Multiple technical models of water and fertilizer integration

Water and fertilizer integrated technology delivers fertilizer and water to crops through an irrigation system. Crops absorb nutrients while absorbing water, making it one of the most water and fertilizer-saving technologies in agricultural production to date.

1 How does water-fertilizer integration achieve water and fertilizer saving?

Crops can absorb nutrients using two "mouths": roots and leaves. Roots are the "big mouth", leaves are the "small mouth". A large amount of nutrients is absorbed through the roots. Foliar fertilization only plays a supplementary role. How can the fertilizer applied to the soil be delivered to the crops' "mouths"? That is, the fertilizer must be dissolved before it can be delivered to the crops' "mouths"; undissolved fertilizer cannot be "eaten" by the crops, which is equivalent to wasted application.

From the underground perspective, after dissolving, the fertilizer enters the soil solution, and the nutrients near the crop roots are absorbed, reducing the concentration. The concentration of the soil solution away from the roots is relatively higher, and it will diffuse towards the area near the crop roots, and the nutrients will move accordingly, eventually being absorbed by the crops. From the aboveground perspective, when there is sunlight, the stomata of the leaves open, and transpiration occurs, leading to water loss. The roots must continuously absorb water to replenish the water lost due to transpiration; therefore, the nutrients dissolved in the water will be transported to various parts of the plant along with the absorption and flow of water. The roots are the crops' "mouth", and water is the fertilizer's "legs". Without "legs", the fertilizer will not "Enter" the crops' mouths.

Water-fertilizer integrated technology, according to the crop's water and fertilizer needs and quantity, dissolves fertilizer into water and delivers it directly and in a timely and quantitative manner to the soil area where crop roots are most concentrated, delivering water and nutrients directly to the crops' "mouths" at any time, allowing the crops to drink when thirsty and eat when hungry; it can also reduce water and fertilizer waste caused by volatilization and leaching, thereby greatly improving the utilization rate of water and fertilizer.

2 Water-fertilizer integration has multiple technical models

1 Cyclic technical model

This model is currently the most effective technology model for saving water and fertilizer. This technology model consists of three parts: a control system, an irrigation system, and a planting system. The planting system consists of PVC pipes and a fixed frame, with PVC pipes horizontally fixed on the fixed frame. Circular holes are drilled at equal distances on the top of the PVC pipes for planting vegetables and strawberries. The irrigation system consists of a nutrient solution storage device and a circulation device. The nutrient solution stored in the storage tank is specially formulated according to the nutrient elements and proportions required by crops at different growth stages and can fully meet the needs of various nutrients at different growth stages. After the crops are planted, the control system will start and stop the irrigation system at set time intervals. After the irrigation system is started, within a certain period of time, the nutrient solution will continuously flow from the front end to the end of the PVC pipe under the control of the circulation device and then flow back to the storage device. Crops also absorb water and nutrients during the nutrient solution circulation process. Experiments show that when using the cyclic water-fertilizer integration cultivation technology mode to cultivate strawberries, the water usage per mu is only 40.9 cubic meters, and the fertilizer usage is 45.5 kilograms. Compared with the drip irrigation water-fertilizer integration cultivation technology mode, it saves nearly 90 cubic meters of water per mu and 14.5 kilograms of chemical fertilizer. Because of its high technical content and high investment, this technology model is suitable for application in sightseeing parks.

2 Drip irrigation technology model

Drip irrigation technology is a very mature technology, but integrating it into water-fertilizer integrated technology is not simply mixing fertilizer into water, because the drip emitter has high requirements for water purity. If the requirements are not met, it will cause blockage, resulting in poor water discharge or even no water discharge. Therefore, the fertilizer for drip irrigation water-fertilizer integrated technology must be a special type of fully soluble fertilizer; otherwise, even if the fertilizer solution is filtered multiple times, it is difficult to meet the requirements, and the nutrients dissolved in the water will condense near the water discharge control components, affecting the smoothness of water discharge and damaging the components.

3 Matrix technology model

The irrigation and fertilization methods of this model are basically the same as those of the cyclic water-fertilizer integrated cultivation technology model, and the water and nutrients consumed by strawberries and other vegetables are also basically the same. The difference is that the remaining water and nutrients absorbed by strawberries and other vegetables are not recycled but are collected through a recovery device and then transported to the corner of the greenhouse for use by crops planted there. This model is suitable for application in the production of high economic value crops, such as strawberries.

 

4 Gravity technology model

Also known as the miniature water-fertilizer integrated cultivation technology model, it is a water-fertilizer integrated cultivation technology model that uses the self-gravity of the fertilizer solution in a water tank installed 1.5-2 meters above the ground as its driving force. Only one water tank bracket is installed at one end of the greenhouse, and a water tank with a capacity of about two cubic meters is installed on the bracket. Then, according to the needs of farmers for irrigation methods (such as drip irrigation, micro-sprinkler irrigation, furrow irrigation under film, furrow irrigation on film, etc.), the corresponding equipment is installed. This model has relatively broad requirements for water sources and water pressure and does not need to meet the requirements of water pressure and water volume for the pipeline system through variable frequency speed regulation. Therefore, it is more suitable for small-scale production, especially household production, where it is inconvenient to install conventional irrigation facilities.

5 Spraying technology model

Also known as foliar fertilization technology or extra-root fertilization technology, this involves spraying the nutrients needed by crops onto the surface of crop leaves, which are absorbed through leaf stomata, supplementing the plant's necessary nutrients to adjust plant growth, supplement deficient elements, prevent premature aging, and increase yield.

Foliar fertilization can directly and quickly supply crops with nutrients, avoid nutrient adsorption and fixation by the soil, improve fertilizer utilization, and is an effective measure to supplement and regulate crop nutrition. This is especially true under adverse conditions, such as in the later stages of crop growth when root fertilization is inconvenient, or when root vitality declines and nutrient absorption capacity decreases. Under conditions where the soil environment is unfavorable for crop growth, such as excessive water, drought, excessive soil acidity or alkalinity, and when the absorption of nutrients by the crop roots is hindered, and the crop needs to quickly resume growth, if the root application method is difficult or cannot meet the needs of the crop in time, foliar fertilization can quickly supplement its nutrition to meet the needs of crop growth and development.

Micronutrients are essential nutrients for crop growth and development, but the application amount is very small, such as molybdenum fertilizer, which is only tens of grams per mu. If root application is difficult or impossible to achieve uniformity, foliar application can achieve uniform results. Studies have shown that the utilization rate of foliar application of boron fertilizer in general crops is more than 8 times that of basal application. Foliar fertilization also has the advantages of reducing soil pollution.

Theoretically, foliar fertilization technology can be applied to various crops, but due to limitations in spraying tools, machinery, topography, and landforms, as well as the impact of planting benefits, it is currently mostly applied to strawberries, vegetables, fruit trees, and crops that are easy for mechanical operation and have high benefits. In addition, foliar fertilization can only provide a small amount of nutrients and cannot fully meet the needs of crops. It cannot replace root fertilization and is only an auxiliary fertilization technology measure.

The application of water and fertilizer integration must be combined with "conform to the growth laws of crops" to achieve true water and fertilizer saving. How to water and fertilize on demand? Agricultural Internet of Things can solve this problem. China's agricultural modernization, especially automation and informatization, is relatively slow, and the level of rural knowledge is relatively low. For the present, the large-scale application of agricultural Internet of Things in agricultural production