiments with the introduction and cultivation of Pinus radiata D. Don in the upper reaches of the Minjiang River， Sichuan Province， China[J]. Journal of Sichuan Forestry Science and Technology， 2005， 26 （3）： 1-10.
[2] XIONG L， PENG XX， WANG ZL， et al. Effect of different sowing time on seedling growth of Pinus radiata[J]. Journal of Sichuan Forestry Science and Technology， 2012， 33 （6）： 54-55.
[3] LUO MF. Experiments design in forestry[M]. Beijing： China Agricultural Publishing House， 1991.
Editor： Na LI Proofreader： Xinxiu ZHU