Biomedical Engineering Reference
In-Depth Information
(3) Bio-based fertilizers
①
Biofertilizer technology
In agriculture, since long ago, farmers have known that feces and urea, waste
garbage, and discarded leaves and other materials can be converted into fertilizer
through composting. These fertilizers can provide plenty of soil humus and nutri-
ents. Its main roles are the following:
(a) It improves the physical properties of the soil, making the soil soft and porous
and increasing its water retention properties.
(b) The cation exchange capacity of humus is much higher than fore clay; thus, N,
P, and K elements and other nutrients can be adsorbed by humus, enhancing the
ability of nutrients to be maintained in the soil.
(c) The chelation of some ingredients in humus can reduce the hazards of heavy
metals on crops.
(d) Compost is a slow-released fertilizer. Nitrogen in the compost almost exists in
the form of protein. When it is released to the field, the protein slowly breaks
down into ammonia or other forms of salts available to the crops.
(e) Compost is rich in microorganisms. Compost can increase the microbial content
of soil. A variety of active ingredients produced by microorganisms can be
directly or indirectly available to plants and play a useful role.
Although composting has many advantages, since the 1960s, with increasing
demands for food caused by the growth of China's population, chemical fertilizer
has played a key role in agriculture. Large-scale use of chemical fertilizers not only
caused environmental pollution but also brought about serious soil compaction and
soil fertility decline. Therefore, converting garbage, agricultural and forestry wastes,
a variety of organic sludge, as well as human and livestock feces into compost-
based materials and preparing highly efficient organic compound fertilizers through
various means have significance in both agriculture and environmental benefits.
Meanwhile, in rural areas, a large number of crop stalks, such as wheat straw,
rice straw, cornstalks, and other fiber crops, are stacked in the fields or combusted in
situ combustion, which not only induces fires and seriously pollutes the environment
but also wastes resources. Therefore, in recent years, the comprehensive utilization
of crop straw has become a hot topic for scientists around the world. In recent
years, to solve problems of soil compaction and nutrient depletion of the land
caused by excessive use of fertilizers and pesticides, many countries adopted
bioorganic fertilizer, such as yeast organic fertilizer, EM microbial organic fertilizer,
HM microbial organic fertilizer, and so on. According to the determination of
the National Collection of Type Cultures, various types of microbial organic
fertilizers in parts of China actually are a variety of microorganisms, and multiple
microorganisms combined with organic matter (such as feces, weeds, straw, etc.) can
be fermented to generate organic ecological fertilizer. The main miocroorganisms in
various types of composite microflora are roughly the same, about 80 % of the yeast
group and lactic acid bacteria, actinomycetes, bacillus, fungi, and photosynthetic
microorganisms, with more than 80 kinds of microorganisms.
