When fertilizing potatoes, the ratio of nitrogen, phosphorus and potassium should be appropriate

Potatoes have an equally important demand for nitrogen, phosphorus and potassium. In the process of yield formation, nitrogen supply is the foundation, ensuring the formation of sufficient green leaf area for photosynthesis; phosphorus supply is also indispensable for tuber formation and starch accumulation; on the basis of sufficient nitrogen and phosphorus, potassium supply is essential for carbohydrate assimilation in the early stage and for the later transport from above ground to underground tubers and starch accumulation.

Field tests show that the absorption ratio of nitrogen, phosphorus and potassium by potatoes is about 1:0.5:2.5. In response to this demand characteristic, industry insiders call the potato a potassium-loving crop. However, in actual fertilization decisions in agricultural production, it is necessary to consider both the supply of soil nutrient pools to the nutrient demand of potatoes and the fact that the soil supply levels of nitrogen, phosphorus and potassium are different, and to recommend the application rates of nitrogen, phosphorus and potassium fertilizers separately on the basis of soil supply. For example, soils in the south have low available potassium content, so attention should generally be paid to increasing potassium fertilizer application and to balanced fertilization with coordinated nitrogen, phosphorus and potassium; soils in the north have higher available potassium content than in the south, and potassium fertilizer application to grain crops is not common, but in view of the potato's high potassium demand, potassium fertilizer should be supplemented in an appropriate amount. It is recommended that the suitable ratio of nitrogen, phosphorus and potassium chemical fertilizers be on average 1:0.5:0.6 in northern regions and on average 1:0.4:0.8 in southern regions. Assuming a potato yield level of about 1500 kg per mu, the recommended nitrogen fertilizer application rate is 10-12 kg of pure nitrogen per mu, the potassium fertilizer rate is 5-8 kg of pure potassium per mu, and the phosphorus fertilizer rate is 3-5 kg of pure phosphorus per mu.

In terms of the timing, method and distribution of potato fertilization, both base fertilizer and topdressing should be used. For the base fertilizer, it is best to apply organic fertilizer together with chemical fertilizer, which is beneficial for tuber setting. The distribution of nitrogen, phosphorus and potassium fertilizers in base fertilizer and topdressing differs; generally, only 50% of the nitrogen fertilizer, all of the phosphorus fertilizer and most of the potassium fertilizer are allocated to the base fertilizer. It is also possible to use half of the nitrogen and potassium fertilizer as base fertilizer and the other half of the nitrogen and potassium as topdressing; for the base fertilizer variety, a compound fertilizer with relatively high phosphorus and potassium content (such as 12%-15%) and appropriate nitrogen content (about 10%) can be selected, or single-element chemical fertilizers can be used in combination. The single-element phosphorus fertilizer is best as ordinary calcium superphosphate, and in acidic soil areas of the south, calcium magnesium phosphate fertilizer can also be selected. The distribution principle for phosphorus fertilizer is that most of it should be applied deeply in strips or holes at the bottom of the ridge before ridging, and a small part of the phosphorus fertilizer should be applied obliquely below the seed potatoes when planting. The nitrogen and potassium fertilizer used as topdressing should be applied when the plant tips reach the budding stage (that is, the underground tuber formation stage), applied to the side of the ridge and immediately covered with soil and watered. The topdressing time should not be too early; it is best to carry it out when the tubers enter the expansion stage. Topdressing too early, especially applying a large amount of nitrogen fertilizer, will cause excessive above-ground growth and the problem of small underground tubers. In terms of fertilization position, the base fertilizer should be applied in furrows or holes before planting, with a depth requirement of about 15-20 cm. Topdressing should be applied in strips or holes between rows or at the side of the ridge; the fertilizer should be buried 5-8 cm deep, and after fertilization, irrigation can be carried out and soil should be covered.

In recent years, in actual production, some farmers, in order to obtain high potato yields, have paid great attention to nitrogen fertilizer application, and the application rate of nitrogen fertilizer is very high in both base fertilizer and topdressing. As the amount of organic fertilizer becomes smaller and smaller and cannot guarantee the needs of the rapid development of potato production, more and more farmers mainly rely on chemical fertilizers to produce potatoes. Sometimes excessive nitrogen fertilizer leads to the adverse consequences of rampant above-ground vine growth and very small underground tubers. There are also many farmers who have already initially mastered the relevant techniques. For example, in some potato-producing households in Gansu and Inner Mongolia, the fertilization method of using organic fertilizer as the main component with an appropriate addition of low-concentration compound fertilizer as base fertilizer, and then applying an appropriate amount of nitrogen fertilizer as topdressing when the plant tips reach the budding stage, has achieved good results, reflecting a feasible technique of whole-process balanced fertilization based on the nutritional characteristics of potatoes and their required ratio of nitrogen, phosphorus and potassium nutrients.

In addition, potatoes are relatively sensitive to the trace elements boron and zinc, which can be supplemented in appropriate amounts through seedbed fertilization and foliar topdressing.