In
India, diversity exists in the quality and quantity of natural resources
and their distribution with respect to time and space. For example,
India hosts 15% of the animal population, which, apart from supplying
milk and draught power in agricultural operations, contributes valuable
plant nutrients as supplement to the fertilizer nutrients. Indian
cattle, however, have different genetic make up compared to the those in
developed countries. They are smaller in size with lower body weight,
low in milk production and adapted to the different climatic conditions
and different feeding habits besides their different heritage.
Consequently, the different types of manures, derived under such varying
environments do differ in their physical and chemical composition due
to the differences in the type of animal used to produce dung, animal
density, nutrient density of the feed material, type of work an animal
is put to use and management factors. IISS, Bhopal developed a database
at district level of dung produced and manure availability alongwith its
composition.
Even though the human population is increasing at an alarming rate, the
cattle population growth is almost stagnant. This is evident from the
animal census data of 1997 and 2003 which show a cattle population of
198 and 185 million, respectively. This decrease is primarily due to a
decrease in indigenous cattle. The buffaloes population has increased
from 89 to 98 million but this is not sufficient to compensate the
decrease in cattle population. This shows that the dung manure
availability in the country is also not increasing and is estimated to
be at around 1.5 tonnes/ha of net cultivated area. An allowance of 15%
could be made in this if the dung manure available from other animals
like goats, sheep, poultry, horses, pigs etc are included. The total
dung manure available would be around 1.7 t/ha. The total N,
P2O5, and K2O supply is estimated to be
around 1.5, 1.0, and 1.8 million tonnes, respectively for the whole
country. In addition, based on 2006-07 crop year data, we have estimated
an availability 0.22, 0.16, 0.36 million tonnes of N, P2O5, and K2O
respectively from crop residues, assuming only 5% of the residue would
be recycled in agriculture and rest would be consumed as cattle feed,
burnt or in future might go in for energy generation. Also, some N would
be added through symbiotic and free living nitrogen fixers. The
addition through green manure crops is estimated to be 0.11 million
tonnes. It is estimated that 5-14 million tonnes of compost can be
prepared from municipal solid waste depending upon the method of
composting. This could at maximum add 0.1,0.06, and 0.09 million tonnes
of N,
P2O5, and K2O.
The first estimate of nutrient removal by crops was made by National
Commission on Agriculture (NCA). At a foodgrain production of 82 million
tonnes in 1961, the total N+P205+K20
removal was estimated to be 9.5 million tonnes, including the nutrient
removal by other crops. The figure of nutrient removal for 1971 was 12.3
million tonnes at a production level of 108 million tonnnes of
foodgrain. Based on these nutrient removal data, it was found that there
was a net negative balance of N,
P2O5, and K2O to the tune of 8-10
million tonnes during 60s, 70s, and 80s if only the additions through
fertilizers are taken in computation. This was true for the three
decades. However, this got slightly changed thereafter, owing to a
lesser growth rate in the agricultural production than was projected
but, the application of fertilizer nutrients continued to increase at a
higher rate. For the year 2006-07, we estimated a total nutrient removal
of 10, 4.2. and 12.4 million tonnes of N,
P2O5, and K2O, respectively at a
foodgrain of 217 million tonnes. The additions through fertilizers were
13.8, 5.5, and 2.3 million tonnes of N,
P2O5, and K2O, respectively. This leaves a net negative balance of 5.0 million tonnes of N,
P2O5, and K2O and this again is due
to a heavy negative balance in case of potassium. The total nutrient
imbalance would be corrected to some extent if we include the nutrient
additions through dung manures (4.3 million tonnes of N,
P2O5, and K2O from cattle and
buffaloes) and crop residues (0.74 million tonnes). However, this does
not mean that our soils are adequately fertilized/manured. There are
several areas in Rajasthan, Gujarat, and Madhya Pradesh where the
balancc is negative in case of N. Similarly, even P balance is negative
in some districts of Uttar Pradesh, Madhya Pradesh and Kerala and K
balance is negative in almost 80 per cent districts in India. A higher
growth rate in agriculture is expected in future which would accentuate
the problem further if careful attention is not paid in the areas where
the net budget is negative. These nutrient budgets are only apparent in
nature because they do not take into consideration the nutrient
additions through natural processes like rainfall, irrigation water,
sedimentation from upper reaches and also the losses of nutrients
through leaching, volatilization, run off etc. It is important that work
is initiated in this direction to compute such additions and deletions
so that we could reach to a better understanding of region specific
nutrient budgets to guide us in managing the plant nutrients.
India is endowed with variable climates, different strata of farmers
ranging from marginal to large practicing variable crop and nutrient
management options. These factors change the nutrient recovery from the
applied manure. There is a need to compile the manure preparation and
handling practices in different parts of the country specific to
different situations. The amount and type of the animal feed is
important w.r.t. the milk yield and manure nutrient composition. A
compilation of the crop residues and its composition used as cattle
feed, the availability of concentrated feed material (manufactured and
imported) and composition of different cattle feed, the region- specific
availability of grazing land and amount and type of pasture, the amount
of feed depending upon the type and age of animal is important for
determining not only the quantity and quality of manure but also will be
helpful in computing enteric methane emission coefficients from animals
and methane emission potential of manures.
The availability of fertilizer nutrients (both major and micro) is
important for making an overall assessment of region-specific nutrient
availability in India. Also, the nutrient requirement of crops vary
depending upon the crop species, varieties (hybrid vs. local) and also
with the change in climatic and management conditions. The region
specific nutrient mining data taking into account type of crop, yields
obtained, the amount of residues removed and the partitioning of
nutrients into the above and below ground plant parts will help in
assessing the nutrient balances in different agro-ecoregions. There is
need to establish a connectivity by compiling all the information of
nutrient management with the quantity and quality of nutrients available
from different sources in different regions and management practices so
as to suggest the possible guidelines in the direction of improved
nutrient management. It is important to compile, synthesize and process
the nutrient region- specific information and present it into a user
friendly database as also in the form of spatial maps so that the
information could be used by many.
A. Subba Rao
IISS
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