E. Karamian; M. Navabian; M.H. Biglouei; M. Rabiee
Abstract
IntroductionMany agricultural lands in Guilan province of Iran, especially paddy fields, remain uncultivated in the second half of the year due to various reasons including heavy rainfall, low soil permeability (stickiness of soil particles) and inefficiency of the existing drains. Mole drainage as a ...
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IntroductionMany agricultural lands in Guilan province of Iran, especially paddy fields, remain uncultivated in the second half of the year due to various reasons including heavy rainfall, low soil permeability (stickiness of soil particles) and inefficiency of the existing drains. Mole drainage as a low-cost drainage method, proportion for rice cultivation conditions and easier to implement than pipe drainage, can be a suitable solution in the development of second cropping. Due to the oil content of 40% of the seed, the rapeseed plant is one of the valuable oil plants and has the ability to be cultivated as a second crop in paddy fields. Nitrogen plays a key role in the performance of plants and its deficiency causes limitations in plant production. Equipping paddy fields with mole drains along with the application of appropriate level of nitrogen fertilizer can increase the quantitative and qualitative yield of rapeseed as a second crop and contribute to the food security of the country. Therefore, the development of the cultivated area of rapeseed in paddy fields after rice harvesting in Rasht region, the study of the combined effect of mole drainage and different levels of nitrogen fertilizer on yield and yield components were the aims of this project. Materials and MethodsIn order to investigate the effects of mole drainage and nitrogen fertilizer on the yield and yield components of rapeseed as a second crop in Rasht rice fields, a factorial layout based on a randomized complete block design with three replications at the research field of the Faculty of Agricultural Sciences of Guilan University was implemented in the crop year of 2022-2023. The factors included mole drainage at three levels (without drainage, without gravel and with gravel) as D0, D1 and D2 respectively, and nitrogen fertilizer as urea source at two levels (180 and 240 kg ha-1) as N1 and N2 respectively. Rapeseed plant (Brassica napus) of Delgan cultivar was selected as the second crop after rice harvest. To carry out the experiment, at first the desired land was blocked and divided into plots, then the underground drains of mole were created without gravel and with gravel with a special blade in the desired plots. To drain the drainage from the mole drains, the polyca pipe was installed at the end of each mole tunnel, then the other side of polyca pipe was connected to the sub-pipe collection and finally led to the main surface drain. This experiment was conducted in 18 plots and each one was 9 × 6 meters. The distance between plots was 1.5 m, between replications was two meters, and the distance between plants was 15 and between rows was 25 cm. To avoid the effectiveness of drainage treatments from undrained treatments, undrained plots were considered at the end of the field. Before cultivation, basic chemical fertilizers, 200 kgha-1 of potassium from potassium sulfate source and 200 kgha-1 of phosphorus from ammonium phosphate source were applied. Nitrogen fertilizer from urea source was applied at the level of 180 and 240 kgha-1 in equal amount at three stages. Just before the harvest stage, to determine the traits of the number of seed in the pods of sub-branches, the number of seed per pod, the weight of seed in sub-branches, the weight of seed in the main branch and the weight of seed per plant, ten plants were randomly selected and harvested manually from the crown area. Also, to determine the seed yield, one square meter was randomly selected from each plot, taking into account the borders, and the bushes were manually harvested from the crown area. After the moisture content of the seeds reached the desired level, the seeds were separated from the pods and weighed using a laboratory scale with an accuracy of one thousandth of a gram, and the seed yield was calculated in kgha-1. SOXTEC SYSTEM HT 1043 Extraction Unit set was used to determine oil percentage and Kjeldahl set was used to determine seed protein. Statistical analysis of the data was done using SAS software (version 9.4) and comparison of means was done using the minimum significant difference test at 5% probability level. Excel software was used to draw the graphs. Results and DiscussionThe results of variance analysis of the data showed that the interaction effects of mole drainage and nitrogen fertilizer on the traits of seed weight in the main branches, seed weight in the plant and seed yield was significant at 5% probability level, so that the highest seed weight in the main branch with 0.733 seeds in the mole drainage with gravel with a nitrogen fertilizer level of 180 kgha-1 (D2×N1) treatment was obtained and the highest seed weight in the plant with 1.443 g in the mole drainage without gravel with a nitrogen fertilizer level of 240 kgha-1 (D1×N2) treatment was obtained. Also, the highest seed yield was obtained under 3579.48 kgha-1 in the treatment of mole drainage without gravel using 240 kgha-1 of fertilizer (D1×N2) which is compared to the treatment of without drainage and drainage with gravel with the same level of fertilizer 13.63 and 2.31 percentage was higher, respectively. In addition, rapeseed plant is more important in terms of oil percentage, no significant difference was observed between drainage and nitrogen fertilizer treatments in terms of average oil percentage. Therefore, the mole drainage treatment without gravel with a fertilizer level of 240 kgha-1 (D1×N2) is the most suitable option for rapeseed cultivation as the second crop after rice harvesting. ConclusionThe results of this study showed that mole drainage without gravel by improving soil ventilation conditions and preventing waterlogging of paddy fields along with the level of nitrogen fertilizer of 240 kgha-1 increased the yield of rapeseed compared to the condition of without drainage at the same level of nitrogen fertilizer. Therefore, rapeseed cultivation in vast paddy fields after rice harvesting can be recommended as a basic solution in order to increase the production of oilseeds and provide part of the country's oil consumption.
