Soybean Irrigation Management

Trial Overview

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  • Many farmers are faced with water restrictions and/or limited well13;10;capacity and need information on how to maximize soybean yield while using the13;10;least amount of water.
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Research Objective

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  • The objective of this study was to evaluate13;10;soybean yield response when irrigation is delayed until the R3 and R4 growth13;10;stages and with less water applied compared to soybean yields when supplied13;10;with full irrigation initiated earlier in the season. 
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13;10;Location 13;10;
13;10;Soil Type 13;10;
13;10;Previous Crop 13;10;
13;10;Tillage Type 13;10;
13;10;Planting Date 13;10;
13;10;Harvest Date 13;10;
13;10;Potential Yield 13;10;
13;10;Planting Rate 13;10;
Gothenburg, NE
Hord Silt Loam
Corn
Strip-Till
05/14/2016
09/21/2016
85 bu/acre
160,000 seeds/acre
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13;10; Site Notes:13;10;

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Three13;10;different 2.4 RM soybean products were used in this study.Five different irrigation treatments were tested13;10;plus a dryland control (Table 1): Full irrigation (100% FI), two13;10;treatments above full irrigation to verify that full yield potential was13;10;actually achieved with the 100% FI treatment, and two treatments below full13;10;irrigation initiated at R3 or R4 to evaluate the effect of delayed and deficit13;10;irrigation on soybean yield.The13;10;study was set up as a randomized split-plot with irrigation amount as the whole13;10;plot and soybean product as the subplot with three replications.The13;10;irrigation system was subsurface drip with drip tapes buried 10 to 12 inches13;10;deep and spaced 40 inches apart.
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Understanding the Results

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Figure 1. Soil Water13;10;Chart for the 100% FI Treatment
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Table 1. Irrigation Treatment13;10;Effect on Yield
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  • No differences in yield were observed between13;10;the soybean products; therefore, yields from the three products were combined13;10;for each treatment. However, the irrigation treatments did have a significant13;10;effect on yield and were analyzed individually (Table 1). 
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  • Above average rainfall lead to relatively high13;10;yields in all plots. Of this rainfall, 20.7 inches was received from mid-April13;10;through July; however, rainfall in August and September was only 0.7 and 0.613;10;inches, respectively.
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  • The 50% FI treatment yielded 97% of the 100% FI13;10;treatment while using 3 inches less water.
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  • As shown in Figure 2, the dryland treatment (left) showed earlier senescence while the 50% FI treatment (middle) and the other treatments (right image shows the 150% FI treatment) showed similar senescence, indicating that the dryland field (non-irrigated control) experienced late-season stress but the irrigation treatments did not experience the same level of stress.
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What Does This Mean for Your Farm

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  • For13;10;those farmers with limited water supplies or allocations, a majority of the13;10;soybean yield can be captured if timely irrigation is made during the R4 growth13;10;stage when growing conditions are adequate to meet the needs of the soybean13;10;crop early in the season. 
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