Tamil
=
In
Tamil Nadu, rice is grown in different conditio=
ns and
water availability is dictated by the monsoon rains. The north east monsoon season (NEM)
during September-December is the main rice crop season in both irrigated an=
d rainfed environments.
The irrigated areas also vary in the source of water. Water received from reservoirs (wh=
ich
get filled up during the monsoon seasons) are let
through rivers and canals by Government decisions and availability of
water. Tank irrigated areas r=
eceive
water for irrigation after the tanks get filled up during the monsoon seaso=
n. When water is made available farme=
rs
grow only rice in spite of a strong campaign for less water demanding crops=
.
The
need to reduce the water use in rice production has become a global concern=
and
several strategies like alternate wetting and drying are being advocated. T=
he
principles of System of Rice Intensification (SRI) developed in Madagascar
includes the use of young seedlings, single seedling per hill, wide spacing=
of
transplanted seedlings, limited irrigation, aerated soil condition by frequ=
ent
disturbance of the soil, and the use of organic manures. SRI follows a more comprehensive
approach that addresses various management practices at the same time, with
promising results.
The
scope of limited water use was the main interest in SRI when experimental
evaluation began in 2002. Whi=
le the
basic agronomic practices of irrigated and transplanted rice cultivation
(raising nursery, transplanting, flood water irrigation, weeding) remain the
same, SRI envisages some changes in each of the above agronomic practices.<=
span
style=3D'mso-spacerun:yes'> This paper su=
mmarises
the results of field experiments conducted in Tamil Na=
du
evaluating the different combinations of the SRI principles. =
&nb=
sp; =
&nb=
sp;
In SRI, seedlings, usually 8-12 days and not more tha=
n 15
days old (4th phyllochron) are recommended to be
transplanted. In the experime=
nt
conducted at
Rajendran et al. (2005) found that, =
with
all other SRI principles similar, planting single seedling resulted in 15 t=
o 16
% higher yield than planting 2-3 seedlings per hill. Experiment conducted at Killikulam during 2004 – 05 did not show any yi=
eld
difference due to single seedling per hill and 3 seedlings per hill.
Planting density
Vijaya=
kumar et al. (2004) studied the =
effect
of different plant densities (20 x 20 cm and 25 x 25 cm) and found
significantly higher yields for the spacing of 25 x 25 =
cm for both 14 and 21 d old seedlings with limited
irrigation and weeder use.
In the experiments conducted during 2001 – 2002=
, Senthilkumar (2003) compared the use of rotary weeder five times with ten days interval from 20 days=
after
transplanting till booting stage with the conventional weeding of hand weed=
ing
(three times) for wet season and chemical weeding and two times hand weeding
for dry season. In both the s=
easons,
mechanical weed control significantly increased grain yields. Weeder=
use
alone increased the plant height and enhanced the grain yield by 10.9 %.
&nb=
sp; Vijayakumar et al (2004) also found significant yield
increase of 9.7 % (20 x 20 cm plant density) and 11.1 % (25 x 25 cm plant
density ) due to the weeder use when compared to
conventional weeding ( herbicide + hand weeding) with 14 d old seedlings and
limited irrigation. =
&nb=
sp; =
Ramamo=
orthy (2004) found that non-remo=
val of
left out weeds rotary weeder was used can
significantly reduce the yields in weed infested lands. He also found that the=
stirring
effect of the weeder has positive impact on the=
grain
yield.
Ramamo=
orthy (2004) found that the weeder use has a sort of earthin=
g
up effect and the plants produce new roots which probably help in additional
nutrient uptake. Rajendran et al., (2005) found 22 – 24 % yield
increase due to weeder use.
In
the experiments conducted at Coimbatore by Senthilkumar (2003) and at Killi=
kulam
by Ramamoorthy (2004), shallow and non-submerged
irrigation was followed (field irrigated to 2.5 cm depth : after formation =
of
surface hairline cracks on soil up to PI and one day after the disappearanc=
e of
water on the soil surface after PI).
Conventional field was irrigated to 5 cm depth one day after
disappearance of previously pounded water). Water flow was measured with parshal plume in all these experiments. Water productivity increases were =
53 %
and 77 % in these two experiments. <=
/span>Vijayakumar et al. (2004) did not report yield advant=
age
due to the limited irrigation, while Rajendran
et al.(2005) reported2 % yield increase.&n=
bsp;
The interactive effects between the components of SRI
were clearly seen in all the experiments conducted. The yield increase due to SRI prin=
ciples
in these experiments ranged from 603 to 2316 kg/ha. The following factors were identif=
ied in
these experiments as the causes for the increased yield.
-&nb=
sp; =
root
growth
-&nb=
sp; =
tiller
density
-&nb=
sp; =
panicle
density
-&nb=
sp; =
number
of grains per panicle
-&nb=
sp; =
dry
matter production during the grain filling period
-&nb=
sp; =
uptake
of nutrients
Conclusions
The field experiments conducted in Tamil Nadu showed that the new cultivation method involving=
SRI
components has definite advantages of yield increase of about
0.6 to 2.3 t ha-1 and water saving of about 40
– 50 %. SRI has been
evaluated in farmers’ fields through adaptive research trials and has
been recommended for adoption in the state. Further studies are needed to find=
out
the long term effects as well the nutrient requirements.
*=
***
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