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Reclamation of saline soil in the Northeast

          Saline soil means soil which its salinity level is high enough to be dangerous for economic crops.

          How to observe saline soil area in the Northeast
          1. To find salty dust among soil texture in summer or the land is left empty. In rainy season, salty dust is melt and could not be seen.
          2. To find weeds like Namdang, Nampec, Namcom and Yakikrag.
          3. In saline soil area, rice does not grow. Its trunk is thin and its leaves are pale. Some are died.

          Area where saline soil is found 
          There are 17.8 million rai of saline soil area in the Northeast. Moreover, there are 19.4 million rai of area where it is easy for the spread of soil salinity. Saline soil is found almost every provinces in the Northeast.

          Saline soil area division 
          In the Northeast, saline soil area can be divided into 4 types : 
          1. High-level saline soil area is in the area where salty dust is found among soil texture more than 10% of the area. Plant can not be grown and the area is left empty.. It takes much money for soil improvement.
          2. Middle-level saline soil is in the area where salty dust is found among soil texture 1-10% of the area. Plant can be grow but crops yield decreases.
          3. Low-level saline soil is in the area where salty dust is found among soil texture less than 1% of the area. Subsurface flow is brackish or brine and its depth is 2 m. from soil surface. Such area is the paddy-field.
          4. Area where it is easy for the spread of soil salinity. Nowadays, such area is the highland where crops are planted. Salty dust is not found among soil texture but below the soil, there is salty stone. When the rain falls, water from soil surface flows pass salty stone layers and becomes salty water flowing to the next plain area.

          Management of Middle-level and low-level saline soil for growing rice 
          Most saline soil area in the Northeast is the paddy-field. Its soil texture is sandy. There are water filled in the plain field 3-4 months. In rainy season, there is low soil fertility suitable for growing rice. Because of saline soil, rice production decreases (200-300 liters/rai) and such amount is not enough for consuming in family. Land Development Department has researched for an increase in rice production in low-level saline soil area. The result is rice production which is equivalent to 600-1,000 liters/rai.

          Steps for an increase of rice production in saline soil area 
          1. Fill some water (rain-water or irrigated water) in the field in order to leach salt from the soil and drain it. Drain water when it becomes pale brown. Soil salinity will decreases. Do it 2-3 times before ploughing.

          2. Add organic matter like husk, animal manure or compost 2 ton/rai in soil preparation period in order to make rice grows rapisly. Green manure like the sesbania rostrata could be scattered in the ratio of 7 kg./rai and incorporate it after 60 days when it blooms. S.speciosa or S. aculeata could be use. Soil amendments like slaked lime, marl could be used to decrease acidity in soil. Add gypsum for the alkaline saline soil like Kularonghai series which are dense. Its advantage is to leach salt from the soil and make better water ventilation in soil.

          3. Make levels of soil surface in the field smooth and be in the same level. Its purpose is to fill water in all part of the field and prevent salt accumulated in some area. Plough the soil as deep as 30 cm.

          4. Select salt tolerant varieties of rice. Land Development Department has researched and found varieties of rice suitable for growing in the Northeast.
                    Native varieties of rice : More-on, Kaotau, Koredeawbao, Dangnoi, Jekkadod.
                    Suggested varieties of rice : RD1, RD6, RD7, RD8, RD15, KDML105, Sanpatong, Kaotahang, Kampai41, Kaopakmore148

          5. When the rice is small, it can not bear high-level salinity in soil. So,select area where its salinity is middle. Select salt tolerant seeds of rice 5 kg./rai.

          6. Transplantation the rice's age for transplantation should be 30-35 days (maybe 45 days depending on rice varieties). An increase in the rice's age will increase its ability for salt tolerance.
                    One of the important factors for transplanting rice in saline soil is the weather. The weather should be very hot and the shade of light is in low level. Such weather is in the period of rainfall before or after transplantation.
                    The transplanting area is 20x20 cm. and take 5-8 plants/time in order to get high amount of safe rice/area since salinity in soil prevents rice from growing. Keep the leavings to replace the died ones.

          7. Chemical fertilizer application. Since soil in the Northeast is sandy, the fertilizer should consist of Nitrogen, Phosphorus and Potassium. The suggested amount is 16-16-8 in the ratio of 30 kg./rai and divide it into 3 equal parts : 
                    Add the first part 7-10 days after transplantation.
                    Add the second part in the high-tillering period.
                    Add the third part when rice starts to have panicle.

          8. Maintenance  
                    After transplanting, the rice's leaves become withered and blue. Some are rolled up. After a period of time, its leaves become brown. After transplanting a week , if its leave does not appear, it dies. Transplant new rice to replace the died ones and drain the water when it is pale brown and the rice leaves are burned.
                    Rice can not bear salinity in soil in the period of transplanting and blooming.
                    In blooming period, rice can not lack water. If it does, Salinity will increase, the rice seed is thin and rice production decreases. If rice lacks water, fill water in the field. Prevent rice's disease and kill insects until the harvest.

          9. Mulching 
                    After the harvest, do not leave the field empty because water evaporation will increase salinity in soil. Cover the soil with the mulch like rice straw, crop residue and husk to prevent the sunlight and decrease wate evaporation. When harvest the rice, tread on stubbles to cover soil. Incorporation the mulch in soil preparation period will add organic matter and improve soil properties.

          Saline soil management for crops planting
          After rice harvest in irrigated area or in area near water source, crops could be planted in saline soil area. Before planting, reclaim the soil as the following :
          1. Ploughing deeply. This method is suitable for soil hard to absorb water located among layers easy to absorb water. Ploughing deeply would leach salt from the plant's root. Plough as deep as 40-50 cm. and make the soil surface smooth.
          2. Shatter the below soil by ploughing roughly. Each plough pulled by the tractor should be far from each other 50-90 cm. to make the furrow for water absorption. 
          3. Chemical application. Mix gypsum with alkaline soil to decrease alkalinity. Calsium in gypsum will drive Sodium out of the soil. Then, apply water to leach Sodium from the area.
          4. Leaching salt from the soil to decrease salinity in soil. Apply water to leach salt and drain water out of the area without destroying the environment. Leaching the soil as the following :
                    - Kill weeds in the soil.
                    - Make the soil surface smooth.
                    - Plough the soil deep more than 30 cm. Statter the below soil until the furror appears and make the soil surface smooth.
                    - Divide the field into small plot (1-5 rai). Buil the dike around each plot.
                    - Release water gradually 250-300 cubic meters/rai. Water will percolate through soil and leach salt to the below soil. Add water 250-300 cubic meters/rai after water percolation. Check the concentrated amount of the drained salt.
          5. Selection of salt tolerant plants. This method is effective, safe and available.

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Types of salt tolerant plants grown in different soil levels 

          1. Plants grown in low-level saline soil
                    Truck Crops : cowpea, lettuce, celery, pepper, melon, a large variety of cucumber.
                    Flowers : gerbira
                    Farm crops and forage : mung bean, soybean, peanut, princess bean, green pea
                    Trees : avocado, banana, lichce, citron, orange, mango

          2. Plants grown in middle-level saline soil
                    Truch crops : luffa, cauliflower, cabbage, garden pea, potato, bottle gourd, garlic, sweet corn, water melon, grape, parsley, pineapple
                    Flowers : rose
                    Farm crops and forage : rice, S. speciosa, ramic, genus Hibiscus, sunflower, corn, Indian mulberry, sorghum, cassava, cowpea, Jackbean

          3. Plants grown in high-level saline soil
                    Truck crops : Boerhavia, turnips, tomato, cowpea, asparagus, genus Terminalia, acacia, basil
                    Flowers : allamanda, globe amaranth, hibiscus, bougainvillaea
                    Farm crops and forage : salt tolerant rice, sesbania rostrata, sweet potato, cotton
                    Trees : genus cassia, guava, eucalyptus,cashew nut, genus Terminalia, otaheite goose-berry, mimusops, hibiscus, tamarind, coconut palm, date palm, pine,nim, camachile.

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