Environmental Sciences Group, School of Agriculture & Environment, Massey Univ., Manawatu, Private Bag 11 222, Palmerston North, 4442, New Zealand.
Dep. of Crop Science, Faculty of Agriculture, Eastern Univ., Vantharumoolai, Chenkalady, 30350, Sri Lanka.
J Environ Qual. 2020 Jul;49(4):987-999. doi: 10.1002/jeq2.20089. Epub 2020 Jun 11.
The soil fluorine (F) concentration in New Zealand agricultural soils has increased with time as a direct result of the widespread application of phosphate fertilizer to land. Elevated soil F concentrations may potentially harm soil microorganisms, which are important for nutrient cycling and soil formation. Rhizobium leguminosarum is a N -fixing soil bacterium that is a fundamental component in New Zealand legume-based pastoral farming. Any impact of F on Rhizobium leguminosarum would have an adverse effect on New Zealand pasture production. In this study, F toxicity to Rhizobium leguminosarum was examined as a first step to develop F guideline values for New Zealand agricultural soils. Bottle-based experiments were conducted to examine the effect of the F ion on Rhizobium-white clover (Trifolium repens L.) symbiosis by observing nodule morphology and growth. Results indicate that the F concentration that causes 10% inhibition of Rhizobium respiration (IC ) for F toxicity to Rhizobium leguminosarum was >100 mg F L . Significant morphological changes occurred when Rhizobium was exposed to F concentrations of 500 and 1000 mg L . Both light and transmission electron micrographs confirmed that the Rhizobium leguminosarum-white clover interaction was not influenced by F concentrations >100 mg L . The toxic F concentration for Rhizobium leguminosarum determined in this study is orders of magnitude higher than the F concentration in New Zealand agriculture soils under "normal conditions." There appears to be no indication of imminent risk of soil F to Rhizobium leguminosarum.
新西兰农业土壤中的土壤氟（F）浓度随着时间的推移而增加，这直接是由于广泛应用磷肥到土地上的结果。升高的土壤 F 浓度可能潜在地伤害土壤微生物，这些微生物对养分循环和土壤形成很重要。根瘤菌是一种固氮土壤细菌，是新西兰豆科牧草养殖的基本组成部分。F 对根瘤菌的任何影响都会对新西兰牧场生产产生不利影响。在这项研究中，F 对根瘤菌的毒性被检查，作为为新西兰农业土壤制定 F 指导值的第一步。通过观察根瘤的形态和生长，进行了基于瓶的实验，以研究 F 离子对根瘤菌-白三叶草（Trifolium repens L.）共生的影响。结果表明，引起根瘤菌呼吸抑制 10%的 F 浓度（IC）对于根瘤菌的 F 毒性大于 100 mg F L。当根瘤菌暴露于 500 和 1000 mg L 的 F 浓度时，会发生显著的形态变化。明场和透射电子显微镜都证实，F 浓度大于 100 mg L 时，根瘤菌-白三叶草的相互作用不受影响。本研究中确定的根瘤菌的毒性 F 浓度比“正常条件”下新西兰农业土壤中的 F 浓度高出几个数量级。似乎没有迹象表明土壤 F 对根瘤菌的迫在眉睫的风险。
