Technology of soil testing and Formula fertilization for Sweet Potato

1. Characteristics of fertilizer requirement:

The demand of sweet potato for nitrogen, phosphorus and potassium is the highest in potassium, followed by nitrogen, followed by phosphorus. Sweet potato likes potassium, and the application of potassium fertilizer has obvious effect on yield and quality. The sweet potato absorbed less nutrients at the seedling stage. From the branching stage to the vigorous growth period of stems and leaves, the rate of nutrient absorption accelerated, the amount of nutrients absorbed increased, and decreased gradually in the later stage. In the period of rapid expansion of sweet potato, the absorption of nitrogen and phosphorus decreased, while the absorption of potassium remained at a high level. Due to nitrogen deficiency, the old leaves showed green deficiency at first, the number of leaves and branches decreased, the leaves shrank, the internodes shortened, and the leaves were prone to yellowing and premature senescence, which seriously affected the yield. Lack of phosphorus will cause the leaves to become smaller, dark green, lose luster, stem elongation is blocked, old leaves appear large macula, turn purple, and will soon fall off. Potassium deficiency showed small leaves, shorter internodes and petioles, dark green leaves, and brown spots on the back of the leaves in the later stage. Sweet potato avoid chlorine, when the application of chlorine-containing chemical fertilizer exceeds a certain amount, the starch content of sweet potato will be reduced, and the potato is not resistant to storage.

2. Fertilization technology:

Under the medium fertility level, the amount of fertilizer applied per mu of sweet potato during the whole growth period was 2500m3 kg of farm fertilizer (or 350ml 400kg of commercial organic fertilizer), 14kg of nitrogen fertilizer, 8kg of phosphate fertilizer and 11kg of potash fertilizer. Nitrogen and potash fertilizer were divided into base fertilizer and secondary topdressing, all phosphate fertilizer was used as base fertilizer, chemical fertilizer and farm manure (or commercial organic fertilizer) were mixed.

Base fertilizer: 2500 MUE 3000 kg of farm manure or 300 MUE 400 kg of commercial organic fertilizer, 5 kg of urea, 13 kg of diammonium phosphate and 7 kg of potassium sulfate. Long-acting fertilizer is recommended.

Topdressing: topdressing during the expansion period of potato cubes, applying urea 16mur19kg and potassium sulfate 13mu 15kg per mu.

Extra-root topdressing: in the middle and later stages of sweet potato growth, 0.5% urea diluent, or 2% Murray 3% calcium superphosphate solution, or 5% plant ash water, or 0.2% potassium dihydrogen phosphate solution can be sprayed on the leaves. 6Mel is sprayed once every 7 days, and 2MUR is sprayed 3 times. Huang Chunrong