any one knows please answer it of question 8 and 9
Answers
Step-by-step explanation:
8:-The necessary conditions required to hear an echo are: There needs to be a minimum distance between the observer and the obstacle and that is equal to 17 m in the air. This distance may vary from medium to medium depending upon the sound's speed in that particular medium.
9:-(i)Green manure is a term used to describe specific plant or crop varieties that are grown and turned into the soil to improve its overall quality. A green manure crop can be cut and then plowed into the soil or simply left in the ground for an extended period prior to tilling garden areas
(ii)A biofertilizer is a substance which contains living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant.
Answer:
answer 9 :-- a) Green manure is a cover crop sown on an agricultural plot in order to fertilize the soil for the following crop mainly through the intake of nitrogen. ... Green manure consists of legume-based cover crops.
b) Biofertilizers are the substance that contains microbes, which helps in promoting the growth of plants and trees by increasing the supply of essential nutrients to the plants. It comprises living organisms which include mycorrhizal fungi, blue-green algae, and bacteria.