[Interactive effect of N and Ca on N uptake by tomato].

To study the effect of fertilizer N and Ca on tomato plant, a pot experiment was conducted with meadow soil in Shenyang. The results showed that under the experimental condition, the N contents in stems, leaves and fruits decreased gradually along with the growth stages. For all treatments, the NO3(-)-N content in fruits, which was within the raw eatable standard, had a positive correlation to N fertilization level. Adequate application of Ca was useful to control the NO3(-)-N content. The response of N contents in stems, leaves and fruits to fertilizer N and Ca was in line with the law of diminishing marginal returns. From flowering stage to fruit expanding stage, the response of fertilizer N was most activated. The nitrate reductase activity in leaves might be greatly affected by fertilizer N, while adequate Ca fertilization could decrease it. A combined application of N and Ca could promote the nitrate reductase activity. Both soil NO3(-)-N content and electric conductivity (EC) were increased with the increasing amount of applied fertilizer N.