Project Details:

Improving Micronutrient Fertilization for Soybean Production

Parent Project: Improving Micronutrient Fertilization for Soybean Production
Checkoff Organization:Louisiana Soybean and Grain Research and Promotion Board
Categories:Soil fertility, Agronomy
Organization Project Code:
Project Year:2020
Lead Principal Investigator:Jim Wang (Louisiana State University)
Co-Principal Investigators:

Information and Results

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Project Summary

Soybeans are one of the most adaptable crops for different soil types and varied climatic conditions found in Louisiana and it continues to play a big part in the state’s agricultural economy. Many micronutrients can affect crop growth including soybeans. Frequently, micronutrient molybdenum (Mo) is found deficient in acid soils while boron (B), iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) are found deficient in alkaline soils due to the nature of their presence in soils and their interactions with other elements. For soybean production, molybdenum, iron and boron are especially important. For instance, molybdenum is an important part of Mo-containing enzyme, nitrogenase, which is needed by root nodule bacteria for nitrogen fixation. The molybdenum requirement by soybean is greater than by other crops. In acid soils, molybdenum tends to be deficient due to its strong bonding to iron/aluminum oxides. In addition, application of sulfate fertilizer can exacerbate the molybdenum deficiency due to the competition of both sulfate and plant available molybdenum (in the form of MoO42-) for root uptake sites. Over last twenty years, there has been very little work concerning micronutrient fertilization particularly in soybean production. With today’s efficient new varieties, much is unknown for molybdenum fertilization in soybean crop. In addition, there is no adequate soil test even offered by the LSU AgCenter Soil Testing Laboratory and other labs due to the fact that molybdenum is not integrated in commonly used soil testing procedures such as Mehlich III extraction.

Iron deficiency often cause chlorosis symptoms in soybean due to its effect on the development of chlorophyll. On the other hand, iron is also necessary for soybean root nodule formation and has a role in N fixation. Its deficiency in especially in alkaline soils such as red river soils is an issue. The risk of iron chlorosis in soybean depends on soil carbonate content and salinity and generally increases with these two parameters. Red river alluvial soils contain generally high calcium carbonate contents which make them the most likely region for soybean iron chlorosis to occur. On the other hand, while in past Fe-EDTA chelate has historically been used to correct an iron deficiency, it is often not effective due to its short-term Fe availability and is not stable at soil pH > 6.5. Fe-DTPA is also not stable in calcareous soils above pH 7. In recent years, new chelates such as Fe-EDDHA (ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid)) are available, which have longer Fe availability and can maintain its stability up to soil pH 11. Such products have not been adequately evaluated for soybean production in red river soils. As new crop varieties have been developed over the years, macronutrient fertilization of nitrogen has also changed from the previously dominant urea to the use of a UAN application. This could change dynamics of micronutrient availability in soils for plant uptake. For instance, high nitrate-N presence could induce or amplify iron chlorosis in soybean crop.

Project Objectives

1) Compare molybdenum source and application for improving soybean production in acid soils

2) Evaluate new iron chelates for improving soybean nutrition in alkaline soils.

3) Determine applicability of boron fertilizer in alkaline soils for soybean production

Project Deliverables

The overall goal of this proposed research is to figure out the optimum application rates and methods of micronutrients particularly molybdenum, iron and boron for soybean production as well as their rate efficiency affected by blending with macronutrients.

Progress of Work

Final Project Results

Benefit to Soybean Farmers

Soybean micronutrient fertilization management plans for Louisiana can help boost yields.

Performance Metrics

Project Years