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                        Cover crops and ground cover management 
                        The undulating topography coupled with the high rainfall of the traditional rubber-growing
                        belt predispose the soil towards erosion. In order to conserve soil and improve
                        soil fertility, cover crops are grown and maintained. Leguminous ground cover enhances
                        the growth and yield of rubber. 
                        Advantages of cover crops 
                        Prevent the beating action of rain and effectively reduces run offIncrease
                            soil moisture and keep down the temperature during summerSmother weeds
                                Add large quantities of organic matter and improve soil structureFix atmospheric
                                    nitrogen resulting in improved soil fertility 
                        Common leguminous cover crops grown in rubber plantations 
                        Pueraria phaseoloides 
                        This is a vigorous twiner and creeper and forms a dense thick ground cover when
                        established. It can withstand strong sun and smother weeds. Seed rate is about 3-4
                        kg per ha. A disadvantage is that it is grazed by cattle unless afforded protection. 
                        Mucuna bracteata 
                        It is a deep-rooted fast growing legume with moderate drought resistance and shade
                        tolerance. A native of Tripura, it forms a thick luxuriant cover and suppresses
                        all weeds. The dried leaves form thick mulch and it is less palatable to cattle.
                        The seeds are comparatively big and the seed rate is 200 g/ha. 
                        Calopogonium mucunoides 
                        It is a twiner and creeper with tolerance for poor soils. It has a rapid initial
                        growth and dies off during the dry months and is a prolific seeder. Seed rate is
                        3.0 to 4.5 kg per ha. 
                        Centrosema pubescens 
                        It is a perennial climber and creeper that can grow in shade. It grows slowly and
                        is not tolerant to wet conditions. It smothers weeds. Seed rate is 5.5 kg per ha. 
                        Since the seeds of cover crops often have very hard seed coats, it is advisable
                        to have certain pre-sowing seed treatment such as acid treatment, hot water treatment,
                        and abrasion treatment to obtain a high percentage of germination 
                        Establishment of cover crop 
                        Cover crops are generally established from seeds. However, Pueraria phaseoloides
                        and Mucuna bracteata can also be propagated by stem cuttings. About 420 beds of
                        1.2 m x 1.0 m per ha are prepared immediately after the pre-monsoon rains. If cuttings
                        are used, fresh cuttings two or three feet long should be planted when frequent
                        rains are available during the month of June or July. On the other hand, if seeds
                        are used, they should be sown in prepared patches during May after the pre-monsoon
                        rains. 
                        Seeds of cover crops have very hard seed coat, which delays or inhibits germination.
                        Therefore pre-sowing treatment is done to ensure uniformity and higher percentage
                        of germination. This also helps in reducing the toxic compounds present in the seed
                        coat, which inhibit the nodule forming bacteria. 
                        Acid treatment 
                        Seeds are treated with concentrated sulphuric acid for a period of 10 min for P.
                            phaseoloides, 30 min for M. bracteata and 20-30 min for C. mucunoides. 
                        Hot water treatment 
                        This method is suitable for the seeds of P. phaseoloides and C. mucunoides. Hot
                        water treatment is carried out by pouring water at 60-80oC over the seeds in a container
                        till all the seeds are submerged, for a period of 4-6 hours before sowing. 
                        Abrasion treatment 
                        Abrasion treatment is done by mixing the seeds with sand (about 1-2 times the quantity
                        of seeds) and then grinding them gently in a mortar. Scarification of seeds by rotating
                        in drums lined with sand paper can also be adopted. After treatment, the seeds may
                        be soaked in water overnight before sowing. 
                        The pretreated seeds are mixed with equal quantity of rock phosphate and sown in
                        rows or in equidistant patches between the plant rows. 
                        Powdered rock phosphate (20% P2O5) @ 150 kg. per ha is applied
                        in two equal splits, the first one month after sowing and the second two months
                        after the first application. In areas where the soils are known to be deficient
                        in available potassium, application of a mixture of 150 kg of rock phosphate and
                        50 kg of muriate of potash is recommended. 
                        Cover crop should not be allowed to grow in a circle of about 2 m diameter around
                        the plants or along the contour terraces for 3 to 4 years to prevent its competition
                        with the young rubber. 
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