(a) What are the major sources of water pollution in India ? What are the ways to check it ? (10 marks) (b) What are the basic…

(a) Water pollution in India: sources and control (10 marks)

Major sources. Point sources: untreated or partly treated domestic sewage from towns, which is the largest load on rivers, and industrial effluents from tanneries, textiles, distilleries, sugar, paper and chemical units carrying organic matter, heavy metals and toxic chemicals. Non-point sources: agricultural runoff with fertilisers (nitrate and phosphate, causing eutrophication) and pesticide residues, urban storm runoff, mining and oil spills, solid waste dumped in water, and thermal discharge from power plants. Groundwater also carries geogenic fluoride and arsenic.

Ways to check it:

• Treatment of sewage in sewage treatment plants, and of industrial effluent in effluent treatment plants, with zero liquid discharge for the most polluting units.
• Enforcement of the Water (Prevention and Control of Pollution) Act, 1974 through the CPCB and State Pollution Control Boards, with the polluter-pays principle.
• Integrated nutrient and pest management, and buffer strips, to cut agricultural runoff.
• River programmes such as Namami Gange, reuse of treated water, and rainwater harvesting.
• Monitoring and public awareness.

(b) Farming system and indigenous farming systems (10 marks)

Basic concepts. A farming system is a resource-management strategy that integrates crops, livestock, fish, trees and other enterprises, along with the farm household, to gain higher and sustainable income from limited resources. Its concepts are: the system and its sub-systems with a boundary; inputs and outputs, with recycling of by-products (straw to cattle, dung to crops); interaction and synergy among components; diversity and risk spreading; resource-use efficiency; the farm household as the decision-making unit; and sustainability and stability.

Three indigenous systems:

• Shifting cultivation (jhum) in the North-East: forest is cut and burned, mixed crops are grown for one to three years, and the plot is then left fallow.
• Homestead or home-garden system of Kerala and coastal areas: multi-storeyed combinations of coconut, arecanut, spices, fruit trees, vegetables and livestock.
• Apatani rice-fish culture of Arunachal Pradesh: fish reared in irrigated paddy fields, with bunds carrying crops, needing no fertiliser.

(c) Tree species suitable for agroforestry (10 marks)

Suitable species share the following characteristics: fast growth and a short rotation; multiple uses (fodder, fuel, timber, fruit, green manure); nitrogen fixation; deep taproot, which avoids competition with crops; light or narrow crown that allows sunlight through; ability to coppice and to withstand lopping; tolerance of drought, salinity or waterlogging as the site requires; and freedom from allelopathic effect and from harbouring pests.

Examples: Leucaena leucocephala (subabul), a fast-growing nitrogen fixer giving fodder and fuel, for alley cropping; Gliricidia sepium, for green manure and live fences; Prosopis cineraria (khejri) of arid areas, a nitrogen fixer giving pods and lopped fodder; Dalbergia sissoo (shisham) and Populus deltoides (poplar) for timber on farm boundaries, poplar with winter crops as it sheds its leaves; Azadirachta indica (neem) for oil cake and pest control; Casuarina equisetifolia for coastal sands; Acacia nilotica, Albizia lebbeck, Melia dubia and Grevillea robusta (shade for tea and coffee).

(d) Dissemination of weeds (10 marks)

Weeds spread by:

• Wind: light seeds with a pappus or wings, such as Tridax procumbens, Parthenium hysterophorus, Sonchus and Typha.
• Water: irrigation channels and floods carry seeds and vegetative parts, as in Eichhornia (water hyacinth), Alternanthera and rice weeds.
• Animals and birds: seeds with hooks or spines cling to fur (Xanthium, Achyranthes, Cenchrus), or pass through droppings after being eaten (Lantana).
• Man and machinery: contaminated crop seed, such as Phalaris minor in wheat seed and Cuscuta in lucerne, implements, vehicles and imported grain (Parthenium came with imported wheat); unrotted farmyard manure.
• Vegetative propagules: tubers and rhizomes spread by tillage, such as Cyperus rotundus and Cynodon dactylon.
• Explosive fruit dehiscence, as in Oxalis and Euphorbia hirta. Prevention therefore relies on clean seed, quarantine, cleaning machinery, composted manure and clean irrigation water.

(e) Secondary nutrients: functions and deficiency symptoms (10 marks)

The secondary nutrients are calcium, magnesium and sulphur.

Calcium: forms calcium pectate of the cell wall and middle lamella, keeps membranes intact, and helps cell division, root growth and enzyme activation. It is immobile, so deficiency shows in young tissues: stunted, distorted new leaves, death of growing tips, poor root growth, blossom-end rot of tomato and "pops" in groundnut.

Magnesium: the central atom of chlorophyll and an activator of enzymes of phosphate transfer (ATP-related). It is mobile, so interveinal chlorosis begins on older leaves, with leaf margins later turning red or purple; grass tetany appears in animals.

Sulphur: a component of the amino acids cysteine and methionine, proteins, coenzyme A, vitamins (biotin, thiamine), and mustard oils and glucosinolates, raising oil content. It is immobile, so a pale yellow chlorosis affects young leaves first, with thin stems and delayed maturity; "tea yellows" is an example.