Science M.C.Q. [I MARKS]

In a field many other undesirable plants may grow naturally along with the crop. These undesirable plants are called weeds. The removal of weeds is called weeding. Weeds are also controlled by using certain chemicals, called weedicides.

Weedicides are sprayed during the vegetative growth of weeds 'before' flowering and seed formation. Rest, all the statements are correct.

Organic manure are obtained from decomposition of plant and animal wastes that are rich in nutrients and humus. But all nutrients might not be present in a proportionate amount in it, thus will not solve the problem if soil is particularly deficient in one or more specific nutrient.

Option a is correctly suggesting the harmful effects of weeds. Weeds are the undesirable plants that grow along the main crops. Removal of weeds is necessary because they interfere and affect the major crop’s growth, by competing for light, water, nutrients and space. They also interfere during harvesting procedure. Weeds do not help in healthy growth of crop plants.

Fertilisers are not environment friendly as they are chemical substances rich in particular nutrient, Though, they increase the crop yield, the repeated and excessive use of fertilisers in the same field reduces the soil fertility, It also pollutes water bodies as they get dissolved and washed away by rain and also seeps in the water table posing threats to humans.

Turning and loosening soil are two most important steps in soil preparation. The process of turning brings deep layer of soil that is rich in nutrients to topmost layer or topsoil. Loosening of soil allows roots to easily penetrate the soil and also helps in growth of earthworms and microbes that in turn help in formation of humus.

The process of loosening and turning of soil is called tilling and ploughing. It is the first step, in preparation of soil for cultivation of crop. Ploughing is done using a plough, made of wood or iron.

Drip irrigation is a technique in which water flows through a filter into special drip pipes. It helps in releasing water drop by drop into the soil near the roots of plants. In contrast to other types of irrigation systems such as overhead sprinklers, water can be more precisely applied to the plant roots. If designed, installed and managed properly, this method contributes greatly to water conservation by reducing evaporation.