جستجوی مقالات مرتبط با کلیدواژه "end-season drainage" در نشریات گروه "آب و خاک"

This research was carried out to determine the simultaneous optimal management of nitrogen (N) fertilizer and the time and duration of mid-season drainage (MSD) of rice from an environmental point of view. This experiment was conducted in three treatments: application of N fertilizer and then drainage 7 days later for 7 days (T1), drainage for 7 days and then application of N fertilizer (T2), and drainage for 10 days and then application of N fertilizer (T3). The control treatment included fertilization at the same time as T1 treatment and without mid-season drainage.The quality parameters of drain water were measured. The results indicated that the time of applying fertilizer and drainage has a direct effect on pH. The average EC during the growth period in T2 and T3 decreased by 46 and 73%, respectively, compared to T1. The trend of NH4+ changes was upward before MSD, but after MSD, it decreased by 23% in T1 and 54% on average in T2 and T3. The average concentration of NO3- in the end season in T1, T2, and T3 was 22, 36, and 69% lower, respectively, and PO43- was 29, 31, and 67% lower than in MSD. The statistical analysis showed that the effect of time and treatments on SAR, and Cl- was insignificant. Applying fertilizer after drainage for 10 days has lower negative impact on environment. Compating yield and component yield in treatments show that T2 (7 days mid drainage and then appling nitrogen fertilizer) is a more appropriate option.

It is possible to effectively control water in paddy fields, prevent flooding problems, and create optimal conditions for the growth of agricultural products with simultaneous and correct management of irrigation and drainage. Due to the high initial cost of the construction of subsurface drainage, Mole drainage is a suitable and more economical alternative in clay soils. Constructing the mole drain at a critical depth and passing the water through the cracks, improves the soil conditions and removes excess water from the soil surface. Mulqueen (1985), reported that gravel mole drain is a suitable alternative to traditional mole drain. Considering the limited studies in the field of mole drainage, the purpose of this study is to evaluate the performance of low-cost mole drainage for draining excess water from paddy fields and its environmental effects. Therefore, the effect of traditional mole and gravel mole drain on drainage water quality and control of the water table of paddy fields in the mid and end of rice season was investigated.

The experiment was conducted in the agricultural year of 2022-2023 in the research farm of the Faculty of Agricultural Sciences, University of Guilan (IRAN). The split-plot experiment was implemented in a randomized complete block design in three replications under the main drainage treatment on two levels: (1) Traditional mole drain (without gravel) and (2) Gravel mole drain and the sub-treatment of irrigation method in two levels: (1) Flood irrigation and (2) Alternative irrigation. In the stages of tillering and harvesting, mid and end season drainage were done respectively. During the drainage period, the water table was measured with a piezometer. By sampling the drainage water, its quality parameters including acidity, electrical conductivity, nitrate, nitrite, phosphate, sulfate, chloride, total suspended and dissolved solids, sodium, calcium, magnesium, and ammonium were measured. The results of the investigated treatments were statistically analyzed using SAS software.

With the start of mid season drainage, after one day, the water table reached the middle of the soil profile and more than half of the root development depth was in anaerobic conditions. Five days after the drainage in the traditional mole drain, the depth of root development was in aerobic conditions. The highest value in average acidity and sodium adsorption ratio was 6.99 and 4.65 meq/l respectively in mid season in gravel mole drain and flood irrigation. The highest concentration of ammonium and nitrate in mid season drainage was 0.20 and 0.21 mg/l, respectively, and the highest average electrical conductivity and total dissolved solids at the end season were 3845 µS/cm and 2475 mg/l, respectively, in traditional mole drain and flood irrigation. In mid and end season drainage, the amount of total suspended solids in the mole drain with gravel was 60% and 88% higher than the traditional mole drain, respectively. The highest concentration of nitrite was obtained in the gravel mole drain and flood irrigation with a value of 6.75 mg/l during mid season drainage. The average concentration of phosphate and sulfate in gravel mole drain compared to the traditional mole in mid and end season decreased by 25 and 30%, respectively, and sulfate by 3 and 5.5%. Also, the average concentration of chloride in the gravel mole drain was lower than the traditional one.

The comparison of results indicated that the average amounts of electrical conductivity, total dissolved solids, sodium adsorption ratio, sodium, ammonium, phosphate, sulfate, and chloride of drainage water in mid and end season were lower in gravel mole drain than the traditional one. The results of statistical analysis showed that the treatment of drainage, irrigation, and time at the level of one and five percent were effective on most of the parameters, while the values of electrical conductivity, total dissolved solids, and nitrite of the drainage water showed that their difference was not significant. The traditional mole drain was more successful in controlling the water table. A comparison of the quality parameters of drainage water with the standard of the Iranian Environmental Protection Organization for the discharge of drainage water into surface waters showed that most of the parameters, except for ammonium and total suspended solids, were within the permissible limits.

In rice cultivation, mid-season and end-season drainage at harvest time are two important operations of water management which, respectively, increase yield and provide better conditions for harvesting rice. Due to the unique conditions of paddy fields of Guilan province, making decisions about the spacing and depth of drains and proper equation to determine the drainage spacing in paddy field requires research on the mid-season and end-season drainage. Therefore, in this research, the efficiency of drains spacing (L) and depth (D) of subsurface drainage in controlling water table and also accuracy of the steady and non-steady equations were evaluated at mid-season and end-season drainage stages in Guilan’s rice fields. Drainage treatments included six conventional subsurface drainage systems with rice husk envelope including drainage system with drain depth of 0.8 m and drain spacing of 7.5 m (L7.5 D0.8), (L10 D0.8), (L15 D0.8), (L7.5 D1), (L10 D1), and (L15 D1). All drain lines were 40 m long and made of PVC corrugated pipes with a diameter of 125 mm. Results showed that subsurface drainage with spacing of 15 m and depth of 80 cm (due to the proper water table depth and higher yield) and subsurface drainage with distance of 10 m and depth of 80 cm (due to the highest resistance to pentrometer penetration and the lowest soil moisture content) are recommended as the best drainage treatment for mid-season and end-season drainage, respectively. Dagan, Hooghoudt and Bouwer & Van Schilfgaarde equations combined with Hooghoudt equation were suitable equations for determining drainage spacing at mid-season drainage stage. Hooghoudt, Kirkham, Dagan, Bouwer & Van Schilfgaarde equations combined with Hooghoudt equation and Glover-Dumm equation were selected as suitable formulas for determining the spacing of subsurface drains for end-season drainage.