Irrigation
R. Saeidi
Abstract
IntroductionSalinity stress causes reduction of crop evapotranspiration (ETc) and yield. An unsuitable seed planting date can result in negative atmospheric effects, such as temperature stress, during the crop growth period. Consequently, salinity stress and unfavorable climatic conditions during this ...
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IntroductionSalinity stress causes reduction of crop evapotranspiration (ETc) and yield. An unsuitable seed planting date can result in negative atmospheric effects, such as temperature stress, during the crop growth period. Consequently, salinity stress and unfavorable climatic conditions during this period interact to reduce crop water uptake. The mentioned conditions effect, should be investigated on crop transpiration amount (actual water requirement) and soil surface evaporation losses. This research results will have a determinative effect on the optimal use of water resources. Materials and MethodsThe studied crop in this research was S.C 704 maize. The crop planting was conducted in mini-lysimeters with a diameter of 40 cm and a height of 70 cm. The experiment factors included soil salinity stress and seed planting date. Soil salinity treatments were selected at four levels of 1.7 (S1), 2.5 (S2), 3.8 (S3), 5.9 (S4) dS.m-1. Seed planting date included of 5 May (P1), 25 May (P2) 14 June (P3) and 4 July (P4). Crop growth period for all planting date treatments, was 140 days (FAO-56). Experiment was conducted as factorial based on completely randomized design with 16 treatments and three repetitions. Variance analysis and average comparison of data was done by SPSS software and with Duncan's multi-range test (at 5% probability level). Daily soil moisture amount was measured by a moisture meter. Irrigation time was determined for without water stress conditions. Readily available water limit was determined 0.4. Irrigation volume was calculated according to soil moisture deficit (up to FC limit), soil density, root depth, leaching fraction and soil surface area. To separate the evapotranspiration components, all treatments were performed in two series of mini-lysimeters. In the first series, soil moisture reduction was related to crop evapotranspiration amount. But in the second series, the plastic mulch was placed on soil surface. Soil moisture reduction in the second series, was only related to crop transpiration amount. Difference of data in the first and second series was equal to the evaporation amount. Linear function of Mass and Hoffman (1977) was used as the function of evapotranspiration-salinity, transpiration-salinity, and evaporation-salinity. Results and DiscussionAs salinity increased from S1 to S4 levels, evapotranspiration, transpiration, and evaporation amounts were measured on the planting dates P1, P2, P3, and P4. The measurements were as follows:Evapotranspiration (mm): 619-548 (P1), 621-549 (P2), 624-547 (P3), and 625-544 (P4)Transpiration (mm): 429-309 (P1), 421-295 (P2), 418-281 (P3), and 412-265 (P4)Evaporation (mm): 190-239 (P1), 200-254 (P2), 206-266 (P3), and 213-279 (P4)These ranges reflect the measured amounts for each variable under increasing salinity levels across the different planting dates. Under the influence of salinity stress, soil water potential decreases, leading to a reduction in water uptake by the crop and subsequently decreased crop transpiration. As a result of this reduction in crop water uptake, the remaining water in the soil is utilized for evaporation. In S4 level and on dates of: P1, P2, P3 and P4, crop transpiration portion decreased to 12.9%, 14.1%, 15.6% and 17.2%, respectively, and evaporation portion increased to the same amount. By adjusting the seed planting date to optimize the utilization of favorable atmospheric conditions during crop growth stages, the increase in the portion of evaporation is prevented. In initial stage of growth period, only 0 to 10% of soil surface is covered by crops (FAO-56) causing the evaporation component to have a dominant portion in the crop evapotranspiration parameter. As a result, placing of initial growth stage in warm days of year caused an increase in evaporation losses. It seems that S1P1 treatment was the optimal condition for transpiration increase and evaporation decrease. The estimated functions showed that (in salinity stress conditions) crop transpiration decreased more than ETc. Therefore, the transpiration rate should be considered as the crop's net water requirement instead of ETc (crop evapotranspiration). According to the Mass-Hoffman function, under stress conditions, the decreasing slope of transpiration and evapotranspiration and the increasing slope of evaporation become more pronounced. For instance, in planting dates of P1, P2, P3, and P4, for each unit (dS.m-1) of increase in soil salinity, the evapotranspiration rates decreased by 2.51%, 2.82%, 3.3%, and 3.65%, respectively. Similarly, the transpiration rates decreased by 6.1%, 7.34%, 8.42%, and 9.2%, respectively, while the evaporation rates increased by 5.5%, 6.7%, 7%, and 7.82%. ConclusionSalinity and atmospheric temperature stresses had interaction effects on evapotranspiration and components rates. Postponing the seed planting date and not utilizing optimal weather conditions, especially during spring, can lead to damage to transpiration, which is a favorable aspect; however it is unfavorable in evaporation,. Therefore, in irrigated crops, it is advisable not to plant seeds during the warm months of the year, especially in July and August. Consequently, by controlling soil salinity and selecting the appropriate planting date, water can be optimally utilized.
Irrigation
R. Saeidi
Abstract
Introduction: Adeqiate water use in the agricultural sector requires accurate knowledge of crop sensitivity to environmental stresses (such as water stress). The crop sensitivity to water stress may be different at different growth stages and may have a different effect on the actual amount of crop evapotranspiration ...
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Introduction: Adeqiate water use in the agricultural sector requires accurate knowledge of crop sensitivity to environmental stresses (such as water stress). The crop sensitivity to water stress may be different at different growth stages and may have a different effect on the actual amount of crop evapotranspiration compared to the standard conditions. At different levels of water stress, studying the sensitivity of crop evapotranspiration at different growth stages can be provided management strategies for optimal water consumption. In the present research, the intra-seasonal sensitivity coefficients of maize were modeled by using the Jensen model. Materials and Methods: In this research, the effect of water stress levels and growth stage sensitivity on the amount of maize (S.C 704) evapotranspiration was investigated. The experiment was performed as factorial based on randomized complete block design. The treatments included four irrigation levels of 100 (I0), 80 (I1), 60 (I2), and 40 (I3) percent of the crop water requirement and four growth stages of initial, development, middle and final. In between two irrigations, the amount of daily soil moisture was measured in the center of each plot and the depth of the crop root zone. Therefore, the amount of evapotranspiration of crops per unit area was estimated according to the soil water balance. Analysis of variance and mean data comparison of evapotranspiration and dry biomass yield were performed by SPSS software and using Duncan's multiple tests. By actual evapotranspiration and yield data, intra-seasonal sensitivity coefficients of maize to water stress (λ1 to λ4) were determined by SPSS software. Results and Discussion: Evapotranspiration The effect of irrigation water amount and growth stage on the maize evapotranspiration amount was significant at the probability level of 1%. Evapotranspiration amounts at the initial, developmental, middle, and final of maize growth stages were estimated equal to 79, 201.8, 123.8 and 14.6 mm (in I0 treatment), 78.3, 196, 126.6 and 14.6 mm (in I1 treatment), 72, 173.6, 99 and 11.7 mm (in I2 treatment), 62.8, 147.5, 81.5 and 8.4 mm (in I3 treatment), respectively. Reduction of evapotranspiration compared to control treatment (I0) in the initial, developmental, middle, and final growth stages were estimated equal to 0.9, 2.8, 9, and 0 (in I1 treatment), 8.8, 14, 20, and 19.8 (in I2 treatment), 20.5, 26.9, 34.2 and 42.4 (in I3 treatment) percent, respectively. The results showed that the slope of evapotranspiration reduction was not the same at different irrigation levels. Also, the relative evapotranspiration of maize (in all growth seasons) at irrigation levels of I1, I2, and I3 were estimated equal to 95.6, 85, and 71.6 percent, respectively. Therefore, when applying water stress, the optimal evapotranspiration rate can be adjusted by selecting the suitable growth stage. Yield The effect of irrigation levels on the dry biomass yield of maize was significant at the level of 1% probability. The dry yield of maize in treatments of I0, I1, I2, and I3 were equal to 17.1, 15.8, 12.6, and 8.7 (tons per hectare), respectively. The relative yield of maize at irrigation levels of I1, I2, and I3 were estimated to be 92.4, 73.7, and 50.9 percent, respectively, in the Qazvin region. The reduction of soil available water affected the water uptake by the crop and reduced the yield of maize. Modeling of intra-seasonal sensitivity coefficients of water stress At the initial, developmental, middle, and final growth stages of maize, stress sensitivity coefficients of λ1, λ2, λ3, and λ4 were estimated in water stress treatments. The mean of mentioned coefficients in stress treatments was calculated to be 0.421, 1.37, 0.274, and 0.133, respectively. The results showed that during the development stage of maize growth, the effect of water stress on yield reduction was more. The model efficiency for estimating the amount of relative yield was evaluated. Evaluation statistics of R2, EF, RMSE, ME and CRM were estimated to be 0.998, 0.986, 2.753, 0.026 and 0.021, respectively. The results showed that the Jensen model efficiency was good, and it can be used in planning the low irrigation for different growth stages of maize. Yield-Evapotranspiration Function of Maize in all of the growth stages Across different irrigation levels, a simple linear relationship of Y=69.935ET-12281 (with a correlation coefficient of 0.999) was fitted between two parameters of evapotranspiration and dry biomass yield of maize. Therefore, using the above equation in low irrigation management, the amount of maize yield can be estimated based on the evapotranspiration amount. In this research, 175 mm evapotranspiration was needed for the production of the initial unit of maize biomass. That is, the transpiration portion in the above amount was negligible, and it was mostly allocated to the soil evaporation portion. Conclusion: The crop sensitivity to water stress and different needs to transpiration at different growth stages were the reasons for the different reduction of maize evapotranspiration. Reduction of soil available water reduced the water uptake and transpiration, and crop biomass. The results showed that reducing the water stress was effective in increase of maize evapotranspiration efficiency. In order to produce the maximum crop biomass, the sensitivity of the maize growth stage and the water stress level must be considered.
R. Saeidi; H. Ramezani Etedali; A. Sotoodehnia; .B Nazari; A. Kaviani
Abstract
Introduction: Supplying human and animal nutritional needs requires suitable use of water resources. Due to the decrease of fresh water resources for agriculture, saline water resources cannot be ignored. Increasing water salinity reduces the water absorption by plant, due to decreasing the water potential. ...
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Introduction: Supplying human and animal nutritional needs requires suitable use of water resources. Due to the decrease of fresh water resources for agriculture, saline water resources cannot be ignored. Increasing water salinity reduces the water absorption by plant, due to decreasing the water potential. On the other hand, soil infertility (such as nitrogen deficiency) decreases the evapotranspiration and crop yield. The present study was to increase the water and nitrogen fertilizer use efficiency of maize, under salinity stress condition. This was done by managing the consumption of saline water and nitrogen fertilizer. In this research, irrigation requirement was determined proportional to the plant evapotranspiration to avoid excessive saline water use. Materials and Methods: In this research, two treatments of water salinity and nitrogen deficiency in four levels and three replications were implemented as a factorial experiment in a randomized complete block design. The studied plant was maize (S. C. 704 cultivar) sown in plots with dimensions of 3 × 3 meters and 1.5 meters distance. In this research, fertility stress was in the form of nitrogen fertilizer consumption and at four levels. Treatments of ، ، and consisted of consumption of 100, 75, 50 and 25% of nitrogen fertilizer, respectively. Salinity stress has been applied by irrigation of the plant with saline water. Water salinity treatments were selected based on the yield potential of maize, at four levels of 100, 90, 75 and 50%. According to the above four performance levels, treatments of ، ، and included irrigation water with electric conductivity of 0.5, 1.2, 3.5 and 7.5 (dS/m), respectively. The soil moisture content was measured at the depth of root development during the interval between two irrigations. Daily maize evapotranspiration was measured by the volumetric balance of water at the depth of root development. The stomata resistance of maize leaf was measured by the AP4 porometer device between two irrigations interval. Variance analysis and mean comparison of data were done by SPSS software and Duncan's multiple range test, respectively. Results and Discussion: Water use efficiency In this research, the evapotranspiration and dry matter yield of maize decreased under salinity stress and nitrogen deficiency treatments. This seems to be caused by the water potential decrease (due to salinity stress) and the nitrogen deficit in the soil. Under these conditions, optimum use of water and fertilizer increased water use efficiency. At first without water and fertilizer management, water use efficiency in different treatments ( to ), ranged from 2.74 to 4.4 kg/ (in 2017) and from 2.57 to 4.35 kg/ (in 2018). With suitable management of irrigation, water use efficiency, however, increased in stress treatments and approached to optimum treatment. The range of water use efficiency was from 4.2 to 4.4 kg/ (in 2017) and from 4.15 to 4.32 kg/ (in 2018). The reason for this was the management of irrigation volume based on actual evapotranspiration in stress treatments. On the other hand, increasing soil nitrogen was an appropriate strategy to increase water use efficiency. But in high salinity stress, despite the optimum use of water and fertilizer, it was not possible to achieve optimal water use efficiency. This is explainable by the harmful effect of salinity on the reduction of nutrient uptake (especially nitrogen) by the plant. Nitrogen use efficiency Soil nitrogen deficiency and increasing water salinity reduced nitrogen use efficiency. In different stress treatments, nitrogen use efficiency ranged from 3.34 to 5.11 kg/kg (in 2017) and from 3.06 to 5 kg/kg (in 2018). The results showed the destructive effect of salinity on nitrogen uptake by the plant. Under these conditions, the ions in the soil (especially the sodium and calcium) caused the plant to be unable to absorb nitrogen from the soil. Therefore, the production of plant matter was reduced. The results showed that proper management of nitrogen can increase nitrogen use efficiency under salinity stress. At high salinity levels, the nitrogen fertilizer was not, however, absorbed by the plant and accumulated in the soil. Conclusion: The results showed that water use management could increase the water use efficiency under stress treatments, by controlling evapotranspiration. On the other hand, soil fertility increased nitrogen fertilizer use efficiency under salinity stress. Among all treatments, had optimum water and nitrogen use efficiency. Overall, the volume of water used in the field should be adjusted to the actual requirement of the plant to prevent excessive consumption under salinity stress. In addition, increasing soil nitrogen, rather than more irrigation water, appears to be a suitable strategy to increase crop yield.
reza saeidi; abbas Sotoodehnia; Hadi Ramezani Etedali; Bizhan Nazari; Abbas Kaviani
Abstract
Introduction: Estimating the actual evapotranspiration of the crops, is so important for determining the irrigation needs. Typically, the climatic, vegetative and management parameters are effective on actual evapotranspiration. If the crops are exposed to salinity, fertility and other stresses, reduce ...
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Introduction: Estimating the actual evapotranspiration of the crops, is so important for determining the irrigation needs. Typically, the climatic, vegetative and management parameters are effective on actual evapotranspiration. If the crops are exposed to salinity, fertility and other stresses, reduce actual evapotranspiration and yield. The correct estimation of the actual evapotranspiration of crop will allow agricultural planners to the better agricultural water management. Previous researches show water stress and soil nitrogen deficiency (as management stresses), effect on increasing of stomatal resistance and reducing of crops evapotranspiration. Thus, goal of this study was to investigate the effect of salinity and soil nitrogen deficiency on the amount of Ks coefficient and readily available water of maize.
Materials and Methods: This study was conducted in research farm at University of Imam Khomeini International, Qazvin, Iran during June to November 2017. In this research, the effects of saline water and soil nitrogen deficiency on Maize (SC 704) evapotranspiration, were investigated. The applied treatments included irrigation with saline water (in four levels: 0.5 (S_0), 1.2 (S_1), 3.5 (S_2) and 5.7 (S_3) dS/m) and soil fertility (in four levels: nitrogen fertilizer consumption at 100 (N_0), 75 (N_1), 50 (N_2) and 25% (N_3)). The experimental design used in this research was a completely randomized block design with three replications. In this experiment, maize seeds were cultivated in the plots with Length and width of 3×3 meters. The prometer device (Model: AP4) was also used to measure stomatal resistance of maize leaf. Determining the irrigation schedule, was based on the soil moisture reached to the limit of RAW (Readily Available Water). At the same time, with increasing stomatal resistance, RAW was calculated and irrigation was done. Evapotranspiration of the under stress plants were ET_(c-adj) and evapotranspiration of S_0 N_0 treatment was ET_c. The stress factor (K_s ) is calculated by ET_(c-adj)/ET_c. The values of RAW and K_s were analyzed by SPSS software. K_s coefficient was modeled with amounts of salinity stresses and soil nitrogen deficiency.
Results and Discussion: The results of this study showed that the interaction between two factors of salinity stress and nitrogen deficiency on the K_s and RAW parameters (in level: 1%) are significant. K_s coefficient at the levels of S_1, S_2 and S_3, were 0.95, 088 and 0.77, respectively. In saline water of 0.5 (dS/m), the K_s coefficient of N_1, N_2 and N_3 were 0.98, 0.96 and 0.95, respectively. With increasing the 1(dS/m) salinity of water and 25% reduction in nitrogen consumption, decreased the K_s amount about 4.5% and 1.7%, respectively. The reason of results is that with increasing of water salinity, decreases the osmotic potential of water in the soil and the crop needs to consume more energy to obtain water. Thus, amount of crop transpiration is reduced and soil water content is remained. The linear, exponential, logarithmic, polynomial and power functions were fitted between N_i/N_0 and S_i/S_0 data. The ability of the above functions to estimate the K_s coefficient value was evaluated. The polynomial function has a good function for estimating the K_s coefficient. In the S_0، S_1، S_2 and S_3 treatments, by changing the fertility value from N_0 to N_3, amounts of RAW were 63.7, 58.7, 55.4 and 42% , respectively. Also in N_0، N_1، N_2 and N_3 treatments, with changing the salinity of water from S_0 to S_3, RAW values were 51.7, 46.3, 42.7 and 42%, respectively. Therefore, stresses that reduce crop evapotranspiration are effective on reducing the amount of RAW. In this situation, the actual water requirement of the crop is less than the potential evapotranspiration of the area.
Conclusions: Increasing water salinity and nitrogen deficiency decrease evapotranspiration of maize and increase soil water content. By calculating the stress coefficient (K_s ), it is possible to estimate the actual evapotranspiration of maize, in Qazvin. Thus, the amount of irrigation water is adjusted according to the actual water requirement of maize. Under salt stress conditions with increasing the soil nitrogen, Can be increased the K_s coefficient and evapotranspiration of maize. Therefore, calculating the crop's water requirement based on the existence of strtesse, it will help to saving water.
reza saeidi; Hadi Ramezani Etedali; Amir Samadi; Ali Reza Tavakoli
Abstract
Introduction: Rainfed agriculture plays an important role in food production. In Iran, 6 million hectares of cultivated landsare rainfed. Moreover, about10% of raw agricultural products are being produced by rainfed agriculture. Yields of rainfed fields are decreased due to drought in recent years in ...
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Introduction: Rainfed agriculture plays an important role in food production. In Iran, 6 million hectares of cultivated landsare rainfed. Moreover, about10% of raw agricultural products are being produced by rainfed agriculture. Yields of rainfed fields are decreased due to drought in recent years in Iran. Supplementary irrigation is a suitable management to improve and enhance the yield of rainfed agriculture. Determination of appropriate time of supplementary irrigation is necessary in each region. But water allocation for this practice is the main challenge, because water resources are restricted. Therefore, water allocation management between irrigated and rainfedfields could be a viable strategy. Water resources for supplementary irrigation in rainfed fields are saved through deficit irrigation in irrigated lands or from rivers. The purpose of this study is optimum water allocation for supplementary irrigation in wheat and barley farms from rivers to around rainfed fields in Kamyaran region. In this study, supplementary irrigation is considered in three management methods of autumn irrigation, spring irrigation and both of them.
Materials and Methods:Kamyaran is located in Kurdistan province in west of Iran. The area of rainfed field is very vast in this region. Usually, rainfed fields are located in high slop lands and far from water resources in Kamyaran region. Supplementary irrigation is possible in rainfed fields around to water resources and with slope of less than 8%. The area of sub-basins with appropriate situations in Kamyaran region was calculated by geographic information system (GIS). Ratio of wheat to barley in rainfed fields is 3 to 1. Rivers in each sub-basin is the only water resources for supplementary irrigation in Kamyarn region. In this study, the objective function is maximizing net benefit. Also, constraints are total available water volumes in rivers at supplementary irrigations times and rainfed fields with appropriate situation for supplementary irrigation. Decision variable is rainfed area with different irrigation managements (autumn supplementary irrigation, spring supplementary irrigation, autumn+spring supplementary irrigations and rainfed managements). The total costs and income of agricultural production are found in statistical books of agriculture jihad in 2008-2009 growing season.
Results and Discussion: The lands around of rivers with suitable slope are about 30% of rainfed land of Kamyaran. The appropriate rainfed fields in sub-basins of A, B, C, D, E, F and INT were 125.39, 15.52, 18.11, 1111.26, 96.51, 48.13 and 49.55 Km2, respectively. The results of Optimization model showed the supplementary irrigation managements are different in each sub-basin because of different discharge of river in each sub-basin in different months. The optimal supplementary irrigation management for barley rainfed fields is autumnsupplementary irrigation. The yields of barley rainfed fields increase about 90% by autumn supplementary irrigation. The optimal supplementary irrigation managements for wheat are different in each sub-basin, but autumn+spring supplementary irrigations is best managed if water resources will be enough in each sub-basin. Due to restriction of water in rivers at supplementary irrigation time, some of wheat and barley fields remain rainfed in A+B+C and D sub-basin. The results showed minimum and maximum increase of wheat production in D and INT sub-basins are 29 and 134%, respectively. Also production increasing are 87, 112 and 126% in A+B+C, E and F, respectively. Increasing of barley production in the sub-basins of E, F and INT, are 61, 96 and 96%, respectively. Other sub-basins of A+B+C and D remained in rainfed farming. Net benefit increase about 65 and 275% for wheat and barley fields respectively, in 2014. Water productivity in all sub-basins for both wheat and barley is 74.8 and 44.5%, respectively.
Conclusions:This study showed supplementary irrigation management increased the yield and net benefit in rainfed fields of Kamyaran sub-basins. Resultsshowed about 30% of rainfed land of Kamyaran, are suitable for supplementary irrigation. The results of optimization models showed total increase of wheat production in A+B+C,E, F, D and INT sub-basins are 87, 112, 126, 29, 134%, respectively. Also increase of barley production in the sub-basins of E, F and INT, are 61, 96 and 96%, respectively. The result showed production increase about double in Kamayaran region. Also, net benefit increase about 65 and 275% in wheat and barley fields respectively.It has been suggested in A, B, C sub-basin, autumn supplementary irrigation of wheat, in E, F and INT sub-basins, autumn and spring supplementary irrigation for wheat and autumn supplementary irrigation for barley and in D sub-basin, autumn and spring supplementary irrigation for wheat.
