MSc 1999

An investigation was underta:z~i;atthe State Seed Farm, Kottarakkara dur-
ing Virippu 1998 to evolve ecofriendly weed management practices in transplanted
rice. The experiment was laid out as factorial randornised block design with three
replications. The treatments included, two levels each of summer ploughings, stale
seed bed technique, and nitrogen application along with four controls (complete
weed free, weedy check, hand weeded twice and pre-emergent herbicide followed
by hand weeding).
Two summer ploughings enhanced the growth characters of rice such as plant
height, tiller count and 'lA!. Dry matter production and nutrient uptake of rice
were also enhanced by two summer ploughings. Yield attributes and grain yield
was significantly improved by two summer ploughings. The count of grasses,
sedges and BLW and the total weed population was reduced by this practice. The
dry matter production of weeds and NPK uptake by weeds were reduced by two
summer ploghings. Weed control efficiency was also increased at all stages.
Adoption of stale seed bed technique enhanced the plant height, tiller count,
LAI, dry matter production and nutrient uptake of rice. The yield attributes and
grain yield were significantly increased by the practice and the weed index was
significantly reduced. The total weed population was also reduced at all observa-
tions, The count of grasses and BLW reduced up to 40 DAT, while sedge popula-
I
tion was unaffected by the adoption of stale seed bed practice. Relative density of
grasses and sedges were also reduced by this technique. The v, ced dry matter
production, and nutrient uptake were reduced and weed control efficiency was
increased by the stale seed bed practice.

Delaying the basal application of nitrogen up to 10 DAT had no influence on
the crop-weed competition and yield.
The treatment combinations enhanced the growth and yield. T7 and T" re-
corded the higher dry matter production and nutrient uptake of rice. These treat-
ments also resulted in higher grain yield and lower weed index than other combi-
nations. They also recorded the lowest total weed count, weed frequency and
weed density at all stage of observations. Moreover, the combinations of summer
ploughing, stale seed bed and nitrogen application helped to reduce the weed dry
matter production and nutrient uptake.
Compared to existing hand weeding practice all treatments showed their
superiority in increasing the net income especially. T7 and Tg. T, registered the
highest benefit cost ratio. The benefit cost ratio of treatment combinations was
comparable to herbicide application.