Agriculture Reference
In-Depth Information
Keywords:
Biofertilizers, PGPR, Mycorrhiza,
Azospirillum
,
Rhizobium
, Biological fertilizer,
Organic fertilizer, Chemical fertilizer, Integrated Plant Nutrition System
I
NTRODUCTION
Biofertilizers, also known as bioinoculants, microbial inoculants or soil inoculants are
agricultural biotechnology products that contain living or dormant microorganisms (bacteria
or fungi, alone or in combination) that are added to agricultural crops to boost their growth
and productivity.
The term ―biofertilizer‖ derives from the words, biological and fertilizer, so that it refers
to a biological fertilizer. In this context, a biofertilizer contains living microorganisms that
have the capacity for improving the nutritional status of the plants. Conversely, organic
products such as manure, crop residues, compost and vermicompost, which are also added to
the crops to improve their nutrition, are not considered as biofertilizers but as
organi
c
fertilizer
; although they indeed contain microorganisms, their identity and concentration
normally remain unknown.
Due to the relative novelty of this technology in México and to the great impulse the
government has settled for promoting the use of the biofertilizers in the Mexican agriculture
many companies try their products be considered as biofertilizers, despite they do not meet
the basic requirement of having axenically grown microorganisms. Also, in the worst cases
these products can contain pathogenic microorganisms not only for plants but also for animals
and the human being itself.
Currently, there are good perspectives for using biofertilizers as a mean to reduce
pesticides and increase crop production, because the ever rising prices of the chemical
fertilizers and cumulating evidence for environmental degradation caused by the use of
agrochemicals is leading agricultural producers to look for cheaper and safer production
practices not only for organic but also for conventional agriculture. Within these strategies, it
is very important to consider an integrated plant nutrition system based on the use of low
doses of chemical fertilizers, application of organic fertilizers (compost, vermicompost) and
inoculation of microorganisms possessing capacities for improving the assimilation of the
nutrients contained in chemical and organic fertilizers. In this chapter we will review the
benefits and mechanisms by which the microorganisms can improve the nutrient and health
status of the plants and show the advantages of considering an integrated plant nutrition
system for crop production.
C
LASSIFICATION OF
B
IOFERTILIZERS
The microorganisms possess a wide diversity of mechanisms by which they promote
plant growth. Based on these mechanisms we recognize four major groups of plant growth
promoting microorganisms:
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