Water is one of the main factors that strongly influence the level of production. Drought and water shortage in Soil can negate the effect of technological provisions such as: fertilization, quality of planting material, crop protection, etc., for which large expenditures are incurred. As a result, water can be considered the most important production limiting factor, which largely determines the profitability of the crop in non-irrigated conditions. (Ianosi I. Sigismund et al.) The cultivation of potatoes until recently was considered to have moderate water claims, which can be grown under Changed irrigation throughout Romania, with the exception of arid steppe regions. This statement cannot be justified, since the level of annual precipitation of more than 2000 mm in the regions of potato origin (Andes Mountains in Central and South America) is immeasurably higher than the annual level of precipitation of 500-700 mm in our country. Research conducted in recent decades in Romania showed that during the vegetation period, the water consumption of the potato crop exceeded 500-700 mm, While the natural precipitation in the same period was only 250-450 mm. It follows that there is a deficit in almost all areas of culture Large waters that must be covered by irrigation, without which no higher quality and stable production can be achieved. Due to the continental climate in Romania, which is characterized by hot summers and low precipitation, in the second part of the period of potato plants, dry periods appear frequently in all cultivation areas, which negatively affects the formation and accumulation of production. It has been established that by watering, the yield can be obtained, on average, by 20-50% higher, and the production of commercial-quality tubers increases by 10-20%, which makes this technological procedure profitable. Irrigation in addition to providing the water needed by plants An important role in the regulation of the thermal regime of air, especially of soil. After each watering, the air temperature decreases by 1-2 ° C, and the soil temperature (at a depth of 0-20 cm) by 6-10 °. Celsius. The evaporation of more water after irrigation increases the relative humidity of the air. High soil moisture aids heat loss during the night, which stimulates tuberculosis and production accumulation by converting the products of photosynthesis into starch. The climatic study of potato growing areas shows that irrigation in the forest-steppe and forest-steppe is necessary in 85-97% of Years, in the hilly region in 65-71% of years, and in the mountainous region in about 45-55% of years. The total amount of precipitation in a given period does not sufficiently reflect the degree of water supply to the potato crop. to Equally important is the manner in which these deposits are distributed during the vegetation period according to the requirements of the culture. Irrigation is a costly technical procedure that requires significant investments in irrigation systems and equipment. The cost of water and energy is also high. In addition, it requires a set of theoretical and practical knowledge from farmers for the correct application of irrigation.
If irrigation is not applied properly, it can have negative effects on production and soil. Watering applied late They can no longer compensate for the production losses caused by drought. If the watering is not done correctly, the number does not matter Total watering, but only those watering that occurred on time.
Potato water consumption
Water consumption is the amount of water lost from the soil, per unit area, over a period of time, through vegetation and evaporation from the soil surface. Depending on the length of the period for which the water consumption is calculated, we can talk about the daily, decadal, monthly or total (throughout the entire vegetation period) consumption. Check water consumption Of the limited natural resources (from precipitation, soil water reserves, ground water supplies) it is true consumption or true evapotranspiration (ETR). If water is supplied at the optimum level, from natural sources and from irrigation, the potential consumption or potential evaporation is achieved, respectively, the maximum real evapotranspiration (ETRM), in which case the production approaches the potential level, if the rest of the conditions are favorable. The total water consumption of the crop is determined by: the variety grown, the length of the period vegetation and its calendar classification; climatic conditions in the region (temperature, solar radiation, light, air humidity, etc.); the degree of water supply; the state of vegetation, its size and integrity on the surface of the leaf; agricultural conditions. The total water consumption of potatoes, according to different authors, is between 320 and 850 mm (3200-8500 m3/ha). These different values of total water consumption are due to a variety of conditions in which they were specify. In Romania (according to the determinations made by SI Ianosi and collaborators), with existing varieties grown in ultra-technological conditions, in an ordinary year, maximum production can be achieved with a total consumption of 450-550 mm of water, in the case of early varieties, and 650-750 mm For semi-late and late varieties. According to MP Harris, for a tuber production of 30-40 t / ha, in addition to the vegetative mass (in total 12-15 t of dry matter / ha (ton / su / ha), a total consumption of 550-750 mm of water is required, depending on Area conditions, year and technology provided.
Usually a well-developed potato crop, which covers the soil well, consumes 20,000-70,000 liters of water / ha per day, respectively 0.5-1.2 liters of water / plant. Early varieties or those with lower vegetative mass and leaf area consume less water.
When the stomata are open a maximum of 1 square decimeter of the leaf is lost 1.5 grams / hour, and on the whole plant 100-150 grams of water / hour, which is equivalent to about 1 kg (l) / day. In a crop with a density of 60,000 nests/ha, this consumption represents 60 m3 of water/ha/day, respectively 6 mm of water.
According to W.G. Burton, 250 grams of water is consumed per gram of carbon dioxide, along with a significant amount of energy. Remember: 1 cubic meter of water = 1000 liters; 1 cubic meter of water / hectare = 0.1 mm or 0.1 liters of water / square meter, and 1 millimeter of water = 1 liter of water / square meter or 10 cubic meters of water / hectare. Water consumption is not the same intensity all the timePotato plants. The most intense water consumption occurs during the period of formation and growth of tubers, successively from budding to the physiological maturity of plants (shedding and yellowing of leaves at the base). Drought greatly affects production during this period. Average Consumption Values Potato daily water, during the months of the growing season, in different crop areas gradually increases from April to July, then freezes and then decreases to September, and depending on the main vegetation stages it grows from the eastern planting stage and reaches its peak during the period of maximum flowering – maturity.
More than 50% of the water consumed by potato plants is extracted from the soil layer 0-30 cm and 80% from the beginning of 0-60 cm. This depth must be taken into account when planting the crop. Also according to these values, drought under non-irrigated conditions can be estimated It installs relatively quickly, in just 6-10 days. The shallower depth of water extraction determines the need to ensure a greater number of irrigations, at relatively low standards and applied at shorter intervals.
The amount of water supplied from different sources
In non-irrigated conditions, the water consumption of the potato crop is covered by precipitation by only 25-30% in the steppe zone and 45-60% in the hilly and mountainous regions; 5-15% of the soil water supply and 2-5% of the ground water supply (where This source is available. It turns out that about 25-55% of potential water consumption is not provided under natural conditions, which translates into a significant decrease in production and its variability from year to year. Due to the fact that precipitation due to losses (evaporation, runoff, etc.) has a lower degree of recovery, It does not fully contribute to the balance of water consumption. According to J. Balogh, the capitalization coefficient of precision in April and May is 0.6-0.8; In June and August 0.6, and in September – 0.4-0.5.
The more precipitation (in a month or a decade) consisting of several small rains, less than 5 mm, the lower their recovery coefficient. By analyzing the structure of precipitation with different volumes and different precipitation frequency during April-September in the Kovasna basin, it was found that the precipitation is less than 5 mm, which contributes less to the restoration of water supply in the soil, which makes it difficult to perform mechanized work, especially if It took place on several consecutive days.
Water shortage in potato cultivation
Water shortage is the difference between the water requirements of a crop during the growing season and the amount of water supplied under natural conditions through rainfall, soil water supply, ground water supply, etc. The potato plant reacts quickly, by reducing production, even with a relatively lack of water in the soil. significant water deficit in June, July and August, Which without irrigation of potato plants can not be compensated, cause significant losses in production. A lack of 1 mm of water can reduce production, on average, by 330 kg tubers/ha (PM Harris).
After a study comparing the potential water consumption of potatoes with the level of precipitation during the vegetation period, it turned out that potato crops in almost all of Romania suffer from a large water deficit.
According to the size of the water deficit, three main districts were established on the territory of the state, and within them three more sub-regions, in descending order of the water deficit. In the first driest zone, the water deficit reaches values of 350-420 mm. In this region, potatoes can only be grown under irrigation conditions, which require an average of 8-10 waterings. In the second zone, where the water deficit is about 235-345 mm, 5-8 irrigations are required. In the third, coldest and wetter zone (high plateaus, internal depressions), a deficit of about 160-260 mm is achieved. Water, which in some years may limit potato production. In these areas, where possible (especially in river meadows, in local systems) it is recommended to apply 3-5 waterings, depending on the conditions of the year. Production losses due to drought in May and June are 10-20%, and in July and August 45-55%. For each water deficit of 10 mm during the vegetation period of potatoes, the production decreases on average by 1.2-1.5 t / ha in the first zone; By 0.9-1.0 t / ha in the second zone and by 0.5-0.7 t / ha in the third zone.