Fertilization Techniques for Potatoes

The potato, a perennial herbaceous plant of the Solanaceae family, has edible tubers and is the third most important food crop in the world, after wheat and corn. The potato is also known as earth egg, tudou, foreign taro, etc., and is the tuber of a Solanaceae plant. Together with wheat, corn, rice, and sorghum, it is one of the world's five major crops.

Potato protein has high nutritional value. Potato tubers contain about 2% protein, and the protein content in dried potatoes is 8% to 9%. According to research, potato protein has very high nutritional value, and its quality is equivalent to that of egg protein; it is easy to digest and absorb, and is superior to the protein of other crops. Moreover, potato protein contains 18 amino acids, including various essential amino acids that the human body cannot synthesize. The high evaluation of the nutritional value of potatoes is inseparable from the presence of high-quality protein and the essential amino acids lysine, tryptophan, histidine, arginine, phenylalanine, valine, leucine, isoleucine, and methionine in its tubers.

Fertilizer Requirements of Potatoes

During the seedling stage, potatoes absorb very little fertilizer; during the tuber initiation and vine growth stage, fertilizer absorption increases rapidly; it reaches its highest peak at the early tuber bulking stage, and then fertilizer absorption drops sharply. The absorption of the three major elements nitrogen (N), phosphorus (P2O5), and potassium (K2O) during each growth period, calculated as a percentage of total fertilizer absorption, is 6%, 8%, and 9% respectively from germination to emergence; 38%, 34%, and 36% respectively during the vine growth stage; and 56%, 58%, and 55% during the tuber bulking stage. Among the three elements, potatoes absorb the most potassium, followed by nitrogen, and the least phosphorus. Experiments show that for every 1000 kg of tubers produced, potatoes need to absorb 5 to 6 kg of nitrogen (N), 1 to 3 kg of phosphorus (P2O5), and 12 to 13 kg of potassium (K2O), with a nitrogen, phosphorus, and potassium ratio of 2.5:1:5.3. The demand of potatoes for nitrogen, phosphorus, and potassium fertilizers increases continuously with the growth of stems, leaves, and tubers. During the peak tuber formation stage, fertilizer demand accounts for about 60% of total fertilizer demand, while the early and late growth stages each require about 20% of total fertilizer demand.

Common Problems in Potato Cultivation

1. Excessive nitrogen and phosphorus, insufficient potassium fertilizer. From the fertilizer requirement patterns of potatoes, we can see that potatoes need twice as much potassium as nitrogen and five times as much as phosphorus, and also require a certain amount of fertilizers such as calcium, magnesium, and sulfur. If the ratio of nitrogen, phosphorus, and potassium in fertilization is unreasonable and cannot meet the fertilizer requirements, high and stable yields cannot be obtained. Some older farmer friends only use nitrogen fertilizer and phosphorus fertilizer when fertilizing potatoes, and do not use potassium fertilizer or medium-element fertilizers at all. As a result, yields are low and unstable year after year, and they mistakenly believe the fertilizer is no good, not knowing that the cause of the low yield is potassium deficiency in the soil and the failure to apply potassium fertilizer and medium-element fertilizers.

2. Some farmers are still applying fertilizers with high chlorine content. Potatoes are chlorine-sensitive crops. If chlorine-containing fertilizers are applied, they affect the formation and accumulation of starch and affect tuber quality. For growing potatoes, it is best to choose potassium sulfate type fertilizers. In addition, continuous repeated cropping causes single-nutrient depletion, leading to decreased soil fertility and severe disease. Potato cultivation should involve regular crop rotation to avoid continuous cropping year after year, which can lead to decreased soil fertility, nutrient imbalance, and aggravated soil-borne diseases, causing root growth to be inhibited and nutrient absorption capacity to drop substantially. 

Potato Fertilization Techniques

Potato fertilization techniques should follow the principles of giving priority to farmyard manure with chemical fertilizers as a supplement, and giving priority to base fertilizer with appropriate topdressing.

1) Apply heavy base fertilizer. The amount of base fertilizer generally accounts for more than 2/3 of the total fertilization amount. The base fertilizer is mainly fully decomposed farmyard manure, with a certain amount of chemical fertilizer added, especially phosphorus and potassium chemical fertilizers as base fertilizer, which can improve the physical properties of the soil and benefit growth and tuber formation. The amount of nitrogen fertilizer in the base fertilizer accounts for about 50%. The application method for base fertilizer is furrow application or hole application before planting, at a depth of about 15 cm. The specific fertilization amount for plots producing about 1500 kg per 667 sq m is 1500 to 2500 kg of organic fertilizer, 20 kg of urea, 20 to 30 kg of calcium superphosphate, and 10 to 12 kg of potassium fertilizer per 667 sq m, or 40 to 60 kg of potato-specific fertilizer. In high-yield areas, the fertilization amount can be appropriately increased. Chemical fertilizers should be applied 2 to 3 cm away from the seed potatoes to avoid direct contact with the seed potatoes, and soil should be covered after fertilization.

2) Apply topdressing early. Topdressing should be reasonably applied in combination with the growth stages of potatoes. During the seedling stage, nitrogen fertilizer should be applied as topdressing. Combined with intertillage and hilling, 5 to 8 kg of urea per 667 sq m can be diluted with water and poured on, which helps preserve the seedlings. After potatoes bloom, root-zone topdressing is generally not carried out, especially nitrogen topdressing, which must not be applied. After potatoes bloom, phosphorus and potassium fertilizers are mainly applied by foliar spraying, spraying 50 kg of 0.3% to 0.5% potassium dihydrogen phosphate solution per 667 sq m. If nitrogen is deficient, 100 to 150 g of urea can be added, sprayed once every 10 to 15 days, for 2 to 3 consecutive sprays. Potatoes are relatively sensitive to boron and zinc. If the soil is deficient in boron or zinc, 0.1% to 0.3% borax or zinc sulfate can be used for foliar spraying, generally once every 7 days, for two consecutive sprays, using 50 to 70 kg of solution per 667 sq m.

Note: Potatoes are potassium-loving crops, so special attention should be paid to the application of potassium fertilizer in balanced fertilization. At the same time, excessive application of chlorine-containing fertilizers such as potassium chloride should be avoided; potassium sulfate should be selected instead, otherwise potato quality will be affected.