Effects Of Nitrogen And Phosphorus Application Rate On The Growth And Element Absorption Of Moringa Oleifera

Moringa oleifera is a perennial fast-growing tree with broad prospects for research and utilization.However,the research of fertilizer management techniques on Moringa oleifera is still weak.From May to August in 2017,a pot experiment was conducted using the Moringa oleifera PKM I as experimental materials in the ecological farm of the College of Natural Resources and Environment,South China Agricultural University.These included the combinations of nitrogen(N),N0(0 g N/pot),N1(0.6 g N/pot),N2(1.8 g N/pot),N3(3.6 g N/pot),and phosphorus(P),P0(0 g P/pot),P1(0.1 g P/pot),P2(0.3 g P/pot),P3(0.6 g P/pot),16 treatments in total,and N0P0 was defined as CK.This study investigated the effects of N and P combinations on the seedling growth,biomass allocation,branch pattern,element absorption characteristics and stoichiometry in different organs,root morphology,soil pH and nutrient contents,and explored the demand for N and P and the response to different N and P combinations of Moringa oleifera,aiming at selecting the optimal scheme of N and P addition Moringa oleifera for growth.The main results were as follows:(1)The height and ground diameter of P3 treatment were obviously higher than that of P0,P1 or P2 under N0 treatments,while the height and ground diameter of N3 treatment were clearly lower than that of N0,N1 or N2 treatments;N addition increased the biomass of leaf,branch and stem,while P addition had no significant effects on the biomass of leaf,branch or stem;N and P addition to some extent decreased the root biomass and R/S.The SI of P0 was significantly higher than P1,P2 and P3 under N1,N2 and N3,respectively,and the SI of P3 treatment was significantly higher than that of P0;however,there was no significant differences among four N treatments under the same P treatment.(2)N addition enhanced the root length(RL)of Moringa oleifera,and P addition had positive effects on the RL and SRL;the RL and root surface area of N3P3 were the largest,both of them were significantly higher than that of CK.In the same P treatments,there were no significant difference among different N treatments on the root volume.(3)N and P addition had weak effects on the carbon(C)concentrations of different tissues;with increasing addition of N,the N contents of root,stem,branch and leaf were gradually increased;P addition significantly enhanced the P contents of root,stem,branch and leaf,with the increasing application of P,the P concentrations of root,stem,branch and leaf were also gradually increased.N addition increased tissue N:P ratio,while P addition decreased N:P ratios.(4)With the same N treatments,P addition had no significant effects on soil pH;the pH of N3 treatment was significantly lower than that of N0,N1 or N2 under the P2 treatment,however,the soil pH tended to decrease with the increasing addition of N,suggesting higher N application would induce soil acidification;N and P addition had no significant effects on soil organic matter;and P addition significantly enhanced the total P,while N addition to some extent increased soil total N contents,suggesting that N and P application would efficiently improve the soil nutrient status.(5)The fuzzy membership function method was used to evaluate the indexes of Moringa oleifera.The average function value of N3P3 was the largest,that was,the comprehensive evaluation was the best,followed by N2P3 and N2P2.This indicates that N3P3 combination has the most obvious effect on promoting the growth of Moringa oleifera.