SITE SPECIFIC AND DYNAMIC NITROGEN MANAGEMENT IN RICE
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Date
2013
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
The present investigation entitled “Site specific and dynamic nitrogen
management in rice (Oryza sativa L.)” was carried out during kharif season 2012 to study
the effects of different dynamic nitrogen management options and performance of rice crop
in terms of yield and N use efficiency and to arrive at a best N management option. The
experiment was conducted in randomized complete block design with eight treatments
replicated thrice. The treatments include recommended fertilizer dose (T1), soil test based
fertilizer application (T2), SPAD chlorophyll meter based approach i.e., apply N30 if SPAD
value < 37(T3), < 39 (T4) and < 41 (T5) and LCC based approach i.e., apply N30 if LCC
reading < 4.0(T6), < 4.5 (T7) and < 5.0 (T8).
The experimental field was neutral in reaction, non saline in nature and medium in
organic carbon, low in available nitrogen, medium in available phosphorus and potassium.
The N received by the crop under different treatments ranged from 90 to 210 kg ha-1
in 3 to 7 splits. The effects of different treatments were evaluated in terms of rice grain
yield, nutrient uptake, N use efficiency and B:C ratio. Leaf samples were analyzed for
nutrient composition (N, P and K) at every 10 days intervals up to flowering stage, grain
and straw samples at harvest and nutrient uptake was computed. The lowest N dose of 90
kg ha-1 was received in T3 in 3 split applications and the highest N dose of 210 kg ha-1 was
received in T8 in 6 splits. In general SPAD and LCC values increased gradually from
initial tillering stage to flowering stage.
Nitrogen content in leaves also increased up to flowering and was significantly
influenced by different N management options. Highest N content of 3.7% in leaves was
observed in T8 at flowering. The highest grain yield of rice (5879 kg ha-1) was recorded in
T7 (N30 if LCC value < 4.5) which received 180 kg N ha-1 in 6 splits but was found on par
with T5 (N30 if SPAD value < 41) which received 180 kg N ha-1 in 6 splits, T2 (soil test
based approach) that received 159 kg N ha-1 and T8 (apply N30 if LCC value < 5.0). SPAD
values at 65 DAT & LCC 55 and 65 DAT correlated significantly and positively with N
content in leaves and grain yield indicating that simple tools like leaf colour chart and
SPAD chlorophyll meter can be effectively used for monitoring leaf N content in rice and
there by N application for achieving higher yields synchronizing the N demand. N
application if LCC value is < 4.5 or SPAD value < 41 seems to be good N management
option as grain yield, net returns and benefit cost ratio were highest
Description
Keywords
rice, yields, grain, nitrogen, fertilizers, crops, planting, environmental factors, land resources, developmental stages