STATE HIGH SCHOOL
Comparison of fertilizers on plant growth
Year 11 Biology
Year 11 Biology
An investigation was carried out to compare the effect between inorganic and organic fertilizers on plant growth. Tomato seedlings were used, which were divided into 3 groups - the inorganic fertilizer group, the organic fertilizer group and the control group. Besides using different fertilizers, all of the seedlings were planted in the same condition. The result has shown that the plants using organic fertilizer has a faster and healthier growth in contrast to the inorganic group and the control group under the same environmental condition.
All forms of life need energy, food and water, and plants are no exception. Without water, oxygen, carbon dioxide and numerous mineral elements, they would not able to survive. Plants take nutrients from the air, the soil, and the water. Of the minerals, plants need comparatively large amounts of nitrogen, phosphorus, potassium, calcium, magnesium and sulphur, which are called major or macronutrients. Numerous other elements, called micro-nutrients, are also needed in much smaller amounts. (Windridge 2000) The main three ingredients, Nitrogen (N), Phosphorus (P) and Potassium (K), together comprise over 75% of the mineral nutrients found in the plant. These three elements form the main ingredients of most fertilizers. These are marketed as N-P-K fertilizers, which stand for Nitrogen (N), Phosphorus (P) and Potassium (K), or compound fertilizers. They are labelled or named according to the content of these three elements. (Whiting 2009) Fertilizers are chemical compounds spread on or worked into soil to increase its capacity to support plant growth. Fertilizers are categorized into two major types. The two types of fertilizers are organic and inorganic fertilizers. Both fertilizers can provide most nutrients that plants need. Organic fertilizer is made of bio-matter or those that originated in a living organism such as a plant or an animal, including crop residues, livestock manure, green manures, household waste, compost, and woodland litter. Inorganic fertilizer is composed of simple, inorganic chemicals or minerals usually mined from the Earth and either applied as is or combined into one mixture. Inorganic fertilizers vary in appearance depending on the process of manufacture. (Govindarajan 2008) The nutrients needed by plants are taken from the air and from the soil. This publication deals only with the nutrients taken from the soil. If the supply of nutrients in the soil is ample, crops will be more likely to grow well and produce high yields. If, however, even only one of the nutrients needed is in short supply, plant growth is limited and crop yields are reduced. Therefore, in order to obtain high yields, fertilizers are needed to supply the crops with the nutrients the soil is lacking. With fertilizers, crop yields can often be doubled or even tripled, (Alley; Vanlauwe 2009) which is highly significant while the population growth in this century has often outstripped the rather meagre growth in economic and food output. Contamination of water with nitrates and phosphates is the main environmental problem associated with inorganic fertilizer use. The nitrogen from fertilizers and manures are eventually converted by bacteria to nitrates in the soil. These nitrates can be be washed out of the soil surface into streams and rivers or leached into the groundwater. High nitrate levels in drinking water are considered to be dangerous to human health. The phosphorus from inorganic fertilizers cannot be readily washed out of the soil, but is bound to soil particles and moves together with them. Phosphorus can therefore be washed into surface waters together with the soil that is being eroded. The phosphorus is not considered to be dangerous, but in slow moving water, it stimulates the growth of algae. The process of eutrophication...
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