Effects Of Nano-iron Oxide And Fulvic Acid-coated Nano-iron Oxide On The Nutrient Uptake And Growth Of Soybean

Currently,fabrication of nano-fertilizers and nano-pesticides using nanomaterials provide a viable application prospect for improving crop yield and quality.Presently,many studies have revealed that plants can uptake nano-iron oxide and thereby enhance plant physiological performance,including increased seed germination rate,promoted root growth,increased chlorophyll synthesis and plant biomass.Nano-iron oxide can be used as a source of iron nutrient for plants,and it is expected to become a new type of effective fertilizer to correct the deficiency of traditional iron fertilization.However,it is still unclear result whether nano-iron oxide will effect plants growth.Hence,there is an urgent need to investigate the interaction between nano-iron oxide and plants.This study was conducted to investigate the effects of different materials on soybean nutrient uptake and growth.In the first stage,foliar or soil amendments of different application amounts of nano-iron oxide?NP?,fulvic acid-coated nano-iron oxide?NP-FA4?,Fe-EDTA as well as bulk iron oxide?BK?on growth and nutrient absorption of soybean seedlings.In addition,on the basis of preliminary experiment,the effects of foliar application of different ratios of NP and FA?NP-FA1,NP-FA2,NP-FA3,NP-FA4?on soybean nutrient uptake and growth were further investigated.The chlorophyll content,nodule formation,soybean root and shoot biomass,root morphology and mineral composition of the plant were measured and analyzed.The results are as follows:?1?In the first stage,NP and NP-FA4 by foliar application significantly promoted the growth of nodules,shoots and roots,and increased Fe,K,Mg,B,Mn and Zn content of plants.Foliar and soil applications of NP,NP-FA4,Fe-EDTA and BK promoted the chlorophyll synthesis of soybean plants.Both foliar and soil applications of different application amounts of NP and NP-FA4 significantly increased the dry weight of soybean shoots and roots,root length,root surface area and root volume.In the foliar application,the number and fresh weight of nodules in each treatment are higher than soil application,especially NP15 treatment with 15 mg?pot^-1 and NP-FA4 treatment significantly increased the number and fresh weight of nodules compared to the control.Analysis of mineral composition in the shoots of soybean plants revealed that NP and NP-FA4 by foliar application not only increased total Fe content of plants,but also enhanced the absorption of other essential elements including K,Mg,B,Mn and Zn,however all the treatments by soil application significantly decreased P content of shoots.?2?In the second stage,adding appropriate amount of fulvic acid to nano-iron oxide could promote root nodules growth and nutrient absorption.The proportion ratios of nano-iron oxide to fulvic acid?1:1,1:2 and 2:1?,promoted the formation of nodules whereas under ratio of 1:3 with low application amount,no satisfactory results were obtained for nodules growth enhancement.The efficacy of different treatments on soybean biomass enhancement demonstrated that NP-FA4 promoted the growth of shoots,and NP-FA4 at the high application amount increased the dry weight of the roots.Whereas NP-FA3treatments decreased the shoot biomass and significantly decreased the root biomass than the control,indicating that the higher content of fulvic acid,the more obvious the inhibition of plant growth.Among different NP-FA combination ratio,the analysis of shoots elemental composition confirmed the efficiency of NP-FA in promoting the absorption of Fe.In particular,NP-FA4 at the different application amount significantly increased the Fe content,and with the increase of application amount,Fe content increased gradually.NP-FA2 treatments decreased the contents of Mg,Ca,B,Mn and significantly lower than those of the control at high application rates,indicating that NP-FA2 was not conducive to the absorption of these elements by plants.