What should be done to address the overuse of nitrogen fertilizer in rice cultivation?

Nitrogen fertilizer is one of the essential nutrients for rice growth; it promotes plant development and increases yield. However, excessive application can also cause various adverse effects on rice.

I. Harm Caused by Excessive Application of Nitrogen Fertilizer

Excessive application of nitrogen fertilizer can cause significant harm, and the nature of this harm varies across different growth stages. During the tillering stage of rice, over-application of nitrogen promotes excessive vegetative growth while stunting root development; as a result, the roots fail to supply adequate nutrients during tillering, leading to a high incidence of empty or shriveled grains.

During the growth period, excessive application of nitrogen fertilizer can lead to vigorous vegetative growth, but the stems become weak and the plants grow excessively tall, resulting in poor air circulation and higher temperatures and humidity in the lower canopy.

Excessive application of nitrogen fertilizer can lead to lodging in the later growth stages. Nitrogen promotes vigorous vegetative growth and elongates internode lengths, which may increase the risk of late-stage lodging in rice.

Excessive nitrogen fertilization can lead to a surge in pests and diseases. Because the stems, leaves, and other plant parts remain relatively tender, it often makes it difficult to control the rice leafroller. In recent years, stem borers have become particularly severe; in fields with overly vigorous vegetative growth, stem borer damage is especially pronounced. Moreover, excessive nitrogen typically exacerbates sheath blight and blast disease, and in fields severely affected by sheath blight, brown planthopper infestations also tend to be very serious.

II. Handling Methods

1. Excessive application of nitrogen fertilizer can easily lead to premature senescence. Spraying potassium dihydrogen phosphate not only boosts yield but also helps prevent early aging. Typically, apply 100–200 grams of potassium dihydrogen phosphate diluted in 15–20 kilograms of water during the booting and heading stages. This treatment significantly improves rice grain set and grain weight. Since this is a high-concentration spray, it is recommended to use high-purity potassium dihydrogen phosphate; avoid products with high impurity levels to ensure optimal results.

2. Pay attention to the application of silicon fertilizer to enhance rice’s lodging resistance. Where conditions permit, apply it 1–2 additional times as needed to further strengthen this trait, particularly in fields located near lakes or the sea, where winds are strong; lodging prevention is essential.

3. Disease and pest control must be thorough; when applying potassium dihydrogen phosphate, it can be combined with benzo‑propanconazole to help prevent rice false smut and sheath blight. For varieties susceptible to blast, triazolopyrimidine or pyraclostrobin may be added.