Soil Health - Montana State University

Soil Health

MSU Soil Fertility Extension

Clain Jones [email protected] 994-6076

Fairfield MT dust storm, Feb 2020, by Darryl Flowers, Fairfield Sun Times

Montana Farmers UnionVirtual meeting, September 3, 2020

Objectives

• Show agronomic practices that benefit soil health

• Focus on ways to increase soil organic matter• Describe impact of soil pH on plant

productivity and soil health• Present pros and cons of soil health tests• Leave lots of time for questions

Tools• Rotations• Residue

management• Amendments

Measurable impacts• SOM• Soil N/PMN• Microbes/enzymes• Aggregation• Soil pH

Image from Freecreatives

Increasing SOM increases many other soil health parameters

Agronomic practices that benefit soil

Less productivity → less SOM. This is a big deal to soil health (and income)! For example:

Fisher et al., 2007Australia, irrigated, variety of soil types

Small SOM increases → large improvement in soil structure Water infiltrationRoot growthReduced water and wind

erosion

The basis for soil health is biological activity, OM is the fuel for that activity. In Montana, 10 yrs of recrop or CRP increased SOM (‘02- ’12)

Engel et al. 2017, Gallatin Valley, MT

For higher OM soil in say 20 years, you need to start now.

Best way: recrop and apply recommended fertilizer rates, or grow perennials

SOM change depends on residue returned & inputs

Engel et al. 2017, Gallatin Valley MT, 16” precip zone

Need ~1.8 ton shoot residue/ac/yr (Shrestha et al. 2013 SK; Engel et al. 2017 MT) to maintain SOM in more productive NGP regions.

CRP

forage

Why? Slope = 0.4

What % of residue C still in soil after 10 yrs?

Why?

Annual wheat and pulse systems

Diversify – how could you & how would it help SOM?• Rotate species across time• Polycultures = mix species w/in field• Genetic diversity = mix varieties w/in

field• Mixed cover crops:More stable yearly production, reduced

risk. Unlikely all species in the mix will produce poorly or completely fail (Miller et al. unpub. data, Khan & McVay 2019)

More biomass when include legumes in low N soil (Miller et al. unpub. data)

Legumes increase available N if >40% of biomass (Sullivan & Andrews 2016)

Image by P. Miller

Norton et al. 2012, Albin WY; Ingram et al. 2008, Cheyenne WY. P 0.05 for 0-12” total SOM

Cultivated systems have lower SOM than perennial

Soil acidification is threatening productivity and SOM input. It is a major problem in parts of Montana.

Caused by N fertilization Leads to: Reduced nodulation in legumes Aluminum toxicity Changed herbicide effectiveness and

residual Increased disease - Fusarium crown

rot and Ceph strip Prevent by:

• Increase N use efficiency• Include legumes to supply N• Plant crops that require less N

Barley crop loss due to acidic soilPhoto courtesy Rick Engel

pH 3.8

pH 5.1

Legume cover crops increase microbial populations

Biederbeck et al. 2005, 6 yrs of rotations, SK. Organisms in top 4”, sampled after wheat phase in Oct, 15 months after cover crop termination.

Agrees with MT study at 4 & 2 locations after 2 & 4 rotations: pea or mixed cover crop generally greater microbial biomass than fallow (Tallman 2014, Housman 2016, D’Agati unpub data).

Soil Health Tests, e.g. Haney or Cornell

• Measure and monitor over time or between fields

• Useful to assess effect of management or evaluate problem areas

• Standardized methods may not yet be in place

• Currently no calibration between test values and fertilizer recommendations for N. Great Plains

Jones and Boss, 2014 unpub data, Havre, MT

How much does Haney test and standard fertility testing explain winter wheat yield variability?• Haney (15%) - Dissolved organic C most important variable• “Standard” (25%) 6 – 24” Nitrate most important• Haney + “Standard” (39%) 6 – 24” Nitrate most important

How can I manage for healthy soils?

Know your soil properties and only add amendments as needed

Avoid compaction:• Reduce tillage and traffic when wet

Feed the microbial community, increase organic matter content:

• Minimize fallow, possibly add cover crops• Moderate grazing

Maintain cover with vegetation or residue Be patient, but start now

Thank you!Questions?

Image by Meg Housman

This presentation and additional information on soil fertility topics are available at

http://landresources.montana.edu/soilfertility