Central Asia ‘Solutions for Water’ (S4W) Living Lab under the Central Asia Water & Energy program (CAWEP) Report: Pilot Testing and Development of Efficient Techniques for the Conservation and Rational Use of Takyr Catchment Areas for Pasture Water Supply and Small-Scale Oasis Agriculture Expert: Dr. B.K. Mamedov (Turkmenistan) 2021 1 The findings, interpretations and conclusions expressed herein are those of the authors and do not necessarily reflect the views of the World Bank Group, its Board of Executive Directors of the governments they represent. Table of contents 1. Developing efficient practices of moving sand amelioration around takyrs 1.1 Conducting phyto-amelioration activities 1.2 Planting and sowing desert shrubs 1.3 Experiment of using of collector-drainage water for irrigation 1.4 Reforestation and reproduction of planting material 1.4.1 Setting up nurseries to produce planting material 1.4.2 Cultivating psammophyte seedlings with a closed root system 1.4.3 Recommendation for maintaining the plantings 1.5 Stabilizing sand with takyr clay 1.6 Assessment of cost-effectiveness of amelioration activities 2. Studying runoff properties of takyr catchments 3. Findings 4. References 2 1. Developing efficient practices of moving sand amelioration around takyrs By 1936, the nomadic economy in the desert was almost entirely replaced by distant pasture cattle breeding after the establishment of collective farms and state farms [5]. In the past, the population mainly engaged in cattle breeding but following the discovery of fossil raw materials and development of their deposits, people of various occupations started working and living in the desert. Unstabilized sands near settlements gradually turned into moving barkhans (dunes) and subsequently began to bury the buildings and takyr plots around them. The quantity of shrub vegetation in the areas with favorable forest sites (desert forests) reached up to 300-600 piece/ha, in the same time on the severe degraded plots – less than 1 piece/ha [18]. The grazing of livestock on low-productivity pastures inevitably results in a gradual depletion of the vegetation cover, especially on poorly fixed sands that are already short of forage resources. 1.1 Phyto-amelioration activities The extremely complex wind conditions in Central Karakums cause submeridional vibrational-progressive movement of sands during the year (Figure 1), and at the same time result in the shifting of barkhans southward (averaging 4-6 m per year). As a result, bare barkhan sands fill up household facilities, wells and takyr catchments. The best way to stabilize moving sands is through phyto- amelioration. As a result, moving sands are not only stabilized, but also enriched due to the diversity of plant species and an increase in the overall grazing capacity. We started the stabilization and afforestation of moving sands from the construction of a fencing by means of burying support racks into the sand every 4 to 5 m. Then 3 to 5 rows of barbed wire fencing were stretched along the racks to guard the mechanical fixation and planted psammophyte seedlings from livestock. The materials included reinforced concrete hedgerows, metal fittings (up to 2.5 m long), barbed wire; cane stalks (Phragmites australis); brushwood of cotton (Gossypium hirsutum), shrubs and other plants used to install mechanical fixation; and seedlings of desert shrubs such as saxaul, cherkez (Salsola richteri), and kandym (Calligonum setosum). 3 Figure 1. Schematic map of areas with various types of sand movement Symbols: I – vibrational, II – progressive, III – vibrational – progressive, IV – Daihan association Karakum (by Petrov [20]). Sand stabilization and phyto-amelioration (i.e. planting and sowing of plants) on quicksand were carried out using various techniques depending on the degree of sand surface compartmentalization. On some plots, the installation of mechanical fixation with subsequent planting of seedlings was carried out after slightly levelling the barkhans; on the sands of the Karakum livestock farm, the stabilization and phyto- amelioration of moving sands were carried out without levelling the natural topography. The sizes of mechanical protection checkerboards (i.e. the distances between the rows) were changed to meet the local conditions of their installation sites. They depended on the slope of the protected surface and volume (m3) of sand carried over 1 running meter per year. We considered the well-known fact that vertical mechanical protections installed on flat plots protect the sand surface from deflation at a distance, which is 12 times the height of their aboveground part [19]. Thus, the checkerboard sizes on steep slopes of mechanical protections is reduced to 1.5 x 1.5 m, and on flat surfaces they increase up to 4 x 4 m. However, the general width of mechanical protections varied depending on the aerodynamic conditions (e.g., the level of protection of the area being stabilized from the wind), and the volume of sand being carried over. 4 Fig. 2 Sand-stabilizing mechanical protections made of cane a – vertical row protections; b – vertical checkerboard protections; c – installation layout In general, the area of Central Karakums is difficult for sand stabilization. Every year (for 9 to 19 days) winds of 10-16 m/s have been reported, which are capable of destroying existing barkhans and forming new ones. In addition, we should take into account the inevitable processes of sand burying taking place due an average 30-40 annual number of days with dust storms. In view of the above, it was decided to install vertical mechanical protections in ameliorated areas exposed to winds blowing from one or opposite directions (Figure 2). Vertical mechanical protections are resistant to deflationary processes, are most effective and have the following advantages: vertical mechanical protections 5 are made of brushwood and are environment-friendly; they retain plant seeds and promote vegetation, provide forage and habitat for a number of fauna species; and their destruction (after 5 to 8 years) and gradual decomposition in the sand, to some extent, accelerates the process of soil formation and enriches it with organic matter. Vertical mechanical protections were made of herbal materials 1 to 6 cm thick and about 50 cm long, with half of them buried into the sand. Hence, the height of their aboveground part resulted to 20-25 cm. The distance between the rows varied from 1.5 m on steep slopes to 4 m on flat surfaces. Practically, row protections were installed perpendicular to the direction of prevailing winds. In Central Karakums, winds of different directions prevail during the year: northeastern winds in winter (with frequency account for 25 to 35% of all winds), and north to northeastern winds in summer (with up to 35% of frequency). Respectively, we had to use vertical mechanical protections on ameliorated sand plots exposed to winds coming from all sides. The protections formed an intersection of row protections that were installed on the 2/3 of the windward aeolian slopes, and partly in interbarkhan depressions as shown in Figure 3. For primary piloting sites, cane stems were used to install vertical mechanical protections. Upscaling the sand-stabilizing work, we started to apply branches of desert shrubs, aboveground part of cotton stem, camel thorn (Alhagi persarum), Karelinia caspica, and other plants of 50 cm high. I 6 II Fig. 3 Installation pattern of vertical mechanical protections and planting of seedlings on barkhan sands Symbols: I – for barkhan sands with progressive movement where single- direction wind prevails; II - for barkhan sands with vibrational-progressive movement where winds of different directions prevail. A - prevailing wind direction; B - upper 1/3 of barkhan left bare without installing mechanical protection; B - the same part displaced by the wind to a depression. Around 220-335 m3 of herbal material is used for installation of checkerboard mechanical protections per hectare, depending on herbal type and checkerboard size. Stabilization of moving aeolian forms was carried out during a period when the sand was humid enough, which facilitated the excavation of trenches to install vertical rows of checkerboard mechanical protections. Our observations demonstrated that the height of barkhans gradually decreased and the sands surface got leveled and stabilized on the plots where sand stabilization was carried out. We also discovered the successful rooting of the cuttings of Calligonum setosum used as brushwood for vertical mechanical protections. It was established that to ensure high survival ability of the cuttings of Calligonum setosum they had to be planted to a depth of least 40 cm, with their aboveground part 4 to 5 cm high, with irrigation to be provided several times. For all the plots, it was recommended to repair destroyed mechanical protections and plant new seedlings in the following 2-3 years to substitute the lost ones. 7 1.2 Planting and sowing of desert shrubs As noted above, the installation of mechanical protections was carried out to ensure that their rows lied across the direction of prevailing winds. After a short period of time, the sand began to blow out (up to 18-20 cm per year) from the checkerboards and settle on the windward and leeward sides of protective rows. Consequently, shrub seedlings and seeds were sown at a distance of 7-10 cm from vertical mechanical protections. The best growing conditions were thus created, and the plant root systems were not stripped. Phyto-amelioration (seedling planting and seed sowing) are carried out during a favorable period – mainly in February and March (Table 1). Phyto-amelioration in the desert typically starts after the average daily air temperature steadily exceeds +5°C. In Central Karakums (the Bokurdak Weather Station) this date usually falls on February 23 for the springtime (when psammophytes start growing). Historic winter severity was considered for phyto- amelioration of sands and small-oasis farming (with absolute minimum of air temperature of -28°C and absolute minimum of soil surface temperature comprising -30°C) and the possibility of damage to crops caused by frosts at the beginning and end of vegetation. Thus, the average multi-year date of the last spring freezing is reportedly March 16 (the earliest being February 16, and the latest – April 13), and the first autumn freezing is reportedly November 6 (the earliest being October 11, the latest – December 17). Hence, in Central Karakums, the average duration of the frost-free period is 234 days, while in some years this number decreases to 181 days or increases with up to 286 days. 1. Timelines for planting/sowing on distant pastures of the Karakum Cattle- Breeding Farm, Rukhabat Etrap Name of plant Periods of phyto-amelioration Seedling and English Latin Seed sowing cutting planting Black Saxaul Haloxylon aphyllum 1.02-28.02 1.01-20.02 White Saxaul H.persicum 1.02-1.03 1.01-20.02 8 n/a Salsola richteri 1.02-10.03 25.12-20.02 n/a Calligonum rubens 1.01-20.03 20.12-25.02 n/a C.setosum -do- -do- n/a S.sp. - 01.11-30.03 Prior to planting, desert shrub planting material should be thoroughly screened to prevent cracks, breakdowns and other mechanical damage. Yearlings should be at least 80 cm high, and their underground part should be longer than the aboveground part. Planting holes should be up to 80 cm deep. This allows to use the deep-planting technique, whereby the seedling root neck is buried into the sand by up to 15-20 cm to prevent the roots from being blown off by the wind. Harvested Calligonum cuttings are 45-50 cm long and 1.5 cm or more in diameter. As a practical measure, an indigenous technique for planting large stems without offshoots can be suggested. The technique essentially consists of planting large stems and rods of mature vegetating saxaul harvested with its bedding strips (about 40 cm long) as firewood or building material. This “planting material” is buried deeply into the sand and watered during planting, and subsequently – after vegetation traits are noticed – for 1 to 3 years. Observations have shown that planted large stems first develop sprouts and assimilation shoots (due to the abundance of growth energy in mature stems), and afterwards small lateral roots start growing. There were also cases of the rooting of large stems and rods buried into the sand as a support or fencing. Saxaul stems with a shortened root for the experiment are harvested in dense stands, away from population centers. 9 Fig. 4 The view of a phyto-amelioration plot (with a settlement built on takyr area in the background) Within the area of checkerboard protection (Figure 4) a seedling was planted per each cell, in row protections they were planted every 2-3 m, depending on local conditions. In the course of planting, the seedbeds were spring irrigated at the rate of 10 liters per plant. It should be noted that when psammophytes are planted during large-scale sand stabilization, irrigation is carried out rarely and without subsequent protection of plantations that is why the survival ability and establishment of crops are low. We also experimented with undersowing sand-dweller herbs (selinum – Stipagrostis karelinii, ilak – Carex physodes, etc.), which had a positive effect on the stabilization of loose sand surface. Previous observations had established that in the regeneration areas where herbs were planted, their natural colonization was reported after 3-4 years. On the plots with a strong growth of the top, shrub tops were shaped. On plantations established to improve pastures, regulated seasonal grazing of livestock can be carried out after 5-7 years. 1.3 The practice of using collector and drainage water for irrigation For planting shrubs on the piloting plot, seedlings of black saxaul (Haloxylon aphyllum) and Salsola paletzkiana were used. They were planted in checkerboard 10 format using four options. In each option, seedlings were planted in alternating rows of saxaul and Salsola paletzkiana. Before planting the seedlings on barkhan sands within the piloting plot, semipermeable row and lattice mechanical protection made of cane was installed. Planting was done manually using the 4 x 2 m layout (4-m spaced, row planting every 2 m). The yearlings used were 47 to 96 cm high for saxaul, with a root neck of 1.5-2 cm in diameter, and 25 to 115 cm high for Salsola paletzkiana, with a root neck of 1.0-1.5 cm in diameter. Mineralized collector and drainage water from the Ashgabat Interfarm Collector was used for spring irrigation. The composition of salts and minerals is shown in Table 2. 2. Pattern of chemical composition of collector and drainage water Sampling Solids Principal ions, mg/l TBN Total Total date mg/l mg-eq/l hardness salts mg/l pH mg-eq/l mg-eq/l CO3 HCO3 Cl SO4 Ca Mg NaK 09.05 8.26 2968 --- 2253. 39111. 1438.52 1005.0 19916. 53423. 3.68 21.4 2775.1 68 0 9.95 0 4 2 04.06 8.53 3498 --- 2714.4 44712. 1716.33 1628.1 16913. 70730. 4.44 22.0 3338.1 4 6 5.73 0 9 7 04.07 8.44 3302 --- 2103.4 45012. 1588.13 1507.5 17114. 63427. 3.44 21.6 3099.2 4 7 3.06 0 1 6 18.08 8.29 2916 --- 1462.4 40911. 1437.62 1185.9 17114. 54823. 2.40 20.0 2758.1 0 5 9.93 0 1 8 16.09 8.00 2898 33.61. 48.80.8 40411. 1447.53 1065.3 16213. 56924. 1.92 18.7 2748.9 12 0 4 0.14 0 4 7 15.10 8.42 3016 10.80. 1903.1 41911. 1454.93 1306.5 17514. 56724. 3.48 20.9 2853.7 36 2 8 0.29 0 4 6 As it follows from the Table, the quantity of water-soluble salts varied depending on the month, and during the irrigation period was 2.7-3.3 g/l. The water is dominated by sulphate ions from 1.4 to 1.7 g/l, which had insignificant effect on the growth and development of plants. Moreover, sulfate ions make the soil less salty than chlorides, thus preventing the threat of soil resalting. 11 Irrigation was carried out from May 20 through October 20 aiming at soaking the root habitable horizon: in the first option it was 3 liters every 10 days, in the second option – every 20 days, and in the third option - every 30 days. Plantations of saxaul and Salsola paletzkiana were not irrigated and served for control. The irrigation procedure was as follows: two 1.5-liter plastic containers were buried under each bush near the plant root neck. The upper part of the container with a lid remained above the ground, with a small hole of 0.5 cm in diameter was made in the lower part of the container. Depending on the experiment option, after a certain time interval the containers were filled with collector water through the upper part, thus providing for subsurface drip irrigation from the lower part, with irrigation intensity regulated using the container lid. Field observations showed that Salsola paletzkiana developed the first sprouts a month after planting, and saxaul - at the end of March. All of the seedlings had shoots in the first ten day of April. Plant counting conducted in November recorded a 100% survival ability of saxaul and Salsola paletzkiana in the irrigation options of every 10 and 20 days. Over the three-year growing season, there were no crop failures in the two experiment options. In the third option, with irrigation provided every 30 days, the survival ability of saxaul and Salsola paletzkiana was 83.4% and 87.6%, respectively, and in the control area – below 50%. The crops growth varied strongly depending on the experimental approach undertaken, month, as well as the year of the observation (Table 3). 3. Average crop height (cm) according to the approach Crop Approach Control group (no irrigation) Irrigation every 10 Irrigation every 20 Irrigation every 30 days days days Year 1 Year 2 Year 3 Year 1 Year 2 Year 3 Year 1 Year 2 Year 3 Year 1 Year 2 Year 3 Saxaul 109 177 256 103 168 210 91 148 184 71 95 135 Salsola 135 182 220 128 186 217 96 137 179 98 153 164 In the options where watering was carried out, saxaul growth averaged 33.1 cm per year, and Salsola growth was 27.2 cm. However, in year 2, saxaul growth averaged 65.3 cm, and Salsola growth was 58.3 cm. During year 3, the intensity of 12 vegetation somewhat slowed down, with a similar pattern observed on the control plot. The most promising observations were made during the monthly growth of crops, where intense growth (up to 19.0 cm for saxaul, and up to 17.3 cm for Salsola) occurred during August and September. The maximum growth of crops during the growing period was reported on the plot where plants were watered every 10 days. In this option, the growth of saxaul and Salsola averaged 52 cm for year 1, 70 cm for year 2, and 64 cm for year 3, which resulted in the shaping of saxaul 220 to 290 cm high. For Salsola, the growth for year 1 was – 23 cm, for year 2 – 58 cm, and for year 3 – 28 cm. It is noteworthy that by the end of year 3 of vegetation, plantations 172 cm to 260 cm high took shape. Somewhat lower yet high enough rates of plant growth were reported in the option where watering was carried out every 20 days. In this option, the height of 3- year-old saxaul plants reached from 161 cm to 240 cm, and Salsola got 160 cm to 242 cm high. In the third option, with watering carried out every 30 days, the growth of saxaul was between 100 cm to 212 cm, and for Salsola – between 130 cm and 225 cm. On the control plot, the preserved saxaul during the same period grew from 90 cm to 137 cm, and Salsola – from 148 cm to 165 cm. It is known that every year 5.5-6.0 km3 of low-mineralized collector and drainage water is discharged into Karakums. Currently, this water is collected into a unified system of collectors, with its main channel, which is over 800 km long, crossing Karakums from east to west. According to our estimates, there are over 11 million hectares of pastures that need improvements situated within its catchment area. Our observations demonstrate that rationed use of collector and drainage water can help successfully cultivate desert psammophytes in such areas, thus improving the yield of pastures and the condition of the environment. 1.4 Reforestation and reproduction of planting material The artificial forest plantations of desert shrubs on bare loose sands reduce the speed of active winds by 1.5-2 times, stabilize the movement of barkhans, and protect takyrs from sand drifts. Shrub crops mitigate dust storms and dry hot winds. The reduction in wind speed is to some extent responsible for changes in other weather elements. For example, it feels warmer in artificial forests than in the open area during the winter and spring months, while the temperature slightly decreases 13 during the summer months. In winter, the air temperature is by 0.4-1.5°C higher near affected tree and shrubbery plantings, and by 2.1-2.6°C higher near 6-7-year-old plantings, compared to open distant pastures. The snow cover persists much longer among tree and shrubbery plantings. Evaporation decreases in vegetation areas. For example, in spring (April) evaporation in artificial forests is 2-3 mm in daytime, and 1.5-2.6 mm at night. These figures confirm that compared to open space, evaporation in artificial forests is by 12.7-31.4% lower in daytime, and by 26.8-46.4% lower at night [7]. Thus, a kind of microclimate is formed in the areas of artificial forests, which has a favorable effect on the yield of grassland vegetation and its biodiversity. In the silvicultural area, the number of species almost doubles compared to distant natural pastures. Herbaceous plants and ephemers are much thicker there than in natural phytocenoses. Subsequently, their yield grows by 2 to 3 times during the spring months. Gross plant yields are 25% higher than in distant pastures without shrub plantations [13]. Despite their limited area, cultivated forests grown on plots and sands around utility areas and takyrs are used as forage for fauna species. Bountiful shade and the opportunity for camouflage encouraged a number of synanthropes, i.e. plants and animals whose existence is closely linked to man and settlements, to settle down there. Artificial plantations have been gradually turning into not just grazing and camouflaging grounds but also sites for nesting of birds and reproduction sites of many animal species. Forest plantations also provide them with a refuge from summer heat and winter cold. Additionally, artificial plantations clean air from dust and smoke, improve the environmental living conditions and partially create comfortable and favorable conditions for recreation. 1.4.1 Setting up nurseries to produce planting material On the first piloting sand stabilization plots, phyto-amelioration was carried out using imported planting material – seedlings of black and white saxaul, Salsola and Calligonum setosum. As an experiment, a trial planting of cuttings harvested from segmented off-shoots of large saxaul was carried out. The harvesting was conducted in dense natural plantations in the desert. Although the survival ability of such “seedlings” is low and comprises around 60%, their planting is considered appropriate because in case of their successful rooting, well-developed and stable shrubs emerge on stabilized plots. However, with an increase in the area occupied 14 by stabilized barkhans and other aeolian ephemerals causing sand drifts, it becomes necessary to set up a nursery. At the initial stage of afforestation works, the preference was given to the irrigated psammophyte nursery type, although non-irrigated nurseries are also common. This was based on the fact that seedlings of desert shrubs for which irrigation was used, were stronger and better preserved. According to the data [19], the yield of planting material from a typical irrigated nursery is steady and annually reaches up to 150,000-200,000 seedlings per hectare. The nursery was irrigated using ridges 20-25 cm deep and spaced at 60 cm. Given its small size, all the work in the nursery was done by hand. In most cases, the planting material was cultivated using natural soil fertility. However, this technique provided satisfactory results during the first 3 years only. During the subsequent years it is necessary to introduce organomineral fertilizers. In order to prevent seedlings from drying out and dying we practiced outplanting just before afforestation. During the piloting work, for the first time in the practices of phyto- amelioration in the desert, we succeeded in including psammophytes and seedlings of sand acacia (Ammodendron conollyi) in the variety of planting material. The work proved to be labor-intensive though we had an information that some amateur foresters had managed to obtain offshoots of the plant after several years of continuous attempts. Precisely, a few families in Bokurdak village had acacia groves on their small holdings, and their experience proved that the sowed seeds of acacia sprout by year 4 to 7, depending on the weather conditions. The sand acacia seedlings were sent to the Biotechnology Laboratory of the Institute of Desert Research in Israel (under the Agreement on Mutual Scientific and Technical Cooperation) for further treatment using advanced stratification techniques. Conducted experiments helped establishing the optimal chemical solution for stratification of sand acacia seeds was, which ensured fast germination of seeds with a high germination percentage. The produced solution contained sulphuric acid, which affected the hard shell of seeds and destroyed it within 40 minutes [23]. The sowing depth of sand acacia seeds treated in the above way comprised 3 cm, and the seeding rate is 60-40 kg/ha. 1.4.2 Cultivating psammophyte seedlings with a closed root system 15 In recent years, a new type of sand stabilization activities has emerged – preparation of planting material with a closed root system. The use of containers ensures a high efficiency of phyto-amelioration under the extreme conditions of Central Karakums as seedlings root system is not damaged during planting (Figure 5). Figure 5. A nursery for cultivating planting material with a closed root system Perforated PE bags (25-30 cm high and up to 15 cm in diameter) were used as containers that ensure the development of the root system of necessary size and prevent its damage during the planting into the soil. As a substrate to fill the bags, takyr clay was mixed with sand and organomineral fertilizers on the basis of 0.04 g of nitrogen and 0.03 g of phosphorus per kg of soil. The bags with substrate were placed in the nursery in rows and installed by 1/3 of their height in the ridges to ensure their stable vertical position. To preserve moisture in the bags, side rows were covered with PE film and buried with earth. The bed-type surface thus formed was watered using a spraying cone. Depressions between the beds were subsequently used as passages for maintaining the seedlings. This technique used for placing the bags allows growing 100,000-120,000 of seedlings per hectare. 16 Sowing was conducted in March-April after the onset of stable daily average temperatures of 5°C and more. The seeding rate was up to 15-20 seeds per container. Guaranteed saxaul sprouts were obtained when the seeds were covered with a sand layer 1.5 cm thick. The first watering (on the basis of 500-600 m3/ha) was carried out immediately after sowing the seeds, subsequent watering was carried out on the same basis after 7-10 days. The first sprouts in bags were reported roughly after a week, and mass-scale sprouts – 12-15 after seed sowing. To obtain even sprouts, additional watering was carried out, and the crust formed on the substrate surface was destroyed where necessary. The first sprout thinning was conducted in early May, and the second thinning - during the last 10 days of the same month. Two or three plants were left in each bag, while the plants that were weak, suppressed, or had signs of disease were removed. Subsequent care for the seedlings included the removal of the weeds and regular irritation until October. Seedlings were dug out in spring in the course of silvicultural works. Three or four days before digging them out, the nursery was irrigated to supply moisture. After digging out, bed edges were cleared of protective sand layer cutting the roots sticking out the bags to facilitate the removal of seedlings from the nursery. For transportation purposes seedlings should be handled with care, in boxes with a high side wall, where seedlings are placed in housings in an upright, tight position. The seedlings with a closed root system were planted into pits 35-40 deep in the silvicultural area. To ensure a high survival ability and viability, the bottom and walls of the PE bag were сut in. The seedlings root neck was 5-15 cm below the daylight surface and depending on the conditions the soil around the bag was compacted and watered. The watering of seedlings lasted for 3 years, which increased survival ability, and accelerated the crops growth and development. The piloting demonstrated that the best result in survival ability and viability can be obtained only through planting seedlings with a closed root system after the phase of root system lignification. Planting material cultivated in nurseries in winter, before the start of sylvicultural works, helps lengthen the growing season and guarantee the rooting only if regular watering and protection from sand drifts are implemented. 17 1.4.3 Recommendation for maintaining the plantings In order to improve the efficiency of phyto-amelioration works of local desert shrubs, we introduced compulsory crop watering not only during the planting period, but also a limited watering during the growing season. The reason was that Central Karakums with relation to water availability were located at the junction of very arid and dry areas, and were not suitable for annual un-watered seedings and plantings, including phyto-amelioration works. Additional studies [18] demonstrated that guaranteed results of phyto-amelioration were obtained only in case at least 100 mm of precipitation fell between December and April. In the area of Bokurdak where we sowed and planted desert plants, favorable years occur 2-4 times over the 10-year span. Here (at the Bokurdak weather station), the average annual amount of precipitation equated to rainmeter readings accumulates 124 mm, which is clearly inadequate for the arid conditions of Central Karakums where the absolute maximum of the air temperature is 47°C, and the absolute maximum soil surface temperature reaches 73°C. Loose quicksand of barkhans retains a very insignificant amount of moisture. That is why in summer, the upper part of barkhans dries up and starts moving, which is particularly noticeable in the first two years of phyto-amelioration works. Given the harsh conditions of the forest growth, vegetative watering of all sites was carried out every ten days from May 20 to October 20 on the basis of 3 liters per plant. As the aboveground and underground herbage grew and developed, irrigation was reduced, on most plots it was stopped after three years. During the first three years, the crops were substituted with even-aged planting material, i.e. new seedlings were planted in lieu of the dried up ones. Seedings and plantings carried out in compliance with the requirements of agricultural engineering yielded good results. The survival rate of sand-stabilizing shrubs proved very high with viability percentage equaling to 87-95% by the end of vegetation period. As a result of similar work on moving sands, artificial forests of white and black saxaul, Salsola, and Calligonum setosum implemented over various years, as well as acacia, Aristida, wormwood (Artemisia scoparia) and ephemers that had settled down in the process of sand overgrowth, now form fragments of the green belt and securely lock up moving sands (Figure 6). The aforesaid forest plantations composed of desert shrubs reached a height of 2-3 meters and started being partly used for livestock grazing. 18 Figure 6. Forest plantations grown from sand-stabilizing shrubs 1.5 Stabilizing sand with takyr clay Controlling moving sands is a very complex and time-consuming process involving substantial investment. Various techniques are used worldwide for the stabilization and afforestation purposes of moving sands. The most common technique used to stabilize moving sands is installing mechanical protections and cultivating desert plants there. Cane is often used for mechanical protections. Since the 1960s, experimental field work has been underway to study the use of synthetic polymer materials in desert areas of Central Asia and Russia. Thus, in 1964-1965, the Institute of Deserts of the Turkmen Academy of Sciences conducted laboratory research, and in 1966-1970 field experiments were conducted to determine the possibility of using an artificial soil-aggregate stabilizers such as K- 4 polymer, ARM-15 latex emulsion, and polyacrylamide for stabilizing moving sands. The studies established [3, 16] that with concentrations of at least 1% and consumption of 2-3 liters/m2, K-6, K-9 and other polymers (Sunak, VRP-1) can be used to stabilize the sands. However, these products are not produced in the country today, so buying them abroad for stabilization purposes results in a significant increase in the cost of sand stabilization works. 19 The high cost and labor-intensity of mechanical protection works made it necessary to look for new ways to protect national economy assets from sand drifts and aeolation. Since the 1960s, both the USSR and foreign countries have been implementing intensive experimental projects related to the use of crude oil, petroleum products (bitumen, oil, fuel oil, spent oils, etc.) and building materials [10]. Despite the positive results of field and laboratory research, they were not put to good effect due to technology complexity and lack of facilities and units to mechanize (through the use of spraying) this work. At present, in a market-type economy, the use of crude oil or petroleum products is not economically feasible. Moreover, they are to some extent toxic and hazardous for living organisms. Multi-year observations and experiments related to the stabilization and afforestation of moving sands have shown that natural materials such as clay, plaster, limestone, sandstone, etc. can be successfully used for these purposes [2]. Unfortunately, these materials did not receive proper attention despite a number of advantages listed below:  wide availability (accessibility) in desert areas;  possibility to be combined with phyto-amelioration;  low cost;  potential mechanization of the process;  the application of natural materials to sandy surface enriches it and stimulates the growth and development of plants;  environmental safety. In reality, very little use is made of such materials because effective techniques have not been developed yet. The use of clay for stabilization and afforestation of moving sands, along with other natural materials, yields promising results. An attempt to stabilize the surface of barkhan sand using clay material was made as early as in 1935. Experiments conducted by N.N. Bolyshev in 1948 established that the best results are obtained through splashing 10% suspension (clay dissolved in water) on sand surface at the rate of 5.25-7.5 ton/ha normalized to dry clay [9]. However, this work was implemented on a small site (2 x 2 m) and not under desert conditions, and observations of the strengthened layer stability were conducted at wind speeds not exceeding 9-10 m/s. That is why it was impossible to 20 evaluate this moving sand stabilization technique. In addition, after drying out, the resulting thin crust first cracked, and then was easily carried away with wind. The conducted research [17] demonstrated that over the following years experts were looking for more reliable ways to stabilize moving sands using various clay solutions. Those techniques, essentially, consisted in building up a hard clay crust whose resistance depended on the degree of cohesiveness between clay particles and sand surface. To increase the degree of wind resistance of the clay crust, it was treated with polymeric substances. For this purpose, water-soluble polymers such as K-6, K-9, Arm-15 butadiene-styrene latex, polyacrylamide and others were used. To stabilize clays, solutions of 5, 10, 15 and 20% clay suspension and polymers were used [1]. Over the last half of the century, the possibility of sand stabilization using clay coatings [4, 2, 6, 13] has been tested under laboratory and field conditions, and we will describe some of the tests. The techniques proposed for stabilizing moving sands comprised of applying a 10-15 cm thick layer of clay to sand surface and watering it (at the rate of 2 l/m2) until a 2-4 cm thick crust is formed, the consumption of dry clay being about 200 m3/ha. The testing of the crust strength in the wind tunnel showed its stability at wind speeds of up to 7 m/s at a height of 30 cm above the surface. Another way to use clay is putting clay bands. The distance between the axes of the bands is approx. 1 meter, with a height of 10 cm. They are sprayed with water at the rate of 1 liters/m2 or 10 m3/ha. The total clay requirement is 150 m3/ha [6]. As it follows from the above data, these moving sand stabilization techniques were tested under laboratory conditions at a wind speed of 7 m/s. However, along with widespread winds of 7 m/s in Central Asia, there are rare stronger winds, especially during spring-summer seasons. Moreover, according to the authors [6], this type of clay protection is recommended for regions with low and moderate sand flow. At the same time, it is not clear what is meant by low and moderate sand flow. It is not clear either where in Central Asian (including Turkmenistan) deserts are occupied by low and moderate sand flow regions. In regions with strong winds, such protections will be filled up with sand, while the time required for filling up such protections is inversely proportional to the total width of the strip where the protection is installed. The identification study of sand-stabilizing properties of clay was carried out in 1997-1999 on the Annaus sand massif, and on a larger scale since 2001 – in 21 Central Karakums (approx. at 90-110 km of the Ashgabat-Karakums-Dashoguz rail- and motorway). For piloting purposes, a barkhan massif around Mamedyar was chosen, as well as private farm sites in Kekirdek and Bahardok. The total area of sand stabilized with clay and other natural materials in this region comprised 4.2 hectares. Unlike other projects, the researchers of the Institute of Deserts of the Turkmen Academy of Sciences used a different technique for stabilizing moving sands. This included the approach where various size lumps of clay were buried into the sand at a depth of 20-25 cm, and then bands of 10-15 cm high were installed on top (aboveground part). The distance between the rows of bands varied between 2 x 2 m on steep barkhan slopes and 3 x 3 m on flat surfaces (Figure 7). Figure 7. Layout of moving sand stabilization using local clay A – row mechanical protection; B - checkerboard mechanical protection Thus, sections of barkhan sands were stabilized not only at the surface level, but also at a certain depth by means of building clay walls. The work of moving sand stabilization was conducted from December through February. Clay checkerboards were installed up to a height equal to 2/3 of the windward slope of aeolian forms and partly in interbarhan depressions without preliminary levelling of the plots. Private farms used 190 m3 of clay per hectare for stabilization purposes, and public farms used 134 m3. After installing the protections, desert shrubs were planted (black saxaul was planted from February 1 to February 20, and white saxaul, Salsola and Calligonum 22 setosum – from February 1 to March 10). Shrub seedlings were planted at a distance of 7-10 cm from the intersection of bands, one plant per checkerboard. The planting material was carefully screened before planting to eliminate mechanically damaged plants. Two-year-old seedlings were at least 80 cm high, and planting pits were made 50-60 cm deep. This allowed to apply deep-planting techniques whereby the seedling root neck was buried into the sand by up to 15-20 cm to prevent root aeration [13]. Moving sand stabilization and afforestation using clay was carried out concurrently on three plots in Bokurdak. All the plots are covered with barkhan sands lying on takyr surface, barkhan forms are 2 to 3 meters high. The selected plots included both natural and levelled barkhan massifs, with an enclosure provided around them. Then checkerboard mechanical protections were installed using wet clay from the local takyr (if the work is carried out during the dry season, watering is to be provided at the rate of 5 l/1 m2 to ensure soil cohesiveness). As it follows from November observations, lumps of clay buried in the sand got soaked as a result of winter-spring precipitation, and some of them obtained plastic consistency. The clay formed a crust of small thickness on the surface. A portion of the clay bonded and stabilized the sand surface. However, the sand inside the checkerboard kept being blown out by the wind, which resulted in the deepening of the middle part of the checkerboard by 17-22 cm. Subsequently the blowing out stopped, and the sand surface got stable owing to clay bands. The plants were planted in conformity with the requirements of agricultural engineering, and yielded good results. The survival ability of sand-stabilizing shrubs proved very high, and by the end of year 1 the viability was 85-86%. Autumn observations showed that the bulk of the crust was destroyed, but due to the preservation of the intrasand part of the clay the blowing out of the checkerboard had stopped. Over the following years, a small soil layer (5-8 cm) with a weak structure was formed. Yearling and perennial grasses emerged among the shrubs. The number of plant species increased, and subshrubs emerged. By autumn, the height of planted shrubs reached 2-2.5 meters, and in places – 3-3.5 meters (Figure 8). As the work results show, the installation of mechanical protections using clay is more resistant to strong winds compared to protections made of cane, shrub 23 branches, and Asiatic cotton. Over year 2, 10% of clay bands broke down, while mechanical protections made of plants were destroyed by up to 20%. That results in lower costs during year 2 when restoration work becomes necessary on stabilized areas. Fig. 8 Forest plantations on stabilized plots 1.6 Assessment of cost-effectiveness of amelioration Previous studies of the cost-effectiveness of sand-stabilizing works, depending on protection methods used in different bio-regions in Turkmenistan, attested to their high cost [4]. Sand-stabilizing works were carried out based on our recommendations, using mechanical protections to stabilize moving sands, which were made of cane and desert brushwood (saxaul, Salsola, Calligonum setosum), as well as the aboveground part of Asiatic cotton, and local takyr clay soil – for testing purposes. The costs of stabilization and afforestation of sand around takyrs included the stabilizing materials procurement costs, remuneration, transportation costs, and seedling and water costs (Table 4). 24 4. Cost-effectiveness of moving sand stabilization and afforestation (per hectare) Materials Cane Brushwood Asiatic cotton Costs Checkerboard Checkerboard Checkerboard size, m size, m size, m 2x2 3x 3 2x2 3x3 2x2 3x3 Year 1 286 191 172 115 207 136 Year 2 83 55 54 37 61 41 Year 3 14 10 9 9 10 7 Total costs, USD 383 256 235 161 278 184 As the table shows, the most cost-effective technique consists in stabilizing the sands using desert brushwood where material transportation costs are minimal. The costs of stabilizing moving sands with mechanical protections of desert brushwood are 33.7% lower than for cane, and 15.9% lower than for Asiatic cotton. The advantage of clay over other materials is that it is relatively resistant to strong winds and durable. During year 2, 10% of mechanical protection checkerboards made of clay break down compared to 20% for cane, and 15% – for desert brushwood and Asiatic cotton. For year 3, the losses of these materials are the same and are approx. 5%. One seedling is planted into each cell to be watered on the same basis as with other stabilization techniques. Plant survival ability over year 1 is 75%, over year 2 (after replacing dried out plants with new seedlings) – 95%. The cost-effectiveness of moving sand stabilization using takyr clay is shown in Table 5. 5. Cost-effectiveness of sand stabilization and afforestation using clay (per hectare) Checkerboard size, m Indicator 2x2 3x3 2 x 2.5 Total costs for year 1 214 143 182 Total costs for year 2 41 27 34 25 Total costs for year 3 11 8 9 Total costs over the three years, USD 276 178 225 The table shows that the costs of sand stabilization on an area of 1 hectare using clay are 28.1% lower than for cane, and 1.9% lower than for Asiatic cotton. It should be noted that when mechanical protections are installed on an area of 1 hectare, they only cover interbarkhan depressions and two-thirds of barkhan slopes . If the recommended agricultural techniques are complied with, the flow of sand to the takyr surface is significantly reduced, and at the age of 3 the vegetation almost completely fixes the sand. In addition, sand-stabilizing works contribute to natural infestation of sands with mixed herbs. Between year 5 and year 7, following sand stabilization and afforestation, these areas can be used for cattle grazing during the autumn/winter period. The grazed forage supply in stabilized areas for year 3 is up to 13.1 centners/ha (Table 6). 6. Grazed forage supply and grazing capacity on stabilized plots in Central Karakums Average grazed forage supply, centners/ha Grazing capacity, Year Mixed herbs Shrubs Total sheep/ha 1 0.09 4.5 4.59 0.48 2 0.26 8.6 8.86 0.93 3 0.30 13.1 13.4 1.41 The table shows that in year 3, a vegetation cover is formed on stabilized sands, with an average annual grazed forage supply sufficient to carry out limited grazing of sheep and goats (at the rate of 9.5 centners of forage per sheep). According to our calculations [13], the total stand of timber available per hectare of restored pastures is 7.02 tons (Table 7). 26 7. Average stand of timber produced in the course of sand stabilization and afforestation Number of Total raw Air-dry Air-dry Stand of Age of trees per biomass per biomass per stand of timber per plantings hectare, tree, kg tree, kg timber, kg hectare, kg pcs./ha Year 1 3.69 1.78 0.83 2,088 1,733 Year 2 10.37 5.20 2.76 1,566 4,322 Year 3 17.10 8.65 4.72 1,488 7,023 The cost-effectiveness of sand stabilization around takyrs and their use as pastures is determined depending on the amount of profit generated. Limited grazing allows to generate a profit of up to USD46.6 through a crop of wool and a crop of lambs. The total cost of timber per hectare will be USD113.3. The payback time for 3 years using mechanical protections of cane to stabilize the sands (with mechanical checkerboards of 2 x 2 m) was calculated using the equation below: Tp = (ΣSA – Ct)/P = 5.8 years where ΣSA – sum of one-off costs of sand stabilization and afforestation, manats; Ct – cost of timber, manats; P – profit, manats; Tp – payback time of one-off costs, years. A similar method was used to calculate the payback time of sand stabilization and afforestation using desert brushwood, Asiatic cotton, and clay, depending on the size of mechanical protection checkerboards. As it follows from calculations, the payback time of one-off costs, depending on the type of materials used and the size of checkerboards varies from 2.5 to 5.9 years. 2. Studying runoff properties of takyr catchments Given changing environmental conditions, a search for a balance between reasonable environmental management and economic activity is an important prerequisite of sustainable development. According to the Subregional Action 27 Programme to Combat Desertification in Central Asia adopted by all the five countries in 2003, “monitoring and assessment of desertification processes; development of a drought mitigation and early warning system” is a top priority of regional cooperation. A number of measures are in place to establish a monitoring system, including the use of new and conventional methods to combat land degradation and drought based on the population potential. Conventional knowledge regarding runoff harvesting is becoming increasingly important worldwide as water shortages are getting increasingly acute due to changing climatic conditions and mismanagement of available water resources. Harvested surface water is a reserve in case of drought, providing water for livestock and opportunity for small-scale oasis irrigation. To combat drought, a set of agrotechnical and amelioration measures are used aiming at containing the surface runoff and strengthening the soil water-holding capacity in the area of its accumulation [8]. Amelioration measures include vitally important pasture-protecting afforestation when precipitation is accumulated in the soil profile for direct use by the plants. The structure for harvesting rain and melt water is always based on the same principles: water is harvested for use in the storage area or on the crop planting site. The key point is that rainwater is stored in deep layers of soil thus supporting the root system of plants in torrid time. The harvesting of storm water runoff includes micro-catchment, typically featuring a small catchment area C (<1000 m2) and cultivated area СА (< 100 m2) at a ratio of С:СА = 1:1 up to 10:1 [24]. Usually, farmers control both the catchment area and irrigation area, where single trees or annual crops are planted. The work is done mainly by hand or using natural depressions, as an example we can refer to micro-catchments such as “oytak.” A macro-catchment is a system for harvesting water flowing down the surface as a turbulent runoff or streamflow. These systems feature a large catchment area C (the “external” catchment area is 0.1 - 200 hectares) located outside the accumulation area CA at a ratio of C:CA = 10:1 up to 100:1. These include, for example, different types of dams such as “bent” that are common in the west of Turkmenistan. These include, for example, various types of dams, such as the Bent, which are common in western Turkmenistan. Given the low amount of precipitation in the places of takyr distribution and their small slopes, which provides for a slow flow of surface runoff, we included micro-catchments on takyrs with small takyr catchments. 28 The emergence of vegetation cover can hardly be called “degradation”, but all of these factors worsen the hydrophysical properties of takyrs and their runoff- producing capacity. The takyr surface is broken by mud roads and cover sands into smaller fractions, the use of which remains important in desert conditions. To determine the runoff properties of small takyr catchments, field experiments were conducted on the Karrykul takyr. To measure the precipitation-catchment parameters, sites 100, 55, 30 and 15 m long with a total width of 20 m were laid down. The perimeter of each site was delimited with soil bands. In the depressed part of each runoff site, concrete tanks were erected, with an adequate volume to accumulate the maximum quantity of water (Figure 9). Figure 9. Catchment sites on the Karrykul takyr A diver instrument was installed in each of the water tanks to record changes in the tank water level for subsequent calculation of the runoff volume [22]. The instrument had been pre-calibrated to the required range of water depth and temperature. An automatic weather station with a data storage system was installed to measure precipitation, wind speed and direction, air humidity and solar radiation, [21]. 29 Observations on runoff sites are occasionally conducted by the staff of the National Institute of Deserts, Plants and Wildlife. To analyze the results of a continuous series of such observations over a five-year period, we used data from two wet seasons (autumn-winter-spring) of 2001/2002 and 2002/2003 when the amount of precipitation generating runoffs was 104 and 85.2 mm, respectively. Even though precipitation over the above periods varied, the total volume of harvested runoff was similar for each season. Interestingly, the total volume of runoff harvested per season was linearly dependent on the length of catchment area or the path of water draining down the takyr surface (Figure 10). Figure 10. Total volume of consolidated runoff (m3) as a function of the length of site (of surface draining) for two observation seasons Axis Y – Total volume of runoff, m3 Axis X – Length of site, m The results of measurements showed that small takyrs have a higher runoff factor. The runoff factor was calculated as the ratio between the runoff layer and precipitation layer per unit of area, and the results are shown as a graph (Figure 11). 30 The factors have a low value for small precipitation amounts (<6 mm), and a relatively constant value for rains with a precipitation layer >12 mm. Large variations in the runoff factor are typical of the averages of runoff-producing rains (6-12 mm), possibly due to their differing intensity. Figure 11. Runoff factor for runoff-producing precipitation during the observation period (the numbers in the legend refer to the length of sites) Axis Y – Runoff factor Axis X – Precipitation, mm 31 60 y = 0.635x - 4.92 R² = 0.7006 40 Сток, мм 20 0 0 20 40 60 80 Осадки, мм Figure 12. Amount of runoff on the takyr depending on the precipitation layer Axis Y – Runoff, mm Axis X – Precipitation, mm For comparisons, Figure 12 shows the runoff size of the entire Karrykul takyr of 1.75 km2. Runoff on large takyrs starts when precipitation exceeds 7.6 mm, while on runoff sites it is 4 mm and more. The same amount of precipitation varies significantly in terms of the quantity of water flowing down the takyr [14]. The the volume of runoff is obviously influenced by the condition of the takyr surface: degree of humidity, number of microdepressions where water could stagnate, activity of rodents and termites that destroy the takyr crust, etc. The simulation of runoff production showed that three factors are linearly dependent on its volume (wind speed, amount and duration of precipitation) [25]. Wind speed and precipitation duration have a negative effect reducing the quantity of water flowing down the takyr surface. Given that the takyr slope is small, cases have been reported when a strong wind drove the takyr runoff in its own direction (sometimes the opposite of the terrain slope) (Figure 13). 32 Figure 13. View of a takyr after raining The duration of precipitation is linked to the intensity of its fallout: the same amount of precipitation produces a different amount of runoff depending on the time of fallout. That is due to large losses of runoff in the initial period of its production, in particular, for infiltration. Calculations [12] show that the average amount of takyr runoff in Karakums is 122-170 m3/ha per year. On small takyr catchments, the annual amount is up to 500-600 m3/ha. In drought years, the surface layer is insignificant or entirely absent. It is estimated [11] that runoff may be absent in Karakums once every three years, whereas it can be harvested every year from small takyrs. Although the volumes of water harvested from them are small, they cannot be ignored under desert conditions. In our opinion, it is more expedient to use the runoff from small takyrs for protective afforestation on desert pastures, which will help mitigate the negative effect of droughts on the country's distant husbandry. 33 3. Findings To ensure the protection of takyrs as a catchment area, we resorted to the stabilization of the surrounding sand massifs through reasonable management of pastures and amelioration of moving sands. We recommended the optimal timelines for sand-stabilizing works, and planting and seeding of plants to stabilize the sands. Based on experiments, we have proved the feasibility of using of collector and drainage water for phyto-amelioration activities and determined the irrigation rates for ameliorant plants. Seedlings of sand acacia (Ammodendron conollyi) were included in the spectrum of psammophytes for the first time in the practices of phyto- amelioration in the desert. Agricultural techniques for cultivating ameliorant plants both in field experiments and with a closed root system were developed and implemented in the nurseries. Recommendations have been prepared for plantation maintenance aiming at the stabilization of the sand substrate around catchment takyrs. It is proposed to use takyr clay as a material for mechanical protections using the surplus clay left after building wells, canals are ditches. The reliability and durability of this material has been proved, and a technique has been developed to build checkerboard protections using clay. A feasibility study of the amelioration techniques proposed for protecting takyr catchments from destruction and sanding has been carried out. A grading of micro- and macro-catchments has been proposed: a micro- catchment has a small catchment area C (< 1000 m2), and cultivated area CA (< 100 m2) at a ratio of C:CA = 1 : 1 up to 10 : 1; for a macro-catchment the collection area is 0.1 - 200 hectares and located outside the accumulation area at a ratio of C : CA = 10 : 1 up to 100 : 1. The calculations have established that small takyr catchments pertain to the class of micro-catchments (С:СА = 7 : 1). Field experiments have been carried out on different size runoff sites on the Karrykul takyr to determine their runoff properties. The measurements have shown that small takyrs have a higher runoff factor. The factors are low for small precipitation (< 6 mm) and have a relatively constant value for heavy raining (> 12 mm). Large variations in the runoff factor value are typical of average rains (6-12 mm). An empirical dependence has been obtained to determine the volume of takyr runoff based on the precipitation layer. 34 The simulation of runoff processes has shown that three factors are linearly dependent on runoff volume (wind speed, amount and duration of precipitation). The wind speed and precipitation duration have a negative effect reducing the amount of water flowing down the takyr surface. 35 4. References 1. Арипов Э. А., Нурыев Б. Н., Аразмурадов М. А. 1983. Химическая мелиорация подвижных песков. Ашхабад: Ылым. 263 с. 2. Арнагельдыев А., Мамедов Б.К. 2005. 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