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Effect of Salinity and Potassium Levels on Different Morpho-physiological Characters of Two Soybean (glycine Max L.) Genotypese

Hashi US
EXIM Bank Agricultural University, Bangladesh

Karim A
Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh

Saikat HM
Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh

Islam R
Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh

Islam MA *
Department of Genetics and Plant Breeding, EXIM Bank Agricultural University, Bangladesh

Abstract/ Executive Summary:

A field experiment was conducted in the field of Department of Agronomy of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh to assess the effect of potassium on different mineral ions accumulation pattern in leaves of salt affected soybean and to draw the relationship between the dry matter production and mineral ions accumulation in leaves for better understanding the effect of potassium in mitigating salinity stress. The plant height decreased with the increase in salinity levels. In general, Galarsum (V₁) was taller than Bangladesh Soybean-4 (V₂) at all levels of salinity. Potassium in general increased relative plant height under salinity. Galarsum with K₂ (119.52 kg/ha) potassium showed relatively higher plant height at mild salinity, though at the high level of salinity the plant height increased with the higher level of potassium. The minimum relative plant height of Galarsum was obtained at the highest salinity with no potassium fertilizer. Application of different levels of K increased the production of relative stem dry weight at both 5 dS/cm (S₁) and 7.5 dS/cm (S₂) levels of the salinity compared to the control (S₀). At 5 dS salinity the relative stem DW in Galarsum ranged from 46 to 66% and that at 7.5 dS salinity from 35 to 40%. Whereas, in Bangladesh Soybean-4 the stem DW ranged from 58 to 75% at S₁ and that from 34 to 52% at S₂ level of salinity. Therefore, the percent reduction in stem DW due to salinity was more in V₂ than V₁ when salinity increased from S₁ to S₂ under K₀ and K₁ potassium treatments. Moreover, the positive effect of K on the production of relative stems DW under different level of salinity. Irrespective of K levels salinity decreased the leaf dry weight in both the genotypes and the reduction in leaf DW increased with the increasing of salinity levels. The leaf DW of Galarsum (V₁) was much higher than that of Bangladesh Soybean-4 at all level of salinity and potassium. At the control (S0) the increasing levels of K application decreased the leaf DW production in V₁, though in V₂ the weight increased substantially. The relative leaf DW of two soybean genotypes increased with increasing K application in each salinity level except S₁K₂, S₂K₃ treatments of V₁. Bangladesh Soybean-4 showed higher negative relationship (y=-40.89x+17.92, R₂ =0.80) than Galarsum (y=-46.96x+24.22, R₂ =0.74) between Na:Ca ratio and total dry weight. The R₂ value indicates that about 73% of the contribution to the TDW of V₁ and 80% of V₂ can be explained by the Na:Ca ratio. TDW decreased with increasing Na:Ca ratio concentration in leaves of two soybean genotypes.

Keywords: Salinity; Potassium level; Stress; Plant height; Mineral ions accumulation

Location: Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer, Soil salinity

Objectives:

To assess the effect of potassium on different mineral ions accumulation pattern in leaves of salt affected soybean and
To draw the relationship between the dry matter production and mineral ions accumulation in leaves for better understanding the effect of potassium in mitigating salinity stress.

Methodology:

An experiment was carried out at department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh. The plants were grown in plastic pots of 24 cm (diameter) ×30 cm (height) under natural sunlight inside vinyl house. The pots were filled with 14 kg of air-dried soils. Four levels of potassium and three levels of salinity were the treatment variables. The source of potassium was muriate of potash (MP). Genotypes: V₁ = Galarsum and V₂ =Bangladesh Soybean-4, Four different Potassium: Four levels, namely K₀ = Control or native potassium, K₁ = Recommended dose (RD) i.e.59.76 kg/ha, (Fertilizer Recommendation Guide, BARC), K₂ =double to the RD i.e.119.52 kg/ha and K₃ = triple to the RD i.e.179.28 kg/ha. Salinity: Three levels of salinity created by dilution of sea water such as S₀ =Control (tap water), S₁ =5.0 dS/m and S₂ =7.5 dS/m. Eight healthy seeds were sown in each pot on 17 April 2012. Immediately after sowing seed, a light irrigation was given for the ease of seed germination. Nitrogen, phosphorus, sulphur and boron were applied as urea, TSP, gypsum and borax at the rate of 60, 175, 120, 115 and 10 Kg per hectare respectively for all treatment. The amount of different fertilizers for each pot containing 8 kg dry soil was calculated and mixed with soil during pot filling. Thinning was done during the appearance of second trifoliate and kept two uniform and healthy plants in each pot. Weeding was done intensively to keep the pots weed free. To protect the plant from cutworm Carate was sprayed when it was needed. Irrigation was applied with tap water in all the pots up to imposition of salinity treatment. Tap water of 0.1 dS/cm electrical conductivity (EC) was applied to the pots up to the emergence of 1st trifoliate leaf. Afterwards the tap water was applied only to the control plot. Seawater was collected from the Bay of Bengal at the Cox’s Bazar point. The initial EC value of the seawater was 49 dS/m. The seawater was diluted with tap water and a sufficient amount of diluted seawater of 2.5 dS/m was applied to the pots in excess so that the excess seawater dripped out from the bottom of the pots. Two days later the diluted seawater of 5.0 dS/m (S₁) was applied similarly. As the salinity concentration of the applied solution increased by 2.5 dS/cm every alternate day, it increased to 7.5 dS/m (S₂) after 4 days of salinity imposition. Thus, the salinity treatments were S₀ = Control, S₁ =5.0 dS/m and S₂ =7.5 dS/m. The saltwater was applied till harvest, on 27 August, 2013. The salinity was applied for 3 months and 14 days. After harvest, the plants were partitioned into root, stem, leaf and pod (in Bangladesh soybean-4 only). Therefore, it was not possible to collect yield data in either of the two genotypes. The plant parts were oven dried at 70⁰C for 72 hours. Total dry weight (DW) was calculated by summing up the dry weight of roots, stem, leaf and petiole of the plant. Shoot DW was calculated by excluding dry weight of root from total dry weight. Root: shoot ratio was calculated for all the treatments. The sodium, potassium, calcium and magnesium contents of leaves were analyzed. The leaves were collected after harvesting the plants. Leaves those dropped during treatment imposition were also considered for measuring leaf DW. The exchangeable nutrients (Na, K, Ca and Mg) was extracted with neutral and measured with Atomic Absorption Spectrophotometer (Model No 170-30. HITACHI. Japan). The design used for this experiment was Randomized Complete Block Design. The data recorded on different parameters were statistically analyzed with the help of MSTAT program. The difference between the treatments means were compared by the least significant difference (LSD) test at 5% level of significance after calculating analysis of variance (ANOVA). Correlation coefficients were calculated between total dry weight and concentrations of mineral ions accumulated in leaves.

Source of Information: J Rice Res, Volume 3 , Issue 3, 1000143, ISSN: 2375-4338 JRR, an open access journal

Article Link (Online Journal): http://www.esciencecentral.org/journals/effect-of-salinity-and-potassium-levels-on-different-morphophysiologicalcharacters-of-two-soybean-glycine-max-l-genotypese-2375-4338-1000143.pdf

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Therefore, the additional application of potassium could be helpful to reduce harmful effect of salinity in relation to dry matter production in different plant parts and as such K played an important role in improving salinity tolerance in soybean. Potassium also increased the concentrations of K and Ca and decreased the Mg++ concentration, and Na:K and Na:Ca ratio. Under saline conditions, the maintenance of low Na+/Ka+ ratio as as well as low Na+/Ca++ ratio is important mechanism of salt tolerance. High salt stress increased the deposition rate of Na+ in the growing region of the roots and decreased the selectivity for K+. It is plausible that when additional K was applied, root growth of the soybean plants was maintained by plasma membrane selectivity of K+ over Na+. Thus, the rate of reaction in cell was increased by the rate at which K+ enters the cell. The accumulation of K+ in plant roots produced a gradient of osmotic pressure that draws water into the roots. The positive effects of K on dry matter production under saline conditions as found in this study was presumably due to lessening of osmotic and ionic effects on plant growth.

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