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Response at Different Growth Stages of Soybean to Deficit Irrigation Condition

Shakil Uddin Ahmed
Department of Soil, Water & Environment; University of Dhaka Dhaka-1000, Bangladesh

Masateru Senge
Graduate School of Agriculture, Faculty of Applied Biological Science, Gifu University, Yanagido 1-1, Gifu City, Japan.

Kengo Ito
Graduate School of Agriculture, Faculty of Applied Biological Science, Gifu University, Yanagido 1-1, Gifu City, Japan.

Abstract/ Executive Summary:

An attempt was made to assess the effect of deficit irrigation on yield components at individual growth stages of soybean [Glycine max (L.) Merrill]. The deficit irrigation treatments were 0 - 25, 25 - 50, 50 - 75 and 75 - 100% of total available water (TAW). Evapotranspiration was dominated in order by: Flowering > pod formation > development > maturity stage. Water stress coefficient (Ks) or ETa/ETm at Flowering and Pod formation stages were too strong to be tolerated due to the effect of high evapotranspiraton rates. Both water use efficiency (WUE) and yield efficiency (YE) was also very sensitive under water stress conditions at flowering and pod formation stages. Available water deficit level lower than 50 - 75 % (D₃) throughout the different growth stages of soybean was good enough for calculating the yield response factor (Ky = 0.87), and both WUE and YE was higher at 50 - 75 % of TAW (D₃) than the full irrigation (D₁). It may be concluded that deficit irrigation was effective (K_y < 1) for economy of water usage under water deficit lower than 50 - 75 % of TAW (D₃). It reveals from the results that to get a good yield of soybean under limited supply of irrigation water it is better to avoid moisture stress at the reproductive stage (flowering and pod formation) of the crop.

Keywords: Crop water requirement, Water stress coefficient, Water use efficiency, Yield efficiency, Yield response factor.

Location: Gifu University, Japan

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soybean, Irrigation scheduling

Objectives:

To investigate the influence of available water deficit on yield response at different growth stages of soybean, so that the deficit irrigation management for the individual growth stages can be made to ensure optimum growth and production of soybean.

Methodology:

This research was conducted in a vinyl house (surrounding sides were open) of the Gifu University, Japan. Soybean (Glycine max (L.) Merrill were planted in plastic buckets. The average temperature ws 22.4⁰C and the relative humidity was 67.5% during experiment duration. The experimental design was a randomized complete block with four treatments and three replications. The physical, moisture and chemical properties of the soil are describe. Available water was maintained at field capacity level during initial stage of 21 days after sowing (DAS) and total treatment period was 133 days (22 - 154 DAS), as development stage ( 22 - 43 DAS), flowering stage (44 - 63 DAS), pod formation stage (64 - 119 DAS) and maturity stage (119 - 154 DAS). The water stress (D) with four levels of water deficit treatments imposed as D1 (0 - 25%), D2 (25 - 50%), D3 (50-75%) and D4 (75 - 100%) of available water deficit. The water deficit level of D2 (25-50%), for example, meant that the available water was maintained between 25% and 50% of total available water (TAW) throughout the growing season. When the maximum allowable depletion of available water got close to 50% of TAW, water was applied to restore the available water to the deficit level of 25% of TAW. TAW is defined as the water content between field capacity (θ_FC) and permanent wilting point (θ_PWP). Diurnal soil moisture content was monitored by gravimetric method. Daily evapotranspiration (ET) was measured by the following formula: ET: (WD_i-1 - WD_i)/Ac where WD_i is the weight of container at day (i) (gm), WD_i-1 is the weight of container at day (i-1) (gm), and Ac is the surface area of the container. Agronomic variables evaluated in this research were crop water requirement (CWR, g/pot), oven dry weight of total biomass including with roots (TDB, g/pot) and grain yield of soybean (Y, g/pot). CWR was equal to the total evapotranspiration during the irrigated period at individual growth stages of soybean. Daily evapotranspiration (ET), which determined the crop water requirement, was measured by weighing the container every day. The container served as the role of a weighing lysimeter that hydrologically isolates soil surface lateral inflow/outflow. Water use efficiency (WUE) was calculated as the ratio of total dry biomass to CWR at individual growth stages; and yield efficiency (YE) was calculated as the ratio of grain yield to CWR at individual growth stages of soybean. Five seeds were planted in each plastic container (10 liters volume) with a diameter of 23.8 cm, which had been filled with 10 kg air-dried soil, and one week later thinned to only 2 seedlings, which were maintained until the end of the growth period. Basal fertilizers (kg/ha) were applied at 20 N, 180 P₂O₅and 100 K₂O. All fertilizers were applied just once, at seedling stage. Statistical analysis was carried out using F test at 5% significant level and means were separated by LSD test.

Source of Information: Bangladesh J. Sci. Res. 27(2):165-174, 2014 (December)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Crop water requirement (CWR): CWR was equal to the total evapotranspiration during the irrigated period at individual growth stages of soybean. It can be observed from this table that the effects of available water deficit on CWR are quite significant at level of 0.05 based on the LAD test. The table also shows that CWR at individual growth stages of soybean was lowered with increasing water deficit level from D₁ to D₄. It shows that CWR was highest in flower formation stage, followed by pod formation stage, advance stage, maturity stage and then initial stage. In general crops are more sensitive to water deficit during emergence, flowering and early yield formation than they are during early (vegetative, after establishment) and late growth periods (Doorenboss and Kassam 1979). On the basis of above data, it can be presumed that soybean crops are more sensitive to water deficit during reproductive phase (flower formation and pod formation state).

Knowledge Management: Journal