Soybean Top and Root Response to Temporary Water Tables Imposed at Three Different Stages of Growth1

Abstract

AbstractKnowledge of the response that a crop's root system exhibits with respect to changing soil environments can be useful if that change can be altered by man. Such is the case with crops grown on soil where temporary high fluctuation of the water table can occur. Knowing at what growth stages a crop may be more tolerant or susceptible to injury could be valuable in determining to what depth and at what rates drainage should occur.A field‐situated rhizotron study was conducted using two water table heights (45 and 90 cm) to determine the effects of temporary high water tables imposed at different growth periods on the development of the tops and roots of soybean [Glycine max (L.) Merr.] plants. Water‐table heights were established for 7 days during preflowering, postflowering (before podset), and post‐podset growth periods. Top and root growth parameters were monitored continuously throughout the growing season.Results indicated that root tolerance to water‐table level changed as the plant progressed through its growth cycle. Root tolerance is described as the ability of the root system to withstand or adjust to the conditions caused by imposed water tables. During preflowering individual root tolerance was exhibited. Little damage occurred to the roots during imposition or removal of the water table treatments. During postflowering less individual root tolerance, but strong total root system adjustment was evident. Extensive damage to the roots occurred once the water tables were imposed, but the plant's ability to adjust to the situation by initiating new roots in soil areas above the water table levels was quite strong at this particular growth period. No root tolerance of the water‐table conditions was observed for post‐podset growth.