Principles of Soil Science for Managing

Soybean Production:

the Sub-Saharan African Context

Webinar

Wednesday,August 21, 2019

9 a.m. – 10 a.m. CDT

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Meet Today’s PanelistsDr. Andrew Margenot is

the lead Soil Scientist for the

Soybean Innovation Lab. He

is an Assistant Professor at

the University of Illinois,

focused on soil fertility,

water quality and

environmental systems

research. Dr. Margenot has

done extensive soils

research in Kenya in

collaboration with CIAT and

brings a wealth of expertise

to the Soybean Innovation

Lab’s programming across

Sub-Saharan Africa.

Dr. Michelle da Fonseca Santos

is the Program Manager for SIL’s

Pan-African Soybean Variety Trial

program, which introduces

commercial varieties from across

SSA, the U.S., Australia, and Latin

America to fast-track the

identification, registration and

release of new, high-yielding

soybean varieties.

Courtney Tamimie is the

Associate Director for the Soybean

Innovation Lab and manages the

day-to-day operation of the lab’s

45-member international research

team operating across 11 Managed

Research Areas.

Why do soils matter for successful adoption of soybean technologies?

Topic overview1. Principles of Soils: static and dynamic properties

2. Management practices that influence soils and soybean productivity

3. Implications of soil principles for nutrient management of soybean

Goal: understand the basics of soils and how these are relevant to soybean production

Poll 1

Why do soils matter for successful

adoption of soybean technologies?

Soybean field in

western Kenya

• There is no such thing as a “tropical soil” or “African soil”

Dewitte 2013 Geoderma 211:138

Typic Kandiudox (USDA)

Haplic Ferralsol (WRB)Rhodic Kandiudox (USDA)

Rhodic Acric Ferralsol (WRB)

• Myth that damages introduction of technologies such as soybean

• High soil diversity in the continent• Historically overlooked

• Challenges one-size-fits-all blanket recommendations for any crop

Examples of weathered soils (Oxisol / Ferralsol)

not “tropical soils”

Dewitte 2013 Geoderma 211:138

• Understanding and adapting to soil context is critical for effective development and delivery of agricultural intensification technologies such as soybean

• Soil type is a starting point for best management practices

In 2013 the Joint

Research Centre of the

European Commission

produced the Soil Atlas

of Africa

Poll 2

Principles of Soils: static and dynamic properties

Static properties: inherent, immutable. Change little, if at all, with management and land use

Dynamic properties: change with land use, management, and disturbance over the human time scale (decades to centuries)

https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcseprd1343021

Static property: texture

Dynamic property: organic matterS

na

pp, 2

012. M

SU

Exte

nsio

n

Dynamic property: structure

Granular Blocky

Prismatic

Platy

Single grainedMassive

Fox Demo Farms. UW Madison Extension.

Dynamic property: pH

Poll 3

Management practices that influence soybean productivity via soil

How can soil influence soybean?• Chemical

• Nutrient availability

• Toxicity

• Physical• Water holding capacity

• Compaction –limits root growth

• Feedback effect of low water infiltration

• Biological• N-fixing symbiotic bacteria (Bradyrhizobium)

• Plant growth promoting microorganisms (PGPMs)

Chemical fertility

• Nutrient availability• Macronutrients: N, P, K, Ca, Mg

• Micronutrients: Fe, Cu, Mn, Mo, B, Zn

• Toxicity of elements (Al, B, Mn)

• While not a nutrient, soil pH is critical for soybean growth indirectly via its effects on the availability of nutrients

Nitrogen deficiency induced

by molybdenum deficiencyChanges in pH alter nutrient availability

Biological – N fixation

• As with any other legume, biological N fixation by soybean requires a compatible symbiotic rhizobacteria

• Generally from the genus Bradyrhizobium, specifically B. japonicum

• Given its Asian origins and historically recent introduction to Africa, the soybean symbiotic Bradyrhizobium japonicum is generally thought to not be present in soils in the continent

Practices: Tillage

R educed tillage + residue

retention

oC nventional tillage + residue re moval

No-till provides greater yields in the

eastern, southern, and western United

States where high temperatures, soils with

low water-holding capacity, and/or

unfavorable rainfall patterns often cause

drought stress.

pioneer.com/us/agronomy/tillage_soybeanyield.html

Notable yield advantage for soybean

with no-till mediate by soil moisture

Liming

Liming increases

soil pH

• Lime works through multiple mechanisms to alleviate co-constraints to crop growth

1. Decrease Al toxicity to roots

2. Enhance availability of soil nutrients

3. Facilitate N fixation

4. Increase agronomic use efficiency of added nutrients

• Soybean is especially sensitive to acidity responsive to liming applications that increase pH > 5.5-5.8

Fertilization

• Direct addition of nutrients

1. Soybean can fix its own N

2. High soil nitrate can deter nodulation

• P and K

• Micronutrients• Mo is especially important for N-fixation

Ronner 2016 Field Crops Res. 186:133

Example of Potassium DeficiencyExample of Phosphorus Deficiency

Poll 4

Implications of soil principles for soybean nutrient management

• Test your soil!

• Nutrient management best practices include:• Initial soil testing

• Build-up and maintenance rates

• Soil testing to calibrate nutrient balances that are appropriate

Be

nd

er

20

13

Ag

ronom

y J

10

7:5

63

Maintain pH >5.8 by liming

Summary

• Soils diversity across African is tremendous and serves as starting point for targeting and tailoring soybean technologies

• Soils have static and dynamic properties

• Static properties are immutable, dynamic properties can be changed by management practices

• Soils indirectly and directly influence soybean productivity, with implications for management

• Compaction

• Soil acidity

• Nutrient availability: soil test-based fertilization

Q&A Session

Dr. Andrew Margenot is

the lead Soil Scientist for the

Soybean Innovation Lab. He

is an Assistant Professor at

the University of Illinois,

focused on soil fertility,

water quality and

environmental systems

research. Dr. Margenot has

done extensive soils

research in Kenya in

collaboration with CIAT and

brings a wealth of expertise

to the Soybean Innovation

Lab’s programming across

Sub-Saharan Africa.

Dr. Michelle da Fonseca Santos

is the Program Manager for SIL’s

Pan-African Soybean Variety Trial

program, which introduces

commercial varieties from across

SSA, the U.S., Australia, and Latin

America to fast-track the

identification, registration and

release of new, high-yielding

soybean varieties.

Courtney Tamimie is the

Associate Director for the Soybean

Innovation Lab and manages the

day-to-day operation of the lab’s

45-member international research

team operating across 11 Managed

Research Areas.

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Principles of Soil Science for Managing Soybean

Production: the Sub-Saharan African Context

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Feed the Future Soybean Innovation Lab Webinar | August 21,2019