不同氮肥对小麦生长和吸收镉的影响

Effects of Different Nitrogen Fertilizers on Wheat Growth and Cadmium Uptake

为了保证镉含量处于临界值附近土壤上农产品的安全生产,避免不合理施肥引起土壤镉的活化和增加作物吸镉量,研究了4种主要氮肥对不同生育期小麦吸收镉的影响.研究表明,施用硫酸铵、硝酸铵和尿素都比氯化铵促进了小麦生长,明显提高了小麦籽粒产量.所有氮肥处理都比无肥处理增加了小麦对镉的吸收,但不同氮肥处理之间的效果差异显著,其中以氯化铵的促进作用最强,硫酸铵处理的小麦吸收镉最少,尿素处理的小麦对镉的吸收随其用量增加而增加.在小麦整个生育期中,生育前期吸收镉较少,中、后期明显增大;但植株体内镉的浓度却表现为前期高、后期低,呈现随生育期递进而逐渐降低的趋势,只有氯化铵处理表现为拔节期体内镉含量为最高.镉在小麦体内的累积与其生物量的增加呈正相关,从秸秆向籽粒转移的总镉量随小麦籽粒/秸秆比的增加而降低.本试验中土壤的镉含量小于土壤环境质量污染二级标准,但籽粒含镉量均超过国家食品卫生标准允许量(0.1mgkg-1),表明土壤镉污染指标与作物品种密切相关.在镉污染土壤上,应选用低富集镉的小麦品种,避免使用氯化铵,防止过量施用尿素或其它铵态氮肥.

In order to secure safety of agricultural produce originated from the soil that contains cadmium（Cd） close to its critical pollution level and avoid any improper fertilization that can enhance activation and uptake of soil Cd by crops,pot experiments were conducted to study the effects of four major nitrogen（N） fertilizers on Cd uptake by wheat at different growth stages.The results showed that the application of ammonium sulfate,ammonium nitrate and urea significantly improved wheat growth and obviously enhanced wheat yield compared to the ammonium chloride.All N fertilizers increased Cd uptake that differed significantly between the treatments with the highest Cd uptake by the nitrogen chloride treatment and the lowest by the ammonium sulfate treatment.The Cd contents in wheat tissues were increased with an increase in urea dosage.Total amounts of Cd uptake in wheat tissues increased with time,while the Cd concentrations decreased with time from seedling stage to maturity,except ammonium chloride that resulted in the highest Cd content in the tissues at elongation stage.The accumulation of Cd in plant was well related with an increase in wheat biomass,while the amounts of Cd transferred from straw to grains decreased with an increase in grain/straw ratio.It is worth noting that the Cd content in wheat grains surpassed the allowable safety level even when wheat grew on the soil with Cd content below the critical pollution level,indicating that the soil Cd critical values should be set up for each crop or variety rather than a fixed value for all.In order to produce pollution free wheat growing on the soil suffering from Cd pollution or marginal Cd pollution,Cd resistant wheat variety should be adopted,and the use of ammonium chloride or overdoses of urea and other ammonium N fertilizers should be avoided to effectively reduce the activity of soil Cd.