NCERT Solutions For Class 9 Science Chapter 15
Improvement in Food Resources

Abiotic and biotic factors play a significant role in storage losses.

Abiotic factors such as moisture and temperature of the storage area and moisture content of the stored grain Biotic factors like insects, rodents, fungi, mites and bacteria. Both the factors cause degradation in quality, loss in weight and poor germinability of grains.

Manure and fertilisers are used in the field to enrich the soil with the required nutrients. Manure helps in enriching the soil with organic matter and nutrients whereas fertilisers add chemical substances that are rich in nitrogen, phosphorus and potassium. Adding fertilisers and manures improve the fertility and the structure of the soil and ensures a healthy growth and development in plants. It is advised to use a balanced combination of manure and fertilisers in the soil to get a good yield.

For increasing production common activities in poultry, fisheries and bee keeping that should be followed are;

1. Proper and regular cleaning of farms
2. Providing good quality of nutritious food  
3. Proper care and protection from diseases and enemies (predators)

Cattle farming is one of the methods of animal husbandry that is most beneficial to the farmers. Benefits of cattle farming are;

1.  Quality and quantity of milk can be obtained
2. New varieties that are resistant to diseases and  are very robust to be used for agricultural work can be produced  by crossing two varieties with the desired traits

Good animal husbandry practices benefit farmers in the following ways:

1. The economic value of the animals increases when proper shelter and protection from pests and diseases is given.
2. Yield of animals produce such as meat, egg, milk, fur, etc increases when good animal husbandry practices are taken into consideration.
3. Improved breeds of the animal are obtained by good animal husbandry practices.

Crop rotation is one of the methods of crop production that ensures high yield. In this method, two or more varieties of crops are grown on the same land in sequential seasons. Every crop has some specific requirement of nutrients from the soil. If the same crop is grown in the subsequent seasons in a particular field, the field will be deficient in those nutrients that are specifically required by the growing crop. To avoid this, crops having different nutrient requirements are grown in subsequent seasons. For example, legumes which have nitrogen fixing bacteria in their root nodules supply the soil with nitrogen. Therefore, these legumes are rotated with nitrogen requiring cereals such as wheat and maize. This method reduces the need of fertilisers, thereby increasing the overall yield of crops.

Genetic manipulation is a process where a foreign gene from one cell (for a particular character) is introduced into the chromosome of another cell. When the gene for a particular character is introduced in a plant cell, a transgenic plant is produced. These transgenic plants exhibit characters directed by the newly introduced genes.

For example, let us assume there is a wild plant that produces small flowers. If the gene responsible for larger flower size is introduced in this wild plant, this plant would become transgenic, and would produce larger flowers. Similarly genes for higher yield, disease resistance, etc can be introduced in any desired plant. Gene manipulations play following important roles in agricultural practices.

1. Improves crop variety
2. Ensures food security and insect resistant crops
3. Improves the quality and yield of crops.

Intercropping and crop rotation both play an important role in increasing the yield of crops.

        Advantages of intercropping:

1. Prevents the pests and diseases to spread throughout the field,
2. Maintains soil fertility,
3. Reduces the use of fertilisers and
4. Controls the growth of weeds

       Advantages of crop rotation:

1. Prevents soil depletion
2. Increases soil fertility
3. Reduces soil erosion,
4. Reduces the use of fertilisers, and
5. Controls the growth of weeds