Using drip trickle irrigation system for fertilization can provide accurate fertilization supply conditions, significantly improve fertilization and irrigation efficiency, reduce production costs, improve yield and quality, and ultimately improve economic benefits. The technique of drip fertigation is widely promoted and popular around the world.
Through drip fertigation, on the one hand, soluble fertilizers are directly applied to the crop root zone along with drip trickle irrigation water, and there is no fertilizer waste between crop plants. On the other hand, drip trickle irrigation infiltrates the root zone with small flow in droplet form, which is very easy to control. Water and fertilizer will not be wasted due to deep leaching. Nitrogen fertilization using drip trickle irrigation can achieve a fertilizer efficiency of 74%, while traditional methods do not exceed 30%.
As irrigation system manufacturers would testify, the primary disadvantage of using a drip trickle irrigation system for fertilization crops is the potential blockage of the drip emitters. Fertilizers must be soluble, and insoluble fertilizers will quickly block the drip emitters. Chemical reactions between fertilizer raw materials can also produce precipitates, which will block the drip trickle irrigation system after a long time. The uniformity of fertilization depends on the irrigation uniformity. If the drip trickle irrigation system has high uniformity, the fertilization uniformity will also be high. Therefore, drip trickle irrigation uniformity is a very important indicator, and efforts should be made to improve it:
Precisely design the irrigation system;
Use pressure compensating emitters;
Install pressure regulators in appropriate locations in the pipeline.
When using drip trickle irrigation for fertilization, it is necessary to carefully study the solubility of fertilizers. Fertilizers that are insoluble, have low solubility, or are prone to react under certain conditions to form precipitates should be avoided.
Most solid fertilizers are coated. In order to avoid blockage of the drip trickle irrigation system by the coating, a small amount of the sample should be placed in a dissolution tank for stirring. Then, the dissolution of the coating can be observed. If the coating materials precipitate to the bottom of the tank after dissolution, during application, let the injector suck the upper layer of the solution without stirring the fertilizer solution as a whole.
Urea, nitric acid, calcium nitrate, and potassium nitrate absorb heat in water when dissolved, and the temperature of the water drops significantly. At this time, the amount of dissolution may not meet the required amount. In order to fully dissolve, it is best to let the solution stand for a few hours. As the temperature rises, the remaining undissolved part will gradually dissolve, and then it can be injected into the drip irrigation fertilizer system.
Before injection, observational experiments should be conducted to assess the possibility of clogging the drip emitters. Some fertilizers need to be dissolved for 1-2 hours before the presence and amount of precipitates formed can be observed. If the solution is still turbid after being dissolved in water for several hours, the drip trickle irrigation system is likely to be clogged. If multiple fertilizers are applied simultaneously, samples should be taken before injection and mixed in the tank in proportion to observe the dissolution after mixing. Then the decision can be made whether to inject them simultaneously.
Nitrogen fertilizer is the most widely used fertilizer in drip trickle irrigation system. Nitrogen fertilizer is usually water-soluble and easily injected into the crop root zone with irrigation water. However, if not controlled properly, it can also easily cause leaching loss. Because the flow rate of drip trickle irrigation is small (single emitter: 4-8 liters/hour), it is very easy to control the leaching loss by controlling the flow rate. If irrigation and fertilization are actively controlled, leaching loss can be completely avoided.
Among all nitrogen fertilizers, urea and ammonium nitrate are most suitable for drip fertigation because the risk of blockage from these two fertilizers is the lowest. Ammonia water is not recommended for drip fertigation because it increases the PH value of water. The increase in PH value can cause calcium, magnesium, and phosphorus to precipitate in irrigation water and block drip emitters. Ammonium sulfate and calcium nitrate are water-soluble, but also have the risk of blockage.
If nitrogen is continued to be applied, there will still be nitrogen in the water in the irrigation system after the irrigation system is turned off. At this time, the presence of nitrogen will nourish microorganisms in the system and ultimately clog the drip emitters.