Substrate cultivation is the mainstream cultivation mode of modern glass multi-span greenhouses. The physical and chemical properties of the substrate determine the moisture, nutrient absorption performance and air content of the substrate. This not only affects the ability of the crop roots to absorb and transport water and nutrients, but also affects the growth and development of plant root system. Therefore, when choosing a substrate, the adaptability of the plant roots to the growing medium, the applicability and economy of the substrate should be considered. Although some substrates are suitable for crop growth and development, they have low economic performance and are therefore not suitable. 

The material for cultivation substrate should have the following characteristics:

① Excellent breathability and water-holding capacity; ② Little impact on irrigation water, and does not affect the recycling of drained liquid; ③ No pollution; ④ Low cost. The two main substrates that can meet the demand are rock wool and coco coir. According to statistics, rock wool accounts for 57% and coco coir accounts for 39% in greenhouse vegetable production.

Advantages and disadvantages of rock wool cultivation and coco coir cultivation

Advantages of Rock Wool

① Rockwool is an inert substrate, the chemical properties of its material are stable, and the production process has been treated at high temperatures, making it sterile and non-toxic; ② Rock wool fiber is light in texture, has high porosity (more than 90%), strong water absorption, and strong permeability.③ Rock wool has a lighter texture, uniform voids, and better air permeability. It can stably control the EC and pH of the root system, which is beneficial to the growth of plant roots; ④ Rockwool with different structures has different water absorption and drainage capabilities. The arrangement direction of rock wool fibers determines the performance of the rockwool growing medium: the arrangement directions of rock wool fibers are divided into horizontal arrangement and vertical arrangement. The gaps between horizontally arranged rock wool fibers are horizontal, which is conducive to moisture retention in the matrix; vertical arrangement The gaps between the arranged rockwool fibers are vertical, and the water in the matrix is easily transported vertically upward (capillary action), which is conducive to the vertical downward growth of plant roots and is also conducive to drainage, making it easier for growers to control the crop root environment; ⑤ Rockwool matrix The chemical properties are stable and do not react with the nutrient solution or replace the components with the nutrient solution (CEC=0 mmol/kg); ⑥ The irrigation drainage of rock wool cultivation can be recycled from the early stage of planting; ⑦ Nutrients and moisture The distribution in the rockwool strips is relatively uniform, and the root system environment can be quickly adjusted by adjusting irrigation to create the best growth environment for the plant roots.

◆Disadvantages of Rock wool

First, the rock wool matrix cannot decompose by itself after use, and the processing cost is high. Second, rock wool has limited water storage capacity and poor water retention performance. If water is cut off for a long time, it will have a greater impact on the plants. Third, rock wool has high requirements for irrigation and low fault tolerance. Too much or too little watering will affect the growth of the root system.

◆ Advantages of coco coir substrate

① Compared with the rock wool cultivation slabs, the cost of coco coir strips is lower; ② Coco coir is compressible, and the finished product is extremely convenient to transport; ③ Coco coir is a plant material, and growers have the conditions to complete the recycling process by themselves, and here Certain benefits can be produced during the process; ④ The air permeability and water retention of coco coir cultivation strips can be adjusted in a wider range. Since the coco coir strips produced by mainstream coco strip manufacturers are made by mixing coconut chunks and coconut bran with two materials of different particle sizes in a certain proportion, the adjustment of the proportion can make the coconut bran strips meet the needs of more diverse modern greenhouses. Irrigation strategies. For example, in recent years, the emerging trend of increasing dry and wet changes in the substrate to optimize crop irrigation methods requires the substrate to have higher air permeability. Manufacturers only need to increase the proportion of coconut chunks in the coco coir strips to achieve this goal; ⑤ Coconut bran substrate The buffering capacity during use is stronger than rock wool. Irrigation fluctuations caused by accidental operating errors have less impact on crop status. If the greenhouse has insufficient irrigation capacity due to unstable equipment or adjustments to planting strategies, choosing a coco coir substrate can greatly reduce risks during the irrigation process.

◆Disadvantages of coco coir substrate

① In the early stage of use, coco coir strips will fix a large amount of calcium in the nutrient solution, causing growers to misjudge the amount of calcium in the nutrient solution preparation process; ② During use, the tannins released from coconut bran will affect the pH of the nutrient solution and the root system. The environment has a long-term impact; ③ A large amount of fine gray matter produced during the production process of coconut bran strips cannot be completely removed from the product through water washing. Even if a large amount of washing is carried out before planting and production, these impurities will continue to be removed from the coconut palm. The chaff strips are brought out by liquid return. When this part of the return liquid with impurities passes through the ultraviolet disinfection machine during recycling and reuse, it will hinder the transmission of ultraviolet light, affect the disinfection efficiency, and increase the risk of plant protection. Therefore, in the early stages of planting, growers need to adjust the nutrient solution formula in a targeted manner. And depending on the amount of irrigation in the early stage, crops using new coconut bran strips will not be able to recycle nutrient solution for 2 to 4 months, resulting in a lot of waste. Figure 1 shows the comparison of the liquid return from new coconut bran bars (left) and the liquid return after 4 months of use (right); ④ Soaking coconut bran bars is relatively complicated. Choosing coconut bran strips without drainage holes requires a lot of manual work to open them after soaking. If coconut bran strips with drainage holes are used, some coconut bran strips will not be fully soaked; ⑤ The ratio of coconut chunks to coconut bran in the same batch of coco coir substrate products fluctuates greatly, so during use There will be phenomena where individual coconut bran strips have poor air permeability or water holding capacity, and even the bran and pieces in the same matrix bag are unevenly distributed, resulting in large performance differences. If these two types of problems occur frequently, they will directly affect production.

In summary, the selection of cultivation substrate must be based on actual production conditions. In addition to considering the applicability and economy of the substrate, the grower's planting experience must also be considered. In terms of irrigation management, plant regulation and water-saving performance, rock wool is better than coco coir. In terms of cost and environmental protection, coconut peat is a good choice. It is worth noting that whether the grower has rich planting experience in the chosen substrate determines whether the planting advantages of the substrate can be brought into play. When selecting substrate types, each planting enterprise needs to consider multiple factors such as its own situation and development direction to arrive at the optimal option.