(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...

Answer Details

(a) Pasture: A pasture is an area of land covered with grasses and legumes (herbage) which is used for grazing or feeding livestock.

(b) Three features of natural pastures:

• They grow on their own without being deliberately planted or managed by man.
• They contain a mixture of many different, often unimproved, species of grasses and legumes.
• They are usually of low quality and low carrying capacity, and their growth depends on rainfall.

(c) Calculations:

(i) Population of the legume at one seed per stand:

Area of the circular land, \( A = \pi r^{2} \), with \( r = 200\,\text{m} \) and \( \pi = 3.142 \):

\[ A = 3.142 \times (200)^{2} = 3.142 \times 40000 = 125680\ \text{m}^{2} \]

Spacing \( = 1\,\text{m} \times 50\,\text{cm} = 1\,\text{m} \times 0.5\,\text{m} = 0.5\ \text{m}^{2} \) per stand.

\[ \text{Population} = \dfrac{\text{Area}}{\text{Spacing}} = \dfrac{125680}{0.5} = 251360\ \text{stands} \]

At one seed per stand, the population of the legume \( = 251{,}360 \) plants.

(ii) Expected plant population at 75% germination:

\[ \text{Expected population} = \dfrac{75}{100} \times 251360 = 188520\ \text{plants} \]

(iii) Two ways Stylosanthes gracilis is important in agricultural production:

• Being a legume, it fixes atmospheric nitrogen and improves soil fertility (it is also used as green manure and cover crop to check erosion).
• It provides nutritious, protein-rich forage (fodder) for feeding livestock.