(a) State three functions of nitrogen in crop plants. (b) Mention four effects of excess soil nitrogen and three effects of nitrogen deficiency on plants. (c) Apart from lightning, state three other ways by which nitrogen is added to the soil? (d) List six soil micro nutrients.

(a) Describe briefly four methods of weed dispersal. (b) Describe three mechanical and three cultural methods of weed control. 

(a) In a tabular form, name one fungal disease, one viral disease and one pest of any four of the following crops: (i) citrus; (ii) banana; (iii) tomato; (iv) yam; (v) groundnut. (b) State six general control measures of diseases of crops.

(a) (i) What is culling? (ii) Give three reasons why culling is practised in livestock management. (b) State three advantages and three disadvantages of each of the following management systems in poultry production: (i) deep litter system; (ii) battery cage system. 

(a) Define the term "disease." (b) State the difference between resistance and susceptibility to diseases. (c) Enumerate four economic importance of animal disease. (d) List three factors which determine the degree of resistance of an animal to a disease. (e) Outline three conditions that may inactivate a pathogenic organism.