Water is one of the main factors that strongly influence the level of potato production. Drought, respectively, lack of water in the soil, can nullify the effect of some technological provisions such as: fertilization, quality of planting material, protection of crops, etc., which are incurred heavy expenses.
As a result, water can be considered the most important production limiting factor, which largely determines the profitability of the crop under non-irrigated conditions.
The cultivation of potatoes, until recently, was considered moderately demanding on water, which can be grown under non-irrigated conditions in all parts of the country, except in the arid areas of the steppes. This statement cannot be fair, since the annual precipitation level of more than 2000 mm in the regions of potato origin (Andean region of Central and South America) is immeasurably higher than the annual level of precipitation of about 500-700 mm in Romania (in the basins for potato cultivation).
Potatoes respond better to watering than any other crop plant. The increase in production per mm of water supplied by irrigation is contained in the southern part of the country, between 30 and 120 kg/ha.
Average daily water consumption of potatoes in different growing regions in Romania (plain in the west of the country, sand and sandy soils in southern Oltenia; southern (steppe and silvostepes); dry steppes in the south of the country; dry steppes in the southeast; central and northern Moldova; Northwest Transylvania; Southeast Transylvania) varies from month to month, as follows: – April – 1.7 mm/day/ha (with a range of 1.5-2.4 mm/day/ha); – May – 2.9 mm / day / ha (2.6-3.7); – June – 4.5 mm / day / ha (3.2-5.3); – July – 4.8 mm / day / ha (4.2-5.7); – August – 3.4 mm / day / ha (2.0-4.3); – September – 2.7 mm / day / ha (2.2-4.0).
The highest water consumption for potatoes was recorded in the stage of plant growth and maximum flowering period, followed by the consumption in the flowering vegetation stage – physiological yellowing of the basal leaves. Calendar-wise, the highest average daily consumption (5.7 mm/day/ha) was recorded in July, in Dobrogia. In the plain in the south of the country, average consumption of 4.0 mm/day/ha was reached in September.
Water consumption, differentiating varieties by vegetation period, it should be noted that for early varieties the total water consumption was 320-430 mm, for semi-early and semi-late varieties 450-550 mm, and for early varieties. Late varieties 550-650 mm / day / ha.
In the forest-steppe zone, through irrigation, semi-late and late potato varieties are approaching their biological production potential. In general, through irrigation, yield increases are obtained exceeding 35 t / ha in the forest-steppe zone and up to 40 t / ha in the steppe zone. In the humid and cold zone, increases are up to 10 t / ha.
In potato cultivation, watering at shorter intervals is convenient, especially during the growth phase of the tubers, and in this way it ensures a lowering of the temperature in the soil, both at the surface of the soil and at the level of the top. In the southern part of the country and in sandy soils, this element is of particular importance for improving the conditions for the growth of tubers.
Unlike other crops, in potatoes, the best use of water from irrigation is obtained at low soil wetting depths, which are 40 cm with sprinkler irrigation and 60 cm with grooved irrigation.
Watering potatoes requires special attention, especially during the growth of tubers, since during this period the phenomenon of water stress, which may occur between two waterings, clearly affects the quality of tubers, through their sprouting and budding.
Excess moisture resulting from improper watering is especially harmful to the growth and quality of tubers. And in the absence or lack of oxygen in the soil, the tubers stop growing, reducing their starch and vitamin C content, as well as commercial appearance and shelf life.
As a method of watering potatoes, sprinkler irrigation is indicated, since this method ensures that the irrigation parameters are reduced, the relative humidity of the air increases, the air temperature is reduced and the vegetation conditions of potato plants are improved by this method.
In the case of furrow irrigation, it is necessary that the watering grooves be deep, so that the water level in the groove is “less than the level of the planting depth”, and watering should be carried out every two furrows, alternating with intervals from one watering to another.
In the case of grooving irrigation, a very good leveling of the land and a reduction in the length of the grooves (150-200 m) is required. Excess moisture in watering with grooves occurs at the ends of the grooves and on the parts with “depressions”, in the case of proper leveling.
Potato watering is divided into two vegetative stages: tuber formation (lead and tuber growth) and tuber growth. In the first stage, in the steppe zone (from the south, west and east), 3-4 sprinkler irrigation or 2-3 sprinkler irrigation is carried out, with irrigation rates of 400-650 mm, depending on the texture and method of the soil from irrigation, and in the second stage (growth of tubers) 4-5 watering, with watering standards 300-350 mm.
In this region, where the highest water consumption was recorded, 6-7-9 irrigation is carried out during the entire vegetation period, which amounts to 2100-3050 cubic meters of water.
In the first stage of vegetation, a minimum of 50% of the IUA (the interval of active moisture) is taken into account, and in the second stage 70% of the IUA in the forest-steppe zone of the south of the country, 6 – 8 waterings, of which 2-3 are in the stage The first, with a minimum of 50% and 70% respectively of IUA, totaling 1600-2600 m3/ha. The frequency of irrigation is reduced to 3-5 in the forest-steppe in the north of the country (800-1500 m 3 / ha), to 4-7 in the area of \u200b\u200boak forests in the south of the country (1500-2200 m 3 / ha) and 0-2; 1-4 Depending on the soil texture (400-900 m3/ha) in the beech forest area in the north of the country.
In general, in the first phase of vegetation, the interval between watering is 10-12 days, and in the second phase, 6-8 days. Maintaining soil moisture in the roof discussed also takes into account the rainfall that occurs during the growing season.
For early potatoes, watering is less important because they are harvested before the onset of dry periods from July to September. On sandy soils in southern Oltenia, 2-3 waterings (500-750 m 3 / ha) are given in years with normal rainfall or 3-4 waterings (750-1000 m 3 / ha) in years with little precipitation for early potatoes .
Water deficit is the difference between the water needs of a crop during the vegetation period and the amount of water supplied under natural conditions by precipitation, soil water reserves, amount of water, etc.
The potato plant reacts quickly, by reducing production, even with a relatively small deficit of soil water. The large water deficit in June, July and August, which potato plants cannot compensate without irrigation, causes significant production losses. A lack of 1 mm of water can reduce production, on average, by about 330 kg tubers / ha.
After a recent study conducted by specialists of the Ministry of Agriculture, which compared the potential water consumption of potatoes with the level of precipitation during the vegetation period, it was found that the potato crop in almost all of Romania suffers from a large amount of water. inability.
According to the size of the water deficit, three main regions were created on the territory of Romania. Within it are three other sub-regions, in descending order of water scarcity.
In the first, driest zone, the water deficit reaches values of 350-420 mm. In this region, potatoes can be grown only under irrigation conditions, where on average 8-10 waterings are required.
In the second zone, where the water deficit is about 235-345 mm, 5-8 irrigations are required.
In the third, colder and wetter zone (high plateaus, internal depressions), a deficit of 160-260 mm is achieved, which in some years can limit potato production.
In these areas, where possible, (especially in river meadows, in local systems) it is recommended to apply 3-5 irrigations, depending on the climatic conditions of the agricultural year
Production losses due to drought in May and June are 10-20%, and in July and August, 45-55%. For every 10 mm of water deficit achieved during the potato vegetation period, production decreases on average by 1.2-1.5 t/ha in Zone I, by 0.8-1.0 t/ha in Zone II-A and by 0.5-0.7 ton / hectare in the third zone.