چكيده لاتين :
Radiation absorption and use efficiency are affected by genotype and agronomic management (Mondani et al., 2019; Tohidi et al., 2012). Kermanshah province located in an appropriate geographical location in terms of access to radiation during maize development stages (Ahmadi et al., 2018a). However, the radiation absorption by crop canopy depends on the spatial arrangement shoot of plants. The canopy structure by effect on vertical distribution of radiation plays an important role in the crops yield. On the other hand, knowledge of the agricultural management role in optimal utilization from environmental factors such as radiation in order to improve the canopy's ability to use these factors is very important. Therefore, this research was carried out in order to study the effects of water deficit stress on radiation absorption and use efficiency of some common maize cultivars and study the role of growth indices on production formation under Kermanshah climatic conditions.
Materials and Methods
This experiment was done in 2018 growing season at the experimental field of Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran. The experiment was conducted as split plot based on randomized complete block design with three replications. Main-factor was three irrigation regimes (IR) included supplying 130% (1064 mm), 100% (802 mm), 70% (623 mm) water requirement (IR130%, IR100% and IR70% respectively) and sub-factor included three maize cultivars in three levels (KSC704, Simon and BC678) were evaluated randomly. To calculate water requirement, the Penman-Monteith-FAO equation was used. The amount of water for each treatment was calculated and available to plants every seven days. In order to calculate the growth indices, radiation absorption and use efficiency, during different development stages, leaf area and total dry weight of maize plants were measured.
Results and Discussion
The results showed the growth indices such as leaf area index and crop growth rate, and also radiation absorption, radiation use efficiency and total dry weight were relatively similar for KSC704 and Simon cultivars in response to different irrigation regimes but they were higher for BC678 cultivar. The grain yield of Simon cultivar was significantly higher than other cultivars. Regardless of the maize cultivars, in the IR130%, IR100% and IR70% treatments, average value for maximum of leaf area index were 4.8, 4.2 and 2.9 and leaf area duration were 269.5, 235.8 and 168.1 day, respectively. The negative effect of water deficit stress on leaf area index and leaf area duration eventually led to decrease radiation absorption. In the IR130%, IR100% and IR70% treatments, the amount of cumulative radiation absorption were 1318, 1241 and 1059 MJ m-2, radiation use efficiency were 1.14, 1.05 and 1.00 g MJ-1, maximum of crop growth rate were 26, 21.9 and 18.7 g m-2 day-1, respectively. The growth season period of maize (from emergence to physiological maturity) in the IR70% treatment was 4 and 6 days shorter than IR100% and IR130% treatments, respectively. Finally, the reduction of radiation absorption, and growth season caused by water deficit stress led to lower total dry weight and grain yield. In the IR130% treatment, the total dry weight and the grain yield were 16960 kg ha-1 and 7430 kg ha-1, respectively. By reducing of 30% and 60% of irrigation water compared to IR130% treatment, the total dry weight were decreased about 18% and 28% and the grain yield were decreased about 15% and 40%, respectively.
Conclusions
According to results, it can be concluded that by choosing the suitable irrigation regimes in the maize production systems, a canopy with a suitable structure can be obtained. This canopy structure will provide a suitable situation for improving growth indices, efficient use of environmental resources such as radiation and eventually increasing production. In general, the results showed a positive response of the evaluated characteristics to the over-irrigation treatment, which may be due to the fact that the use of the Penman-Monteith-FAO equation is not a suitable method for determining the water requirement of the plant in the study area. Therefore, it is suggested that in case of repetition of the results of this research, alternative methods be used along with the Penman-Montith FAO method to determine the water requirement of the plant.
