(a) Define pasture.
(b) List three features of natural pastures.
(c) A piece of land to be used to establish a pasture of Stylosanthes gracilis was surveyed to be circular.
(i) If the radius of the land is 200m and the spacing of the pasture legume is lm by 50cm, what is the population of the legume at one seed per stand?
(ii) If the germination percentage is 75, calculate the expected plant population. (iii) Give two ways in which Stylosanthes gracilis is important in agricultural production.
Explanation
(a) Definition of natural pastures: Pasture is a piece of land on which forage crops/grasses/mixture of grasses and legumes grow (b) Features of natural pastures: (1) Ability to regenerate easily. (2) Growth may be enhanced by burning. (3) Soils are low in nutrients. (4) Contain obnoxious grasses and legumes. (5) Grasses and legumes are poor in quality. (6) Can withstand trampling by ruminants. (7) Forage crops are resistant to drought.
(c) Calculation: (i) Area of land = π r² = 3.142 x 200m x 200m = 125,680m²
Spacing = 1m x 50cm = 1m x 0.5m = 0.5m² Plant population of stylosanthes gracilis
= Area of land (m²) = 125,680m²
spacing (m²) 0.5m² = 251,360 stands
(ii) Expected plant population: Germination:% = 75
i.e = 75 x 251,360/100
Expected plant population = 188,520 Stands of stylosanthes gracilis
OR Area of land = π r² = 22/7 x 200m x 200m = 125,714.28m²
Spacing = 1m x 50cm = 1m x 0.5m = 0.5m²
Plant population = Area of land (m)/spacing (m) = 125,714.28m²/ 0.5m²
= 251,428.56 stands Approx. = 251,429 stands
Expected plant population: Germination % = 75 = 75 x 251,429/100 = 188,572 stands of stylosanthes gracilis
(iii) Importance of stylosanthes gracilis in agricultural production: (1) Fixation of nitrogen from the atmosphere into the soil. (2) Feed for ruminants. (3) Green manure/fallow crop. (4) Checks soil erosion. (5) Improves soil structure.