The Most Overlooked Things About Tomatoes Fill Lights, Have You Noticed?
The Need For Lights Supplementation is Closely Related To The Cultivation Plan
The weekly growth data of plants can be used to determine whether the greenhouse needs a light supplement. Plant growth, stem diameter, leaf length, flowering rate, and fruiting rate can all reflect whether the crop is in good balance. As the world horticultural production chain is not yet mature enough, there are no special tomato seedling companies, most greenhouses will choose small seedlings for transplanting. As a “source base” system, the photosynthetic products accumulated in the daytime of leaves only need to supply the maintenance respiration and growth respiration of itself before the flowering and fruiting. Generally, the nutrients are relatively abundant, and the crops are shown as thick stalks and thick leaves. Growers can tell whether a day’s photosynthesis is strong or weak by the presence of purple anthocyanins in the vicinity of the growing point. With enough photosynthetic products, the difference in temperature (DIF) between day and night can be controlled to promote growth. However, once the crop enters the vegetative growth stage and the reproductive stage, the fruit’s demand for photosynthetic products will rise rapidly. Many growers would even see a significant weakening of crop growth, with thinning stems, thinning leaves and the size and weight of the newly grown fruit at the growing point. In this case, if the external light is abundant and the net photosynthetic products accumulated during the day are sufficient, the increasing fruit consumption can be satisfied. However, as soon as the reproductive stage (45 weeks) begins, natural light gradually decreases, which means that there are fewer photosynthetic products available for crops.
The Lighting Strategy is Closely Related To The Design of The Lighting System
At present, the main sources of greenhouse light supplement lamps on the market are high-voltage sodium lamp and LED plant. High-pressure sodium lamp is more general use lamp, its price is moderate, can be accepted by broad farmer place, short-term effect is remarkable, the complementary fill light technology has been relatively mature, still at present in large-scale use. The LED plant lamp has a narrow spectral adjustability, high safety, and reliability. It has flexibility in the application of plant physiological tests and has a good prospect of development. In the specific use, we should choose rationally according to the practical situation of cultivation demand, application target, investment ability, and cost control.
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Rather than outdoor light, growers should know exactly how much light they actually get from the plants in their greenhouses, and thus determine the amount of light they need to fill. The design, location, and use of each greenhouse will affect the actual indoor lighting. Growers can obtain the average light parameters from greenhouses or from the city’s weather stations over the years.
In addition, it is easy to overlook that the greenhouse glass is cleaned. In winter, the outdoor temperature is below zero for a long time, which brings a risk to the use of roof cleaning machine. In addition, with less rain, the top glass is not cleaned in time, which will greatly reduce the light transmittance of the greenhouse. So below this kind of circumstance, strengthen indoor illumination to appear particularly important.
Fill Light’s Pattern
The yield of a large canopy crop like tomato is also related to the total light interception of the canopy, while the total light and Leaf Area Index (LAI) that can be intercepted by the canopy are in a negative exponential function relationship, and the light interception is almost saturated when LAI reaches 4 or so. When the blade occlusion is serious, the canopy photosynthetic efficiency will be reduced. The use of scattered glass and curtain is to allow light to permeate the leaves in the lower part of crops and improve the overall photosynthetic efficiency of crops. The lower and middle leaves were more closed and the light decreased obviously after the plant entered into the stubble and increased the density. If the greenhouse is equipped with interplant light supplementation, it can make more direct use of the dynamic leaves in the middle and lower parts. Different from the consideration of top light to light saturation, the lower and middle leaves cannot set a limit value due to less natural light that can be directly irradiated, but is used all the time when there is light supplement demand. The position of the interplant supplementary light lamp should be more than 40 cm away from the bottom leaf.
The data showed that interplant light supplementation improved the light environment of the greenhouse tomato canopy and improved the photosynthesis of the canopy and the plant, the tomato yield increased by 22.7% ~ 28.5%, and the dry matter of the fruit increased by 31% ~ 38.6%. The light absorption rate and the maximum net photosynthetic rate Pmax of the leaves at the position of interplant light supplementation at 500 ~ 650nm were both higher than those of the plants without light supplementation. The specific leaf area of the leaf was reduced by interplant light supplementation. Different proportion of red and blue light had a significant effect on the accumulation of total dry matter and the formation of the yield of tomato, but there was no significant difference between the different proportion of red and blue light.
Lighting Strategy and Greenhouse Management
In greenhouse management, all environmental factors are interconnected. After supplementing light, only other corresponding ring control coordination can maximize the advantage of the supplementary light. If the grower can control all the factors of production well, it can control the growth rhythm of the crop subjectively.
Glow + Temperature
When the light is good, the temperature strategy system Settings interface can often set a light intensity for the influence of temperature, such as 300 W/m2 rose to 400 W/m2, temperature of heating and ventilation plus 1 ℃, or accumulation of daylight to 1000 J/cm2 can be appropriately increased total light on night temperature influence, enhance the respiration, photosynthesis production consumption of abundance. Generally, the greenhouse is equipped with the total radiation sensor outside, but the plant photosynthetic effective radiation sensor inside is seldom equipped with the PAR. Growers also need to take into account the additional radiation from light supplementation when adjusting the effects of light on temperature. In fact, in the case of a light supplement, it has been found that the fruit loading rate increased significantly in winter when the temperature was kept high.
Supplementary lighting + irrigation
The irrigation strategy is mainly controlled by the factors of light and time to ensure that the plants have sufficient water for photosynthesis under good light. The first irrigation is often two hours after sunrise, and the substrate bag has a “rapid morning drop” in water content. After the greenhouse is replenished, the crop’s biological clock is slowly adjusted as the light-filling time moves forward. Irrigation strategies need to be adjusted according to the curve drop, content and time of water distribution in the substrate bag. In the practical application, “fast drop in the morning” also appears earlier than under natural light conditions, indicating that the crops have begun to be active and use the moisture in the substrate bag. In this case, a suitable irrigation can be added after supplementing the light. As the intensity of supplementary light is lower than the external natural light, the irrigation quantity should not be too much, and the water loss rate of the cultivated substrate bag for 24 hours can be controlled at about 15%.
Light and Humidity
When the darn time is advanced to sunrise, the humidity in the greenhouse begins to rise as the plants’ pores open and begin to transpiration. High-pressure sodium lamp releases heat, which widens the vapor pressure difference between the air and the leaf cavity, further exacerbating the transpiration. However, due to the limitation of outdoor low temperature in winter and indoor ventilation temperature, the relative humidity of greenhouse will remain high. If the humidity is over 90% at night, the disease risk caused by high humidity should be considered. A gap can be set for the curtain to cooperate with the window on the leeward side, and the heating pipe can be drained.
Supplementary Light + Crop Management
Under the condition of less light, in order to ensure that the nutrition part of the crop does not overconsume and affect the later growth vigor and yield, it is often necessary to thin the flowers and fruits of the tomato. After adding light, the degree of flower thinning and fruit thinning was reduced, and the flower flowering rate and fruit setting rate were relatively stable every week. The plant could maintain good vegetative growth and reproductive growth. In addition, the time of plant density increase can be advanced with the state of the plant, and higher density can be attempted.
Planter Level Affects The Benefits of Light Supplementation
According to the total illumination accumulation and total production of the entire production season, the utilization rate of natural light for growers can be calculated. Excellent growers of large fruit and tomato in the Netherlands can use up to 11–12 g/mol of natural light, while the current level of better growers in China can only reach 6–7 g/mol. This means that good growers have a higher capacity to convert light into yield when given the same amount of time, so improving the cultivation techniques is critical to improving the benefits.
In short, the greenhouse light compensation needs to be determined according to the greenhouse location, crop selection, cultivation plan, and other specific conditions. Second, considering the investment and use cost of different light sources, as well as the impact on other energy consumption (natural gas, electricity), the grower should choose a suitable lighting system. In the actual use process, the growers still need to adjust other factors of the greenhouse, so that the utilization rate of a light supplement is the highest. Since the benefits of supplemental light depend very much on the level of the grower, a good grower has a higher ability to convert light into yield and can do so by adjusting other factors in the greenhouse. Therefore, while using the supplementary light, the grower should also constantly improve his cultivation techniques and make full use of the free natural light. Through the combination of the two, planting can obtain greater benefits.