The effect of topdressing Chinese cabbage is good according to the growing period.

Chinese cabbage has a high yield and needs a large amount of fertilizer. On the basis of applying sufficient base fertilizer, don't worry about topdressing. Topdressing should be determined according to different growth periods and seedling conditions. There is no topdressing in the seedling stage. If the base fertilizer is insufficient, for the first time, 10 kg of ammonium sulfate per mu can be applied at the stage of 3 to 4 true leaves, sprinkled on both sides of the seedling, and immediately watered, called "seedling fertilizer"; for the second time, 15 kg of ammonium sulfate per mu is applied after seedling setting or seedling transplanting, which is called "hair fertilizer". The third time in the rosette stage, the application of ammonium sulfate 25kg / mu, calcium superphosphate 10kg / mu, fertilizer into the ditch or hole, and then slightly add soil to help ridge, and then watering, called "big topdressing"; the fourth time in the middle of heading, ammonium sulfate 1520kg per mu can be flushed with water, called "heart-filling fertilizer". Chinese cabbage from Tuanzhu to rosette stage, the temperature drops day by day, the weather is mild, can be properly watered during this period, the end of rosette can be properly controlled for a few days, and then watered after the third topdressing. After entering the heading stage, Chinese cabbage needs the most water, so it is necessary to water the squatting seedlings once and then water the second time every 2-3 days. This time is very important. If the soil is dry and cracked, the lateral roots will be broken, the fine roots will die, and the ball will be affected. After that, water is usually watered every 5-6 days to keep the soil moist.