Agriculture Reference
In-Depth Information
materials and release inorganic and available forms of nitrogen in the soil. While de-
grading organic materials, microorganisms also assimilate some of the major plant
nutrients for the production of their cell and protoplasm (Alexender
1983
).
Similar to nitrogen, phosphorus and potassium are also important inorganic nu-
trients and plays an important physiological role in the accumulation and release
of energy during cellular metabolism. All the element are also added to the soil
either as chemical fertilizers or organic manures and transformed in the soil through
microorganisms. Thus in order to overcome microbial immobilization to increase
the nutrient status of composts and to reduce the time of composting, it was sug-
gested by many workers to enrich the compost with inorganic fertilizers like phos-
phates, rock phosphates, urea, ammonium sulphate or potassium salts to be added
to the crop residues with wide C/N ratio prior to degradation (Gaur
1984
). Craw-
ford (
1983
) reported that composted farm and garden waste contain 0.4 to 3.5 %
nitrogen, 0.3 to 3.5 % phosphorus (P
2
O
5
) and 0.5 to 2.0 % potassium (K
2
O). Vimal
and Talashilkar (
1986
) reported that the normal nutrient content of the farm com-
post (N—0.5 %, P
2
O
5
—0.2 %, K
2
O—0.5 %) is low and imbalanced which makes
the organic manures unsuitable for majority of the crops (Allision
1973
). On the
otherhand, Gaur (
1984
) expressed that the rate and extent of liberation of nitrogen
from applied organic manures is adequate for normal plant growth when their C/N
ratio is less than 10:1 or nitrogen content is more than 2.5 %. Thus the low quality
of manures like dry dung, paddy and groundnut husks, raw dust, tobacco wastes,
wheat straw and any other materials can utilized effectively by the addition of urea
or ammonium sulfate to add 2 % more nitrogen and rise the total nitrogen content
to 2.5 %. In
1952
, Kaila studied on humification used chopped or ground rye straw
supplemented with urea and potassium phosphate. It is interesting in this study that
enrichment results into short term decomposition at higher temperature (50-60 °C)
and obtain better yield of valuable product in short span of time. Das and Khan
(
1967
) observed that when urea was supplied to soil it was hydrolyzed quickly and
the considerable part of ammonia tended to volatilize it into atmosphere but ap-
plication of urea below the surface reduced such loss to a considerable level as evi-
denced by Chattarjee and Maiti (
1977
). The loss of nitrogen was due to leaching de-
nitrification and immobilization. However, organic manures alone cannot meet the
demand of growing crops in the fields. For the maximum production from the high
yielding varieties, the nutrient contents in the leaves must be maintained at desired
level throughout the growth of crops since their yield showed relationship with ni-
trogen content in the leaves and the leaf area duration of the crop from flowering to
maturity. Thus they concluded that the best method of using organic manures was in
conjunction with fertilizers so that organic manures make the nutrients slowly avail-
able to crop and minimize the losses of the organic manures, the efficiency of fertil-
izer use can also appreciably be improved (Lu et al.
2011
). Chakraborty et al. (
2011
)
studied the effect of NPK fertilizers and green manures on soil characteristics.
The organic manures are allowed to decompose in the presence of fertilizers either
applied mineral nitrogen got transformed into amino acids or more green manure
protein could get hydrolyzed providing more amino acid in the presence of fertil-
izers (Boland et al.
2013
).
