Alleviation of Copper Toictiy to Maize by Phosphours Fertilizer in Purple Soil

A pot experiment was conducted to evaluate the effects of phosphours fertilizer in inhibiting the copper toxicity to maizce(Zea mays L.) in neutral purple soil.Results indicated that the growth of the shoot and roots of maize plant was obviously reduced by copper and the height and biomass were significantly negatively correlated to the application levels of copper(r=-0.899^**--0.994^**) at no P and low P(100 mg kg^-1).However,the maize biomass was relatively increased and the high Cu(100 and 200 mg kg^-1) induced toxicity of maize was greatly alleviated in all treatments with medium P( 300mg kg^-1) and high P (500mg kg^-1). to maintain the normal growth of miaze plant(≥3.68 g pot^-1),the critical application rates of phosphours fertilizer shouled be 160,210,300 and 500 mg P kg^-1 at 10,50,100 and 200mg Cu kg-1 levels of the soil,respectively,The increases in polyphenol oxdase and catalase activities in maize leaf and dehydrogenase activity in roots by phosphorus fertilizer were in the order of medium P>high P>low P>no P.Activites of polyphenol oxidase an catalase were significantly positively correlated to the application levels of copper(r=0.892^**-0.924^**),whereas that of edhydrogenase was just rvers(r=-0.966^**) at no P.Medium and high P represed the influence of copper on activities of three enzymes.Phosphorus fertilizer reduced the copper concentrations of maize roots and leaf and the change ranges of the P/Cu ratio of miaze roots and the P/Cu,N/Cu and K/Cu ratios of maize leaf ,The three ratios of maize leaf were 253±71.5 ,2643±839 and 1133±440 at normal growth of maize plant. respectively,Soil avaiable Cu could be markedly cut down by application of phosphours fertilizer ,especiallly at hight phosphorus level.