营养液pH和氮形态对小白菜生长、氮素吸收及品质的影响

Effects of pH and Nitrogen Forms of Hydroponic Nutrient Solution on the Growth,Nitrogen Absorption and Edible Quality of Pakchoi(Brassica chinensis L.)

采用温室水培方法,研究了营养液pH和氮形态对小白菜生长、品质和氮吸收的影响,以及pH对小白菜吸收各形态氮的影响机制。结果表明,在中性及微碱性条件下,硝铵混合氮源较硝态氮处理小白菜生物量差异不显著,但有利于提高可溶性糖和游离氨基酸含量,降低硝酸盐含量。小白菜根系对不同形态氮吸收受营养液pH影响差异显著(P<0.05),微酸性环境中吸收硝态氮较快,微碱性吸收铵态氮较快。小白菜根系对铵态氮的吸收速率大于硝态氮,但铵态氮吸收量较低。硝铵混合氮源处理中,小白菜地上部鲜重(y)与营养液pH值(x)的回归方程为y=-0.331x2+4.440x-10.660(r=0.944,P<0.01),pH为6.7时小白菜生物量最大,较pH值为5.5,6.0,6.5分别高12.9%,4.1%,1.3%,表明通过调节营养液pH可以明显提高小白菜产量。

A greenhouse hydroponic experiment was conducted to study the effects of pH and nitrogen forms of hydroponic nutrient solution on the growth,nitrogen absorption and edible quality of pakchoi（Brassica chinensis L.）,and the effects of pH on absorption mechanisms of different nitrogen forms by pakchoi.The results showed that under the neutral and alkalescent conditions,compared with nitrate,the ammonium and nitrate mixed nitrogen sources did not inhibit the growth of pakchoi,and increased the contents of soluble sugar and free amino acids,and reduced nitrate content.The effects of pH on nitrogen absorption rate of pakchoi root were different for different nitrogen forms（P〈0.05）.The nitrate absorption rate of pakchoi root was relatively higher in subacid environment,while the ammonium absorption was relatively higher in alkalescent environment.Pakchoi absorbed ammonium faster than absorbed nitrate,but the absorption amount of ammonium was quite low.Regression analysis showed that in the treatment with ammonium and nitrate mixed nitrogen sources,the equation between the fresh weight of pakchoi（y）and pH value（x）was y=-0.331x2＋4.440x-10.660（r=0.944,P〈0.01）.Under the test condition,the optimal pH was 6.7.Compared to the fresh weights of pakchoi under the pH values of 5.5,6.0and 6.5,the fresh weight under the optimal pH increased by12.9%,4.1% and 1.3%,respectively,showing that by adjusting the pH of hydroponic solution,the pakchoi production could be obviously improved.