Field experiments were conducted in Punjab, India, in 2011 and 2012 to study
the integrated effect of planting pattern [uniform rows (20-cm spacing) and
paired rows (15-, 25-, and 15-cm spacing)], cultivars (PR-115 and
IET-21214), and weed control treatments (nontreated control, pendimethalin
750 g ai ha−1, bispyribac-sodium 25 g ai ha−1, and
pendimethalin 750 g ha−1 followed by bispyribac-sodium 25 g
ha−1) on weed suppression and rice grain yield in dry-seeded
rice. In the nontreated control, IET-21214 had higher grain yield than
PR-115 in both planting patterns. However, such differences were not
observed within the herbicide treatment. IET-21214 in paired rows, even in
nontreated control, provided grain yield (4.7 t ha−1) similar to
that in uniform rows coupled with the sole application of pendimethalin (4.3
t ha−1) and bispyribac-sodium (5.0 t ha−1). In uniform
rows, sequential application of pendimethalin (PRE) and bispyribac-sodium
(POST) provided the highest grain yield among all the weed control
treatments and this treatment produced grain yield of 5.9 and 6.1 t
ha−1 for PR-115 and IET-21214, respectively. Similarly, in
paired rows, PR-115 in paired rows treated with sequential application of
pendimethalin and bispyribac-sodium had highest grain yield (6.1 t
ha−1) among all the weed control treatments. However,
IET-21214 with the sole application of bispyribac-sodium produced grain
yield similar to the sequential application of pendimethalin and
bispyribac-sodium. At 30 days after sowing, PR-115 in paired rows coupled
with pendimethalin application accrued weed biomass (10.7 g m−2)
similar to the sequential application of pendimethalin and bispyribac-sodium
coupled with uniform rows (8.1 g m−2). Similarly, IET-21214 with
bispyribac-sodium application provided weed control similar to the
sequential application of pendimethalin and bispyribac-sodium. Our study
implied that grain yield of some cultivars could be improved by exploring
their competitiveness through paired-row planting patterns with less use of
herbicides.