Optimizing Lime Application and Symbiotic Nitrogen Fixation in Soybean Cultivation
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Questions and Answers

What is the main source of nitrogen for a soybean crop at a 65 bu/ac yield level in Nebraska?

  • Symbiotic fixation of nitrogen from the atmosphere
  • Nodules formation on soybean roots
  • Residual nitrogen in the soil and nitrogen from mineralized organic matter (correct)
  • Nitrogen fertilizer application
  • What is the expected outcome of applying micronutrients like boron, copper, and molybdenum to soybeans grown in Nebraska?

  • Significant increase in yield
  • Increased disease resistance
  • Decrease in yield
  • No significant yield increase (correct)
  • Which factor makes it less likely for elevated postharvest soil nitrate levels to result in significant nitrate leaching below the root zone?

  • Deficiencies of micronutrients like manganese
  • Symbiotic fixation of nitrogen from the atmosphere (correct)
  • Application of nitrogen fertilizer
  • Presence of white mold
  • What is the consequence of applying manure for narrow-row soybeans based on research findings in other states?

    <p>Increase in white mold</p> Signup and view all the answers

    Why are deficiencies of boron, chlorine, copper, manganese, and molybdenum not observed in soybeans grown in Nebraska?

    <p>Sufficient levels of these micronutrients in Nebraska soils</p> Signup and view all the answers

    What is the preferred practice for short- and long-term benefits to improve soybean yield?

    <p>Seed inoculation with Bradyrhizobium japonicum bacteria</p> Signup and view all the answers

    In which type of soil conditions is soybean yield more likely to benefit from nitrogen fertilizer application?

    <p>Soil with less than 1.5 percent organic matter</p> Signup and view all the answers

    What can be inferred if active nodules (dark pink center) are absent from soybean roots?

    <p>There is a deficiency of Bradyrhizobium japonicum bacteria</p> Signup and view all the answers

    When should nitrogen fertilizer be ideally applied to soybean fields?

    <p>As late as early pod fill</p> Signup and view all the answers

    Why is routine nitrogen application not recommended for soybean crops?

    <p>It leads to lodging-induced yield reduction</p> Signup and view all the answers

    Where does soybean obtain 25 to 75 percent of its plant nitrogen from?

    <p>Soil</p> Signup and view all the answers

    When do nodules start to appear on soybean roots?

    <p>After the first trifoliolate leaf emerges</p> Signup and view all the answers

    In which scenario is seed inoculation recommended for soybean production?

    <p>When Bradyrhizobium japonicum bacteria presence is doubtful</p> Signup and view all the answers

    What percentage of nitrogen needed by soybean can be supplied by symbiotic fixation with Bradyrhizobium japonicum bacteria?

    <p>Approximately 75%</p> Signup and view all the answers

    Under what conditions may the supply of nitrogen from soil and nodules be inadequate for soybean?

    <p>Low pH</p> Signup and view all the answers

    What is the main reason for iron chlorosis in plants according to the text?

    <p>Inability of the plant to effectively use iron</p> Signup and view all the answers

    How can high levels of nitrate-nitrogen in the soil affect iron availability to soybean plants?

    <p>Decrease iron availability</p> Signup and view all the answers

    What is a recommended management practice to address iron chlorosis in soybean plants?

    <p>Consulting with a seed dealer for tolerant varieties</p> Signup and view all the answers

    In which scenario is it unlikely that tolerant soybean varieties will produce well?

    <p>When there was severe iron chlorosis in corn or grain sorghum</p> Signup and view all the answers

    How does low soybean plant density affect the severity of iron chlorosis?

    <p>It makes iron chlorosis more severe</p> Signup and view all the answers

    What is a method producers can use to control fertilizer application based on management zone maps?

    <p>Manual application using a global positioning system (GPS)</p> Signup and view all the answers

    In which field conditions is zinc fertilization likely to be beneficial?

    <p>Fields low in organic matter and eroded</p> Signup and view all the answers

    What happens if soybean does not show zinc deficiency after a previous corn crop?

    <p>Soybean will not exhibit deficiency symptoms due to the previous corn crop</p> Signup and view all the answers

    How can manure application before planting soybean affect yield?

    <p>Increase yield by about 3 bu/ac in the first year</p> Signup and view all the answers

    To avoid surpassing the soybean nitrogen removal rate, how should manure rates be calculated?

    <p>To not surpass half of the soybean nitrogen removal rate</p> Signup and view all the answers

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