BIODIVERSITAS ISSN: 1412-033X Volume 20, Number 8, August 2019 E-ISSN: 2085-4722 Pages: 2266-2272 DOI: 10.13057/biodiv/d200822 Physiological responses of four soybean varieties and their effect to the yield in several saturated soil culture modification TOYIP 1,2 , MUNIF GHULAMAHDI 3,♥ , DIDY SOPANDIE 3 , SANDRA A. AZIZ 3 , ATANG SUTANDI 4 , M. YANUAR J. PURWANTO 5 1 Graduate School of Institut Pertanian Bogor. Jl. Raya Dramaga, Bogor 16680, West Java, Indonesia 2 Program of Agrotechnology, Faculty of Agriculture, Universitas Sintuwu Maroso. Jl. Pulau Timor No.1, Poso 94612, Central Sulawesi, Indonesia. 3 Department of Agronomy and Horticulture, Faculty of Agriculture, Institut Pertanian Bogor. Jl. Meranti, Bogor 16680, West Java, Indonesia. Tel.: +62-251-8629354, Fax.: +62-251-8629352,  email: mghulamahdi@yahoo.com, th.amazon36@gmail.com 4 Department of Soil Sciences and Land Resources, Faculty of Agriculture, Institut Pertanian Bogor. Jl. Meranti, Bogor 16680, West Java, Indonesia 5 Department of Civil and Environmental Engineering, Faculty of Agricultural Technology, Institut Pertanian Bogor. Jl. Lingkar Akademik, Bogor 16680, West Java, Indonesia Manuscript received: 21 May 2019. Revision accepted: 23 July 2019. Abstract. Toyip, Ghulamahdi M, Sopandie D, Aziz SA, Sutandi A, Purwanto MYJ. 2019. Physiological responses of four soybean varieties and their effect to the yield in several saturated soil culture modification. Biodiversitas 20: 2266-2272. This study aimed to evaluate the production and physiological response of four soybean varieties in saturated soil culture (SSC), compared to conventional dry culture on tidal swamp soil growing media. Four popular varieties in Indonesia, namely Anjasmoro, Grobogan, Tanggamus and Malika, were planted on undisturbed intact tidal swamp soil from Jambi from November 2016 to March 2017 at Bogor. Randomized completely block design with two factors applied in this work, i.e. 4 varieties namely Anjasmoro, Grobogan, Tanggamus and Malika; and 9 culture methods such as dry culture as control of no SSC (i), 1 months SSC (ii), 1.5 months SSC (iii), 2 months SSC (iv), continuous SSC (v), 1 months SSC with water improvement (vi), 1.5 months SSC with water improvement (vii), 2 months SSC with water improvement (viii), and continuous SSC with water improvement (ix). The results showed that (i) pod production per plant was significantly affected by the interaction of both factors; (ii) different varieties lead to significant different of physiological response, i.e. photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency; (iii) the variation of culture methods only showed a significant effect on photosynthetic rate, i.e. saturated soil culture with water improvement (SSC WI) showed 48% and 18% higher photosynthetic rate than dry culture and regular SSC methods, respectively. Pod production was positively correlated to photosynthetic rates and water use efficiency; and negatively correlated to transpiration and stomatal conductance. The highest number of pod production per plant was achieved by Malika variety that planted in 2 months SSC WI. Keywords: Leaf stomatal conductance, photosynthetic rate, transpiration, water improvement, WUE Abbreviations: DC: dry culture, SSC: saturated soil culture, SSC WI: saturated soil culture with water improvement, WUE: water use efficiency INTRODUCTION Soybean (Glycine max (L.) Merr) is one of commercial food crops commodity for Indonesian, along with rice and maize, due to its important role in various local food products. The demand for this commodity increases as the growth of population. The average of soybean demand in 2017 is 3.1 million tons. Most of the domestic demand was filled with importing soybean from out of the country. The contribution of domestic soybean production is only 30%, while the rest is supported by the import activities (BPS 2017). There is a need to accelerate the domestic soybean production to impede the soybean import. There are two main strategies to gain domestic soybean production, i.e intensification (giving additional input) and extensification (expanding production area). Tidal swamp is one of highly found marginal lands in Indonesia, i.e. ±20 million ha that potentially used as future soybean production area (Suwanda et al. 2014). Soybean cultivation in marginal land such as tidal swamp needs several adjustments through improvement of cultural practice. Saturated soil culture (SSC) was promoted as the appropriate technology to maintain the growth of soybean under various environmental stress on tidal swampland leading to the improvement of harvested yield (Ghulamahdi et al. 2010; Sagala et al. 2011). Saturated soil culture for soybean was applied by maintaining the water surface on the stable condition, i.e. 20 cm under soil surface (Ghulamahdi et al. 2009), so the detrimental effect of water excess (Troedson et al. 1983) and pyrite oxidation could be minimized (Sagala et al. 2011). The quality of water used in SSC system also influences the success of soybean production. The water quality surrounding the tidal land is categorized as a low irrigation water quality (Anda et al. 2009) due to its high acidity (Imanudin dan Armanto 2012) caused by the excessive aluminum and iron content (Bhakty 2005; Noya et al. 2014). This low water quality could damage the soybean root leading to the decrease of soybean yield. To gain the soybean yield, there is a need to