Page 20 - Introduction to Agriculture by: Aqleem Abbas

Introduction to Agriculture Notes prepared by: Aqleem Abbas

An organism or cell or a group of organisms or cells produced asexually from one
ancestor to which they are genetically identical. E.g. by vegetatively i.e. cutting,
budding, grafting, layering.

 Line
It is also called if it is produced (by seed)

It is produced by pure breeding that is self pollinated. E.g. called pure line.

Open pollinated variety

They are reproduced by cross pollination in field. It is done automatically. E.g. maize

Hybrid variety

It is created artificially or manually by controlled crosses. Cross pollination should be
done each time to develop hybrid. It is more vigorous form.

FERTILIZER COMPOSITION AND MEASUREMENT FOR
AGRONOMIC CROPS

Fertilizer, natural or synthetic chemical substance or mixture used to enrich soil so as to promote
plant growth. Plants do not require complex chemical compounds analogous to the vitamins and
amino acids required for human nutrition, because plants are able to synthesize whatever
compounds they need. They do require more than a dozen different chemical elements and these
elements must be present in such forms as to allow an adequate availability for plant use. Within
this restriction, nitrogen, for example, can be supplied with equal effectiveness in the form of
urea, nitrates, ammonium compounds, or pure ammonia.

Virgin soil usually contains adequate amounts of all the elements required for proper plant
nutrition. When a particular crop is grown on the same parcel of land year after year, however,
the land may become exhausted of one or more specific nutrients. If such exhaustion occurs,
nutrients in the form of fertilizers must be added to the soil. Plants can also be made to grow
more lushly with suitable fertilizers.

Of the required nutrients, hydrogen, oxygen, and carbon are supplied in inexhaustible form by air
and water. Sulfur, calcium, and iron are necessary nutrients that usually are present in soil in
ample quantities. Lime (calcium) is often added to soil, but its function is primarily to reduce
acidity and not, in the strict sense, to act as a fertilizer. Nitrogen is present in enormous quantities
in the atmosphere, but plants are not able to use nitrogen in this form; bacteria provide nitrogen
from the air to plants of the legume family through a process called nitrogen fixation. The three
elements that most commonly must be supplied in fertilizers are nitrogen, phosphorus, and
potassium. Certain other elements, such as boron, copper, and manganese, sometimes need to be
included in small quantities.