Subsurface irrigation as a highly efficient method of vineyard irrigation

One of the progressive irrigation methods for vineyards currently being developed by research institutions in Ukraine, Moldova, and Uzbekistan. Its application significantly changes the cultivation technology of grapes, as the irrigation water is supplied directly to the root zone of the soil. In the republics of Central Asia, Armenia, and Azerbaijan, where there is no rainfall during the summer, the surface layer of the soil remains in a parched state, which eliminates the possibility of weed development.

With the subsurface irrigation method, there is no need to cut irrigation furrows or cultivate them after irrigation. This method allows for the application of mineral fertilizers directly with the irrigation water. The absence of direct contact between irrigation water and the air eliminates its loss due to evaporation, which makes this irrigation method highly economical. Targeted delivery of irrigation water to the root zone of the soil creates favorable conditions for the development of the root system, which has a positive effect on the growth, development, and productivity of grape plants. For example, according to the All-Union Research Institute of Viticulture and Winemaking "Magarach," at the "Gurzuf" state farm in the Crimean region, over an average of 7 years, on plots where subsurface irrigation was used, the grape yield of the White Muscat cultivar was 9.46 t/ha, while in the control group without irrigation, it was 3.41 t/ha. Significant yield increases on plots with subsurface irrigation were obtained at the "Livadia" and "Tavrida" state farms. The productivity of vineyards in these farms increased by 1.5–3 times with the subsurface irrigation method. A two-year field trial of the subsurface irrigation method conducted in Uzbekistan on Black Kishmish grapevines showed that the productivity of the plantations increased by an average of 4.1 t/ha. It is also very important that compared to furrow irrigation, the savings in irrigation water with the subsurface irrigation method amount to 32–34%. The number of waterings is reduced from four to five with furrow irrigation to three with the subsurface method.

The organizational forms and technical solutions for subsurface irrigation can vary. If this irrigation method is planned for a vineyard before it is established, the moisture-supplying pipes through which irrigation water is delivered within the plot are laid directly under the future row at a depth of 50 cm. If the transition to the subsurface irrigation method is carried out in an already established vineyard, the moisture-supplying pipes are laid at the same depth in the middle of each row spacing, provided its width does not exceed 3–3.5 m. In wider row spacings (4 m and above), two pipe lines are laid. The criterion for determining the optimal distance between the moisture-supplying pipes is the indicator of the closure of soil moisture contours, which depends primarily on the water-physical and mechanical properties of the soil.

The subsurface irrigation method is most effective on loamy and clayey soils. It is less suitable for sandy loam and sandy soils, which do not have the ability to retain capillary moisture.

Recently, pottery pipes have been replaced by polyethylene ones, which have openings on their surface for the exit of irrigation water into the soil. Pipe-laying machines with a capacity of 600–800 m/h have been developed and are undergoing field trials.

Irrigation water enters the moisture-supplying pipes located directly in the vineyard from sedimentation reservoirs through underground reinforced concrete channels laid in the peripheral, head part of the irrigated area, across the rows. In the lower part of the plot, inspection wells are installed on separate rows, through which the passage of irrigation water through the moisture-supplying pipes is monitored. The costs of installing a subsurface irrigation system pay off on average within 2 years after the plantations enter fruiting.

The efficiency of the subsurface irrigation method can be increased by the simultaneous application of mineral fertilizers with irrigation water. In this case:

• labor costs for their execution are reduced by combining two operations into one technological process;
• high soil moisture promotes the effective absorption of fertilizers by the roots of grape plants.

Drip irrigation is one of the newest irrigation methods for vineyards, gaining popularity in Ukraine, the Krasnodar Territory, Moldova, and Uzbekistan. Its fundamental difference from previous methods is the metered supply of irrigation water to each plant, which makes this method the most economical in terms of consumption and targeted use of irrigation water. Its undeniable advantages include the possibility of not only full mechanization but also automation of irrigation. In addition, it can be used on plots with complex topography. An important advantage of the drip irrigation method for vineyards on mountain slopes is the prevention of soil water erosion and the accumulation of salts in its root zone.

The irrigation system consists of a water reservoir, which often acts as a water tower; a supply system; and pumps that create the necessary pressure for the irrigation water. Directly on the irrigated plot, supply hoses or tubes made of polyethylene are suspended on trellis posts and wires in each row. From these, there is a connection to each bush, terminating in a dropper of various types, through which the irrigation water rate is metered. The dropper can be located on the soil surface near the trunk of the bush or buried in the soil.

Irrigation automation and irrigation efficiency

Irrigation automation makes it possible to maintain optimal soil moisture in the root zone of each bush without unnecessary labor. When the moisture drops below a set level, the sensor automatically sends a signal to turn on, and water flows through the droppers to the plants. Upon reaching the required moisture level, the system stops irrigation by itself.

• Yield increase — 24.8–106.1%
• Irrigation water savings — 30–40%

When choosing an irrigation method for vineyards, the key assessment criterion remains the saving of irrigation water. According to field trial data, three methods provide the highest yields with minimal resource expenditure. Comparative data on irrigation efficiency are given in the table.

How to estimate harvest and determine berry maturity

Preliminary harvest determination is carried out once or twice per growing season for timely preparation for harvesting and sales. The first count is performed after flowering, when the berries reach the size of a pea. A second count at the onset of ripening is necessary only if the plantation has suffered from hail, wind, or frost.

1. In the first row, select the second bush, in the second row — the third, in the fourth — the fifth, and so on diagonally across the plot.
2. Count the number of bunches on the selected sample bushes.
3. Multiply the number of bunches by the multi-year average bunch weight indicator for a specific cultivar.
4. Multiply the obtained yield weight per bush by the number of bushes per 1 ha.

To monitor conditions, berries are sent for chemical analysis. Samples start to be taken 10–15 days after the beginning of ripening at 5-day intervals, and closer to technical maturity — every 3 days. The sugar content of the juice is determined by a refractometer, and acidity — by the alkali titration method.

Harvesting of table grapes in the European and Transcaucasian regions begins at a sugar content of 2%, and in the republics of Central Asia and in the south of Kazakhstan — at 15%. For dried products, the indicators should be higher: at least 23% for seedless cultivars and not less than 22% for raisin cultivars. If the grapes are intended for jam, pekmez, vacuum must, dessert or liqueur wines, the berries are harvested at a maximum sugar content of 23–25% or more.

For wine grape cultivars intended for the production of juices and wine, titratable acidity is of critical importance. Harvesting is carried out strictly upon reaching the planned technological conditions. After determining the optimal timeframe, harvesting must be organized and completed as quickly as possible.

• violation of the chemical composition conditions of the berry juice;
• increased risk of harvest loss from pests and diseases;
• unproductive losses of harvest weight as a result of wilting and raisin formation of berries, which is especially noticeable in the southern regions of our country;
• lengthening the harvest protection period.

According to the V. I. Lenin State Farm in the Anapa District of the Krasnodar Territory, the highest yield per 1 ha is ensured when harvesting begins during the period of reaching condition. In the following days, the weight of the harvest begins to decrease, and by the 11th day compared to the optimal period, its losses, primarily from rotting, reach a maximum. At the "Vinogradny" state farm of the Crimean region, for only three cultivars: Rkatsiteli, Kokur Bely, and Muscat Bely, occupying 983.3 ha, the yield shortfall due to the delay in harvesting compared to the optimal period amounted to more than 1400 tons in 1980, worth 465 thousand rubles. This example, taken from the practice of a leading viticultural state farm, clearly testifies to the importance of timely harvesting and the inadmissibility of delaying it.