Germination and emergence of soybean under crusted soil conditions
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Attempts were made to work out the effect of crust impedance to seedling emergence under natural field conditions by photographing a series of positions taken by the emerging hypocotyls. Being epigeal in germination, the seedling had to work through a large volume of soil to pull the cotyledons out of the ground. Since the hypocotyl was brittle, it often collapsed at the stress point between the emerging hypocotyl and the buried cotyledons. A number of seedlings subjected to severe impedance stresses often broke off at the hypocotyl hook when the soil surface ruptured. The emergence force of the varieties tested was closely related to their seed weight. The large seeded variety ‘Bragg’ exerted the greatest emergence force (1.86×105 dynes) and the small seeded variety ‘Type-1’ exerted the least (1.24×105 dynes). The variety ‘UPSS-38’ was intermediate both in hundred seed weight and the force that it exerted (1.49×105 dynes). The time taken to develop the steady maximum force was 78, 67 and 60 hours for Bragg, UPSS-38 and Type-1 respectively.
Key WordsSeedling emergence Soil crusting Soybean
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