Phosphorus is one of the least available and the least mobile mineral nutrients in soil for plant growth. However, it is vital for plants and they absorb only inorganic form of phosphorous but the level of inorganic phosphorus is very low in soil because most of the phosphorous is present as insoluble forms. Unlike nitrogen, there is no large atmospheric source that can be made biologically available to plants. P chemical fertilizer is widely applied in agricultural production. However, a large proportion of these fertilizers are also converted to insoluble form leads to low-fertilizer efficiency where the volume of phosphatic fertilizers as low as 15-20% are only utilized by plants due to fixation of P in acidic and alkaline soils.
Phosphorus deficiency is the most important problem of Ethiopian soils and more than 70-75% of highland soils are characterized by phosphorus deficiency. Around 70% of Ethiopian vertisols have available phosphorus below 5 ppm, which is very low for supporting good plant growth; and, fixation in vertisols is related more to calcium, than Al3+ and Fe3+. Yield is usually low under traditional farming system because of poor cultural practices that is compounded with poor soil fertility.
Insecticides are a class of pesticides used to
kill, harm, or repel different species of insects. They act in different ways
in organisms based on their active ingredients. For instance, corn plantations
commonly use insecticides that have organophosphates and carbamate as the
active ingredient, which acts on the enzyme acetylcholinesterase within an
insect nervous system. In many cases, these standard insecticide products are
being phased out for a new class of insecticide known as neonicotinoids, which use
nicotine as the active ingredient. Neonicotinoid compounds interact withnicotinic acetylcholine receptors (nAChR) of the central nervous systems ofinsects. Nicotine acts in an insect’s system in the same way that it acts in
the human body. However, neonicotinoids are more toxic for invertebrates than
they are to mammals, birds and other higher organisms.
Neonicotinoids became
popular because of their high water solubility, which makes their soil
application travel through the entire plant. Nowadays, neonicotinoids are one
of the most widely used class of insecticides for controlling sucking insects
and soil insects. In 2004, the worldwide annual usage of neonicotinoids was
approximately 11-15% of the total insecticides in the market. Differentgenerations of neonicotinoids have been created over time. They have the sameprinciple of action in the nervous system; however, the specific active
ingredients are different. The first generation of this pesticide class used
was 1-(6-chloro-1,3-thiazol- 5-ylmethyl)-1,3,5-oxadiazinan-4-ylidenene(nitro)amine,
known as Imidacloprid. It was first registered for use in the United States by
the United States Environmental Protection Agency in 1994.
Endorhizospheric bacteria also known as endophytic bacteria
that resides within living plant tissues without substantially harming plants
have found a large number of applications in today’s agriculture such as
nutrient cycling, tolerance to biotic and abiotic stress as well as promotion
ofplant growth. In present study an attempt has been made to test biodiversity ofendophytic plant growth promoting bacteria from different plant species. As
nitrogen fixation is one of the prime mechanism of plant growth promoting
activity exerted by microorganisms, endophytic nitrogen fixing bacteria were
isolated from from surface sterilized plant parts viz. root, stem and leaves of
species Cynodondactylon (Durva), Pothosscandens (Money plant), Ipomeabatata
(Sweet potato), Saccharumofficinarum (Sugarcane) cv. CO.LK-8001 and CO.-84135,
Musa paradica (Banana) and Zea mays (maize)cv. GM-6 by using nitrogen free
media selective for growth of nitrogen fixing bacteria. In all total 10
isolates were obtained from different plant species and parts and showed
variation in their biochemical and physiological characteristics. All the
isolates were found to fix nitrogen and nitrogen fixation rates of all the
isolates ranged from 4.0 to 36.3 mg N fixed/gm of sugar consumed. Moreover,
they also showed solubilizing tri calcium phosphate in Pikovskaya’s broth.
