Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Compost: Its Microbiology and Disease Management
C.M. Mehta and A. K. Sharma
Department of Biological Sciences, C.B.S.H., G.B.P.U.A.&T. Pantnagar- 263 145 (UK)
Compost is organic matter that has been decomposed and recycled as a fertilizer and a
key ingredient in organic farming. Composting is a biological process in which various organic
biodegradable wastes are converted into hygienic, humus rich product (compost) which could be
used as a soil conditioner and an organic fertilizer (Popkin, 1995). Composts of various origins are
also used to provide biological control against various plant pathogens (Hoitink and Grebus, 1994).
The addition of composts to agricultural soils has beneficial effects on crop development and
yields by improving soil physical and biological properties (Zheljazkov and Warman, 2004). Poultry
manure application in Java citronella plants, significantly increased the herbage, essential oil
content and dry matter yield (Adholeya and Prakash, 2004). Compost is also an inhabiting place
for various microbes due to which biological activities are markedly enhanced in the rhizosphere of
plants (Tilak and Reddy, 2006). Such syntrophic associations are of ecological importance with
implied agricultural significance. Aqueous extracts of compost have also been efficient in replacing
synthetic fungicides (Zhang et al., 1998). Utilization of compost with disease suppressive
properties is a relatively new biological way of decreasing stress in plant production.
Steps Involve in Composting Process
Composting process involves four different steps viz., (a) Decomposition: breakdown of
plant and animal remains into stable organic materials, (b) Humification: conversion of organic
matter into humus (resistant to microbial attack), (c) Immobilization: microbial tie up of inorganic
molecules into their own cells and (d) Mineralization: microbial release of inorganic ions (nutrients
like nitrate, ammonium and phosphate).
Types of Composting
There are three different types of composting, according to its nature. First is Aerobic
composting, where air directly involve in composting process. In this process, high nitrogenous
waste (like grass clippings or other green material) helps bacteria to grow and create high
temperatures (up to 160 degrees). This result, break down of organic waste quickly and is not
prone to smell. This type of composting requires high maintenance, since it needs to be turned
every couple days to keep air in the system and temperatures up. It is also likely to require
accurate moisture monitoring. This type of compost is good for large volumes of compost. Second
is Anaerobic composting where composting process completed without air. Anaerobic composting
is low maintenance but this process took a couple years. In this type of composting a pile was
made by stack of debris. It generally compact to the point where there is no available air for
beneficial organisms to live. Very slow working bacteria grow in these piles that do not require air.
It may take years to break down of raw material in compost. Anaerobic composts create the awful
smell. Third is Vermicomposting which is most beneficial for composting food waste. Along
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