After the seeds germinate and emerge, the seedlings first use the nutrients stored in the seeds and absorb little nutrients from the outside. With the growth of seedlings, the amount of nutrients absorbed increased continuously until the flowering and fruiting stage, and the amount of nutrients absorbed reached the maximum. In the later stage of crop growth, the growth trend gradually weakens, and the demand for nutrients is also obviously reduced, and it stops absorbing nutrients when it matures. When crops age, nutrients may overflow from the roots.
Although the specific amount of nutrients absorbed by various crops is different, the trend of nutrient absorption and plant dry matter accumulation in different growth stages is consistent. Generally speaking, in the early stage of growth, dry matter accumulation is small, and the amount of nutrients absorbed is not much; At the peak of growth and development, dry matter accumulation increases rapidly, and the quantity and absorption intensity of absorbed nutrients also increase. At maturity, the accumulation rate of dry matter slows down and the amount of nutrients absorbed gradually decreases.
In the stage of crop nutrition, according to the intensity and sensitivity of crop response to nutrients, the response of crops to nutrients is divided into critical period and maximum efficiency period. If the demand for nutrients in these two important periods can be met in time, the growth and development of crops can be significantly promoted.