Deformed tubers affect marketability: how to reduce the rate of deformed potatoes

    Deformed tubers often appear during tuber growth, especially in the second-crop spring cultivation, where high temperature and drought lead to a high proportion of deformed tubers, seriously affecting potato marketability and reducing the profitability of potato growing. The causes of potato deformation and control measures are described below for reference only.

Deformed potatoes

    1. Causes of deformed tubers:

    Deformed potato tubers are mainly caused by secondary growth. The main cause of secondary growth is sudden rainfall or watering after high temperature and drought, which puts the tubers that had stopped growing back under suitable growing conditions, but at this time part or all of the tuber skin has already aged, while the buds in the non-aged parts resume growth and starch synthesis, thus forming various deformed tubers.

    2. Control measures:

   (1) Select excellent varieties:

    Deformed tubers occur mostly in medium-maturing or medium-late-maturing potato varieties, so when planting, on poorly drained or heavy clay soil, or in areas without watering conditions where the potato growing period coincides with high temperature and little rain, potato varieties that are not prone to secondary growth should be selected according to local conditions.

   (2) Apply more organic fertilizer:

    Organic fertilizer contains all the elements needed for potato growth. Applying organic fertilizer can make the soil loose and fertile, improve soil aeration, enhance the soil's water- and fertilizer-holding capacity, avoid potato deformation caused by soil that is too dry or too wet, and also promote tuber expansion, helping tubers take on a uniform shape with smooth skin and increasing yield. Potatoes planted on clay soil in particular need more organic fertilizer to improve soil conditions. Organic fertilizer is generally used as a base fertilizer and should be applied deeply; for plots with ordinary fertility, apply 4000-5000 kg per mu.

   (3) Fertilize appropriately:

    Excessive fertilization of potatoes easily leads to vigorous growth or even excessive vegetative growth; if corresponding cultivation measures are not taken in time, it will inhibit tuber expansion and thus cause deformation. Potato is a potassium-demanding crop, absorbing the most potassium, followed by nitrogen, and the least phosphorus. Fertilizer can be applied in two ways: base fertilizer and topdressing. The base fertilizer is mainly organic fertilizer, and early topdressing is mainly nitrogen fertilizer to promote the rapid growth of aboveground stems and leaves of potatoes. Generally, apply 10-15 kg of urea or 40-50 kg of ammonium bicarbonate per mu, with 1-2 topdressings during the whole growth period. The amount and frequency of topdressing depend on soil fertility and potato growth conditions, and excessive fertilization is strictly prohibited. During the tuber-setting period, to promote tuber growth, a moderate supplement of potassium fertilizer can be applied by foliar spraying, generally using monopotassium phosphate at a concentration of 1‰.

   (4) Water in time:

    Potatoes generally do not need watering at the seedling stage. When the soil is too dry, watering is necessary, but after watering, timely hoeing should be carried out to break up crusting and raise soil temperature. After potatoes bud, they should be watered frequently in small amounts according to soil moisture to keep the soil moist and the surface from drying out, generally once every 7-10 days. According to soil conditions, stop watering 5-7 days before harvest, which helps with storage after harvest. Avoid drought during the growing period, especially during the tuber expansion period; watering after drought occurs will cause secondary growth of tubers and form deformities.

   (5) Strengthen hoeing and earthing up:

    The role of hoeing and earthing up is to improve soil aeration, increase the soil's moisture- and fertilizer-holding capacity, make the tuber skin smooth and the tuber shape uniform, and reduce the deformity rate. During the whole growth period, potatoes need 2-3 hoeings and 2 earthings up depending on conditions. 3-5 days before emergence, carry out the first hoeing; after the seedlings emerge completely, carry out the second hoeing; the last hoeing is completed before the potato rows close. At the potato budding stage, when the tips of the stolons begin to expand, carry out the first earthing up to prevent stolons from emerging above the ground and turning into new shoots. When potatoes enter the peak expansion period, to prevent tubers from being exposed above the ground, carry out the second earthing up, with a soil thickness of 4-5 cm, forming high ridges about 25 cm tall, so that watering does not submerge the tops, the ridges do not crust, and the soil has good air permeability, which is conducive to tuber expansion.