Effect of early bolting on onion yield causes and prevention methods of onion bolting

In overwintering crops, onion and rape often lead to large area early bolting and yield reduction due to warm winter and planting varieties with strong spring. In order to effectively prevent bolting, the causes and preventive measures of early bolting of onion are discussed.

Onion bolting

1. The main reasons:

The main results are as follows: 1. related to the variety: the strong spring onion variety is too sensitive to low temperature and is easy to pass through the vernalization stage under the condition of low temperature, which leads to bolting.

2. related to warm winter: onion is a low-temperature sensing plant, and the green body passes through vernalization. Temperature and sunshine are important conditions to induce bolting of onion. When the onion seedling has 4 true leaves, the pseudostem is more than 0.7cm, and the seedling weighs 10Mel 15g, it feels the low temperature of 2Mel and 5 ℃. Vernalization is completed after 60Mel 130 days, and bolting, flowering and fruiting can be achieved in the next spring under long sunshine and higher temperature. It has been observed for many years that the more serious the warm winter, the higher the bolting rate of onion.

3. Related to cultivation techniques: the bolting severity of onion is related to the early or late sowing date, and the bolting rate of the same variety with early sowing date is higher than that with late sowing date.

4. it is related to density: early planting time, sparse density, too much fertilizer and water, overgrowth of seedlings, excessive nutrition, or lack of fertilizer and water in the later stage, malnutrition, growth imbalance, promoting flower bud differentiation and early bolting.

5, related to fertilizer and water: too many times of topdressing, in the case of high temperature, it is also easy to encourage bolting.

2. Preventive measures:

1. Selecting suitable varieties: selecting suitable varieties according to local conditions can not only increase production and income, but also effectively reduce bolting rate.

2. Sowing at the right time: timely sowing is not only the key measure to prevent early bolting of onion, but also the key to high yield. it can not only avoid the increase of seedling growth, pseudostem diameter and bolting rate caused by sowing prematurely, but also avoid small seedling growth, small bulb and low yield due to sowing too late.

Onion fertilization

3. Rational fertilization: the demand ratio of nitrogen, phosphorus and potassium fertilizer for high-yield onion is 2.1. The root system of onion is shallow in the soil, so in the application of fertilizer, it is mainly mature farm manure, compost and plant ash. After transplanting, about 750 kg of rotten acquaintance feces and urine were applied per mu, and topdressing was applied twice, and potassium sulfate was added at the same time as nitrogen fertilizer, adding 5Mel 7.5 kg of potassium sulfate or 75MUR 150 kg of plant ash.

4. Reasonable close planting: good soil moisture and good ditch roads should be opened when planting, so as to prevent winter drought. In addition, we should also pay attention to ploughing and loosening the soil and get rid of weeds in time.

5. Prevent warm winter: warm winter is one of the key factors of immature bolting of onion. Therefore, great attention should be paid to controlling water and fertilizer during overwintering in warm winter years, promoting vegetative growth, controlling reproductive growth, reducing immature bolting rate, and bolting when immature bolting onion appears in the field, so as to reduce yield loss.