Nano-Fe nutrition improves soybean physiological characteristics, yield, root features and water productivity in different planting dates under drought stress conditions

Abstract

Soybean production as an oil and protein crop, especially in water limited conditions, is of global importance. Suitable Nano-iron fertilizer application method can be a useful nutrition technique under water limitation stress. The aim of this study was to investigate the response of yield, physiological and morphological characteristics of soybean to drought stress, planting date and nutrition with iron Nano-oxide in two separate experiments (i.e. 2-year field and a pot) in 2021–2022. Field experiments included planting date (April 09: early planting date, May 05: optimum planting date and June 10: late planting date), nutrition with iron Nano-oxide (control, seed priming 300 ppm, foliar spraying 15 ppm, priming 300 ppm + foliar spraying 15 ppm) and drought stress (100 %, 75 % and 50 % FC). In the pot experiment, all field treatments were applied except planting date. Then, morphological and biochemical characteristics of the root were investigated. The results showed that drought stress, planting date and different methods of iron Nano-oxide nutrition had significant effects on gas exchanges, chlorophyll fluorescence, antioxidant activity and grain yield. The highest gas exchanges, net photosynthesis rate, the maximum photosystem quantum efficiency (FV/Fm) and grain yield were obtained by iron Nano-oxide nutrition as seed priming + spraying in optimum planting date and 100 % FC. However, these traits were decreased with increasing drought intensity (50 % FC), non-use of iron Nano-oxide (control) in early planting date. By increasing the drought severity in the field to 50 % FC, the antioxidant enzyme’s activity increased. The highest activity of catalase and superoxide dismutase were observed in early planting date + non-use of iron Nano-oxide +50 % FC. Based on the results of the pot test, the highest root length, number of nitrogen-fixing nodules, root dry weight, and nitrogenase activity were observed by iron Nano-oxide nutrition (nano priming 300 ppm + 15 ppm spraying) under 100 % FC. The mentioned parameters were reduced by drought, but the number of root branches increased. Combined nutrition (priming + spraying) had more positive effects on the root's morphological and biochemical properties compared with iron spraying only. The water productivity increased due to late plantings, but the negative effect of early planting on this indicator was higher. The maximum water productivity (0.73 kg/m3) obtained from iron Nano-oxide nutrition (seed priming 300 ppm + foliar spraying 15 ppm) in late planting date under 50 % FC conditions and its lowest (0.35 kg/m3) in no iron Nano-oxide nutrition in early planting date under 100 % FC. In general, the optimum planting date (05 May), supply of 100 % FC and combined iron Nano-oxide nutrition (seed priming + foliar application) is suggestible for soybean (Kosar cultivar) production in the climate conditions like the present study.