Application of Sulfur and Biofertilizers on Growth Indices, Radiation Absorption, and Use Efficiency of Chickpea (Cicer arietinum L.)

 Leaf area index, radiation absorption and radiation use efficiency are important ecophysiological characteristics, which is useful in assessing the amount of light absorbed for dry matter production. Understanding how and managing the effects of ecological factors on plant reproduction is essential for achieving sustainability in agricultural production systems. On the other hand, the use of efficient crops in utilization of resources, especially solar radiation, is one of the fundamental approaches towards achieving this goal. The purpose of this study was to investigate the effect of sulfur and biofertilizers applications on growth indices, radiation absorption and use efficiency of chickpea.

 In order to determine the growth indices, radiation absorption, and radiation use efficiency (RUE) of chickpea, a field experiment was conducted in 2019 at the Agricultural Research Station of Ferdowsi University of Mashhad based on a completely randomized block design with ten treatments and three replications. The experimental treatments including: 1-Spa, 2-Spo, 3-Spa+SOB, 4-Spa+SOB+NFB+PSB+KSB, 5-Spo+SOB 6-Spo+SOB+NFB+PSB+KSB, 7-SOB+NFB+PSB+KSB, 8- NFB+PSB+KSB, 9-SOB and 10-Control. Sampling was started 20 days after planting by taking six destructive samples. The plant was sampled two weekly intervals to determine the growth parameters of chickpea including leaf area index (LAI), dry matter accumulation (DM), crop growth rate (CGR) and radiation use efficiency (RUE). For calculations of radiation use efficiency, it was necessary to estimate daily LAI and daily absorbed, the RUE was calculated based on g MJ-1 through the slope of a linear regression between total dry weight accumulations (g m-2), and cumulative absorbed the total daily solar radiation.

 The results showed that the highest leaf area index was obtained in Spa + SOB + NFB + PSB + KSB and Spo + SOB + NFB + PSB + KSB treatment which was 29 and 26 %  more than control, respectively. The application of pa + SOB and Spo + SOB treatment, which increased 12 and 7 % compared to control, respectively. In this study, sulfur was more important than other fertilizer treatments. The highest dry matter accumulation was obtained in Spo + SOB + NFB + PSB + KSB and Spa + SOB + NFB + PSB + KSB treatment which was 31 and 27% more than control. SOB and NFB + PSB + KSB treatments had the lowest amount of dry matter after control. The results showed that the highest crop growth rate observed in Spo + SOB + NFB + PSB + KSB treatment, which increased by 14% compared to control. The maximum absorbed radiation coincided with the highest leaf area index of chickpea. Then, Due to the decrease in leaf area index until the end of the growth period, the absorbed fraction of light absorbed a decreasing trend. The estimated RUE levels in different treatments were significantly different (P≤0.01). The highest radiation use efficiency was in Spa + SOB + NFB + PSB + KSB treatment (R2 = 0.91**) which was 18% more than control. Also, increasing leaf area can increase the plant's photosynthetic potential and increase dry matter, at finally to increased RUE.

The results showed that treatments (Spo + SOB + NFB + PSB + KSB) and (Spa + SOB + NFB + PSB + KSB) with higher leaf area index resulted in more efficient use of canopy light absorbed by chickpea leaves as a result of increased radiation and dry matter efficiency. High slope radiation use efficiency indicates the high efficiency of a plant using sunlight and converting it to dry matter. Giving attention to a more frequent application of biological fertilizers could be considered as an essential agro-ecological approach, which results in healthier soil and water resources.