Theory question 102
Weeds and Weed Control(a) Complete the table below: for each of the weeds goat weed, siam weed and water leaf, give its botanical name and method of dispersal.
(b) List three examples of each of the following factors affecting land availability for agriculture: (i) physical factors; (ii) economic factors.
(c) Enumerate four effects of pollution on agricultural lands and ponds.
(d) State two ways of minimizing land and pond pollution.
Show the model answer
(a) Goat weed: Ageratum conyzoides – wind (also animals). Siam weed: Chromolaena odorata – wind. Water leaf: Talinum triangulare – explosive/self dispersal (also water).
(b)(i) Physical (any three): topography; soil type/fertility; climate (rainfall); erosion; flooding. (ii) Economic (any three): industrial development; mining; road and building construction; cost of land; urbanisation; tourism.
(c) Any four: kills soil organisms and fish; makes soil and water toxic to crops/animals; lowers soil fertility and crop yield; changes soil pH; reduces oxygen in pond water; contaminates food; makes land unfit for farming.
(d) Any two: proper disposal/treatment of wastes; control use of agrochemicals; laws against dumping and oil spills; recycling; public education.
Give the scientific names in full.