AbstractThe distribution of roots of cassava, pigeon pea, coffee, and four grasses growing in Ultisols was studied. Cassava was the most shallow rooted of the crops with no roots extending below 105 cm, and few below a 30-cm soil depth. It also had the lowest density of roots at different depths. Coffee was much more deeply rooted with numerous roots down to 120 cm, and some reaching a depth of 180 cm. Coffee also had many more roots/L of soil at all depths than did cassava. Pigeon peas were very deep rooted with over a thousand em of roots per liter of soil down to a depth of 120 cm, and many roots down to a depth of 180 cm. This deep rooting characteristic explains the well known resistance of pigeon pea to drought and their capacity to extract nutrients from relatively infertile soils. Guinea grass, and, to a lesser extent, Stargrass, rooted very profusely down to 180 cm in the soil, with guinea grass averaging over 1,000 cm of roots per liter of soil at all depths down to 150 cm. The deep profuse rooting of guinea grass explains its drought resistance and its ability to outyield other grasses in the semiarid region. The data presented are important in developing recommendations for irrigating, cultivating, and fertilizing the crops studied and in determining the areas best suited to their production.
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