How to raise the temperature for greenhouse grapes? These methods must be mastered

For greenhouse grapes, going from raising the temperature to bud break takes 25 to 50 days. There are two main methods for raising the temperature: the high-temperature closed-greenhouse method and the gradual temperature-raising method.

1. High-temperature closed-greenhouse method.

That is, uncover the straw curtains during the day and do not ventilate all day. When the temperature reaches 35°C, lower the curtains and reduce the temperature inside the greenhouse by shading. When the temperature inside the greenhouse drops to 20°C, raise the straw curtains again. Repeat this operation 1 to 2 times throughout the day to ensure that the pre-bud-break stage remains at a relatively high temperature.

With the high-temperature closed-greenhouse method, the bud-break period is short, generally budding within 25 to 35 days, which can greatly advance the ripening period; the humidity inside the greenhouse is high (above 90%), and in a high-humidity environment, even at high temperatures, "bud scorching" (bud eyes losing water due to high temperature) rarely occurs; the high-temperature environment is conducive to breaking dormancy and offsetting dormancy obstacles; daytime temperatures are high, the ground accumulates more heat, night temperatures are high, and the risk of secondary dormancy is small; however, the high-temperature closed-greenhouse model has a relatively greater risk factor, because the duration of bud eye germination is short, which has an adverse effect on further differentiation of flower clusters, and problems such as poor flower bud differentiation and inflorescence degeneration are prone to occur. It is recommended for use on varieties such as Zesexiang, Red Balado, Jingxiu, and Muscat series such as Zaoxia Rose and 87-1, as well as varieties with good flower bud differentiation, tightly set berries, and a high fruit-setting rate.

2. Gradual temperature-raising method.

The gradual temperature-raising model applies the natural pre-bud-break temperatures of open-field cultivation: daytime temperatures gradually transition from 10°C to 25°C, with the temperature controlled to rise by 5°C every week, and the maximum temperature not higher than 25°C. When the temperature exceeds the planned temperature, open the upper vents to ventilate and cool down; when the temperature drops, close the vents again to raise the temperature. Opening and closing operations need to be repeated within a day. With the gradual temperature-raising method, because the average temperature inside the greenhouse is low, bud break is delayed, generally 40 to 50 days, which is not conducive to early marketing, but this method follows the natural laws of plant growth and has relatively low risk. It is recommended for use on varieties such as Kyoho and Fujiminori. Bleeding after raising the temperature is a sign that the grapevines have awakened.

Li Nongguan