1. First, increase the light transmittance of greenhouse lighting surface, improve lighting conditions and make full use of light energy. Light is the energy source of photosynthesis, and the intensity and duration of light in greenhouse are the main factors that determine photosynthetic yield. Maximizing the use of light energy is not only the main condition for plants to improve photosynthetic yield, but also the heat source of greenhouse in cold weather. Indoor light intensity is not only determined by seasonal changes, but also influenced by factors such as the shape and angle of transparent surface, types and conditions of plastic film, greenhouse support and group structure.
According to Professor Xing Yuxian of Shandong Agricultural University, with the change of the angle between the slope and the ground, the solar transmittance and incident energy change obviously. During the three months from 65438+February to February of the following year, when the illumination surface is 10 degree, the incident amount of sunlight at noon is 6467 kJ/m2℃ hour; When the illumination surface is at 20 degrees, the incident amount of sunlight is 7557 kJ/m2 hour, which is 16.9% higher than that at 10 degrees. When the illumination surface is at 30 degrees, the incident amount of sunlight is 8699.7 kJ/m2 hour, which is higher than that at 20 degrees 15. 1%. At 40 degrees, the increase is even greater.
Therefore, when we build a greenhouse, under the premise of not affecting the wind-proof and thermal insulation performance, as long as conditions permit, the larger the angle of the light-transmitting surface, the more conducive to light transmission.
In addition, as mentioned above, the shape of the lighting surface, the type and condition of the film, the projection ratio between the lighting surface and the back slope, and the hanging reflective curtain can all significantly affect the lighting conditions in the greenhouse.
2. Extend the lighting time. In winter, the sunshine time is short. Under the condition that the heat preservation is not obviously affected, we should pull the straw curtain as early as possible in the morning, put the straw curtain at night and put the straw curtain in time on cloudy days, so as to make full use of the sunshine, extend the illumination time and improve the photosynthetic yield.
3. Improve the photosynthetic efficiency of crops. Select varieties with low light tolerance and high photosynthetic efficiency, and continuously and meticulously spray 600 times of "Tianda -2 1 16" liquid medicine or Kang Kai, brassinolide, photosynthetic micro-fertilizer, etc. on the plants to start the crop vitality and improve the photosynthetic efficiency of the leaves.
4. The optimum temperature for maintaining the growth and development of crops. The photosynthetic intensity of plants is closely related to temperature, and each plant can only carry out photosynthesis under suitable temperature conditions. Generally speaking, the lowest temperature for photosynthesis of most vegetable crops is 0-2℃, the suitable temperature range is 10-35℃, and the optimum temperature is 25-30℃. When the temperature is higher than 35℃, photosynthesis will decrease obviously and stop at 40-45℃. Therefore, in order to improve photosynthetic efficiency and reduce respiratory consumption, the indoor temperature should be adjusted to the most suitable or basically suitable temperature range when cultivating vegetables.
5. Increase the application of carbon dioxide gas fertilizer to improve photosynthetic efficiency.
6. Scientific and reasonable water supply and fertilization: water is the raw material of plant photosynthesis and the necessary condition for all life activities of plants; Mineral elements are important components necessary for plant cell nutrition. Plants absorb water and various mineral elements from soil through roots to maintain normal life activities. Therefore, it is one of the most important and effective ways to improve the efficiency of photosynthetic production by scientifically and timely applying organic fertilizer, chemical fertilizer and micro-fertilizer, timely and properly irrigating, ensuring the supply of fertilizer and water, constantly meeting the demand of plants for water and mineral elements, and improving the vitality of plants.
7. Adjust the population structure to increase and maintain the large and effective photosynthetic area as much as possible. Plants are green factories for photosynthesis and organic matter production, and leaves are workshops. Chloroplast and chlorophyll are energy converters that convert light energy into chemical energy and produce organic matter, so leaf area and chlorophyll are another main factor affecting photosynthetic yield.
① Leaf area refers to numbers: leaf area is expressed by leaf area index. Generally, in the open field, when the leaf area index is less than 3, the photosynthetic yield will decrease with the decrease of leaf area index. If the leaf area index is greater than 5, the photosynthetic yield will decrease with the increase of leaf area index because of the mutual shading of leaves. The reasonable leaf area index is 3-5. Therefore, only the effective leaf area is positively correlated with the yield. In production practice, we must not blindly expand the leaf area, so as not to waste, consume fertilizer and water, worsen the lighting conditions, and cause the yield to drop, but the loss outweighs the gain.
In view of the fact that the light intensity in the greenhouse is obviously lower than that in the open field, and the indoor light distribution is uneven, in order to make full use of light energy and increase the effective leaf area, firstly, it should be dense before planting, short before planting and high after planting, and the overall management height should not exceed 2/3 of the greenhouse height; Reasonable or variable close planting should be implemented, and the north-south direction should be implemented to reduce the shading between rows; It is necessary to promote intercropping, interplanting and three-dimensional planting, promote the early leaf area to expand as soon as possible, and control the later leaf area index (line) between 2 and 2.5 (empirical data); It is necessary to cut off dense branches and leaves, aged leaves and diseased leaves in time, drop seedlings in time, avoid mutual shading, maintain a large effective leaf area and increase photosynthetic yield.
(2) Leaf age and leaf dynamics: the photosynthetic capacity of young leaves of crops is very weak, and it is the strongest when it is fully grown into strong leaves, and it drops rapidly after the leaves are aged. Therefore, in greenhouse management, we should try our best to meet the early light, temperature, fertilizer and water conditions, promote its early leaf development and rapid leaf growth, expand its leaf area as soon as possible and improve its yield. However, with the growth of crops, the leaf area index is enlarged and the mutual shading phenomenon is gradually aggravated. Therefore, when the leaf area index reaches 2.5, it should be controlled to continue to grow, and buds and branches should be erased in time to remove the old leaves at the base, so as to increase the proportion of mature leaves, reduce consumption, improve lighting conditions and maintain strong photosynthesis.
8. The increase of chlorophyll content in leaves is closely related to photosynthetic intensity. The photosynthetic intensity of leaves with dark green leaves and high chlorophyll content is obviously higher than that of leaves with light leaves and low chlorophyll content, sometimes the difference is 2-3 times. Chlorophyll, like other organic substances in plants, is constantly updated. For example, the chlorophyll of spinach can be updated by more than 95% after 72 hours.
The formation of chlorophyll is closely related to light, temperature, water and mineral nutrition supply.
Illumination: Light is a necessary condition for chlorophyll formation. Only through illumination can the leaves of crops produce chlorophyll and turn green.
Temperature: Chlorophyll production needs a certain temperature. Generally, the lowest temperature is 2-4℃, the highest temperature is 40-48℃, and the most suitable temperature is 26-30℃.
Water: The lack of water in leaves not only hinders the formation of chlorophyll, but also accelerates the decomposition of chlorophyll. Therefore, when crops encounter drought, chlorophyll is destroyed, which is the main reason why leaves turn yellow.
Mineral elements: nitrogen, magnesium, sulfur, iron, etc. It is the main component of chlorophyll, which is an indispensable condition for chlorophyll formation. For example, leaves are yellow-green when nitrogen is lacking, and dark green when nitrogen is sufficient; Without magnesium, chlorophyll is difficult to form or be destroyed, which shows that the veins turn green and yellow.
To sum up, in order to improve the chlorophyll content and photosynthetic productivity of plants, it is necessary to improve the lighting conditions, maintain a suitable temperature, and increase the supply of water and various mineral elements.
9. Choose good varieties. Excellent varieties have high photosynthetic efficiency, strong adaptability and high yield. Under the same conditions, higher output and benefits can be achieved. In greenhouse vegetable cultivation, according to the characteristics of greenhouse, we should choose those middle and late-maturing varieties with low light tolerance, strong disease resistance, strong growth potential, high quality and high yield, so as to obtain high yield and high benefit.
10. Apply "no deep ploughing" soil conditioner when preparing soil. After planting, use 1000 times of "drought and flood harvest" or 600 times of "Tianda -2 1 16" to irrigate roots, improve soil structure, increase soil porosity, deepen the thickness of living soil layer and promote deep soil loosening.
1 1. Coordinate and balance the relationship between vegetative growth and reproductive growth, which not only ensures the robust growth of plants, but also enables flower buds to continuously differentiate into flowers and fruits, thus maximizing the production cycle and increasing the yield.
12, do a good job in integrated pest control, maintain the robust growth potential of crops, and obtain high quality and high yield.