Effects of Nitrogen Fertilizer Forms and Ratios on Rhizospheric Environment and Growth of the Juglans sigillata Seedlings

Effects of different forms and ratios of nitrogen fertilizers on rhizospheric ecological factors of the Juglans sigillata Dode were investigated.The objective of the present study was to provide a scientific foundation for fertilizer application.Using NH4+-N,NO3--N and CO(NH2)2 as nitrogen sources,pot experiment was conducted to examine the effects of different nitrogen fertilizer forms and ratios on organic acids with low molecular weight,microorganism and enzyme activities in rhizosphere soil of the J.sigillata Dode seedlings.Further,the correlation among organic acids,microorganism and enzyme activities was analyzed as well.The obtained results showed that under the mixed supply of NO3--N and NH4+-N at same ratio,the plant height,stem base diameter,plant wet weight,shoots wet weight and roots wet weight of the seedlings were the largest,the values of them were 58.03 cm,18.21 mm,238.19 g,147.68 g and 90.51 g,respectively.Significant differences(P 0.05)with other treatments were shown.The total content of organic acids,the amounts of bacteria,fungi,actinomycetes and microbial diversity indices were also the largest,they were 16.72 μg · g-1 FW,592.00 ×105 CFU · g-1,34.33 × 104 CFU · g-1,19.33 × 105 CFU · g-1 and 0.1738,respectively,significantly higher than other treatments.The activity ofacid phosphatase,neutral phosphatase,alkaline phosphatase,sucrase and diastase were the strongest,they were 9.54,0.24,3.60,61.98 and 8.03 mg · g-1,respectively.Compared with other treatments,the significant differences(P 0.05)also existed.The sole supply of CO(NH2)2,NO3--N or NH4+-N went against the increase of the organic acids content,microorganism amount and microbial J.sigillata Dode seedlings was reduced while the ratio of NO3--N was increased.However,the extremely significant positive correlation among the amount of bacteria,fungi,actinomyces and the activity of neutral diversity indices.Under the mixed supply of NH4+-N and NO3--N,the protease activity in rhizosphere soil of the phosphatase,alkaline phosphatase,nitrate reductase,sucrase and diastase were clearly displayed.Significant positive correlation among bacteria amount and acid phosphatase activity was found in this study.Also,the positive correlation among the total content of organic acids and the activity of urase,neutral phosphatase,alkaline phosphatase,nitrate reductase,sucrase and diastase and microorganism amount were extremely significant.Meanwhile,the extremely significant negative correlation among microorganism amount,the total content of organic acids and catalase were found.The present results indicated that application of mixed forms of NO3--N and NH4+-N at same ratio,the rhizosphere environment was obviously improved and the growth of the Juglans sigillata Dode seedlings was significantly promoted.