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.
Duration and severity are the two most important parameters used for drought characterization. In this study, we used a bivariate copula‐based approach to understand the joint dependence of drought duration and severity of three different drought types. Three types of bivariate copulas (Gumbel, Frank and Plackett) are estimated for modelling and the best fit copula is selected over 1,162 grid points (at a resolution of 0.5° × 0.5°) of India. Further, the joint dependence of drought duration and severity are analysed to infer important properties in terms of exceedance probability and return periods. Finally, conditional probability and conditional return periods of drought characteristics are also derived, which could be useful for proper planning and management of the water resource system. From the investigation, it is observed that drought events in the Western and Central India are longer and more severe whereas the ones in the south Indian river basins are more frequent but less severe. Moreover, similar results were also obtained for the conditional probability and conditional return periods. This study provides information regarding the severe and longer drought event hotspots all over the study area and thus helpful for the policymakers in developing effective drought prevention and mitigation strategies comprehensively at a national scale.
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