ICAR AIEEA PG Practice Set 1

Explanation: Liebig's Law of the Minimum states that plant growth is controlled not by the total amount of resources available but by the scarcest resource (the limiting factor). It was proposed by Justus von Liebig in 1840.

Explanation: A pedon is the smallest volume of soil that can be called a 'soil'. It is a three-dimensional body large enough to study the nature and arrangement of horizons, typically 1-10 m² in area and extending to the depth of the soil profile.

Explanation: Vermiculite has the highest CEC among clay minerals (100-150 cmol(+)/kg) due to its 2:1 expanding lattice structure with isomorphous substitution, which creates a large number of negative charge sites on the clay surfaces.

Explanation: The permanent wilting point is the soil moisture content at which plants can no longer extract water from the soil and wilt permanently. It corresponds to a soil moisture tension of approximately 15 bars (−1500 kPa or pF 4.2).

Explanation: Azotobacter is an aerobic, free-living, heterotrophic nitrogen-fixing bacterium commonly found in neutral to alkaline soils. It can fix 20-40 kg N/ha/year and also produces growth-promoting substances.

Explanation: Contour bunding involves constructing bunds (embankments) along the contour lines of a slope. It is most effective on gentle slopes (up to 6% gradient) in low-rainfall areas where it retards runoff, increases infiltration, and reduces soil erosion.

Explanation: N.I. Vavilov, a Russian botanist and geneticist, proposed the concept of 'Centres of Origin' of cultivated plants (1926). He identified eight primary centres of diversity where most crop plants originated.

Explanation: Allopolyploidy (amphiploidy) involves the combination and doubling of chromosome sets from two different species through hybridisation followed by chromosome doubling. Bread wheat (Triticum aestivum, 6x = 42) is a natural allopolyploid.

Explanation: Narrow-sense heritability (h²) is the ratio of additive genetic variance (VA) to the total phenotypic variance (VP). It is more useful than broad-sense heritability for predicting response to selection because only additive variance is transmitted from parents to offspring.

Explanation: The pedigree method is most suitable for self-pollinated crops such as wheat, rice, and pulses. Individual plant selections are made in segregating generations (F2 onward) and their progeny records (pedigree) are maintained to trace superior lines.

Explanation: CMS provides a natural mechanism to prevent self-pollination, eliminating the need for manual emasculation (removal of anthers) in the female parent. This greatly reduces the cost and labour of hybrid seed production in crops like rice, sorghum, and sunflower.

Explanation: Bt cotton contains the cry gene (cry1Ac, cry2Ab) from the soil bacterium Bacillus thuringiensis. This gene produces Bt toxin (Cry protein) which is lethal to bollworm larvae (Lepidoptera), providing built-in insect resistance.

Explanation: The safe moisture content for storage of wheat grain is 12% (or below). At higher moisture levels, fungal growth, insect activity, and grain respiration increase, leading to quality deterioration and storage losses.

Explanation: IPM is an ecosystem-based strategy that uses a combination of biological, cultural, physical, and chemical methods to manage pests, keeping them below the Economic Threshold Level (ETL) while minimising environmental and health risks.

Explanation: Lepidoptera is the insect order that includes butterflies and moths. Their larvae (caterpillars) are major crop pests. Key agricultural pests in this order include bollworms, armyworms, and stem borers.

Explanation: Late blight of potato is caused by Phytophthora infestans, an oomycete. This disease was responsible for the Irish Potato Famine (1845-1849). It causes rapid destruction of foliage and tuber rot under cool, humid conditions.

Explanation: Citrus canker is a serious bacterial disease caused by Xanthomonas citri (syn. X. axonopodis pv. citri). It produces raised, corky lesions on leaves, stems, and fruit, leading to fruit drop and reduced market value.

Explanation: Bordeaux mixture is a protective contact fungicide made from copper sulphate (CuSO₄) and lime (calcium hydroxide, Ca(OH)₂) mixed in water. It was first used by Millardet in 1885 against downy mildew of grapevine in Bordeaux, France.

Explanation: The Benefit-Cost Ratio is calculated as the ratio of gross returns (total revenue from the farm enterprise) to total cost of production. A B:C ratio greater than 1 indicates that the enterprise is profitable.

Explanation: The Minimum Support Price (MSP) is announced by the Government of India on the recommendation of the Commission for Agricultural Costs and Prices (CACP). MSP is declared for 22 mandated crops and fair and remunerative price (FRP) for sugarcane.

Explanation: The Training and Visit (T&V) system was introduced in India in 1974 (started in Rajasthan) with financial and technical support from the World Bank. Developed by Daniel Benor, it emphasised regular training of extension workers and scheduled visits to contact farmers.

Explanation: Rejuvenation pruning involves heading back old, unproductive mango trees by cutting main branches at 1.5-2.0 m from the ground. It restores vigour and productivity in senile trees by inducing new vegetative growth that eventually becomes productive.

Explanation: The recommended spacing for tomato transplanting is 60 cm × 45 cm (row to row × plant to plant) for determinate varieties and 75-90 cm × 60 cm for indeterminate varieties. This allows adequate sunlight, air circulation, and space for cultural operations.

Explanation: Wheat is a cereal (field crop), not a plantation crop. Major plantation crops include tea, coffee, rubber, coconut, oil palm, and cocoa. Plantation crops are perennial, grown on large estates, and are typically export-oriented.

Explanation: Jersey cattle produce milk with the highest butterfat content (4.5-5.5%) among major dairy breeds. Although their total milk yield is lower than Holstein, the higher fat percentage makes their milk preferred for butter and cheese production.

Explanation: The TDN system measures the sum of the digestible portions of crude protein, crude fibre, nitrogen-free extract, and ether extract (fat × 2.25, since fat yields about 2.25 times as much energy as carbohydrate). It gives the overall energy value of a feed.

Explanation: HTST (High Temperature Short Time) pasteurisation involves heating milk to 72°C for 15 seconds followed by rapid cooling. This kills most pathogenic bacteria while preserving milk quality and nutritional value. The older LTLT method uses 63°C for 30 minutes.

Explanation: A commercial layer hen reaches peak egg production at about 28-30 weeks of age and the standard laying cycle lasts approximately 72 weeks (about 18 months from first egg to end of production cycle), after which production drops and the flock may be culled or moulted.

Explanation: Foot-and-mouth disease is caused by an Aphthovirus of the family Picornaviridae. It is a highly contagious viral disease affecting cloven-hoofed animals, characterised by fever and vesicles in the mouth and on the feet. Seven serotypes (O, A, C, SAT1-3, Asia1) exist.

Explanation: A balanced ration for a lactating dairy cow should contain approximately 16-18% crude protein on a dry matter basis. Protein is essential for milk production, body maintenance, and reproduction. Deficit leads to reduced milk yield and poor body condition.