Increased heat stress risk for maize in arid-based climates as affected by climate change: threats and solutions.

Heat stress in combination with drought has become the biggest concern and threat for maize yield production, especially in arid and hot regions. Accordingly, different optimal solutions should be considered in order to maintain maize production and reduce the risk of heat stress under the changing climate. In the current study, the risk of heat stress across Iranian maize agro-ecosystems was analyzed in terms of both intensity and frequency. The study areas comprised 16 provinces and 24 locations classified into five climate categories: arid and hot, arid and temperate, semi-arid and hot, semi-arid and temperate, and semi-arid and cold. The impact of heat stress on maize under a future climate was based on a 5-multi-model ensemble under two optimistic and pessimistic emission scenarios (RCP4.5 and RCP8.5, respectively) for 2040-2070 using the APSIM crop model. Simulation results illustrated that in the period of 2040-2070, intensity and the frequency of heat stress events increased by 2.37 °C and 79.7%, respectively, during maize flowering time compared to the baseline. The risk of heat stress would be almost 100% in hot regions in the future climate under current management practices, mostly because of the increasing high-risk window for heat stress which will result in a yield reduction of 0.83 t ha-1. However, under optimal management practices,farmers will economically obtain acceptable yields (6.6 t ha-1). The results also indicated that the high-risk windows in the future will be lengthening from 12 to 33 days in different climate types. Rising temperatures in cold regions as a result of global warming would provide better climate situations for maize growth, so that under optimistic emission scenarios and optimal management practices, farmers will be able to boost grain yield up to 9.2 t ha-1. Overall, it is concluded that farmers in hot and temperate regions need to be persuaded to choose optimal sowing dates and new maize cultivars which are well adapted to each climate to reduce heat stress risk and to shift maize production to cold regions.

Future climate change could reduce irrigated and rainfed wheat water footprint in arid environments.

The concept of water footprint (WF) has been used to manage freshwater resources for the past two decades and is considered as indicator of the sustainability of agricultural systems. Accordingly, the current study aimed to quantify WF and its components in the future climate for rainfed and irrigated wheat agro-ecosystems in 17 provinces of Iran located in arid or semi-arid environments. The provinces were divided into five climate classes. The simulations were conducted under current (1980-2010) and future climate (2040-2070) using the Agricultural Production Systems sIMulator (APSIM) crop model, following the Agricultural Model Intercomparison and Improvement Project (AgMIP) protocol. Baseline simulations indicated that the total WF, averaged across all climate classes, was 1148 m3 t-1 for irrigated and 1155 m3 t-1 for rainfed wheat. WF was projected to decline in the future compared to baseline in both irrigated and rainfed systems mostly because of increases in yield of +9% in rainfed systems and 3.5% in irrigated systems, and decreases in water consumption by -5.4% and -10.1%, respectively. However, the share of gray water footprint (WFgray) was projected to increase in the near future for both rainfed (+5.4%) and irrigated (+6.9%) systems. These findings suggest that cleaner and more sustainable production (i.e. obtaining grain yield under optimal water and nitrogen consumption) could be achieved in irrigated and rainfed wheat ago-ecosystems if optimal N fertilizer management is adopted. Additionally, rainfed cultivation can be further expanded in some areas which is expected to result in a substantial reduction in blue water (i.e. less irrigation), especially in sub-humid and semi-arid cool areas.

Risk assessment of frost damage to sugar beet simulated under cold and semi-arid environments.

In the semi-arid climatic conditions, water shortage is a key factor to generate crop production. Planting in autumn and winter and using precipitation can help cope with the problem. But in the semi-arid areas with cold winter, frost is another limited factor affecting crop production. For this purpose, in the present study, a simple and universal crop growth simulator (SUCROS) model was used to estimate the potential yield of sugar beets and frost damage from 1993 to 2009 for four autumn sowing dates (2 October, 17 October, 1 November, and 16 November) and two spring dates (6 March and 6 May) in eight locations (Birjand, Bojnord, Ghaen, Mashhad, Torbat-e Heydarieh, Neyshabor, Torbat-e Jam, and Ghochan) of the Khorasan province in northeastern Iran as a semi-arid and cold area. There was a large variability between locations and years in terms of frost damage. The crop failure from frost for the autumn sowing dates ranged from 62.5 to 100% at Neyshabor and Ghochan, respectively. Although autumn sowing dates performed better than spring sowing dates in terms of fresh storage organ yield (~ 109.9 t ha-1 vs. ~ 78.4 t ha-1), the risk of frost stress under autumn sowing dates was high at all studied locations. To maximize potential yield and minimize frost risk, sugar beet farmers under semi-arid and frost-prone conditions in the world such as Khorasan province should choose optimum sowing dates outside the high frost risk period to avoid crop damage. The last frost day under these areas normally happened between the 15th and 28th of February, after which no frost events occurred. Accordingly, it is recommended to farmers to sow sugar beet after the period during which no frost risk for sugar beet occurred.

Assessing energy efficiencies, economy, and global warming potential (GWP) effects of major crop production systems in Iran: a case study in East Azerbaijan province.

Efficient use of energy in farming systems is one of the most important implications for decreasing greenhouse gas (GHG) emissions and mitigating global warming (GW). This paper describes the energy use patterns, analyze the economics, and report global warming potential effects of major crop production systems in East Azerbaijan province, Iran. For this purpose, 110 farmers whose main activity was major crop production in the region, including wheat, barley, carrot, tomato, onion, potato, alfalfa, corn silage, canola, and saffron, were surveyed. Some other data was obtained from the Ministry of Agriculture Jihad of Iran. Results showed that, in terms of total energy input, onion (87,556 Mj ha-1) and potato (80,869 Mj ha-1) production systems were more energy-intensive than other crops. Among the studied crops, the highest values of net return (6563.8 $ ha-1) and benefit/cost ratio (1.95) were related to carrot and corn silage production systems, respectively. Studies have also shown that onion and saffron production systems emit the highest (5332.6 kg CO2eq ha-1) and lowest (646.24 kg CO2eq ha-1) CO2 eq. emission, respectively. When it was averaged across crops, diesel fuel accounted for the greatest GHG contribution with 43% of the total, followed by electric power (28%) and nitrogen fertilizer (21%). In the present study, eco-efficiency was calculated as a ratio of the gross production value and global warming potential effect for the studied crops. Out of all the studied crops, the highest values of eco-efficiency were calculated to be 8.65 $ kg CO2eq-1 for the saffron production system followed by the carrot (3.65 $ kg CO2eq-1) production. Generally, from the aspect of energy balance and use efficiency, the alfalfa production system was the best; however, from an economical point of view, the carrot production system was better than the other crops.

Fingerprinting aliphatic hydrocarbon pollutants over agricultural lands surrounding Tehran oil refinery.

The analysis of aliphatic hydrocarbons, which are composed of n-alkanes as well as branched and cyclic alkanes, can be used to distinguish between the sources of hydrocarbon contamination. In this study, the concentration of aliphatic hydrocarbons, soil pH, and organic matter in agricultural soils located south of Tehran were monitored. Eighty-three soil samples were taken from two depth ranges of 0-30 and 30-60 cm. The results showed that aliphatic compounds ranged from 0.22-68.11 mg kg-1 at the top to 0.33-53.18 mg kg-1 at subsoil. The amount of hydrocarbons increases from the northern parts toward the south, and hydrocarbon pollutants originated from both petroleum and non-petroleum sources. Higher concentrations of aliphatic compounds in the southern parts indicated that, aside from the practice of irrigating with untreated wastewater, leakage from oil refinery storage tanks possibly contributed to soil pollution. The results also showed that several sources have polluted the agricultural soils. It is necessary to develop a new local pollution criterion as a diagnostic index that includes not only hydrocarbons but also other parameters such as heavy metal content in both soil and untreated wastewater, surface runoff, and other irrigation water resources to determine the exact origin of pollution.

Large-scale characterization of drought pattern: a continent-wide modelling approach applied to the Australian wheatbelt--spatial and temporal trends.

Plant response to drought is complex, so that traits adapted to a specific drought type can confer disadvantage in another drought type. Understanding which type(s) of drought to target is of prime importance for crop improvement. Modelling was used to quantify seasonal drought patterns for a check variety across the Australian wheatbelt, using 123 yr of weather data for representative locations and managements. Two other genotypes were used to simulate the impact of maturity on drought pattern. Four major environment types summarized the variability in drought pattern over time and space. Severe stress beginning before flowering was common (44% of occurrences), with (24%) or without (20%) relief during grain filling. High variability occurred from year to year, differing with geographical region. With few exceptions, all four environment types occurred in most seasons, for each location, management system and genotype. Applications of such environment characterization are proposed to assist breeding and research to focus on germplasm, traits and genes of interest for target environments. The method was applied at a continental scale to highly variable environments and could be extended to other crops, to other drought-prone regions around the world, and to quantify potential changes in drought patterns under future climates.

Municipal solid waste management in Tehran: current practices, opportunities and challenges.

Tehran, the capital city of Iran and a metropolis with a population of 8.2 million and containing 2.4 million households, generated 2,626,519 tons of solid waste in 2005. The present study is aimed at evaluating the generation, characteristics and management of solid waste in Tehran. Municipal solid waste comprises more than 97% of Tehran's solid waste, while three other types of solid waste comprise less than 3% of it, namely hospital waste (1.0%), industrial waste (0.6%) and construction and demolition waste (0.5%). The contribution of household solid waste to total municipal solid waste is about 62.5%. The municipality of Tehran is responsible for the solid waste management of the city; the waste is mainly landfilled in three centers in Tehran, with a small part of it usually recycled or processed as compost. However, an informal sector is also active in collecting recyclable materials from solid waste. The municipality has recently initiated some activities to mechanize solid waste management and reduce waste generation. There remain important challenges in solid waste management in Tehran which include: the proper collection and management of hospital waste; public education aimed at reducing and separating household waste and educating municipal workers in order to optimize the waste collection system; and the participation of other related organizations and the private sector in solid waste management.

Herbicide risk assessment during the Wheat Self-sufficiency Project in Iran.

BACKGROUND: The present study describes the quantitative changes in herbicide use during the specific observation periods in the Wheat Self-sufficiency Project in Iran from 1994 to 2004 and the associated changes in herbicide risk, area and yield in this context. A risk index, the environmental impact quotient (EIQ), was used to estimate the environmental impacts (EIs) of herbicides applied to wheat agroecosystems. RESULTS: The results suggest that, during this period, the overall risk posed by the herbicides applied to wheat agroecosystems increased substantially, as evidenced by a 71% increase in herbicide usage (weight of pesticide applied) and a 62.2% increase in EI rating, in spite of an 8.2% decrease in overall EIQ rating and an 89.2% decrease in mean application rate. Furthermore, a 0.57% increase in the area and a 23.6% and 22.7% increase in irrigated and rainfed yields, respectively, were observed. The results also indicate that the EIQ(FUR) of two herbicides, dichlorprop-P/mecoprop-P/MCPA and difenzoquat, is much higher than that of other herbicides, and they could be qualified as high-risk herbicides. CONCLUSION: As a whole, an increase in herbicide usage (weight of pesticide applied) was an important factor on herbicide environmental impact boost. However, this increase has not led to a similar increase in wheat yield, which could be attributed in part to the negative impact of high herbicide consumption in wheat fields and subsequent threat to the long-term sustainability of these agroecosystems.