小白菜(Brassica chinensis)叶片硝酸盐与矿质元素含量的研究

在施用氮肥的基础上 ,配施足量的磷、钾肥显著提高小白菜产量 ;配施适量的氯化钠 ,其增产效果与氯化钾相近。故在蔬菜生产中 ,可适量施用人粪尿 ,这对于缓解我国钾肥紧张的状况和提高蔬菜产量有一定意义。小白菜叶片的硝酸盐和钠离子含量苗期 >旺长期 >成熟期 ;磷、钾含量成熟期 >旺长期 >苗期 ;全氮含量各生育期相似。所以 ,从减少硝酸盐和增加矿质元素的摄入的角度看 ,食用成熟蔬菜优于幼嫩蔬菜。施用磷、钾、钠一般能提高小白菜叶片的磷、钾、钠含量 ,但在旺盛生长的蔬菜叶片内 ,磷、钾出现稀释效应 ;营养不良和生长受到抑制时 ,磷、钾出现浓缩效应。此外 ,蔬菜叶片的硝酸盐与钾、有机态氮含量之间呈显著负相关 ,与钠含量呈显著正相关。所以 ,为了降低蔬菜硝酸盐和增加矿质元素的含量 ,方便有效的控制措施是成熟时采收 ,提倡施用磷、钾肥 ,防止钠离子过度积累

VARIATIONS OF NITRATE AND MINERAL ELEMENTS IN CHINESE CABBAGE (BRASSICA CHINENSIS)

Combined supply of phosphorus and potassium on the basis of nitrogen fertilization significantly increased the yield of Chinese cabbage (Brassia chinensis) .Application of NaCl gave similar yield-promoting effect similar to that of K application, suggesting that adequate rate of application of human excreta may be of significance for reducing K fertilizer demand and increasing yield in Chinese cabbage production. The concentration of NO 3 - and Na in the leaves of the plant appeared in the order of seedling stage>vigorous growth stage>maturing stage. In contrast, the concentration of P and K varied in an opposite order, i.e. maturing stage>vigorous growth stage>seedling stage. Total nitrogen in the leaves stayed relatively constant throughout the growing period. It is, therefore, recommended that vegetables be consumed when they have fully ripened in order to reduce nitrate intake and increase the intake of minerals. P,K and Na contents in the leaves increased with fertilization rate. Dilution occurred, however, when the plants grew vigorously, and concentration occurred when their growth was inhibited. Nitrate in the leaves was correlated negatively with K and organic nitrogen and positively with Na.