Fishes are good for health because they are highly nutritious and rich in vitamin-A and vitamin-D. They are an important source of animal food in coastal areas.

Paddy requires a lot of water. So, it cannot be grown in winter season. It is grown only in the rainy season.

Agriculture is the applied branch of biology which involves the practice of cultivating crops as well as rearing animals.

(i) Manures are organic substances while fertilizers are chemical substances.
(ii) Manures are prepared in fields, while fertilizers are prepared in factories.
(iii) Manures contain all the nutrients, while fertilizers are rich in certain nutrients.
(iv) Manures provide humus, while fertilizers do not provide it.

If despite favourable climatic conditions, farmer's crop failed to give good yield, the possibilities may be
(i) he did not use good quality and healthy seeds.
(ii) his field was not well irrigated.
(iii) manures/fertilisers were not timely and properly applied.
(iv) weeds were not removed.
(v) seeds were not sown at appropriate distance.
(vi) the soil was not ploughed and levelled properly.

Various agricultural practices are as follows:
(i) Preparation of soil The first step is preparation of soil. The soil is loosened and turned up. It helps the plants to grow and develop. The process of lossening and turning of the soil is called tilling or ploughing. Sometimes manure is added to soil before tilling.
(ii) Sowing After preparation of soil, the second step called sowing takes place. Before sowing good quality seeds are selected. The seeds should be clean and healthy.
(iii) Adding manure and fertilisers Soil supplies minerals and nutrients to the crops. These nutrients are essential for growth of plants. Sometimes these nutrients are lacking, so substances are added to maintain or to replenish the soil. These substances are called manures and fertilisers. Manures and fertilisers are essential to increase the crop production
(iv) Irrigation The process of watering the crop plants is called irrigation. Plants take all the nutrients and minerals in dissolved form. So, water is most essential for germination of seeds, growth and development of plants.
(v) Harvesting After maturation of crop, it is cut off. This process is called harvesting. It is done by a sickle or by a machine called harvester.
(vi) Storage Storage of product is one of the most important tasks. To keep the grains for longer time, it should be safe from moisture, pest, insects and other microorganisms.

The ability of soil to supply all the essential plant nutrients to a crop in adequate quantity is called soil fertility. Repeated growing of crops in the same soil removes various nutrient elements from the soil due to which the soil loses its fertility.
The soil fertility can be replenished or regained by the following methods:
(i) By keeping the field fallow (uncultivated) for one or two seasons.
(ii) By putting manures and fertilisers in the soil.
(iii) By practising crop rotation .
(iv) By practising multiple cropping (mixed cropping).