From MSU Extension
Soil acidification can cause misshapen roots that lack functionality, resulting in stunted and unthrifty plants; this is true of all crops. It can affect an entire field, but generally starts in specific spots within the field. Oilseeds, legumes, and durum wheat may be particularly affected.
Look for unexplained poor plant health, generally in low or mid-slope areas. Yellowing and purpling of leaves, combined with poor root development and stunted plants, can be early symptoms of plants affected by acidification (Figures 1 and 2).
Test your soil pH if you are concerned! Toxicity can start below pH 6. We recommend testing the top 3 inches from both ‘bad’ and ‘good’ areas. You can test soil yourself, send it off to a soil testing laboratory, or contact your crop advisor (see resources below).
Soil acidification can dramatically affect the health and viability of a crop and cause considerable economic losses. Soil acidification is a relatively new problem in Montana, where soils are often basic (pH greater than 7). Acid soils can form when nitrogen fertilizer is applied at the soil surface and oxidizes. This process releases acid that makes naturally occurring aluminum in clay more plant available. The resulting aluminum toxicity shows up as above-ground yellowing and purpling of leaf and stem tissue and overall stunting. In addition, acidification can reduce root nodulation in pulses. This Soil Extension video is a great overview of the issue.
Montana State University Extension has many resources for managing soil acidification. Management may include the following:
- Liming soil
- Seed-placed phosphorus fertilizer can increase small grain yields by reducing aluminum toxicity in a given growing season.
- Consider planting small grain species or varieties that are aluminum or low-pH tolerant.
- Consider low-pH tolerant perennials such as intermediate wheatgrass and meadow brome.
- Ammonium-based fertilizer causes soil acidification, even when used at rates within research-based guidelines. Including legumes in rotation reduces N-fertilizer input and soil acidification, while perennials can slowly reverse soil acidification.
- Take steps to increase N fertilizer use efficiency by soil sampling close to seeding time, reduce N rates when possible, and plant crops with low N requirements. Prevention can be much less expensive than liming.
- Leaving plant stubble in-field can help buffer pH drops
Additional Resources
- More information on soil and tissue testing laboratories
- More information on soil acidification: measuring and managing the issue
Contacts Erin Gunnink Troth, Extension Plant Pathologist, erin.troth@montana.edu
Clain Jones, Extension Soil Fertility Specialist, clainj@montana.edu, 406-994-6076
Uta McKelvy, Extension Plant Diagnostician, uta.mckelvy@montana.edu, 406-994-5572
###
MSU Extension
