Kolsom Davoodi; abdollah darzi; Ghasem Aghajani- Mazandarani
Abstract
Subsurface drainage, as a structural modification to improve the productivity of paddy fields, changes the hydrology of the fields. In this research, the response of water balance and drainage water salinity to free and controlled subsurface drainage systems during winter cropping in paddy fields was ...
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Subsurface drainage, as a structural modification to improve the productivity of paddy fields, changes the hydrology of the fields. In this research, the response of water balance and drainage water salinity to free and controlled subsurface drainage systems during winter cropping in paddy fields was investigated by using the DRAINMOD-S model. The data were collected during two canola growing seasons (2015-2017) from a paddy field with a subsurface drainage system (drain depth of 0.65 m and drain spacing of 30 m). The calibrated and validated model was applied to explore effects of conventional and controlled (by controlling water table depth at 40 cm)- subsurface drainage on water balance and soil and drainage water salinity. The model showed acceptable capability for simulating water table depth and drainage water salinity during calibration and validation processes. Based on the simulations, for drain depth of 1.5 m, increase in drain spacing from 30 to 70 m resulted in 805.3 and 741.6 kg ha-1 decrease in total salt load under free and controlled drainage systems, respectively. For drain spacing of 30 m, increase in drain depth from 0.5 to 1.8 m, caused 2.7- 9 mm and 5.1- 14.3 mm increase in drainage water in controlled and free drainage systems, respectively. Simulation results indicated that, to decrease salt load, a drainage system with 30 m drain spacing and 0.5 m drain depth is suitable for both free and controlled drainage conditions. Based on the results, controlled drainage can be used as a management tool to diminish environmental problems in heavy paddy soils from the viewpoint of salt load and drainage water volume.
Sajad Azimi; mojtaba khoshravesh; abdolah darzi; Meysam Abedinpour
Abstract
Kashmar plain is located in an arid region and recent consecutive drought events have attracted serious attention to water use management. In this research, the effects of four levels of super absorbent polymer A200 (0(V0), 0.1% (V1), 0.2% (V2) and 0.3% (V3) wt%), four levels of vermicompost (0(V0), ...
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Kashmar plain is located in an arid region and recent consecutive drought events have attracted serious attention to water use management. In this research, the effects of four levels of super absorbent polymer A200 (0(V0), 0.1% (V1), 0.2% (V2) and 0.3% (V3) wt%), four levels of vermicompost (0(V0), 7(V1), 10(V2) and 15(V3) tons per hectare), and three levels of irrigation (60%(W1), 80%(W2) and 100%(W3) of water requirement) were evaluated on water use efficiency (Irrigation water and rain) (WUE) and irrigation water use (WUEi) of wheat. The study was conducted in research farm of Kashmar Higher Education Institute. Factorial experiment was performed using a completely randomized design with 144 pots. The results showed the highest WUE and WUEi in S3V3W3 treatment as 1.49 kg/m3/ha and 2.26 kg/m3/ha, respectively. The lowest WUE and WUEi were observed in S0V0W1 treatment and were 1.03 kg/m3/ha and 1.56 kg/m3/ha, respectively. Totally, it can be concluded that superabsorbent and vermicompost increased the WUE and WUEi. Under the conditions of this experiment, according to the analysis of variance, the combined application of superabsorbent and vermicompost was not significant. Also, according to the comparison of means at 5% significance level, in separate application of superabsorbent and vermicompost, the best value for achieving maximum WUE and WUEi is 0.2% (weight percent) superabsorbent or 10 ton/ha of vermicompost. By using the maximum superabsorbent and vermicompost and increasing water application from 60% to 80% and from 80% to 100%, WUEi increased by 6.5 percent and 19.7 percent, respectively.
A D; F K
Abstract
Climate change will affect rice water requirement through changes in rice physiology and phenology, soil water balance, evapotranspiration, and green water. Adapting with this major environmental challenge is necessary to maintain or improve the current level of rice production in the future. Considering ...
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Climate change will affect rice water requirement through changes in rice physiology and phenology, soil water balance, evapotranspiration, and green water. Adapting with this major environmental challenge is necessary to maintain or improve the current level of rice production in the future. Considering the vital role of Mazandaran province in supplying rice demand of Iran, this study was conducted to quantify the effects of climate change and different cropping calendars on irrigation water requirement and amounts of green water of the province during rice growing season. Using climatic data of Babolsar, Ghaemshahr, Noshahr, and Ramsar for the base period (1980- 2010) and LARS-WG downscaling model, the weather data of 2011- 2100 were generated under different climate scenarios. Based on the minimum and maximum temperatures, the same cultivation period between current and future periods was selected. Rice water requirement was determined by Neuro-fuzzy inference system. Performance evaluation of LARS-WG model using different statistics indicated suitability of the model to simulate future climate conditions in the region. Under climate change, rice cultivation can start 2 to 23 days earlier and the number of days to physiological maturity will be reduced by one to 20 days. Despite shortening the growing period, due to the negative effects of high temperature and decrease in green water, late planting dates will increase irrigation water requirement. However, suitable cultivation time will reduce rice water requirement of the future up to 681 m3 ha-1. The results demonstrated that management of rice cultivation calendar can be an effective way to achieve sustainable agriculture under future climate condition in Mazandaran province.
M GH; A D; A M
Abstract
Intermittent irrigation is a method to increase water productivity of rice (Oryza sativa L.). In this study, the effects of this type of irrigation combined with two periods of midseason drainage on growth parameters of two rice cultivars were investigated in subsurface drained paddy fields. The experiment ...
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Intermittent irrigation is a method to increase water productivity of rice (Oryza sativa L.). In this study, the effects of this type of irrigation combined with two periods of midseason drainage on growth parameters of two rice cultivars were investigated in subsurface drained paddy fields. The experiment was laid out as split plot in a randomized complete block design with three replications during 2014 growing season. The main factor consisted of drainage systems in the study field including three conventional subsurface drainage systems with drain depths and spacing of, respectively, 0.9 m and 30 m (D0.9L30), 0.65 m and 30 m (D0.65L30), and 0.65 m and 15 m (D0.65L15). In addition, a bi-level subsurface drainage system with drain spacing of 15 m and drain depths of 0.65 and 0.9 m as alternate depths (bilevel), and a treatment without subsurface drainage (control) were included in the study. Sub-factors including rice cultivars Hashemi and Daylamani Tarom were planted in the study area. Midseason drainage was conducted in two periods of 10- day (25 to 34 days after transplanting) and 5-day (43 to 47 days after transplanting). During the growing season, sampling was done to determine leaf area index (LAI), total shoot dry weight (TDW), crop growth rate (CGR), relative growth rate (RGR), leaf area ratio (LAR) and net assimilation rate (NAR). Conducting such water management through subsurface drainage systems increased most of the studied parameters of Hashemi cultivar so that significant differences were found between CGR, NAR, and RGR of D0.9L30 and the control treatment. Maximum dry weights of Hashemei and Daylamani cultivars were 858.8 and 1006.6 g m-2 related to D0.65L15 treatment and maximum leaf area indexes of these cultivars were 4.87 and 5.43 related to bilevel and control treatments, respectively. However, there were not significant differences among different treatments for each cultivar. Based on the results, two periods of midseason drainage through subsurface drainage would improve rice growth characteristics if proper drainage time is selected.