Quality assessment of organic manures and their effect on okra
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Date
2018
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Department of Agronomy, College of Horticulture, Vellanikkara
Abstract
The present study entitled “Quality assessment of organic manures and their
effect on okra” was conducted in the Department of Agronomy, College of
Horticulture, Vellanikkara during 2017-2018 to evaluate the properties of organic
manures, and their effect on soil quality and crop productivity.
The physical, chemical and biological properties of organic manures viz., cow
dung (desi), cow dung (cross bred), buffalo manure, goat manure, chicken manure, pig
manure, elephant dung, horse manure, quail manure and vermicompost were studied
in the first experiment. The moisture content was the highest in cow dung (cross bred)
and quail manure (80%). All the manures were neutral to alkaline with a pH ranging
from 7.3 to 8.6 and the electrical conductivity ranged from 0.01 to 0.16 dS m-1. Values
for the highest organic carbon and C: N ratio were recorded in elephant dung (49.12
and 98:1). The N, P and K content of organic manures showed significant variation
among the treatments. Rabbit manure and vermicompost recorded the highest N
(1.8%), while the highest P content was found in pig manure (0.8%), and highest K
content in rabbit manure (1.3%). The highest population of bacteria was found in
chicken manure (35.00 x 104 cfu g-1), while quail manure had the highest fungal
population of 17.00 x 103 cfu g-1.The presence of Escherichia coli was detected in cow
dung (desi and cross bred), chicken manure, pig manure and quail manure. Heavy
metals like Cd, Cr, Ni, Pb, As and Hg were within the safe limit. Mercury and arsenic
exceeded the FCO specifications in goat, rabbit, pig and quail manure. Therefore, these
manures could be used in smaller quantities, instead of bulk application in field. The
heavy metal contents of animal manures depend mainly on the feed consumed and the
efficiency of feed conversion by the animals. The activity of IAA and dehydrogenase
was found to be the highest in vermicompost (17.5 g-1 soil day-1 and 18.11 TPF g-1soil
day -1).
Based on the results of experiment I, all the manures were used for the second
experiment to study their influence on soil quality, growth and yield of okra. All the
manures were applied as basal dose so as to give N equivalent to that in FYM @ 20 t
ha-1. All the other management practices were adopted as per the Adhoc POP
recommendation for organic farming: crops (KAU, 2009) except for Kerala
Agricultural University (Package of practices recommendation) and control.
Application of organic manures increased the water holding capacity of soil by three
per cent whereas there was no significant variation in bulk density. The increase in pH
was the highest in chicken manure treated plots. The organic carbon and available NPK
content in soil increased in all the plots supplied with organic manures. The total
bacteria, fungi and actinomycetes populations were found to be high in all the treated
plots as compared to control. Traces of Ni and Pb were observed in the soil after the
experiment.
Basal application of chicken manure @ 6.9 t ha-1 recorded the highest number
of leaves at 60 DAS (26), total dry matter production at last harvest (5.3 t ha-1), number
of fruits (26.3), weight of fruits per plant (451.79 g), number of seeds per fruit (65) as
well as yield (25.24 t ha-1), resulting in the highest gross and net returns and B: C ratio
(2.34). The lowest crude fibre content (8.4%) in fruits was observed in vermicompost
applied plots.
The results revealed the advantage of application of all the common organic
manures since the quality parameters are according to the specifications prescribed in
the FCO. Application of chicken manure and vermicompost improved the soil quality,
growth and yield of okra.
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