Abstract
An experiment was conducted at Punjab Agricultural University, Ludhiana, India during kharif 2017 and 2018 to determine the effect of seedling age on growth, phenology and thermal energy utilization by different rice genotypes. The field experiment was laid–out in factorial RCBD design keeping three seedling age (25, 35, 45 days) and four rice genotypes (PR 121, PR 122,PR 124, PR 126) with three replicates. The prevalence of dry weather conditions especially during September month of 2017, which coincides with graingrowth phase was congenial for rice crop and was reflected in the yield and yield attributes. There was consistent decline in grain and straw yield of rice with increase in seedling age due to reduced leaf area index (LAI), dry matter partitioning to grain/culm and SPAD value. This may be due to prevalence of higher range of minimum temperature resulting into more respiratory losses and thereby leading to lower heat use efficiency. Among genotypes, PR 126 was found to be most heat use efficient owing to its shorter duration (93.9 days), where as PR 121 and PR 122 recorded the highest grain and straw yield due to higher accumulation of growing degree and more congenial temperature leading to more number of panicles m-2 along with the bold grains. It was also observed that increasing seedling age beyond 25 days caused sharp decline in grain and straw yield of PR 124 and PR 126 through effect on panicles m-2,SPAD value and AGDD; while PR 121 and PR 122 gave similar yield when transplanted using 25 to 45 days older seedlings. Harvest index did not differ due to various treatments.
Highlights
Crop productivity is a result of complex interactions between genetic, environmental and cultural management factors (Dhillon et al, 2017)
Field experiments were conducted at Research Farm of Punjab Agricultural University, Ludhiana, India [30°56' N latitude; 75°52' E longitude; 247 m altitude] located in the Indo–Gangetic Plains Region (IGPR) during kharif 2017 and 2018
Databrings out that hike in mean maximum temperature under 45 days old seedlings treatment as compared to 25 days old seedling was just 0.3 to 0.4 oC but mean minimum temperature difference under similar treatments were to the tune of 0.7 oC due to prevalence of higher range of minimum temperature, leading to hike in respiration rate resulting into lower net photosynthesis
Summary
Crop productivity is a result of complex interactions between genetic, environmental and cultural management factors (Dhillon et al, 2017). Optimum seedling age for transplanting varies with genotypes due to variation in their crop duration, phenology and tillering potential (Mobasser et al, 2007). The ability of the crop to utilize heat energy for dry matter accumulation is determined by environmental conditions in addition to genetic factors (Rao et al, 1999). Rice is determined plant and reaches flowering stage at almost fixed time as this character is under strong genetic control.Varying seedling age is supposed to cause variation in occurrence of phenological events of rice crop. Studies were conducted to find out optimum seedling age of rice genotypes for obtaining higher productivity and heat use efficiency
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