NITROGEN DYNAMICS AS INFLUENCED BY LONGTERM EFFECT OF PRESCRIPTION BASED FERTILIZER APPLICATION IN AN ACID ALFISOL
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Date
2014-07-07
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CSHHPKV Palampur
Abstract
The present investigation was carried out in the ongoing long-term experiment on soil test crop
response correlation studies (STCR) initiated during kharif, 2007 at the experimental farm of
Department of Soil Science, College of Agriculture, CSK HPKV, Palampur in randomized block
design with eight treatments comprising control, farmers’ practice, general fertilizer dose,
conventional soil test based fertilizer application and fertilizer application based on STCR
approach with and without FYM for yield targets of 30 and 40 q ha-1
. The soil of the experimental
site was Typic Hapludalf, silty clay loam in texture, acidic in reaction, medium in organic carbon,
low in available N, high in P and medium in K at the initiation of the experiment. Soil samples
(0-0.15m) taken after the harvest of maize (kharif, 2013) were analyzed for different forms of
nitrogen and pH, OC, CEC, microbial biomass carbon and available N, P and K. Grain and stover
yields of maize were recorded and uptake of various nutrients by maize was also worked out after
the plant analysis. Continuous application of chemical fertilizers either alone or in combination
with FYM enhanced the contents of different organic and inorganic nitrogen fractions. However,
prescription based fertilizer application involving conjunctive use of fertilizers and FYM for yield
targets of 30 and 40 q ha-1 proved superior to general fertilizer recommendation as well as
conventional soil test based fertilizer application in influencing various forms of nitrogen.
Likewise, highest contents of OC (8.3 g kg-1
), CEC (13.4 c mol (p+
) kg-1
), microbial biomass
carbon (119.5 mg kg-1
), available N (282 kg ha-1
), P (61 kg ha-1
) and K (279 kg ha-1
) were found
under STCR (IPNS) based treatment for target yield of 40 q ha-1 which ultimately, resulted in the
highest productivity of maize (37.6 q ha-1
). In general, the contribution of different organic as
well as inorganic forms of nitrogen viz., hydrolysable ammonical-N, amino acid-N,
serine+threonine-N, hexosamine-N, unidentified-N, non hydrolysable-N, ammonical-N and
nitrate-N, towards the total-N was 24.3, 24.4, 5.4, 7, 23, 6.4, 5.5 and 3.6 percent, respectively.
Continuous cropping without fertilization resulted in depletion in hydrolysable ammonical-N,
amino acid-N, serine+threonine-N, hexoseamine-N, unidentified-N and non-hydrolysable-N to
the extent of 24, 17, 23, 3.6, 12 and 8 per cent, respectively. Hydrolysable ammonical-N
exhibited highest correlation with available N (r=0.882) and accounted for 78 percent variation in
available N. Hydrolysable ammonical-N recorded highest correlation with grain yield (r=0.898)
and accounted for about 88 per cent of the variation, whereas, amino acid-N showed the highest
correlation with stover yield (r=0.902) and accounted for about 81 per cent of the variation.
Different fractions of nitrogen were found to be positively and significantly correlated with one
another except non hydrolysable-N.