What to Do About Fertilizer Burn in Rice? Symptom Identification and Control Measures
Fertilizing is an important part of the rice growing process. Topdressing must be applied multiple times throughout the entire growth period, and each fertilization is important for rice, as it is fundamental to its growth and development. If improper fertilization causes fertilizer burn, how should it be controlled? Let's take a look.
1. Ammonia water fumigation injury
Symptoms and causes: The leaves initially turn a uniform bright yellow, and as time goes on, the entire leaf turns yellowish-brown or reddish-brown, and in severe cases the leaves die off. The main cause is ammonia gas volatilized from applied ammonia water, which is dispersed by wind and causes leaf fumigation injury. When ammonium bicarbonate is broadcast on the field surface during fertilization, ammonia gas is volatilized during decomposition, causing localized leaf fumigation injury, especially severe on the basal leaves.
Control measures: When using ammonia water, pay attention to keeping shallow water in the field, and immediately plow after fertilization so that the ammonium is adsorbed by the soil, thus preventing ammonia gas from volatilizing and also facilitating root absorption. Fertilization should not be carried out at noon, and the concentration for topdressing should preferably be 1%-2%. Also pay attention to wind direction to avoid leaf fumigation injury.
2. Ammonium sulfate burn
Symptoms and causes: Affected leaves develop irregular white spots, and sometimes they may also turn black and rot. The main cause is that when ammonium sulfate is applied while dew is still present, the fertilizer adheres to the leaves, creating a locally high concentration on the leaves where the fertilizer sticks. Rainwater dissolves and washes it away, causing leaf burn and bleaching of chlorophyll so the leaves turn white. In the late growth stage, if the field lacks water, applying too much ammonium sulfate or broadcasting it unevenly can cause the roots to turn black and rot.
Control measures: When applying ammonium sulfate, avoid doing so in the morning when dew is still present or when there are water droplets on the leaves, so that the fertilizer does not adhere to the leaves. Maintain a water layer when fertilizing and plow once to facilitate root absorption.
3. Calcium cyanamide burn
Symptoms and causes: Affected leaves first turn dark red, then develop many scattered reddish-brown or dark brown spots of varying sizes from burning, and soon afterward the leaf tips die off and turn reddish-brown, just as if scorched by fire; in severe cases the roots turn black and die. The main cause is contact injury from calcium cyanamide, with powder particles adhering to the leaves and causing brown or dark green water-soaked lesions.
Control measures: When using calcium cyanamide as a base fertilizer, broadcast it and then dry-plow once, and after a week irrigate and transplant the seedlings; this is relatively safe. In addition, calcium cyanamide should not be used directly for topdressing; it must be mixed with 10 times its amount of moist soil and piled for 10-20 days, kept moist, and applied only after its toxicity has dissipated.
The above is an introduction to rice fertilizer burn symptoms and control measures. We hope it helps you. To learn more related knowledge, please follow us.