MSc

A field experiment was conducted at the Instructional Farm, College of
Agriculture, Vellayani during the mundakan season of 200/-2002 in order to
determine the effect of spacing and weed management practices on the yield of
scented basmati rice cv. Pusa Basmati-I.
The field experiment was laid out in Randomised Block Design with two
factors, in fifteen treatment combinations and three replications. The factors
included were spacings viz. 15 x ] 5 cm (S,). 20 x 10 cm (S2) and 15 x 10 cm (S3)
and weed management practices viz. anilofos + 2,4-D EE at 6 OAT followed by
hand weeding at 20 DAT (Wi), anilofos + 2,4-0 EE at 6 OAT followed by 2,4-D
sodium salt at 20 DA T (W2), hand weeding twice at 20 and 40 DA T (Wl). weed
free check 0N4) and unweeded control 0Ns).
Transplanting basmati rice at 20 x 10 cm, which is the recommended
spacing for medium duration rice in Kerala, enhanced the growth characters of
rice such as plant height, tiller count and leaf area index. Dry matter production
and nutrient uptake of rice were also enhanced by this spacing. The count of
grasses, sedges and broad leaved weeds and the total weed population was
reduced by this practice resulting in higher net income and benefit-cost ratio.
The dry matter production of weeds and nutrient uptake by weeds were also
significantly lower at this spacing compared to the other two spacings
Adoption of pre-emergence application of anilofos + 2,4-D EE @ 0.4 +
0.53 kg ai ha" at 6 DAT followed by 2,4-D sodium salt @ ] kg ai ha-' at 20 DAT
resulted in enhanced plant height. tiller count, leaf area index. dry matter
production and nutrient uptake of rice. The yield attributes and grain yield were
significantly increased by this practice and the weed index was significantly
reduced. The total weed population, weed dry matter production and nutrient
uptake were also reduced and weed control efficiency was increased by this
treatment.
The treatment combination involving recommended spacing of 20 x 10 cm
and pre-ernergence application of anilofos + 2,4-D EE @ 0.4 + 0.53 kg ai ha" at


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6DAT followed by 2,4-D sodium salt @ 1 kg ai ha" at 20 DAT, recorded higher
dry matter production and nutrient uptake of rice. This resulted in higher grain
yield and lower weed index than other interactions. The lowest total weed count,
weed frequency and weed density at all stages of observation were registered for
this interaction. Moreover it helped to reduce the weed dry matter production
and nutrient uptake.
Compared to the existing practice of hand weeding twice at 20 and 40
DAT, all weed management practices except unweeded control, showed their
superiority in augmenting the grain yield and thus increased the net income and
benefit cost ratio.