جستجوی مقالات مرتبط با کلیدواژه « بارندگی » در نشریات گروه « زراعت »

Chemical fertilizers have played a significant role in increasing the yield of agricultural products, especially since the 1950s, but the excessive application of these fertilizers in recent years has led to environmental pollution and a drop in agricultural productivity, food security, ecosystem and human health, and economic prosperity. Researchers believed that the best and most accessible approach to solve these problems is the improvement of the efficiency indicators of inputs. So, the purpose of the study was to evaluate the use efficiency indicators for nitrogen and phosphorus and water in wheat-irrigated and dryland systems of Iran.

In this research, provinces with more than 80% production in irrigated and rainfed systems of Iran were determined and, in each province, cities with more than 80% production of this crop were selected. The required data were collected by using face-to-face interviews and recorded statistics. Afterward, the consumption productivity of inputs was determined, and then the Pearson correlation coefficient between the productivity of different sources was computed. Also, multiple regression was used to determine the relationship between yield with climatic variables and fertilizers and water. For this purpose, the two-year average for total precipitation for irrigated and rainfed systems in each region were extracted.

The results revealed that in the main areas of wheat production, the average productivity of nitrogen consumption for irrigated was calculated as 16.69 kg of grains per kg of nitrogen compared to 17.27 kg of grains per kg of nitrogen for rainfed conditions. Contrary to nitrogen, the efficiency of phosphorus consumption in rainfed agriculture was lower than in the irrigated wheat system. Also, the highest correlation between nitrogen and phosphorus productivity for the irrigated system was computed with r=0.506 and the coefficient between nitrogen and water productivity was calculated with r=0.309 for rainfed conditions. The results for regression analysis between yield and climatic and agronomic parameters showed that increases in temperature had a positive effect on grain yield in rainfed conditions. On the other hand, increasing in other parameters such as precipitation, nitrogen, phosphorus, and irrigation in the irrigated and rainfed systems had a direct relationship with grain yield.

Excess use of nitrogen fertilizers in irrigated wheat systems led to lower nitrogen use efficiency. Although, the grain yield in irrigated conditions was higher than in dryland conditions, due to the sensitivity of using nitrogen by farmers and the adverse effects of excessive use in rainfed wheat, the consumption of nitrogen has been used with more precision and sensitivity. This ultimately led to an increase in the efficiency of nitrogen consumption in rainfed compared to irrigated systems. Unlike nitrogen, the phosphorus use efficiency was lower in rainfed compared to the irrigated system due to the direct effect of soil moisture on the release of phosphorus in the soil. According to these results, nitrogen and water were the most important factors affecting the yield in irrigated and rainfed systems. Also, the regression analysis of the relationship between wheat yield and climatic and agronomic parameters showed that in irrigated systems, nitrogen and irrigation and in rainfed conditions, nitrogen and precipitation had the most impact on grain yield.

Saffron (Crocus sativus L.) has been used as food and medicine for Iranians for a long time, from the ancient to the modern period, and several factors have influenced its production and consumption in different provinces, especially Razavi Khorasan. In order to investigate the trend of cultivated area, stigma production and yield of saffron and also the effect of climatic parameters such as altitude above sea level, average temperature, and precipitation on the cultivation and production of this plant in different cities of Khorasan Razavi Province, a study was conducted by using data of Agricultural Jihad Organization during 1984 to 2020. Results indicated that the highest production and cultivated area in the province of Razavi Khorasan in the studied period were related to Zaveh, Torbat Heydarieh, and Roshtkhar, respectively. Zaveh and Torbat Heydarieh also had the largest portion of irrigated production in the province, with 13.3 and 9.4 %, respectively. Upon comparing the yield of saffron across different cities to the provincial average, it became evident that Gonabad and Torbat Heydarieh secured the first and second positions, respectively, in this comparison. Conversely, Kalat exhibited the lowest percentage in terms of cultivated area, irrigated production, and yield ratio compared to the provincial average. Further analysis revealed that elevation above sea level is positively correlated with both cultivated area and saffron production. Interestingly, there exists a non-linear inverse relationship between annual rainfall and cultivated area, production, and yield of saffron. Moreover, the study found that higher average temperatures are associated with increased saffron production, although the average yield of saffron tends to decrease. Regarding similarities across different cities in Khorasan-Razavi province, an investigation at a 75% similarity threshold indicated the possibility of classifying the province's various regions into five distinct clusters. The cities of Bakharz, Gonabad, Kashmer, Mahvalat, and Roshtkhar were in the first cluster, and the cities of Bajastan, Khaf, Torbat Jam, Neishabur, Bardaskan, and Taibad were in the second cluster, and each of the cities of Torbat Heydarieh and Zaveh also formed two separate branches. The rest of the cities were placed in a cluster. In general, the increasing trend of saffron cultivation and production in Khorasan-Razavi province indicates a greater desire to cultivate this plant by the farmers, considering the climatic and soil conditions of this province.

Climate change is one of the most serious environmental challenges and its long-term effects can have serious economic, social and environmental consequences. The agricultural sector is one of the vulnerable parts in terms of climate change. In this regard, this study aimed to investigate the factors affecting the adaptation strategies by saffron farmers Torbat-e Heydarieh using stratified random sampling method and logit model and five-part questionnaire. Data were collected by completing 380 questionnaires from saffron farmers in Torbat-e Heydarieh in 2018. The descriptive results of the study showed that most saffron farmers believe in increasing temperature, reducing rainfall and the emergence of drought and frostbite. Reducing water supply, reducing yields of saffron, reducing economic efficiency, unemployment and migration are among the consequences of climate change in Torbat-e Heydarieh. Also, based on the results, 63% of saffron farmers are willing to use adaptation strategies. The results of the Logit model estimation show that the variables of agricultural experience, land size, access to credit, extention services, media exposure and education affect the likelihood of choosing adaptive strategies. However, the variables of mechanization level and side occupation did not have a significant effect on the likelihood of choosing compatibility strategies. Therefore, government policies should provide the bank with confidence in providing bank facilities to saffron farmers who provide saffron farmers with the ability and flexibility to manage water resources, soil and other inputs in response to climate change.

The basis of monitoring drought in every region is reviewing the specifications of the occurred drought. In recent years, cutting the distributaries of Sepidrood river due to construction of several dams on the upstream has increased the effect of rainfalls in the province on sustainability of rice fields of Guilan province. This study is aimed at investigating the climate-related drought and studying the characteristics of this phenomenon in Guilan province and the difference between the severities of climate-related drought in different price fields of the region over a 35-year period. For this purpose, standardized precipitation index (SPI) was used. The precipitation data of thirty rain-gauge stations regarding the standardized precipitation in two periods, crop season and whole year periods, related to four regions including the central district of Guilan, east of Guilan, Foumanat, and west of Guilan were investigated. The results showed that a great area of the province has been involved in drought in the crop period in 2013, 2008, 1999, and 2014. The highest severity of drought in the crop period drought was related to Foumanat region during the water year 2007-2008 with a SPI value of -2.06. The evaluated value of this index in the crop period relative to its value during the whole year showed that in all of the four regions, severity of the drought in the crop period was more than its severity in the year period, and the frequency of drought occurrence in the crop period was over two times more than the year period. Also, calculation of SPI index in the crop period shows a more accurate performance than the 12-month period during which a significant part of the precipitation potential is wasted and lost from the agricultural system of the Guilan province.

In regions with autumn-sown sugar beet planting, rainfall occurrence during sugar beet growth, especially in winter, has an economic and significant role in supplying the required water. This study was conducted to determine rainfall as well as early and late irrigation proportion on sugar beet performance in randomized complete block design with three replications in Safi-Abad Agricultural Research Center in 2005-06. Treatments were composed of five irrigation levels including irrigation after 100, 150, 200, 250, 300 mm evaporation from evaporation pan (I1-I5, respectively), no-irrigation in spring (I6), seedling emergence by rainfall and spring irrigation after 100 mm evaporation from evaporation pan (I7), irrigation during the growing season after 100 mm evaporation from evaporation pan (I8) and no -rainfall as well as -irrigation in spring (I9). Significant difference was observed among treatments for quantitative and qualitative traits (P

To study the effects of used water in evapotranspiration، seed number per unit area and leaf relative water content on seed weight of canola (Brassica napus L.)، an experiment was conducted as a randomized complete block design، arranged in a split-plot under two conditions، i. e. supplemental irrigation and rainfed in 2005-7. Two cultivars of canola (‘Hyola401’ and ‘RGS003’) as subplots were grown at five sowing dates as main plots، spaced 30 days apart. There was a linear relationship between seed weight and used water in evapotranspiration. Irrigation increased seed weight and seed yield significantly. The mean 1000- seed weight under irrigation and rainfed conditions was 3. 2 and 2. 7g in 2005-6، and 4. 2 and 3. 7g in 2006-7. There was a strong linear relationship between seed weight and leaf relative water content، explaining 92 and 84 percent of the variation for ‘Hyola401’ and ‘RGS003’، respectively. For an each percent increase in leaf relative water content، 1000-seed weight of ‘Hyola401’ and ‘RGS003’ increased 0. 191 and 0. 146g، respectively. The strong relationships of seed weight with used water in evapotranspiration and leaf relative water content، over different environmental conditions and cultivars، showed these variables to be generally applicable in canola seed weight determination

In order to grow plants in any region، suitable weather and climatic condition are required. Climatic parameters such as precipitation، temperature and humidity have significant roles in the growth and yield in a region; therefore، understanding the climate and analyzing the ecophysiological characteristics of plants are the most important factors in the yield of the plant. Saffron is one of the profitable plants in South Khorasan. The yield of saffron from this region has caused Iran to be the targets producer of this plant in the world. The significance of planting saffron in Iran is related to many factors such as the high efficiency of water usage and employment of villagers. The analysis of the effect of climatic parameters on the saffron yield and determining the suitable areas for planting this plant according to these parameters are important for agriculture and economy. The statistics and data of 20 years taken from the Weather Station in the region and the 10 years saffron yield were used. Regression analysis and create of equation using precipitation، relative humidity، and the relation between these parameters was accomplished by the use of JMP 4 software. Digitized climate zonation maps were made by Arc GIS 9. 2 software. The results showed that precipitation was most effect on the saffron yield during the months of December، Feburay، March and April compared with the other months and considering humidity، the most affected months are October، November، Decmber، January and February. Also، after analyzing the equation and the climate zonation maps and the final map، it became obvious that the most of the areas of the Province were able to be ranked as suitable. The North and North-Eastern regions were the best areas regarding the parameters discussed in order to grow saffron. The center of province were considered average region to grow saffron and the Southern and South-Western areas were determined the least suitable for growing saffron.

The effect of environmental factors as temperature, photothermal quotient and rainfall during seed filling period (SFP) on seed weight of different species of Brassica was studied in Gonbad during 2003–2006 growing seasons. Twenty genotypes from different species of Brassica including: five genotypes of spring B. napus, five genotypes of winter B. napus, five genotypes of B. rapa, and five genotypes of B. juncea were sown at optimum sowing date recommended for the area. In all species, there was a linear relationship between 1000- seed weight and mean air temperature, photothermal quotient and rainfall during SFP. Increase in radiation accompanied with relatively moderate temperatures during SFP, hence, increased seed weight. Each millimeter increase in rainfall during SFP increased the rate of 1000-seed weight of spring and winter rapeseeds, mustard and turnip genotypes by 0.0094, 0.0247, 0.0105 and 0.0132 g, respectively. In addition, with an each day increase in duration of SFP, 1000-seed weight of spring and winter rapeseeds, mustard and turnip genotypes increased by 0.0533, 0.1682, 0.0456 and 0.0529 g, respectively. These relationships showed that winter rapeseeds genotypes had more response to favorable environmental factors during SFP. The non-significant relationship between seed number per unit area and seed weight in different species of Brassica showed that under conditions of this study sink size did not affect seed weight, but it was affected by environmental factors during seed filling period.

Increasing terminal drought and heat stresses in Gonbad area necessiate evaluation and selection of superior genotypes from different species of Brassica. A field experiment was conducted at Agricultural Research Station of Gonbad during 2003–2006 growing seasons. Twenty genotypes from three species of Brassica (five genotypes of spring type, B. napus (STN), five genotypes of winter type, B. napus (WTN), five genotypes of B. rapa (turnip), and five genotypes of B. junceae (mustard)] were sown at optimum sowing date. Combined analysis of variance showed that the mean seed yield (SY) of STN genotypes was considerably greater than other genotypes. The mean SY of WTN, STN, turnip, and mustard genotypes were 1381, 2191, 1780, and 1915 kg ha-1, respectively. A great proportion of SY variation was related to environmental factors such as rainfall, and interaction of temperature × radiation (photothermal quotient, PTQ). In STN and turnip genotypes, there was a positive linear relationship between SY and rainfall during growing season. For each 0.1 unit increase in PTQ during flowering period, SY of WTN, mustard, STN, and turnip genotypes increased by 582, 574, 336, and 303 kg ha-1, respectively. For each 0.1 unit increase in PTQ from termination of flowering to physiological maturity, SY of WTN, mustard, STN, and turnip genotypes also increased by 749, 732, 658, and 240 kg ha-1, respectively. The number of days from emergence to physiological maturity in WTN and mustard genotypes was longer than STN and turnip genotypes. Therfore, the reproductive stages of WTN and mustard genotypes coincided with higher temperatures, led to a greater response of SY to increase in PTQ. The SY superiority of STN genotypes showed that STN genotypes are better adapted to rainfed environmental conditions of Gonbad.

Global warming will affect all climatic variables and particularly rainfall patterns. The purpose of present investigation was to predict climatic parameters of Iran under future climate change and to compare them with the present conditions. For this reason, UKMO General Circulation Model was used for the year 2025 and 2050. By running the model, minimum and maximum monthly temperature and also maximum monthly rainfall for the representative climate stations were calculated and finally the effects of climate change on these variables based on pre-determined scenarios was evaluated. The results showed that averaged over all stations, mean temperature increase for spring in the year 2025 and 2050 will be 3.1 and 3.9, for summer 3.8 and 4.7, for autumn 2.3 and 3 and for winter 2.0 and 2.4 ºC, respectively. This increase will be more pronounced from North to the South and from East to the West parts of the country. Mean decrease in autumn rainfall for the target years of 2025 and 2050 will be 8 and 11 percent, respectively. This decrease is negligible for summer months. Length of dry season for the years 2025 and 2050 will be increased, respectively up to 214 and 223 days due to combined effects of increased temperature and decreased rainfall.