Effects of Spray Application of Lanthanum and Cerium on Yield and Quality of Chinese Cabbage (Brassica chinensis L) Based on Different Seasons

The use of single light rare earth elements in agriculture was studied using the application of single rare earth elements (La and Ce) to Chinese cabbage (Brassica chinensis L.) in field plot experiments where the soil conditions remained the same but the season (spring or autumn) in which application occurred was altered. The results showed that the Chinese cabbage's nutrition quality between the two seasons had obvious differences. When planted in the autumn, the soluble sugar and vitamin C content was higher, the titratable acid and nitrate content was lower, and the ratio of sugar to acid was higher, while when planted in spring, the situation was opposite. La or Ce treatments in spring and autumn promoted the growth of the Chinese cabbage, the fresh and dry weight of the stems and leaves increased, the ratio of dry to fresh weight increased, and the observed effects were greater in the Ce treatments than the La treatments. Moreover, the soluble sugar content increased and the titratable acid content decreased, which meant that the ratio of sugar to acid increased. There was an increase in the vitamin C and nitrate content in the spring Chinese cabbage, while there was a decrease in the vitamin C and nitrate content in the autumn. The levels of the heavy metals Cu, Zn, Cd, Pb, and Ni decreased. The La treatment had greater effects on the spring Chinese cabbage, while the Ce affected the autumn Chinese cabbage more.