Main Crop Potatoes

Potatoes Development Stages

Potato takes from 100 to 150 days to give an yield. Most important stages are sprouting, emergence, growth of the aerial part, growth of tubers and ripening. After dormancy, at a temperature of 6-8°C, buds on tubers sprout and seedling start to emerge from soil. Seedling are not “though”, so in this stage crust can hinder the emergence of seedling from the soil. At 3-4°C, tubers are in dormancy: at 8°C sprouting begins, but emergence is very slow: at temperature of 12-15°C sprouting goes quickly. After emergence, sprouts develop in stems that can branch at the leaves insertions. The growth of the aerial part, stems and leaves, is influenced by temperature, optimal being 25-28°C, moisture availability and presence of nutrients into the soil. After the formation of 14 to 19 leaves, or about 50-60 days after emergence of sprouts, first flowers begin to form. Best condition are long days, high moisture and night temperature about 15-18°C. Flowering continues for two weeks in each flower and up to two months on the whole plant: the formation of the terminal flower means the full growth of the plant. Flower forms also fruits that are of no consequence for production.

Crop Rotation

As for the large majority of plants, length of rotation between potato crops and other plants grown in rotation with potatoes can impact potato production and sustainability of soil health status. Many potato pests (weeds, insects as wireworms and Colorado beetle, nematodes and diseases such as white mold, pink rot, pythium leak, Verticillium wilt, and powdery scab) build populations in proportion to the frequency of potato cropping and other host plants presence. In general, longer rotations (3-5 years) result in increased yields, best tubers’ quality and reduced fertilizer and pesticide requirements. The fact that certain rotational crops also serve as a host for potato pests should be considered before selecting fields. For example, dry beans, canola and tomatoes are susceptible to white mold, so they should be excluded from rotation or enter rotation in longer periods. Growing these crops in rotation with potatoes can increase the severity of white mold in the potato crop. Verticillium wilt has many alternative plant hosts, such as mint, alfalfa and many weed species. Nematodes and insects can also have alternative hosts and build significant populations in the years potatoes are not grown. Pasture grasses serve as a good host for wireworms and should be avoided altogether as a rotational crop if the field has a history of wireworm damage. Clover and alfalfa are also hosts for wireworms and other soil dwelling insects.

Potatoes Tuber - Seeds

The choice of cultivars to be planted is a crucial moment for successful cropping. Most important facts to be considered are:
• Final use of product; fresh market or processing industry
• Uniformity of shape, colour and size of the tubers
• Pulp colour
• Cooking qualities (frying, boiling)
• Content in dry matter
• Resistance to diseases
• Length of growing cycle (early, medium, late cultivars).

Planting

Spacing varies depending on varieties, availability of irrigation and soil structure. The target is to get from 130,000 to 180,000 stalks per hectare at harvesting, which means a spacing of 75-90 centimeters between the rows and a spacing of 20-30 centimeters between seeds on the row. This means to put into soil from 50,000 to 70,000 tubers seeds per hectare.

Basal Fertilisation

Requirements for Phosphorous (P2O5) and Potash (K2O) can only be correctly identified following a soil sample on a field by field basis. Once the current fertility of the field has been established the deficit can be calculated from the following table. The table gives kilograms of the actual chemical compound, therefore the percentage of P or K in the proposed fertiliser must be known in order to calculate the gross amount needed.

Ridging or Hilling

When sprouts are well visible on the soil surface, a ridging is performed to enhance stolon development, kill weeds, prevent tubers greening and facilitate harvesting. When the plants have 2 or three leaves, a second ridging is performed with the same goals. The ridge height should be about 20 centimeters. After the second ridging, post emergence herbicides are applied. In some cases, in loose soils and after heavy rains, a third ridging is performed to avoid greening of tubers.

Irrigation

Most important parameters to be considered for correct irrigation are:
• Growth stage of plants: potato has noticeable needs for water. These water requirements, if not satisfied on time, will have negative consequence on yield and tuber size and quality. The most critical stage is formation and growth of tubers, which occurs from 15-20 days before anthesis (the flowering period of a plant, from the opening of the flower buds) to 30 days after anthesis. In this period frequent irrigations are needed, but maximum watering height (volume) per single watering must not exceed 250-350 m3/ha, or 25-30 millimiters.
• Irrigation system: best system when possible is trickle system, because water is delivered directly to the roots on the soil and foliage is not wetted, therefore hindering the spreading of fungi diseases. On large acreage sprinkler systems (pivots and similar) are very common, as well as infiltration systems. These last, however, need higher water volumes and can damage soil structure, which makes harvesting more challenging.
• Water eight must not exceed 350 m3/ha, because the root system of the plant is not very efficient in extracting water fro the soil.