Crop Science 41:93-100 (2001)
© 2001 Crop Science Society of America
CROP ECOLOGY, PRODUCTION & MANAGEMENT
Evaluating On-Farm Flooding Impacts on Soybean
Matthew Sullivana,
Tara VanToaib,
Norman Fauseyb,
James Beuerleina,
Robert Parkinsonc and
Alfred Soboyejoa
a Dep. of Horticulture and Crop Science, The Ohio State Univ., Columbus, OH 43210
b USDA-ARS Soil Drainage Research Unit, Columbus, OH 43210
c USDA-NRCS Columbus, OH
Corresponding author (vantoai.1{at}osu.edu)
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ABSTRACT
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Flooding is a major problem that reduces soybean [Glycine max (L.) Merr.] growth and grain yield in many areas of the USA and the world. Our objective was to identify the plant and soil characteristics associated with different flooding durations in six fields in central Ohio. The soybean plants were at the V2 and V3 stages when rainfall-induced flooding occurred. The outer perimeters of the flooded areas were mapped, using GPS (global positioning system) technology, several times during the flooding event to delineate the change of the flooded area over time. Two 9-m wide transects across the flooded area within each field were divided into plots of 9 m by 9 m according to flooding duration: no flooding, 1 to 3 d, 4 to 6 d, and 6 to 8 d. Soil and plant nutrient levels, grain yield data and grain protein and oil content were determined for each plot. The soil cation-exchange capacity (CEC), pH, P, Ca, Mn, and Zn concentrations had significant positive correlation with flooding duration. There was a significant negative correlation of flooding duration with the population, height, number of pods, and yield of soybean. There was no significant correlation of flooding duration with seed weight, oil, or protein content of the seeds. Leaf tissue Ca, Mg, B, Fe, Cu, and Al concentrations had a significant positive correlation with flooding duration, whereas leaf tissue N concentration had a significant negative correlation with flooding duration.
Abbreviations: CEC, cation-exchange capacity • CH, Champaign site • FA, Fayette site • FR, Franklin site • GPS, global positioning system • P1, Pickaway 1 site • P2, Pickaway 2 site • UN, Union site
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INTRODUCTION
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FLOODING FROM EXCESSIVE rainfall or irrigation compromises soybean growth and grain yield (Stanley et al., 1980; Oosterhuis et al., 1990; Russell et al., 1990). Natural flooding can be classified into two categories: (i) stream flooding, characterized by the overflow of rivers or creeks into a flood plain; and (ii) lowland flooding, characterized by inadequate surface drainage and slow soil permeability of depressional areas. Flooding can be further divided into either waterlogging, where only the roots are flooded, or complete submergence where the entire plants are under water. It was estimated that waterlogging for as little as 2 d at the V4 growth stage (Fehr and Caviness, 1977) reduced soybean grain yield by 18%, while the reduction was 26% at the R2 stage (Scott et al., 1989). According to VanToai et al. (1994), waterlogging for 4 wk at R1 to R2 stages reduced the average grain yield of 84 soybean cultivars by 25%. Heatherly and Pringle (1991) reported that 1 to 2 d of waterlogging caused by flood irrigation did not reduce soybean yield, but longer periods of waterlogging resulted in significant yield losses.
Research at the ARS Soil Drainage Research Unit has shown that contrary to the injury of soybean in flooded fields, it can thrive in stagnant water in the greenhouse (Boru et al., 1997). Soybean grown in hydroponic medium continuously bubbled with N gas where the dissolved oxygen level was not detectable showed no symptoms of stress. Soybean, therefore, is much more tolerant to excessive water and lack of oxygen than previously expected (Grable, 1966; Sallam and Scott, 1987; Russell et al., 1990). The reasons underlying the dramatic differences between responses to flooding in the greenhouse and flooding in the field are not known; however, growth reduction and yield loss in flooded fields could have arisen from root rot diseases (Schmitthenner, 1985), N deficiency (Fausey et al., 1985), nutrient imbalance (Barrick and Noble, 1993), and/or the accumulation of toxic levels of CO2 in the root zone (Boru et al., 1997). Since flooding injury is affected by many factors, including variety, growth stage (Linkemer et al., 1998), flooding duration, soil type, fertility levels, and pathogens, an understanding of the interaction of these variables would provide insight useful to the development of flood-tolerant soybean cultivars.
The objective of this study was to conduct on-farm research to identify plant and soil characteristics associated with different flooding durations in six fields in central Ohio.
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MATERIALS AND METHODS
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Site Description
The study was conducted in 1998 at six production field sites in central Ohio where flooding frequently occurs (Table 1). The Champaign (CH), Franklin (FR), Pickaway 1 (P1), and Union (UN) sites contain depressional areas that are subject to lowland flooding. The Pickaway 2 (P2) and Fayette (FA) sites are in the floodplain where flooding is due to stream overflow. Roundup Ready (Monsanto, St. Louis) soybean cultivars were planted without tillage at all sites. The cultivar names and other agronomic practices are reported in Tables 1 and 2.
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Table 1. Coordinates, soybean variety, planting date, planting density, row spacing and previous crop of each of the six farm sites in this study
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Each field was mapped several times during a flooding event in June, 1998, using a Precision Lightweight Global Receiver model PLGR + 96 (Rockwell, Cedar Rapids, IA) GPS to delineate the change of the flooded area over time. Two parallel transects, each 9-m wide, were laid out across the flooded area and extended into the nonflooded area within each field. Transect length varied from site to site, depending on the size of the flooded area, with the shortest at 64 m (CH) and the longest at 124 m (P1). Each transect was divided into 9- by 9-m plots in which soil and plant parameters and final yields were measured. The plots were grouped into four treatments according to flooding duration: no flooding, 1 to 3 d, 4 to 6 d, and 6 to 8 d. For simplicity, these are referred to as 0-, 3-, 6- and, 8-d flooding durations. The number of plots for each flooding duration and the total number of plots for each site are reported in Table 3.
Each site was represented by more than one soil type (Table 4). The orders of the soil series were Mollisols, Alfisols and Inceptisols with the drainage classification ranging from very poorly drained to well drained, and surface texture from silt loam to silty clay loam. These soils have a low to moderate shrink-swell capacity.
Temperature and rainfall for each site (Table 5) were collected by remote sensing and supplied by Grower Service (Detroit, MI). This information is not site based and may not be as accurate as on-site measurements, but does reflect the weather conditions of each site.
Plant Parameters
Plant population, plant height, leaf tissue elemental analysis, number of nodes and pods, seed size, grain yield, and grain oil and protein content were determined for each treatment plot. Plant population was determined at the V4 growth stage, after flooding, by counting the number of plants per 0.9-m row randomly selected at three places in each plot. Plant height was determined by measuring the distance from ground level to the tallest point of three randomly selected R1 plants per plot. Leaf samples for elemental analysis were collected from the uppermost trifoliate of ten randomly selected R1 plants. The leaves were dried at 70°C for 48 h, ground to powder, and P, K, Ca, Mg, Mn, Zn, B, Fe, Cu, Al, and total N were analyzed by flame ionization (AOAC, 1990) at the Service Testing and Research Laboratory, Ohio Agricultural Research and Development Center, Wooster, OH. Yield components were determined on four randomly selected R8 plants per plot by counting the number of nodes and pods per plant and determining seed size (100-seed wt.). Grain oil and protein content were determined by the near infrared transmittance method (Williams and Norris, 1987) at the USDA-ARS, National Center for Agricultural Utilization Research, Peoria, IL. Grain yield was determined by harvesting the transect with commercial combines equipped with a GPS receiver and yield monitor, except at the Union site where a similarly equipped plot combine was used.
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Soil Parameters
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Three soil samples were randomly collected in each plot to 
0.18-m depth with a 2.5-cm-diam. soil probe when the plants were at the R1 stage. The samples from each plot were combined, air dried, ground and analyzed for pH (1:1 water) (McLean, 1982), organic matter content by loss on ignition (Nelson and Sommers, 1982), and CEC (Warncke and Brown, 1998). Soil chemical analyses to determine P, K, Ca, Mg, Mn, Zn and B concentrations were conducted as described by Warncke and Brown (1998) at the Service Testing and Research Laboratory, Ohio Agricultural Research and Development Center, Wooster, OH.
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Statistical Analysis
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Correlation analysis was performed using the Statgraphics Software Package (Manugistics, Rockville, MD) to quantify the degree of positive or negative linear relationship between flooding duration and each of the associated soil and plant parameters for each of the six sites. The flooding duration was used as the independent variable and was assumed to have a uniform probability density function with a linear cumulative distribution function of zero on the 0th d, and one on the 8th d (Siddall, 1993; Soboyejo, 2000). On the basis of this assumption, the following values were assigned to each flooding duration for the correlation analysis: 0 for 0 d of flooding, 0.375 (3/8) for 3 d of flooding, 0.75 (6/8) for 6 d of flooding and 1 (8/8) for 8 d of flooding. Within each site, the data from plots with similar flooding duration were treated as multiple samples, and comparisons between flooding duration treatments were based on the Student's t test.
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RESULTS
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The total precipitation for the 1998 growing season at the six sites ranged from 44.9 cm at FR to 55.08 cm at CH (Table 5). The normal precipitation in central Ohio during the five-month growing season is 50.5 cm. The rainfall distribution, however, was highly variable. Rainfall on 14 June caused flooding at the CH, FA, and UN sites when the plants were at the V2 growth stage. Rainfall on 30 June caused flooding at the FR, P1, P2, and UN sites when the plants were at the V3 growth stage. The duration of flooding varied from site to site, so the number of plots and treatments varied as shown in Table 3. Late in the growing season, there was evidence of drought stress on the well-drained soils of the FR, P1, and P2 sites, because of low rainfall in July and August.
The degree of positive or negative linear relationship between flooding duration and each plant and soil property at each site are reported in Table 6. The correlation between flooding duration and each plant and soil property is site specific. In general, a significant and negative correlation existed between flooding duration and population, height, number of pods per plant, yield, leaf tissue N concentration, and soil B concentration. There was also significant positive correlation between flooding duration and the following soil and plant parameters: CEC, soil pH, soil P, Ca, Mn, and Zn concentrations, and leaf tissue Ca, Mg, Fe, Cu, and Al concentrations.
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Table 6. The linear association (R) between flooding duration and soil and plant parameters at each site and their probability values (P)
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The plant population for each flooding duration and each site is reported in Fig. 1
. The FR and P2 sites had low populations on the nonflooded areas probably due to poor germination. The stand at the P1 and UN sites was greater than the seeding rate reported by farmers indicating problems with the reported seeding rates. All the plants at FA died after 3 d of flooding but no reduction in population was found at the CH, P1, P2 and UN sites. Flooding for 6 d ultimately reduced the plant population at the P2 and UN sites, but still did not affect the population at the CH and FR sites.
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Fig. 1. The plant population associated with different flooding durations at each site. Standard errors of each mean are presented as vertical bars
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At the R1 stage, mean plant height in the unflooded plots varied between 58 and 94 cm at the different sites (Fig. 2)
. Correlations between plant height and flooding duration were observed at four of the sites. Generally, the longer the flooding duration, the shorter the plants. At the CH site, plant height was not affected even after 6 d of flooding. Flooding for 8 d occurred only at the FR site and the plants in this area were only 20 cm tall.
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Fig. 2. The plant height associated with different flooding durations at each site. Standard errors of each mean are presented as vertical bars
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The grain yield of each flooding duration and each site are shown in Fig. 3
. At the CH site, flooding for up to 6 d showed no reduction of soybean grain yield. Yield at the P1, P2, and UN sites remained unchanged after 3 d of flooding, while yield at the FR and UN sites was reduced by 65 and 93%, respectively, after 6 d of flooding as compared to the nonflooded control.
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Fig. 3. The grain yield associated with different flooding durations at each site. Standard errors of each mean are presented as vertical bars
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Additional details about the correlations of flooding duration and soil and plant parameters at each site are reported in Tables 7 and 8, respectively, and are discussed below.
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Table 7. Comparisons of soil elemental concentrations and other soil parameters between flooding durations at each site
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Table 8. Comparisons of leaf elemental concentrations and other plant parameters between flooding durations at each site
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Champaign Site
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The association between flooding duration and yield and plant parameters was not detected at this site. No change in yield (Fig. 3) and plant parameters (Table 8) was found, even in plots flooded for up to 6 d. Soil from areas flooded for 6 d had higher P, K, Ca, Mg and Mn than nonflooded soil, while soil from areas flooded for 3 d only showed higher Ca and Mg than nonflooded soil (Table 7).
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Franklin Site
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The flooded plots at this site remained flooded for more than 3 d. Plant height (Fig. 2) and yield (Fig. 3) were less for plants flooded for 6 and 8 d compared with nonflooded plants. Leaf tissue N concentration was less in plants flooded for 8 d than in nonflooded plants while leaf tissue concentrations of K, Ca, Mg, Fe, and Al were higher (Table 8). Similar results were also found in plants flooded for 6 d, except for the leaf K concentration that was not different from the nonflooded plants. Soil concentrations of Ca, Mn, and Zn and the CEC were higher in soil flooded for 8 d compared with nonflooded soil (Table 7).
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Pickaway 1 Site
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Flooding at this site was brief. After 3 d of flooding, plants were shorter (Fig. 2), but the flooding did not significantly reduce the population (Fig. 1) and yield (Fig. 3) compared with the nonflooded plants. Leaf tissue Ca and Mg concentrations were higher in the flooded plants compared with the nonflooded plants, while leaf tissue Zn concentration was lower (Table 8). None of the soil parameters differed due to flooding duration (Table 7).
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Union Site
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No difference in plant population was detected at this site due to flooding duration; however, plant height (Fig. 2) and grain yield (Fig. 3) were smaller with 6 d flooding compared with the nonflooded plants. There were no significant differences in any other plant or soil parameters due to flooding duration (Tables 7 and 8).
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Fayette Site
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The flooding at this site was caused by stream overflow. The flooding was brief (3 d), but the plants were thickly coated with sediment. The plants did not recover and died soon after the flooding, thus, no yield and plant parameters were measured at this site. Soil Ca and Mg concentrations and the CEC were greater in the flooded area compared with the nonflooded areas (Table 7).
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Pickaway 2 Site
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The flooding at this site was caused by a major river overflow and persisted for up to 6 d. Plant population (Fig. 1) and plant height (Fig. 2) were reduced in the 6 d flooding plots as compared with the nonflooded plots, but no difference in yield was detected (Fig. 3). Plant height in the 3 d flooding plots was also reduced (Fig. 2), but plant population and yield did not differ from the nonflooded plots. Leaf tissue P, Ca, Mg, B, Cu, and Zn concentrations were all higher in plants flooded for 6 d compared with nonflooded plants (Table 8). Leaf tissue Ca and B were also higher in plants flooded for 3 d than in nonflooded plants (Table 8). Generally, the soil P and Mg concentrations were lower in flooded plots than in nonflooded plots, while the soil Ca, Mn, and Zn concentrations and the CEC were higher (Table 7).
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DISCUSSION
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The 1998 growing season in Central Ohio was very wet in June, creating flooding at all six of the sites studied, and very dry in August, resulting in drought stress at most of the sites. Our study reported a 20% reduction in soybean grain yield associated with 3 d of flooding at the V2 and V3 stage. Up to 93% yield loss was detected after 6 d of flooding. Similar results were reported by Heatherly and Pringle (1991) in a three-year study of soybean cultivars' response to flood irrigation. According to these authors, flood irrigation for >2 d may reduce soybean yield by 20% as compared with a 1 d flood irrigation treatment.
The type of flooding, stream overflow vs. low land depressional, may impact the severity of stresses and yield reduction differently. Sediments carried by stream flooding at the FA and P2 sites were deposited on the leaves of flooded plants. The silt-covered leaves wilted severely after flooding. At the P2 site, light rain three days after flooding washed the sediment off the leaves enabling the plants to recover substantially. At the FA site, the plants died before the sediment was washed off the leaves.
The yield reduction associated with flooding in this study may be attributed to lower plant population, shorter plant height, and fewer pods per plant (Table 6). According to Linkemer et al. (1998) the effects of waterlogging on yield components differed depending on the growth stage. They reported yield loss caused by waterlogging at R5 was due to decreased seed size, while waterlogging at R1 caused fewer pods per reproductive node, and at V2 resulted in lower branch number.
In this study, no change in plant population, plant height, leaf elemental concentrations and grain yield was detected in plots that were waterlogged for up to 6 d at the CH site. The subsoil at the CH site has high sand content (data not shown) and when drained, the root zone quickly returns to an aerated condition. This natural subsurface drainage reduced root zone waterlogging and its damage on soybean plant growth and grain yield. Similar effects are achieved by man-made subsurface drainage to improve crop yield in poorly drained soil (Schwab et al., 1975). Near normal rainfall in August at this site also eliminated a secondary stress present at the other sites.
The lack of injuries at the CH site could also be because of a greater flooding tolerance of the soybean cultivar grown at that site. Heatherly and Pringle (1991) reported that Sharley soybean was more tolerant to flood irrigation than Centennial soybean. Variation in tolerance to flooding was also detected in a field study of 84 soybean genotypes (VanToai et al., 1994).
Flooding for 3 d did not change the yield at the Union site, but increased yield by 56% at the P2 site (Fig. 3). The lack of yield loss due to flooding may have been caused by greater residual soil moisture associated with a flooded area when drought stress occurred in August and September at these two sites. According to Jones et al. (1989), in drought years significant differences in grain yield were found among soybean fields of different elevations. Soybeans on the low interfluve produced higher yield than soybeans on the shoulder or summit where drought stress was greater.
Despite the wide variation in soil types, plant varieties, and weather conditions, some consistent trends in leaf elemental concentration changes due to flooding were detected in our study. The reduction in N concentrations and the increase in P, Ca, Mg, B, Fe, Cu, and Al in flooded soybean leaves reported in our study were similar to the results reported by Fausey et al. (1985) for corn seedling leaves. Flooding has been known to cause nutrient imbalance and mineral toxicity in plants (Barrick and Noble, 1993).
In addition, the plant, soil, and weather results collected in this study are being used in a statistical model to determine the interactions of these factors in reducing soybean grain yield. The determining factor(s) that reduces soybean yield in flooded fields, once identified, will assist in the development and testing of flood tolerant varieties, and also in the decision making process of how to best cope with flooding problems using precision agriculture technology.
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ACKNOWLEDGMENTS
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We wish to thank the Bowling, Hartsock, Leeds, Richards, Sollars and Stadler Farms for providing the research areas and their time in making this project possible. Warren Rayford and Donna Thomas of the USDA, ARS, NCAUR, Peoria, IL, provided the seed oil and protein analysis. We also thank Prof. Randall Reeder, Dr. Steve St. Martin, and Dr. Tim Stombaugh of the Ohio State Univ. for helpful comments and suggestions. Thanks are especially due to Ms. Virginia Schnipke for laboratory assistance and helpful comments.
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NOTES
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funded in part by a grant from The Ohio Soybean Council. Use of trade names is for the benefit of readers and does not imply endorsement of the product by the U.S. Dep. of Agric. Joint contribution of the USDA-ARS, USDA-NRCS, and the Ohio State University. Ohio Agric. Res. Development Center Journal no. HCS-2000-1.
Received for publication October 25, 1999.
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TOP
ABSTRACT
INTRODUCTION
