Mohammad Adib; Nafiseh Rang Zan; Amir Naserin
Abstract
Introduction The highest amount of water consumption is allocated to the agricultural sector, which has led to a water crisis due to increasing demand for food production and non-conservative agriculture and climate change in some countries. Sugarcane needs a lot of water during the growing season and ...
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Introduction The highest amount of water consumption is allocated to the agricultural sector, which has led to a water crisis due to increasing demand for food production and non-conservative agriculture and climate change in some countries. Sugarcane needs a lot of water during the growing season and is sensitive to drought. In drought conditions and water stress, the intensity of reverse flow of water to the soil surface increases and can cause salinization of the soil around the roots of sugarcane, which is a relatively sensitive plant related to salinity. Due to the high-water consumption in sugarcane fields and also the shortage and decline of water quality in dry years, this study aimed to investigate the effect of conventional and deficit irrigation by variable and fixed alternate furrow irrigation on soil salinity and some nutrient concentration consist of phosphorous and potassium in sugarcane field. Materials and Methods To investigate the effect of irrigation methods on salinity distribution and concentration of phosphorous and potassium in soil, this experiment was conducted with independent variables of irrigation method treatment including conventional (complete) irrigation, variable alternate furrow irrigation and fixed alternate furrow irrigation, irrigation round treatment including before irrigation, after one and two times irrigation, sampling location treatment including bottom, middle and top of raised bed and sampling position treatment consist of start, middle and end of furrow. The experiment was performed factorially in a completely randomized design with three replications in sugarcane fields of MianAb in Susa. Statistical analysis was performed using SPSS software and mean comparisons were performed by Duncan's multiple range test. Charts were drawn using Excel software.Results and Discussion The results showed that irrigation method is mainly affects salinity distribution and concentration of phosphorus in soil. The fixed alternate furrow irrigation method had the greatest effect on soil salinity changes and reduced the salinity as compared to the conventional method and the variable alternate furrow irrigation. In general, in the conventional irrigation method (complete irrigation of all furrows) and variable alternate furrow irrigation, there is no constantly dry furrow as compared to the fixed alternate furrow irrigation method, and this intensifies the accumulation of salts on the sides and the top of raise beds. Increasing the frequency of irrigation (irrigation round) reduces the soil salinity so that in soil samples before irrigation, soil salinity was 2.30 dS/m and with one round irrigation, this amount decreased by 7.8% to 2.12 dS/m and with two rounds of irrigation reached to 2.09 dS/m. In terms of locative variation of salinity related to the fixed alternate furrow irrigation method, the lowest amount of salinity was observed in the bottom of the raised bed. With increasing distance from the beginning of furrow, an upward trend in soil salinity was reported. Regarding the change in the amount of available phosphorus in the soil under the influence of irrigation method, any of the deficit irrigation methods can be used as an alternative to conventional irrigation. The highest amount of soil phosphorus was reported in the middle of the raise bed. Soil potassium changes were not directly affected by irrigation method and the highest amount was assessed in the bottom of the raise bed. In terms of salinity, the lowest value was at the bottom of the furrows and the highest value was at the top of the raise bed. Unlike salinity changes, soil phosphorus had the highest accumulation in the middle of the raise bed and reached a minimum at the top of the raise bed. A relatively uniform trend was observed in changes in soil phosphorus from the beginning to the end of the furrow. Contrary to salinity changes, the highest amount of available potassium in soil was observed in the bottom of raise bed and a decreasing trend in soil potassium was reported from the beginning to the end of furrow. In general, based on the results, the average level of soil salinity and potassium and the highest amount of phosphorus were reported in the middle of the raise bed.Conclusion For optimal water use and soil salinity management, application of deficit irrigation methods especially fixed alternate furrow irrigation instead of conventional irrigation method, is recommended. In case of salinity and concentration of mentioned nutrients, the top of the raise bed in all three irrigation methods, would not be a suitable place for plant cultivation.
Ali Monsefi
Abstract
Introduction Herbicides are chemicals that are used to inhibit the growth or to eliminate weeds in agricultural fields to increase the yield of crops in crop production. By the end of the 19th century, with the increasing labor supply problems, the need for chemical methods to control weeds became apparent. ...
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Introduction Herbicides are chemicals that are used to inhibit the growth or to eliminate weeds in agricultural fields to increase the yield of crops in crop production. By the end of the 19th century, with the increasing labor supply problems, the need for chemical methods to control weeds became apparent. It was first reported in France in the 1980s, that sulfuric acid was used in the fight against weeds in sugar beet fields. Nowadays, most of the herbicides used are organic herbicides, which share organic carbon in their chemical structure. The use of herbicides since about a century ago has been suggested as an effective way of eliminating crop competitors, though herbicides that remain in the soil for longer periods of time prolong weed control and thus increase weed management efficiency. On the other hand, their increased stability in soil may be of a magnitude that can damage crops in the following crop rotations. Soil properties can have a significant impact on the stability of herbicides in soil. Materials and Methods For this purpose, soil samples were taken from 0-30 cm depth from field of experiment No. 2 in College of Agriculture Shahid Chamran University of Ahvaz. After sampling and passing through 2 mm sieve, the physical and chemical properties were measured using standard methods. The pot experiment was conducted in a factorial completely randomized design with 32 treatments including soil salinity (at 2.5 and 6 dS / m), Ultimo herbicide rate (at 4 concentration levels of 0, 25, 50 and 100% Recommended dose) and planting time (60 and 120 days after herbicide application) with 3 replication. Wheat was selected as the experimental crop and variety was "Mehregan" which has been cultivated in most of Khozestan province. Herbicide was applied and soil was rested for 60 and 120 days then wheat was sown. For germination percentage, wheat seeds were sown directly in soil after germination test. After germination the percentages were recorded and kept in an equal number of plants in the pot. It should be noted that in order to eliminate the effect of nutrient deficiency on plant growth at appropriate intervals, nutrient solution was applied and irrigated according to the need of the plant.After 9 weeks (before flowering stage) the plant was harvested and the growth components including root length, root dry weight, shoot length, shoot weight and nutrient concentration including nitrogen (in plant dry matter), phosphorus, potassium, calcium, magnesium, iron, zinc, copper and manganese were measured in the extract obtained from dry digestion of plant tissue (aerial parts of plant). Statistical analysis was performed using SAS software and mean comparisons were performed by Duncan's multiple range test. Charts were drawn using Excel software. Results and Discussion According to the results, increasing the level of herbicide decreased the growth parameters of the plant, which is intensive under salinity stress. The results showed that considering 60 days sowing after herbicide application, shoot dry weight in 100% RD herbicide application in salinity of 2.5 dS/m was 1.6 g which was not showed significant difference with 50% herbicide application under salinity of 6 dS/m. Therefore, in higher salinity levels lower herbicide dose can damage the plant as much as higher levels of herbicides in lower salinity, and lower levels of herbicides in more soil salinity produce more negative effects. By increasing planting time from 60 to 120 days the residual effects of herbicides on soil decreased and plant showed better yield. By increasing salinity level from 2.5 to 6 dS / m, all growth components of wheat decreased, except for shoot length and shoot dry weight, this significant decrease was not reported for other components. Conclusion Therefore, it can be concluded that selection of sowing time after herbicide application in crop rotations is very important and by selecting the correct time can greatly reduce the deleterious effects of consuming more herbicides.Planting wheat at 60 days after application of herbicide compared to 120 days after application of herbicide, decreased the growth components of the plant. Therefore, selection of wheat sowing time in crop rotation 60 days after application of herbicide (especially at 100% recommended dose) is not recommended in maize – wheat cropping system. Also considering soil chemical properties such as salinity as an influencing factor on herbicide behavior in soil can be effective in controlling residual effects of herbicides in soil and plant.