Trees, shrubs, grass, row crops, et cetera all need essentially the same key components for maximizing growth and maintaining a healthy plant. Essential needs for plant growth include water availability, soil drainage, soil aeration, access to sunlight, temperature, soil pH, and availability of essential elements.
Water: Helps to maintain the turgidity of cell walls. it helps in cell enlargement due to turgor pressure and cell division which ultimately increases the growth of the plant.it is also essential for the germination of seeds, growth of plant roots, and nutrition and multiplication of soil organism
Air: The two primary reasons plants need is air to photosynthesize (make food) and to breathe. Plants need to breathe for the same reason people and animals must breathe – they need oxygen to convert food into energy
Sunlight: Without sunlight, plants will not get the necessary food needed to grow, reproduce, and survive. Through a process called photosynthesis, the plants use the energy from the sun to convert carbon dioxide, soil nutrients, and water into food.
Nutrients: Plants need nutrients for the same reasons that animals need them. They need them to germinate, grow, fight off diseases and pests to reproduce. Like animals, nutrients are needed in larger, smaller or trace amounts for the plant to stay healthy.
Adequate spacing: Spacing your plants appropriately reduces the risk of disease in two ways: contagion and an improved immune system. It is easy for disease to spread from one plant to another if the plants are growing on top of one another, so plants growing too closely together are not as healthy as plants with enough space.
Soil pH is directly interconnected. Soil pH is a measure of how acidic or alkaline a soil is. Without the adequate amount of nutrients in the soil plants will become stunted and likely become more susceptible to disease. While the nutrient needs will vary from plant to plant, the important thing to understand is that soil nutrients will not be available for a plant to uptake if the soil pH is not in the correct range. A soil test can determine the nutrient content of the soil as well as the pH.
In 1666, Robert Boyle, An Irish Scientist, proved that rainwater alone will not nourish plants. Proper juices such as present in dung must be added to water to nourish plants.Source: Wikipedia