氮肥形态及配比对铁核桃根际环境及幼苗生长的影响

 为了探索不同形态及配比的氮肥对铁核桃（Juglans sigillata Dode.）根际生态因子的影响， 为施肥提供科学依据，采用土壤盆栽试验方法，以铵态氮（NH4 +-N）、硝态氮（NO3 --N）和酰胺态氮CO(NH2)2] 为氮源，研究氮肥形态及配比对实生苗生长和根际土壤中低分子量有机酸含量、微生物数量及多种酶活 性的影响。结果表明：混施等比例NH4 +-N 和NO3 --N 的实生苗株高、基径、植株的鲜质量及地上部和根 系的鲜质量都最大（P < 0.05），分别为58.03 cm、18.21 mm、238.19 g、147.68 g 和90.51 g，根际土壤中 有机酸总量和细菌、真菌、放线菌的数量及微生物多样性指数显著高于其它处理，分别为16.72 μg · g-1 FW、 592.00 × 105 CFU · g-1、34.33 × 104 CFU · g-1、19.33 × 105 CFU · g-1 和0.1738；酸性磷酸酶、中性磷酸酶、 碱性磷酸酶、蔗糖酶和淀粉酶的活性最强（P < 0.05），分别为9.54、0.24、3.60、61.98 和8.03 mg · g-1。 单一施CO(NH2)2、NO3 --N、NH4 +-N 会降低根际土壤中有机酸含量、微生物数量和微生物多样性指数。在 混施NH4 +-N 和NO3 --N 的情况下增加NO3 --N 比例会明显降低根际土壤蛋白酶活性。根际土壤中细菌、真 菌和放线菌的数量与中性磷酸酶、碱性磷酸酶、硝酸还原酶、蔗糖酶和淀粉酶活性呈显著或极显著正相 关；细菌数量与酸性磷酸酶活性呈显著正相关；有机酸总量与脲酶、中性磷酸酶、碱性磷酸酶、硝酸还 原酶、蔗糖酶和淀粉酶的活性及微生物数量呈显著或极显著正相关；微生物数量及有机酸总量与过氧化 氢酶呈极显著负相关。混施等比例的NH4 +-N 和NO3 --N 能够改善铁核桃根际生态环境，促进实生苗的生 长。

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 NO^₃--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 of acid 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.