General Q&A for Class 12 · Page 71
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Why is Crop Rotation Done?
Crop rotation offers multiple agricultural, economic, and environmental benefits: Restores soil fertility: Different crops use nutrients differently. Legumes (peas, beans, lentils) have root nodules with nitrogen-fixing bacteria that convert atmospheric nitrogen into soil nitrogen, naturally replenishing this essential nutrient. When cereals (which deplete nitrogen) are alternated with legumes, soil fertility is maintained without excessive fertilizer use.</li
- GeneralClass 12All
What is meant by harvesting? Name two tools used in India for harvesting. What is Harvesting?
Harvesting is the agricultural process of cutting and gathering mature crops from fields when they have reached optimal maturity for maximum yield and quality. This critical operation marks the culmination of the entire crop production cycle. Proper timing is essential—harvesting too early results in immature, low-quality produce with poor nutritional value and market price, while delayed harvesting causes grain shedding, pest damage, weather-related losses, and quality deterioration.</
- GeneralClass 12All
What is Sowing?
Sowing is the agricultural process of planting seeds in prepared soil at appropriate depth, spacing, and time to initiate crop production. Proper sowing ensures that seeds receive optimal conditions for germination, including adequate moisture, oxygen, and soil contact, while being protected from birds, pests, and environmental stress. The timing and technique of sowing significantly influence crop establishment, growth uniformity, and ultimate yield. Various Methods of Sowing
- GeneralClass 12All
Why is Irrigation Necessary?
Irrigation plays a critical role in agriculture for multiple essential reasons: Insufficient or irregular rainfall: Many regions receive inadequate rainfall or experience erratic rain patterns that cannot meet crop water requirements. Irrigation fills this deficit, enabling agriculture in areas that would otherwise be unsuitable for farming. Seasonal water availability: Even in regions with adequate annual rainfall, water may not be
- GeneralClass 12All
What is Irrigation?
Irrigation is the artificial application of water to agricultural land to supplement natural rainfall and provide crops with adequate moisture for growth. It involves systematically supplying water to fields through various methods like canals, wells, tube wells, sprinklers, or drip systems based on crop requirements, soil type, and climate conditions.
- GeneralClass 12All
Write correct sequence of steps undertaken for farming.
The systematic sequence of farming operations ensures optimal crop production: Soil Preparation Ploughing/tilling to loosen and turn the soil Leveling the field for uniform water distribution Adding manure or compost to enrich soil fertility Selection of Seeds Choosing high-quality, disease-resistant seeds appropriate for the season and region</
- GeneralClass 12All
Explain the factors which are responsible for loss of grains during storage.
rain losses during storage can be substantial, sometimes reaching 20-30% if proper precautions aren't taken. The main factors responsible include: Biotic Factors (Living Organisms): Insect pests: Grain weevils, beetles, and borers infest stored grains, feeding on kernels and contaminating grain with excreta and body parts. Common pests include rice weevils, pulse beetles, and grain borers that reduce both quantity and quality.<
- GeneralClass 12All
What are weeds? Name any one weed found in a crop field. What are Weeds?
Weeds are unwanted plants that grow naturally in cultivated fields alongside desired crops, competing for essential resources. These plants are considered undesirable because they: Compete with crops for water, nutrients, sunlight, and growing space Reduce crop yields by stealing resources needed for optimal crop growth Harbor pests and diseases that can spread to cultivated plants Interfere with harvesting operations and reduce crop quality
- GeneralClass 12All
Describe the sprinkler system of irrigation. State its advantages. What is a Sprinkler System?
A sprinkler irrigation system distributes water through a network of pipes that spray water into the air, which then falls on crops like artificial rainfall. The system consists of a main pipeline connected to a water source (pump or reservoir), lateral pipes with rotating sprinkler heads, and nozzles that create a spray pattern covering the field uniformly. Advantages of Sprinkler Irrigation: Water efficiency: Saves 30-50% more water c
- GeneralClass 12All
Which is the best time for the removal of weeds?
The best time for weed removal is before they produce flowers and seeds, ideally when weeds are still young and small. Early removal is crucial because weeds compete most aggressively with crops during their initial growth stages. Removing weeds before flowering prevents them from setting seeds that would create future weed problems, as a single weed plant can produce thousands of seeds. The most effective approach is to weed regularly throughout the crop's growth cycle, part
- GeneralClass 12All
Why do farmers carry out leveling of ploughed fields?
Field leveling after ploughing addresses several practical challenges that would otherwise reduce crop productivity and create management difficulties throughout the growing season. Uneven fields create water distribution problems during irrigation—water accumulates in depressions while elevated areas remain dry, leading to uneven crop growth. Some plants receive excess water and may suffer from waterlogging and root diseases, while others experience drought stress. This irregul
- GeneralClass 12All
Explain why seeds should be sown at the right spacing.
Proper seed spacing is fundamental to maximizing crop potential, as it determines how efficiently each plant can access the resources necessary for optimal growth and productivity. When seeds are sown too closely, severe competition arises for essential resources—sunlight, water, nutrients, and space. Overcrowded plants develop weak stems as they stretch toward light, producing smaller leaves and reduced photosynthetic capacity. Root systems become intertwined and stunted, unabl
- GeneralClass 12All
What is maximum population growth rate in logistic growth models?
The maximum population growth rate in logistic growth occurs at a specific point: when the population size equals exactly half the carrying capacity (N = K/2). At this inflection point, the population adds the greatest absolute number of individuals per time unit, even though the per capita growth rate is decreasing. The formula for maximum growth rate is: dN/dt maximum = rK/4. For Spotted Fritillary butterflies with carrying capacity K = 500 and r =
- GeneralClass 12All
How do births and deaths affect population growth calculations?
Births and deaths are the primary demographic processes driving population change. The net effect of these processes determines whether a population grows, shrinks, or remains stable. To estimate population growth, you calculate: population change = births - deaths, then divide by the initial population size and time period to get r. Consider the June beetle example: with 400 births and 150 deaths per month in a population of 3,000, the net increase is 250 individuals
- GeneralClass 12All
What is the practice of growing legumes as fodder in one season and wheat in the next season known as?
This agricultural practice is called crop rotation. Specifically, when farmers alternate between leguminous crops (like alfalfa, clover, or berseem) and cereals (like wheat) in successive seasons, it represents a well-planned rotational system designed to maintain soil health and productivity. Crop rotation is one of the oldest and most effective sustainable farming techniques, practiced for centuries across different agricultural systems. In Northern India, this part
- GeneralClass 12All
What are the advantages of sowing seeds using a seed drill instead of the traditional method?
Seed drills represent a significant advancement over traditional broadcasting methods, offering precision and efficiency that directly translate to better crop yields and resource management. The primary advantage of seed drills is uniform seed placement at consistent depths and spacing. This precision ensures that each seed receives adequate space, sunlight, nutrients, and water without competing with neighboring plants—a common problem with hand-sowing where seeds often cluste
- GeneralClass 12All
Why is tilling of the soil carried out before sowing seeds?
Tilling, also known as ploughing, is a crucial preparatory step that transforms soil into an ideal environment for seed germination and plant growth. This practice serves multiple essential purposes that directly impact crop success. When farmers till the soil, they break up compacted earth, creating a loose and aerated structure that allows plant roots to penetrate deeply and spread efficiently. This loosening process also improves soil porosity, enabling better water infiltration an
- GeneralClass 12All
How accurate are population growth predictions?
Population growth predictions are mathematical models that simplify complex ecological realities. Their accuracy depends on several factors: data quality, assumption validity, and environmental stability. Exponential models assume unlimited resources and constant growth rates—conditions that rarely persist in nature—so they're most accurate for short-term predictions or populations well below carrying capacity. Logistic models incorporate resource limitations but assume ca
- GeneralClass 12All
How do you apply population growth models to real-world species management?
Applying population growth models to species management requires combining mathematical frameworks with biological knowledge and monitoring data. For endangered species, managers use r calculations to assess whether populations can recover naturally or need intervention. If r is negative or only slightly positive, active conservation (habitat restoration, captive breeding, predator control) may be necessary. For harvested populations (fisheries, fores
- GeneralClass 12All
Why is understanding population doubling time important for human populations?
Understanding human population doubling time is critical for planning infrastructure, resource allocation, and sustainable development. When the 1995 human population was projected to double in 50 years, this implied r = 0.693 / 50 = approximately 0.0139 per year (about 1.39% annual growth). A doubling population means doubling demand for food, water, housing, energy, healthcare, and education—within a single human generation. This challenges governments to expand services, citi