عنوان مقاله [English]
In recent decades, agricultural production systems have already explored many methods to increase the crops yield. Most of these methods involved increasing the efficiency of resources utilization such as nutrients, solar radiation, and atmospheric CO2. Crop growth and yield are considered as a function of photosynthetically active radiation (PAR) that is intercepted by plant as well its utilization efficiency to produce dry matter. Net primary production has often been found to be linearly related to the photosynthetically active radiation (PAR) intercepted by crops. The slope of this relationship is light use efficiency (LUE). Several authors have found close correlation between crop growth and yield with the radiation absorption and the LUE. Although, it was previously believed that the LUE is constant during the crop growing season and it is controlled more genetically, but environmental factors and management practices such as change in the sowing date, plant density, cultivars, climate, soil fertility, especially soil available nitrogen due to its specific role in photosynthesis, affect greatly the LUE. Therefore, the objectives of the present study were to evaluate light absorption and use efficiency in different sowing date for chickpea cultivars in Kermanshah regionlight absorption and use efficiency in different sowing date for chickpea cultivars in Kermanshah region climatic.
Material and Methods
A split plot experiment was conducted based on Randomized Complete Block Design during 2016-2017 at the research farm of the faculty of agriculture and natural resources of Razi University, Kermanshah, Iran (34°, 19´ N, 47°, 50´ E and altitude 1317 m). The average annual rainfall was 455 mm, and the long-term average of maximum and minimum air temperature was 22.6 and 5.9°C, respectively. Main plots had three sowing dates (February 29, Match 10 and April 6) and sub plots were composed of chickpea cultivars (Bivanij, Adel, Arman and ILC482). The measured indexes were leaf area index (LAI), radiation absorption, total dry matter (TDM), light use efficiency (LUE) and grain yield of chickpea. The LUE was calculated based on g MJ-1 through the slope of linear regression between total dry matter accumulation (g m-2) and cumulative absorbed photosynthetically active radiation. Chickpea grain yield was measured at the physiological maturity stage.
Results and Discussion
The results showed that the maximum LAI of different chickpea cultivars decreased with the delay in sowing date. The greatest LAI (3.8) was related to Arman cultivar with the sowing date of March 1 and the lowest LAI (1.9) was related to ILC482 cultivar with the sowing date of April 6. The light absorption had the similar LAI trend that with the delay in sowing date decreased about 51%. The highest (15.9 MJ m-2) and the lowest (13.4 MJ m-2) light absorption were observed for Arman cultivar with the sowing date of March 1 and ILC482 cultivar with the sowing date of April 6, respectively. Combined analysis of variance of the results indicated that the effects of sowing date and cultivars were significant on TDM and grain yield, but the interactions of sowing date and cultivars were not significant for TDM and grain yield. The results indicated that the delay in sowing date led to reduce in the grain yield (45%) and TDM (33.5%). The highest (158 g m-2) and the lowest (102 g m-2) grain yield were related to Bivanij and Arman cultivars, respectively. The grain yield of Bivanij cultivar was higher (35%) compared to other cultivars. The highest LUE (1.6 g MJ-1) was observed for Adel cultivar with the sowing date of March 1 and the lowest LUE (0.7 g MJ-1) was related to Arman cultivar with the sowing date of April 6. Late sowing dates of March 11 and April 6 reduced LUE compared to early sowing date of February 29 about 4.2% and 2.7% in Bivanij cultivar, 9.4% and 27.3% in Adel cultivar, 43.4% and 40.3% in Arman cultivar and 19.1% and 16.8% in ILC482 cultivar, respectively.
In general, the results of this study show that the delay in sowing date, which is unavoidable under some climatic conditions by the farmer, lead to reduce in measured traits such as grain yield and LUE of chickpea. However, it seems that late sowing could help with the selection of suitable chickpea cultivars that could offset the yield loss due to unsuitable environmental condition such as drought stress by end of the growing season.
Zhang, L., Van der Werf, W., Bastiaans, L., Zhang, S., Li, B., and Spiertz, J. 2008. Light interception and utilization in relay intercrops of wheat and cotton. Field Crops Research 107: 29-42.