Plant Nutrition

Plant nutrients are chemical elements that are essential for plant growth and reproduction.. For an element to be essential, it must be required for a plant to complete its life cycle, it must be required by all plants, and no other nutrient can replace this requirement fully. If an element does not meet all of these requirements,
for example, being required by some plants or only enhancing the growth of plants, the
element may be a beneficial element. Much interest in plant nutrition lies in the development and
use of diagnostic techniques for assessment of the status of plants with respect to plant nutrients and
beneficial elements.
A plant nutrient is a chemical element that is essential for plant growth  Essential
element is a term often used to identify a plant nutrient. The term nutrient implies essentiality, so it
is redundant to call these elements essential nutrients. Commonly, for an element to be a nutrient,
it must fit certain criteria. The principal criterion is that the element must be required for a plant to
complete its life cycle. The second criterion is that no other element substitutes fully for the element
being considered as a nutrient. The third criterion is that all plants require the element. All the
elements that have been identified as plant nutrients, however, do not fully meet these criteria, so,
some debate occurs regarding the standards for classifying an element as a plant nutrient. Issues
related to the identification of new nutrients are addressed below (click)

http://biology4isc.weebly.com/1-mineral-nutrition.html

http://biology4isc.weebly.com/uploads/9/0/8/0/9080078/____________how_plants_obtain_nutrients.swf

Tomato crop guide: Dynamics of nutritional requirements
 
Nitrogen and potassium uptake is initially slow but rapidly increases during the flowering stages. Potassium is peaking during fruit development, and nitrogen uptake occurs mainly after the formation of the first fruit. Phosphorus (P) and secondary nutrients, Ca and Mg, are required at a relatively constant rate, throughout the life cycle of the tomato plant.
Read more. 

Tomato crop guide: Dynamics of nutritional requirements

Why do farmers use FERTILIZERS?

Farmers use fertilizer to prime their soil for optimal plant growth. Important components of plant growth are lost when plants use them. Fertilizer restore these important elements.


The most important component of fertilizer is the nitrogen it contains. Plants need a significant amount of nitrogen to grow, and they cannot absorb it through the air. Farmers test their soil for nitrogen levels and use fertilizer with the right amount to let their plants grow as quickly as possible.
Fertilizer contains other important elements as well. Phosphorous and potassium are important for cellular function, and low levels stunt plant growth. Calcium, magnesium and sulfur are also contained in most fertilizer. Manure is sometimes used to increase the nitrogen levels of soil, but it lacks many of the other chemicals plants need.
In the wild, plants that die decompose on the ground and leave behind the elements they absorbed while they were alive. Farming, however, requires removing plants after they have grown. Soil health is an essential part of farming, and small oversights can be disastrous for farmers and for food supplies. While older farming techniques might mitigate some of the soil harm from large-scale farming, modern agriculture depends on fertilizer to prevent food shortages and famines.

What are the advantages and disadvantages of fertilizers?

Fertilizers can expedite plant growth and provide economic benefits to farmers and nurseries, but they can also introduce toxic substances into the environment. Fertilizers make plants and crops grow more quickly and appear greener, fuller and healthier. However, they often contain synthetic chemicals, which do not biodegrade upon entering surrounding waterways and the atmosphere.

Fertilizers, when used in agricultural facilities and commercial greenhouses, can significantly boost output and appeal. Fertilizers work by providing plants and crops with nutrients they need to grow to their fullest and at a faster rate than achieved through natural processes alone. Chemical-based fertilizers, according to Edublogs, can also help protect plants and vegetation from pests and may prevent the spread of weeds as well. Fertilizers may also be more cost effective and time efficient for gardeners and commercial farmers as well. Many fertilizers are inexpensive to produce, and purchasing them to encourage plant growth instead of buying high-quality soil may save significant amounts of money. However, fertilizers have disadvantages as well. One of the main concerns over fertilizers is that they require frequent reapplication. Furthermore, they contain synthetic (and often harmful) chemicals that pollute streams, lakes and the atmosphere when released. Fertilizers may cause cumulative harmful effects on humans, animals and environments, such as contaminated water supplies and spread of illness.

What are artificial fertilizers?

Artificial fertilizers are man-made chemical compounds that mimic the soil's natural minerals and elements to maximize plant growth. They usually contain different ratios of nitrogen, phosphorus, potassium, calcium, magnesium and other elements.

There are two types of fertilizers: artificial and organic. Artificial fertilizers are convenient, easy to use and readily available in local gardening stores. They immediately supply consistent amounts of precise nutrients to the soil, which is especially helpful for reviving dying or severely malnourished plants. Organic fertilizers include biofertilizers, green manure, organic manure and compost. While natural fertilizers take longer to build soil vitality, they are safer and cause no pollution.
Throughout most of history, agriculture has relied on natural fertilizers to increase the nutrient levels of soil. The release of artificial fertilizers in the late 19th century increased crop yields and launched the agricultural revolution.
Despite its advantages, artificial fertilizers kill beneficial microorganisms in the soil that convert plant and animal remains into nutrient-rich organic matter. They also leach nitrogen and phosphate into groundwater and pollute streams, rivers, lakes and other water bodies to disrupt aquatic ecosystems. Plants grown from synthetic fertilizers contain toxic nitrates that react with hemoglobin to damage the vascular and respiratory systems and cause suffocation and even death in extreme cases. Over time, artificial fertilizers destroy the soil’s natural makeup. Too much fertilizer produces plants deficient in iron, zinc, carotene, vitamin C, copper and protein.
Individuals can minimize the negative effects of artificial fertilizers by mixing them with the soil well enough to prevent rain runoff. Diluting it prevents burning plants. Synthetically grown fruits and vegetables require a thorough wash before eating. Individuals must keep unused fertilizer away from water, pets and children.

You can gain more knowledge on above topic by reading the following article (Click the title to read).

Why do farmers use fertilizers? I’ve heard that fertilizers can have negative effects. Why do farmers use fertilizers?