EVALUATION OF WEED MANAGEMENT PRACTICES UNDER ORGANIC PRODUCTION IN RICE (A) – RICE (W) – TORIA CROPPING SEQUENCE
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Date
2020-08
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AAU, Jorhat
Abstract
An experiment entitled “Evaluation of weed management practices under
organic production in autumn rice-winter rice-toria cropping sequence” was conducted
for two consecutive years during 2018-19 and 2019-20 at Instructional-Cum-Research
Farm of Assam Agricultural University, Jorhat. This study forms a part of the long-term
experiment under All India Coordinated Research Project on Integrated Farming System
with a view to evaluate the efficiency of cultural and mechanical weed management
practices under organic production system. The experiment was laid out in Randomized
Block Design replicating thrice with seven treatments viz., T1: two hand weeding (HW)
in rice and 1 HW in toria, T2: one mechanical weeding (MW) + one HW in rice and
one HW in toria, T3: intercropping (dhaincha in autumn and winter rice and french
bean in toria, at 2:1 ratio in replacement series, T4: stale seedbed + reduced spacing
(25%) + mulching with previous crop mulch + 1 HW ( in all the three crops), T5:
locally available dry weed mulch (3 inch thick) + 1 hand pulling (in all the three crops),
T6: incorporation of oilcake (5 t/ha) + 1 HW (in all the three crops) and T7: deep
ploughing during summer + 1 HW (in all the three crops). Recommended doses of N
were applied as 1/3
rd N through FYM + 1/3
rd N through vermicompost + 1/3
rd N through
mustard oil cake to each crop of the sequence. The soil texture of the experimental site
was sandy loam with acidic in soil reaction (pH 5.40). The initial soil status was
medium in organic carbon (6.82 mg/kg) and available nitrogen (340.50 kg/ha), low in
available phosphorus (8.80 kg/ha), available potash (95.23 kg/ha) and in soil available
sulpher content (6.50 kg/ha).
The results revealed that plant height and other yield attributing
parameters as well as grain (30.90 q/ha in autumn rice and 33.51 q/ha in winter rice)
and straw (42.37 q/ha in autumn rice and 43.17 q/ha in winter rice) yield of rice were
recorded to be the highest in the treatment with stale seedbed + reduced spacing (25%)
+ mulching with previous crop mulch + 1 hand weeding (HW) i.e. treatment T4, while
the lowest values were recorded under the treatment receiving 1 mechanical weeding +
1 hand weeding in rice and 1 HW in toria (T2). The yield attributing parameters as well
as seed (5.92 q/ha) and stover yield (18.82 q/ha) of toria was the highest in T6 treatment.
The highest REY of rice-rice-toria sequence was recorded in T4 (75.39 q/ha) and the
lowest (66.03 q/ha) was under T2 treatment. The highest total weed density and dry
weight of the sequence were found in T2 at 30 DAP/DAS (34.53 no./m2 and 14.56
7
g/m2), 60 DAP/DAS (35.40 no./m2 and 21.02 g/m2) and at harvest (48.69 no./m2 and
22.78 g/m2), whereas the lowest was observed in T4 treatment. The total N, P and K
uptake by the crops were the highest in T4 treatment with values of 147.6, 49.9 and
154.6 Kg/ha respectively and the highest total N, P and K uptake while that by weeds
were recorded in T2 treatment with 102.09, 19.93 and 170.21 Kg/ha in rice-rice-toria
cropping sequence. Soil available N, P, K and S content as well as soil microbial
parameters after completion of the sequence were recorded to be the highest in T3
treatment.
In the present investigation, the gross return (`178974.00), net return
(`27877.00) and B:C ratio (1.18) were found to be the highest under T4 treatment [stale
seedbed + reduced spacing (25%) + mulching with previous crop mulch + 1 HW (in all
the three crops)] and the lowest were recorded under T6 treatment [receiving mustard
oilcake (@5 t/ha) + 1 HW (in all the three crops)]. Thus, considering the system
productivity, and economic feasibility, the practice of stale seedbed + reduced spacing
by 25% + mulching with previous crop mulch + 1 HW in all the three crops (T4) could
be considered as the best organic weed management practice in case of rice- rice- toria
cropping sequence under the prevailing climatic condition of Assam. However, this
practice needs multi-locational trials in all the agro-climatic conditions to derive valid
conclusion before putting forwarded for recommendation to the farmer’s. There is also
need for further study on long term effect of these organic weed management practices
on soil physical, chemical and biological properties.