Determining the physical water productivity of wheat in different climates of Kermanshah province

Introduction

Wheat, with the scientific name Triticum aestivum L., is the world's first agricultural product, which is consumed by 35% of the world's population as the main food source. The cultivation area of this crop in the world is 219153830 ha, of which about 48% of it is under irrigation. The area of wheat cultivation in Iran is 6908545 ha, and about 34.3% of it is under irrigation. The area of irrigated wheat crop in Kermanshah is about 102236 ha. Based on the statistics of the crop year 2021-2022, Kermanshah province ranks sixth, fourth and third in the country in terms of the amount of cultivated area, production and yield of water wheat. Wheat plant is one of the main and major agricultural products of Kermanshah province and it is cultivated under irrigation in a large area of their lands. Therefore, determining wheat physical water productivity is an important indicator in wheat production planning. Considering the increase in population, climate changes, lack of water resources, and the increasing need for wheat production and food supply, it is necessary to improve the wheat water productivity. To improve water productivity, the first step is to know and determine its amount. Unfortunately, there is no accurate information about its amount in Kermanshah province, and only information related to the results of research projects in certain conditions is available, which cannot be generalized due to the difference between those conditions and the conditions of farmers' fields. The purpose of this research is to determine the water productivity of wheat crops in cold, moderate and hot climates of Kermanshah province.

Materials and Methods

Kermanshah province is located in the geographical position of 45° 25ʹ to 48° 6ʹ East longitude and 33° 41ʹ to 35° 17ʹ North latitude. Kermanshah province with an area of 24434.25 km2 covers about 1.5% of the country's area and its average height is 1200 m above sea level. This province generally has three climates: cold, moderate and hot. Based on the statistics of the agricultural year of 2020-2021of the Organization of Agricultural Jahad of Kermanshah province, and in the mentioned climates, Sonqor, Kermanshah and Sarpol Zahab cities respectively have the largest area under wheat cultivation and were selected as the research areas. To carry out the current research, 34 farms were selected under the conditions of farmers and during the growing season, the total volume of irrigation water of each farm was measured. The effective precipitation was determined using the data of the closest synoptic meteorological station to the selected farms and the USDA relationship. The volume of water consumed by each selected farm during the growing season was also calculated from the sum of the total volume of irrigation water and effective precipitation. After harvesting the crop and determining the yield of wheat by dividing it by the amount of water consumed, the amount of physical water productivity in each of the farms was determined. Then, the data obtained in the studied cities were statistically analyzed using SPSS software.

Results and Discussion

The results showed that the average total volume of irrigation water measured in Sonqor, Kermanshah and Sarpol Zahab cities was 5204, 5795, and 4236 m3 ha-1, respectively, and the average volume of wheat water consumption was 6297, 7737, and 5844 m3 ha-1, respectively. Therefore, the total volume of wheat irrigation water in Sarpol Zahab city was 19% and 27% less than in Sonqor and Kermanshah cities, respectively, due to the short duration of the wheat growth period and growth in the cool months of the year. This causes the amount of wheat water consumption volume in this city to be 7 and 24% less than the two cities of Sonqor and Kermanshah, respectively. The average yield of wheat in the mentioned cities was 5799, 7082 and 4937 kg ha-1, respectively. The average physical water productivity of wheat in the mentioned cities was 0.97, 0.95 and 0.86 kg m-3, respectively. Therefore, the results showed that the amount of physical water productivity of wheat in Sarpol Zahab city was lower than the other two cities, and the most important reason was the low yield of wheat in this city.

Conclusion

In this research, the values of the total volume of irrigation water, the volume of wheat water consumption and the physical water productivity of wheat in cold, moderate and hot climates of Kermanshah province were determined. The results generally showed that the total volume of irrigation water and the volume of wheat water consumption in the hot climate of the province were less than in the cold and moderate climates of the province due to the short growth period of wheat and the growth of this plant in the cool months of the year. Therefore, due to the smaller amount of the volume of wheat water consumption in hot climate, it was expected that the physical water productivity of wheat in this climate would be higher than the other two climates of the province. However, due to the lower yield of wheat in the hot climates, this did not happen and the physical water productivity of wheat in the hot climate of Kermanshah province was lower than the two cold and moderate climates of the province. Therefore, it is possible to increase the yield and finally increase the physical water productivity of wheat by managing agronomic and breeding in this city.