How do fertilizers affect plant growth?

Question

this is for my agriculture assignment for year 10 i need a reply b4 the 31/3/08

Answer 1

The main reason for extra growth is the nitrates the fertilizers put into the soil, helping the plant to grow.

Answer 2

Each nutrient is beneficial as long as its application brings the soil's supply into a more perfect balance with the other elements in the soil, a balance driven by the specific requirements of the plant.

Excess nitrogen will be manifest as a shortage of phosphorus or potassium, or one of the more minor requirements. Excess phosphorus will manifest itself as a shortage of nitrate, unless nitrate too is in excess,

That is to say, we get a healthier plant when all nutrients are in perfect balance, but having them in perfect balance with a lower concentration of all of the elements will give us less production.

Water is in a sense a nutrient also. Plants need water to use the other nutrients, partly to transport the other nutrients, partly as part of the chemistry of the plant. When there is a shortage of water, the plant wil leave more of the  fertilizer in the soil. But with excess water, the soil may or may not retain more of the fertilizer.

A small excess of water may be used by the plant,  what is called luxury use of water. Substantial excess may cause leaching of the fertilizer.

Fertilizer can create the appearance of shortage of elements not supplied in the fertilizer when the fertilizer triggers growth greater than the  amount of the element in the soil can provide.

The amount the soil can provide can be reduced greatly by high pH so that a small addition of sulphate often gives an unexpected boost to a crop in high pH soil, not because the crop neeeded the sulphate but because the sulphate lowered the pH enough to make many other nutrients more available.

That result does not occur when soil has lower ph, (below 7)

Answer 3

Fertilizers typically provide, in varying proportions, the three major plant nutrients (nitrogen, phosphorus, and potassium), the secondary plant nutrients (calcium, sulfur, magnesium), and sometimes trace elements (or micronutrients) with a role in plant nutrition: boron, chlorine, manganese, iron, zinc, copper, and molybdenum.

Answer 4

The previous two answers are correct.  Let me add that it it often necessary to add fertilizers to the soil because crops use up the nutrients as they grow.  This means that over several years, the nutrients in the soil will be depleted unless fertilizer was applied to the soil.  Chemical fertilizers are widely used for this.  Many places use manure.

One also has to be careful that the appropriate amount of fertilizer is applied at various stages of a particular plant's growth.  Too much fertilizer applied at the wrong time could r****d the growth.  Lack of a specific nutrient, e.g. nitrogen, could cause leaves to turn yellow in some crops, greatly reducing crop yield.

Answer 5

These are some basic sites that will answer most of the questions that you have about fertilizer and plant growth. Some cover organic sources of fertilizers as well. Consider all sides of these questions and you will be able to write a great report. Luck.

http://www.howstuffworks.com/question181...

http://edis.ifas.ufl.edu/MG090

http://www.madsci.org/posts/archives/200...

Answer 6

Most of the answers are found correct here. But I offer more descriptions. Fertilizers major, minor and trace elements are involved in the metabolism of plants. Phosporos is impotrant in root growth, enzymatic reactions in plant cells, ATP synthesis, Chlorophyll synthesis etc. Nitrogen is important in vegetative growth. Potash is important in keeping water balance (eg.stomatal opening) and decides quality of foos especially fruits. Many of the crops like cabbage will absorb heavy metals like molybdenom and makes problems in diet.

Any way after soil sample collection ,we test soil for majour nutrients and suggest fertiliser doses required for each and every crop. Absorption of soil nutrients is different in different plants, so fertilizer recommendation is also different. For eg. Rice (Paddy-Oryza sativa) may require N:P:K in the ratio 70: 35:35 or 90:45:45 in many tropical soils while Tapioca(Cassava) requires 100:100:100.

Answer 7

The simple answer is that there are 3 macro-nutrients and a dozen micro-nutrients. Macros are the numbered components associated with each formulation; nitrogen, phosphorus, and potassium in order. There has been a lot of infighting by some in the industry to make it a 4 number system and include calcium equivalent but I never heard anything else about that after leaving school. A simple description of each of the main materials are that nitrogen is for leafy development, phosphorus is for good flower and root development as well as being the main "mover" of energy for plants (and animals), and potassium is for good firm tissues. You can find a lot more on these and the "dirty dozen" in wikipedia on fertilizers. All of the materials that are essential all work together so closely that a deficiency in even the least of them will cause huge issues and unbalance them all. With that no mater how much is used, if anything is missing then nothing else matters. Like you, you can have all the food and air in the world, you will die without water. The best of farmers need as a minimum the ability to see a deficiency and recognize it at a glance, being able to immediately tell it from disease, but that is a quick tool in that samples always need laboratory analysis. "Ashing" a sample of plant material and comparing it to established data will tell a grower to a tiny PPM or PPB just what is lacking, and the presence of resulting disease or damage first seen will have been the tip-off. So check out what each nutrient does, how each works with the others, and the general symptoms of the "lack-ahs". Look in wikipedia but also look at hydroponics as that is where a lot of work was originally done and where it is such a huge part of it's production value (in the solutions).

Answer 8

They provide them with every thing so they would grow

Answer 9

Objectives:

     There are two main objectives of this Mini-teach.  The first is to learn

about the structural components of seeds of higher plants and the functions of

each of these components.  The second is to investigate how fertilizer affects

the growth of plants, particularly of seedlings, and how this relates to seed

structure.  An additional objective is to learn to express and interpret

data/results using graphs.  This lesson is fine for grade levels 3-8, with the

level of sophistication (particularly regarding the data analysis) scaled

appropriately.

Materials Needed:

     Each student will need 10 2 inch (5 cm) pots, enough vermiculite to fill

the pots, several peanuts (preferably raw) and 12 or so (dry) lima beans (other

beans will also work).  For the class, there will also be a need for enough

flats to hold the pots, 10 or more one-gallon plastic jugs, a source of

distilled water, a box of dry fertilizer (such as Miracle Grow), and razor

blades (only for dissection of lima beans, if this is desired, and obviously

only for older students).  A space near a window in the classroom large enough

for the flats is also needed, and magnifying glasses are a help.

Strategy:

First Activity: Investigation of Seed Structure

      This activity works particularly well with raw peanut seeds, but can also

be done with lima beans or other types of beans.  If you use peanut seeds, each

student should shell a peanut and remove the feathery coat on each seed.  The

seed (or peanut) can be seen to have two halves, demarcated by a longitudinal

line all around the seed.  Each student should hold the peanut using both hands

and gently push the two halves apart at this longitudinal line.  The peanut can

then be observed with the naked eye, or with the aid of a magnifying glass.  If

the peanut has been separated successfully, there will be two similarly sized

pieces; these are the "cotyledons" (there are two cotyledons in the seeds of

"dicot" plants like peanuts and beans; other plants ("monocots") have seeds with

only one cotyledon).

     One cotyledon will have, at one end, a small structure that looks like a

tiny plant.  In fact, it is a tiny plant (actually a plant embryo).  Close

examination of the embryo will reveal that it has both leaves and a root.  In

the seed the embryo is in a quiescent state until the seed germinates, at which

time it begins to grow.  Until it grows large enough to manufacture its own food

via photosynthesis, the plant depends on food stored in the cotyledons; the

initial growth of the seedling thus depends on the food stored in the

cotyledon(s).

    The same activity can been done with dry beans, although the cotyledons will

have to be pried apart with a razor blade.  Alternatively, the beans (e.g., lima

beans) can be soaked overnight in water, at which time the seed coat will slip

easily from the seed and the cotyledons will separate easily without need of a

razor blade.

Second Activity: Effects of Fertilizer on Seedling Growth

     Each student should take ten pots and fill each with vermiculite.  It is

important to use a non-nutritive support (i.e., vermiculite) rather than potting

soil, as potting soil has lots of nutrients, which will serve to complicate

interpretation of the results.  In other words, we want to control the amount of

nutrients each plant will get and know what this amount is.  A single dry lima

bean should then be planted into each pot.

     Each student (or group of students) should then prepare fertilizer

solutions for the experiment.  Into each of 5 one-gallon jugs, place one gallon

of distilled water.  Leave one of the jugs with water only (i.e., do not add any

fertilizer to it).  To the second jug, add the amount of dry fertilizer

recommended on the fertilizer box for one gallon of water; mix/dissolve (this

will be "full-strength" fertilizer).  To the third jug add twice the recommended

amount of dry fertilizer, and mix/dissolve.  To the fourth jug add one-half the

recommended amount of dry fertilizer and mix/dissolve.  To the fifth jug add

one-tenth the recommended amount of dry fertilizer and mix/dissolve.

     Each student will have two pots/seeds that will be watered throughout the

course of the experiment with the contents of one, and only one of the five jugs

described in the previous paragraph (e.g., there will be two pots watered with

the water only, two pots watered with the one-tenth strength fertilizer only,

etc.). All pots will be watered on exactly the same schedule and with exactly

the same volume of liquid.  This will ensure that every one of the ten pots will

always get the same amount of water; only the amount of fertilizer that each

gets (from none to double-strength) will vary (because of the varying

concentration of fertilizer (from none to double-strength) in each of the five

jugs).  The first watering should occur just after the seeds are planted;

subsequent waterings should be on an as need basis (i.e., when the vermiculite

is dry).

     Students should record their observations in notebooks.  In particular,

after the seeds have sprouted, they should measure the height of each plant

(using a ruler).  It is very important when recording data to note the date that

those data were recorded (it is also very important to record the date of the

initial planting).

Performance Assessment:

     Regarding the second activity, all of the seedlings will grow initially to

a certain point, because of the food stored in the cotyledons.  Beyond this,

growth is dependent on photosynthesis and nutrients absorbed by the plants'

roots.  The latter is, in turn, dependent on the concentration of fertilizer

added to each plant.

     Thus, we might expect that the seedlings watered with water only (no

fertilizer added) will grow to a certain height and then stop growing, when the

food in the cotyledons is exhausted.  But if the water contains fertilizer, it

should support additional growth.

     The data (seedling height versus days since planting) should be plotted.  

Students should use the resulting graphs to help in interpreting the results of

the experiment, particularly in a quantitative way (e.g., How long is growth

supported by the cotyledons alone?  What percentage of the growth with full-

strength fertilizer is due to the food in the cotyledons?  Is one-tenth strength

fertilizer enough to support as much growth as full-strength fertilizer, and if

not, at least some growth above that due to the cotyledons alone?  Does double-

strength fertilizer afford better growth than full-strength fertilizer?  Does

half-strength fertilizer result in as good growth as double-strength and full-

strength fertilizer?, etc.).

     It may also be helpful for the students to review the first activity as the

second activity is progressing, i.e., to remember what the cotyledons and embryo

look like in the seed before germination, compared to how the seedlings appear

as they are growing.