the application of nitrogen fertilizer

China ranks first in the world in terms of nitrogen yield and nitrogen application rate, but its utilization rate is not high and its loss is great. According to the results of experiments on 528 rice plants and 254 wheat plants (wheat, barley and barley), the average nitrogen utilization rate was 33%-38% and 28%-41% respectively. The nitrogen use efficiency of crops refers to the proportion of nitrogen fertilizer applied to farmland that is absorbed into the body of crops in the current season:

Nitrogen use efficiency is usually measured by two methods, one is difference method and the other is isotope 15N dilution method. The former is often used to calculate the amount of nitrogen fertilizer, while the latter is often used to study the fate of nitrogen fertilizer applied to soil.

Nitrogen use efficiency is generally consistent with fertilizer efficiency (yield per unit nutrient applied). However, under some special circumstances, such as excessive nitrogen fertilizer crops green lodging, may also be inconsistent. Therefore, rational application of nitrogen fertilizer is to improve the utilization rate and fertilizer efficiency of nitrogen fertilizer. Based on our many years of experience, we must master the following main technologies.

1. Nitrogen fertilizer is applied in combination with phosphorus and potassium fertilizer to achieve balanced fertilization. In the 1950s or so, nitrogen fertilizer alone was highly effective. Since then, due to the consumption of phosphorus and potassium in the soil, it has not been able to meet the needs of high yield of crops, and has become a nutrient limiting factor to improve crop yield. Nitrogen alone is often ineffective under these conditions and must be applied in conjunction with phosphorus and potassium. For example, from 1981 to 1982, the Institute of Soil and Fertilizer, Chinese Academy of Agricultural Sciences, conducted an experiment on nitrogen (urea) application rate of wheat on a relatively barren tidal land in Jing County, Hebei Province. Because of the serious phosphorus deficiency in the soil of this plot, nitrogen fertilizer application alone almost did not increase yield, but nitrogen fertilizer application on the basis of 7.5 kg P 2O 5(calcium superphosphate) per mu achieved significant yield increase effect. There was no positive interaction between nitrogen and phosphorus. In Shangrao district, Jiangxi province, the average yield per mu of rice was 275 kg when nitrogen fertilizer (N 10 kg/mu) was applied alone for three consecutive seasons. The average yield per mu of nitrogen fertilizer combined with phosphorus fertilizer (P 2O 53 kg/mu) was 324 kg. The average yield per mu of nitrogen fertilizer combined with potassium fertilizer (K 2O 6 kg/mu) was 317 kg. The average yield per mu of nitrogen, phosphorus and potassium fertilizer combined was 344 kg. Nitrogen fertilizer combined with phosphorus and potassium fertilizer not only increased rice yield, but also increased rice yield and protein content in brown rice.

Under the condition of deficiency of P and K fertilizer, nitrogen fertilizer combined with organic fertilizer also had a good yield increase effect. Because organic fertilizer is a complete fertilizer, it is often rich in phosphorus, potassium and trace elements.

Second, master the appropriate amount of nitrogen fertilizer. Generally speaking, yield per unit area increased with the increase of nitrogen application rate, but nitrogen use efficiency and fertilizer efficiency showed a significant downward trend. In 1985, the Soil and Fertilizer Institute of Jilin Province Academy of Agricultural Sciences had done experiments on different urea dosage and utilization rate on corn:

Nitrogen fertilizer application (kg/mu)

0

8.5

11.9

15.3

18.7

Corn yield (kg/mu)

253

444

447

437

435

Nitrogen use efficiency (%)

-

45.2

41.1

35.4

26.4