Soil Science and Fertilizers

When garbage such as leftover food, plant and animals waste is collected in heaps, decomposers such as bacteria, insects such as earthworms and fungi act on it and break it down. This product which is formed by this action of decomposers is called compost. This process is called composting and the compost can be used to increase the plant yield. Thus the correct answer is option C.

Compost  is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At the simplest level, the process of composting simply requires making a heap of wetted organic matter known as green waste (leaves, food waste) and waiting for the materials to break down into humus after a period of weeks or months. Modern, methodical composting is a multi-step, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture. Worms and fungi further break up the material. Compost is rich in nutrients. It is used in gardens, landscaping, horticulture, and agriculture. The compost itself is beneficial for the land in many ways, including as a soil conditioner, a fertilizer, addition of vital humus or humic acids, and as a natural pesticide for soil. In ecosystems, compost is useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover.

Soil fertility can be improved by used fertilizers. Excessive use of chemical fertilizers decreases the soil fertility. Fertilizers like organic manure, vermicompost etc. helps in increasing the soil fertility.

Hydroponics is the method of growing plants without soil. The gravel or sand is used in soilless culture system to provide plant support and retain mineral nutrient and water. 
Thus, the correct answer is option (A). 

When garbage such as leftover food, fruit and vegetable peels, paper and animals waste is collected in heaps, decomposers such as bacteria, insects such as earthworms and fungi act on it and break it down as these components are organic in nature. This product which is formed by this action of decomposers is called compost. This process is called composting and the compost can be used to increase the plant yield. Thus the correct answer is option A.

Compost is an organic matter that has been decomposed for the better growth of crops. Compost is added to the soil so that the plants get sufficient nutrients from the soil. Composts are rich in nutrients.

When the soil is polluted, there is a decrease in the quality and fertility of the soil. The nutrients which were present in the soil has been lost. This results in a reduction in the number of microbes which were inhabited in the soil. So, when there is a decrease in the level of the microbial flora of the soil, it indicates that the soil has been polluted.

The removal or addition of substances and factors which decrease its productivity, quality of plants and ground water is called as soil pollution, reduction in soil productivity due to the addition of undesirable substances is a positive soil pollution and negative soil pollution is the reduction in soil productivity due to erosion and overuse. The neutral pollution mainly caused due to change in the pH of the soil. Thus, the correct answer is option B.

Most soils are naturally fertile but to maintain the fertile nature, fertilizers are needed. Green manure and biofertilizers contains range of nutrients in different proportions which are essential for plants.

Soil contamination is largely driven by the accumulation of non-biodegradable or toxic materials introduced by human activity, such as industrial waste, plastics, and chemicals.

Acid rain introduces acidic compounds into the soil, which alters its chemical balance (pH) and leaches essential nutrients, thereby negatively affecting soil fertility.

The harmful change in the colour, texture, and quality of soil due to addition and removal of any material is called soil pollution. Soil pollution reduces the productivity of the soil. There are several pollutants that cause soil pollution. For example, agricultural wastes, radioactive wastes and discarded materials of hospitals etc. The agricultural waste includes pesticides, insecticides, fertilizers, weedicides etc. These are the chemicals that are involved in changing the pH of the soil. For example, repeated use of fertilizers makes the soil acidic which in turn decreases the productivity of the soil. So, the correct option is C.