Class 9 biology Improvement in food Resources notes

These are the CBSE class 9 biology notes on chapter Improvement in food resources Topics covered in this page are

Manures and fertilizers:

The deficiency of plant nutrients and organic matter in the soil is made up by adding manures and fertilizers to the soil of crop-fields.


  • Manures are natural fertilizers. They are bulky sources of organic matter which supply nutrients in small quantities but organic matter in large quantities.
  • Manures are prepared by the decomposition of animal excreta and plant waste. Manures include farmyard manure (FYM), compost, green manure etc.

Functions or advantages of manure:

  1. Manure helps in enriching soil with nutrients and organic matter and increasing soil fertility.
  2. The bulk of organic matter in manure helps in improving the soil structure. This involves increasing the water holding capacity in sandy soil.
  3. Manures provide food to soil organisms (like bacteria, fungi, etc.) which help in making nutrient available to plants.
  4. In using manure we use biological waste material, which is advantageous in protecting our environment from excessive use of fertilizers.
  5. Manures contain substances which act as stimulants for seed germination and plant growth.

Types of manures:

Based on the kind of biological waste material used, the manures are classified as:
  1. Farmyard manure (FYM): It is the decomposed mixture of cattle excreta (dung) and urine along with litter and leftover organic matter such as roughage or fodder. The waste materials are collected daily from the cattle shed and stored in a pit for decomposition by the microorganisms (bacteria and fungi etc.). FYM contains nitrogen, phosphorous and potassium.
  2. Compost: It is a mixture of decomposed organic matter derived from garbage, sewage, vegetable waste etc. the mixture is decomposed in pits and the process is known as composting.
  3. Vermicompost: The degradation of organic waste through the consumption by the earthworms is called vermicomposting. Earthworms used in vermicomposting are Dichogaster bolani and Drawida willisi.
  4. Green manure: It is prepared by cultivating fast growing green manure crops like Sunhemp, Horse gram, Guar, Cow pea before sowing of seeds. The fast growing crop is then ploughed back under the soil. Green manure enriches the soil with nitrogen, phosphorous as well as organic matter and provides protection against erosion and leaching.


Fertilizers are commonly produced plant nutrients. Fertilizers supply nitrogen, phosphorous and potassium. They are used to ensure good vegetative growth, giving rise to healthy plants.
Type of Fertilizers
Availability of nutrient
Nitrogenous fertilizers
Urea CO(NH2)2, Ammonium sulphate (NH4)2SO4, Sodium nitrate NaNO3
Phosphatic fertilizers
Single superphosphate, Dicalcium phosphate
Potassic fertilizers
Potassium chloride KCl, Potassium nitrate KNO3
Complex fertilizers
Two or more nutrients (N, P2O5, K2O)
Nitrophosphate, Ammonium phosphate
Fertilizers should be applied scientifically in terms of proper dose, pre- and post-application precautions for their utilization. These should not get washed away due to excessive irrigation.


Most agriculture in India is rain-fed, that is, the success of crops in most areas is dependent on timely monsoons and sufficient rainfall spread through most of the growing season. The extra water required by crops is met through irrigation.
The process of supplying water to crop plants through human efforts by means of canal, wells, reservoirs, tube-wells etc., is known as irrigation.

Irrigation systems or Sources of irrigation:

Our country is awarded with large water and land resources with varied climatic conditions under such circumstances, various types of irrigation systems have been adopted to supply water to the agricultural lands. Some most commonly used irrigation systems are the following:
  1. Wells: these are constructed in the region where enough ground water is available. They are of two types- Dug wells and tube wells.
  2. Dug wells: In the dug wells, the water is collected from water bearing strata. From these wells water is lifted by bullock-operated devices or by pumps.
  3. Tube wells: a tube well can tap water from the deeper strata. From these wells, water is lifted by diesel or electricity run pumps.
  4. Tanks: tanks are small storage reservoirs, which catch and store the runoff of smaller catchment areas.
  5. Canal system: This is usually an elaborate and extensive irrigation system. In this system canals receive water from on or more reservoirs or from rivers. The main canal is divided into branch canals having further distributaries to irrigate fields.
  6. River lift system: It is more useful in those areas where canal flow is insufficient or irregular due to inadequate water release. In this system, water is directly drawn from the river for supplementing irrigation.
  7. Other sources are river valley system and Drip and sprinkle system. Fresh initiatives for increasing the water available for agriculture include rainwater harvesting and watershed management.
    • Rainwater harvesting: Rainwater is collected and recycled into ground by digging canals.
    • Watershed management: Small check dams are built up in watershed areas to increase percolation of water into ground, reduce flow of rainwater to prevent soil erosion.

Advantages of irrigation:

Irrigation has many advantages over reliance on natural water supplies:
  1. Water supplied by irrigation supplies hydrogen and oxygen elements to the crop plants.
  2. Irrigation of crops makes the soil moist, which is required for the germination of seeds.
  3. With irrigation, cultivation can be done round the year and during the rainy season only.
  4. Irrigation loosens the soil and thus helps in elongation and growth of roots.
  5. The supply of water by irrigation is regular and reliable, where as rainfall is often seasonal or unpredictable.
  6. Modern multipurpose dams not only provide water for irrigation but also control floods and generate hydroelectric power.

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