Document Type : Research Article
Authors
Department of Agronomy, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
Abstract
Introduction
Rapeseed (Brassica napus L.) has a special rank among oilseeds due to its outstanding agronomic characteristics. Planting date is an important factor that affects grain yield, oil content and fatty acid composition. Delay in rapeseed planting reduces vegetative growth period and produces plants with less biomass, and reduces yield components and grain yield due to the exposure of the reproductive stage to high temperatures. Proper nutrition of the plant is one of the important factors in improving the quantity and quality of the product. Silicon is not considered an essential element for excellent plants. However, silicon has an effect on improving plant growth, biomass, seed yield and quality, photosynthesis and resistance to biotic and abiotic stresses. Zinc also regulates plant growth and activates many enzymes. This element is necessary for the synthesis of chlorophyll and the formation of carbohydrates.
Materials and Methods
In order to conduct this research, a field experiment was conducted as a split-factorial in a randomized complete block design with three replications at Qhaemshahr Agricultural Research Station (Qarakheil) during 2017-18. Planting dates as the main plot at two levels (normal planting [7 October] and delayed planting [22 October]), silicon fertilizer sources at three levels (control [no consumption], calcium silicate, nano-Si) and zinc fertilizer sources at three levels (control [no consumption], zinc sulfate, nano-Zn) were considered as sub-plots. Calcium silicate and zinc sulfate (200 kg ha-1) were added to the soil before rapeseed planting. Silica and zinc nanoparticles (50 mg l-1) were sprayed in two stages of flowering and pod formation. The soil of the test site had clay loamy texture with pH 7.5, organic matter 3.2%, total nitrogen 0.16%, absorbable P 15.7 mg kg-1 and absorbable K 101 mg kg-1. The average annual rainfall at the test site was 745 mm. Data were analyzed by Mstat-C statistical software and the means were compared with LSD test at a probability level of 5%.
Results and Discussion
Plant height, number of pods per plant, number of seeds per pod, 1000-seed weight, grain yield, seed oil, grain silica and grain zinc were the studied traits that other than grain silica (non-significant) other traits decreased with delay in planting. The present study showed that for each day of delay in planting, 39.15 kg ha-1 of grain yield was reduced. With the delay of planting from 7 October to 22 October, the total grain yield decreased by 22.03% due to the decrease in the number of pods per plant, 1000-seed weight and number of seeds per pod. Seed oil also decreased by 3.3% with a delay in planting. Number of pods per plant (10.30 and 12.11%), grain yield (11.15 and 12.43%), and grain silica (9.63 and 11.57%) increased with the use of calcium silicate and nano-silica, respectively, compared to the control. The number of seeds in pods (14.85 and 13.01%) and grain zinc (21.47 and 26.57%) also increased with the use of zinc sulfate and nano-zinc, respectively, compared to the control. Nano-zinc increased the number of pods per plant, 1000-seed weight and grain yield compared to the control (18.66, 15.64 and 20.50%, respectively). The maximum number of seeds per pod was obtained in normal planting date with calcium silicate (49.8 seeds) and the maximum seed oil was obtained under the combined treatments of nano-silica and zinc sulfate (47.3%) and nano-silica and nano-zinc (47.5%).
Conclusion
In general, the results of the current study showed that the highest grain yield and grain silica concentration were obtained by application different sources of silica as well as nano-zinc foliar application. The maximum concentration of grain zinc was obtained by application different sources of zinc. The highest percentage of oil was recorded with the simultaneous application of nano-silica and different sources of zinc.
Keywords
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