CBSE Class 9 Science Chapter 15: Improvement in Food Resources NCERT Solutions

Solution: We obtain essential nutrients from various food groups:

1. Cereals: These are a primary source of carbohydrates, which are vital for providing energy to our bodies. Examples include wheat, rice, and maize.
2. Pulses: Pulses, such as lentils, beans, and peas, are rich in proteins, which are essential for growth and repair of body tissues.
3. Fruits and Vegetables: These are excellent sources of vitamins and minerals, which play crucial roles in various bodily functions, including immunity and metabolism. They may also contain small amounts of proteins, carbohydrates, and fats.

Solution: Both living (biotic) and non-living (abiotic) factors can significantly impact the yield and success of crop production.

Biotic Factors: These include living organisms that can harm crops. Pests (like insects that feed on plants), nematodes (microscopic worms that damage roots), and various diseases caused by fungi, bacteria, or viruses can reduce the net crop production. Weeds also compete with the main crop for essential resources like nutrients, sunlight, and space, thereby lowering productivity.

Abiotic Factors: These are non-living environmental conditions. Factors such as extreme temperatures (too hot or too cold), salinity (high salt content in soil or water), and water availability (droughts or waterlogging) can adversely affect plant growth. Natural calamities like floods and droughts are unpredictable abiotic events that can sometimes lead to the complete destruction of crops.

Solution: Desirable agronomic characteristics are specific traits that breeders aim for when improving crop varieties to enhance productivity and suitability for cultivation. Key characteristics include:

1. For Fodder Crops: Tallness and profuse branching are desirable. Taller plants with more branches can yield more fodder for livestock.
2. For Cereals: Dwarfness is often a desirable trait. Shorter plants are more resistant to lodging (falling over) due to wind and rain, and they often allow for more efficient use of nutrients and sunlight, leading to higher grain yields.

Developing crops with these characteristics helps in increasing overall food and fodder production.

Solution: Macro-nutrients are essential mineral elements that plants require in relatively large quantities for their healthy growth, development, and metabolic functions. They are called macro-nutrients precisely because of the substantial amounts needed by the plant. There are six such essential macro-nutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S).

Solution: Plants obtain a total of sixteen essential nutrients required for their growth and development from their environment. These nutrients are sourced from three primary places: air, water, and soil.

The major source of nutrients for most plants is the soil, which provides thirteen of the sixteen essential nutrients. The remaining three crucial nutrients – carbon (C), oxygen (O), and hydrogen (H) – are obtained by the plants from air and water through processes like photosynthesis and transpiration.

Solution: Both manure and fertilizers are used to enrich the soil and improve crop production, but they differ significantly in their composition, effects, and impact on soil health.

Manure: Manure is an organic substance prepared from the decomposition of animal excreta and plant waste. Its use enriches the soil with organic matter and essential nutrients. Organic matter improves soil structure, increases water-holding capacity, and promotes the activity of beneficial soil micro-organisms. This leads to a sustainable improvement in soil fertility over time.

Fertilizers: Fertilizers are typically inorganic compounds produced industrially, containing specific plant nutrients like nitrogen, phosphorus, and potassium. While they provide nutrients quickly and can boost crop yields in the short term, their excessive use can be detrimental. Overuse can harm beneficial symbiotic micro-organisms in the soil, disrupt the soil's natural balance, and potentially lead to a decrease in long-term soil fertility and environmental pollution.

In summary, while fertilizers offer a quick nutrient boost, manure provides a more holistic and sustainable approach to maintaining and improving soil fertility.