State two ways in which weeds are economically important and describe eight methods used in water harvesting.

You're on a roll — Here are the answers to your questions: 16. c) State two ways in which the weed is economically important (source of employment). (2 mks) i) Weeds create employment opportunities* for manual laborers involved in weeding, either by hand or using simple tools. ii) The manufacture and sale of herbicides and weeding tools* provide employment and generate income for industries. SECTION C: 17. A) Describe eight methods used in water harvesting (8 mks) i) Roof catchment*: Collecting rainwater from rooftops and storing it in tanks or cisterns. ii) Surface runoff harvesting*: Collecting rainwater that flows over land surfaces, often directed into ponds, dams, or reservoirs. iii) In-situ water harvesting*: Practices that aim to retain water where it falls, such as contour farming, terracing, and construction of small bunds or ridges. iv) Sub-surface dams*: Underground structures built across seasonal riverbeds to store water in the sand, reducing evaporation. v) Rock catchments*: Utilizing natural rock outcrops to collect and channel rainwater into storage facilities. vi) Pans and micro-catchments*: Small depressions or structures designed to collect water around individual plants or small groups of plants. vii) Farm ponds/dams*: Excavating or constructing large depressions to collect and store surface runoff for irrigation or livestock. viii) Roadside runoff harvesting*: Collecting water that flows along roadsides and diverting it to agricultural fields or storage. B) Describe nine ways in which biotic factors influence agricultural production (9 mks) i) Pests*: Insects, mites, and other organisms directly damage crops and livestock, reducing yields and quality. ii) Diseases*: Pathogens (bacteria, fungi, viruses) infect crops and livestock, causing illness, reduced productivity, and death. iii) Weeds*: Compete with crops for nutrients, water, light, and space, leading to reduced crop yields. iv) Pollinators*: Insects (e.g., bees) and other animals are essential for the pollination of many crops, directly impacting fruit and seed set. v) Beneficial organisms*: Predators and parasites of pests help control pest populations, reducing crop damage. vi) Soil microorganisms*: Bacteria, fungi, and other microbes decompose organic matter, cycle nutrients, and improve soil structure and fertility. vii) Livestock*: Provide products (meat, milk, eggs), manure for fertilizer, and draught power, contributing to agricultural output. viii) Humans*: Provide labor, management, and technological innovation, directly influencing all aspects of agricultural production. ix) Wildlife*: Can damage crops (e.g., birds, rodents, elephants) or livestock (e.g., predators), leading to losses. C) Describe the preparation of green manure (3 mks) Green manure involves growing specific crops (e.g., legumes like lucerne, clover, or non-legumes like oats) for a period. These crops are then ploughed or tilled into the soil while still green and succulent*. This process adds organic matter, nitrogen (especially from legumes), and other nutrients to the soil, improving its fertility and structure. 18. A) Explain 5 cultural methods of weed control (10 mks) i) Crop rotation*: Alternating different crops in a sequence disrupts weed life cycles, preventing the build-up of specific weed species adapted to a particular crop. ii) Timely planting*: Planting crops at the optimal time allows them to establish quickly and outcompete weeds for resources. iii) Proper spacing*: Planting crops at appropriate densities ensures good canopy cover, shading out weeds and reducing their growth. iv) Mulching*: Applying a layer of organic or inorganic material on the soil surface suppresses weed growth by blocking sunlight and physically impeding emergence. v) Hand weeding/hoeing*: Manually removing weeds from the field using hands or simple tools, effective for small areas or specific weeds. vi) Cover cropping*: Growing non-cash crops to cover the soil, which suppresses weeds, prevents erosion, and can add organic matter. vii) Use of clean planting material*: Ensuring that seeds or vegetative propagules are free from weed seeds prevents the introduction of new weeds into the field. viii) Field sanitation*: Removing and destroying weed residues after harvest prevents them from producing seeds or regrowing. B) Explain the factors considered when selecting planting material (10 mks) i) Purity*: The planting material should be free from weed seeds, other crop seeds, inert matter, and pathogens to ensure a uniform and healthy crop. ii) Germination percentage*: A high germination rate ensures a good stand establishment and reduces the need for replanting. iii) Adaptability to ecological environment*: The planting material should be suited to the local climate, soil type, and other environmental conditions to thrive. iv) Resistance to pests and diseases*: Selecting varieties that are resistant or tolerant to common pests and diseases in the area reduces crop losses and the need for chemical control. v) Yield potential*: The chosen variety should have a high potential for yield under good management practices to ensure profitability. vi) Maturity period*: The planting material should have a suitable maturity period that fits the growing season and market demands. vii) Market demand*: The crop produced from the planting material should be in demand in the market to ensure good prices and sales. viii) Cost and availability*: The planting material should be affordable and readily available in sufficient quantities. ix) Quality of produce*: The planting material should produce high-quality produce that meets consumer preferences and standards. C) What is chitting in potatoes? (2 mks) Chitting* is the process of encouraging potato tubers to sprout or produce short, sturdy shoots (chits) before planting. This is typically done by exposing the tubers to light and cool temperatures, which helps to break dormancy and promotes earlier and more uniform emergence and higher yields after planting. 19. A) Describe five field management practices for onions (5 mks) i) Weed control*: Onions are poor competitors with weeds, so regular weeding (manual or chemical) is crucial, especially during early growth stages. ii) Fertilizer application*: Onions require adequate nutrients, particularly nitrogen for leaf growth and potassium for bulb development. Fertilizers should be applied based on soil test results. iii) Pest and disease control*: Monitoring for common pests (e.g., thrips, onion maggots) and diseases (e.g., downy mildew, purple blotch) and applying appropriate control measures. iv) Irrigation*: Onions need consistent moisture, especially during bulb formation. Regular and adequate watering is essential, avoiding waterlogging. v) Thinning*: If direct-sown, seedlings may need to be thinned to achieve optimal plant spacing for proper bulb development. vi) Top dressing*: Applying additional fertilizer during the growing season to meet the crop's nutrient demands. B) State five disadvantages of communal land tenure system (5 mks) i) Lack of individual incentive*: Individuals may not invest in long-term land improvements as they do not have exclusive ownership rights. ii) Overgrazing/overuse*: The "tragedy of the commons" can occur, leading to degradation of shared resources due to lack of regulation and individual responsibility. iii) Difficulty in obtaining credit*: Without individual title deeds, farmers cannot use land as collateral for loans, limiting access to capital. iv) Land disputes*: Ambiguous boundaries and shared rights can lead to frequent conflicts among community members. v) Resistance to innovation*: Introducing new farming techniques or crops can be difficult due to the need for collective agreement. vi) Inefficient land use*: Land may not be utilized to its full potential due to lack of clear individual management plans. C) Describe 10 safety measures a farmer should observe when using herbicides (10 mks) i) Read and follow label instructions*: Always adhere to the manufacturer's guidelines for mixing, application rates, and safety precautions. ii) Wear appropriate Personal Protective Equipment (PPE)*: This includes gloves, protective clothing (long-sleeved shirts, long pants), eye protection (goggles), and a respirator or mask. iii) Calibrate equipment*: Ensure spraying equipment is properly calibrated to apply the correct dosage and avoid over-application. iv) Avoid spraying in windy conditions*: Wind can cause drift, leading to herbicide exposure to non-target areas, crops, or individuals. v) Mix herbicides in a well-ventilated area*: Prevent inhalation of fumes during mixing. vi) Do not eat, drink, or smoke while handling herbicides*: This prevents accidental ingestion. vii) Store herbicides safely*: Keep them in their original containers, clearly labeled, in a locked, cool, dry place away from children, unauthorized persons, food, and animal feeds. viii) Dispose of empty containers properly*: Follow local regulations for disposing of herbicide containers, often involving triple rinsing and puncturing. ix) Wash thoroughly after use*: Wash hands and exposed skin with soap and water immediately after handling herbicides. x) Observe re-entry intervals (REI)*: Do not allow people or animals to enter treated areas until the specified re-entry interval has passed. xi) Avoid contamination of water sources*: Prevent herbicides from entering rivers, ponds, or wells during mixing, application, or disposal. xii) Keep a record of application*: Document the date, herbicide used, application rate, and weather conditions. 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