Abstract Detail

Crops and Wild Relatives

Robertson, Marisa M. [1], Bohn, China H. [1], Hildebrand, Terri [2].

Wheat and Native Grass Development and Reproduction When Grown in Prairie, Organically Farmed, and Long-term Glyphosate Treated Agricultural Soils.

The herbicide glyphosate (Round-up©), often with 2, 4–D, is widely used to control weeds in agricultural fields, particularly under chemical fallow management practices.  We sought to determine growth and reproductive effects on wheat and two native grasses, Bouteloua gracilis and Pascopyrum smithii, when grown in prairie, as well as organic and herbicide treated field soils. Agricultural soil sampling occurred from fields in which organic management or glyphosate treatments occurred for a period of five or more years.  Individual plants (n=405) grown in a greenhouse during 2017 produced data at three season intervals in addition to harvest. Stem number and height, above- and below-ground biomass, and leaf production yielded information on plant development.  Inflorescence number and length, as well as glume number (surrogate measure for seed production) generated reproduction data. Analysis of a subset of soil samples (n=108) further investigated plant-soil relationships. Our results showed only ca. 60% of wheat seeds geminated in chemically managed soils compared to 82% and 85% in organically farmed and native soils.  Wheat out-performed native grass germination only in organically farmed soils.  Wheat stems grown in glyphosate treated soils were 75% shorter, but B. gracilis stems showed little variation in plant height, and P. smithii did not vary significantly in height among soil types.  Mean wheat and P. smithii mass was 5.6- and 1.7-fold greater in native than chemically treated soils, respectively, and 3.1- and 1.2-fold greater in organic than chemically treated soils, respectively.  Reproduction varied significantly by soil as well.  Wheat and B. gracilis produced significantly more inflorescences when grown in organically farmed soils and glume number for each structure was greater as well.  Lowest reproduction for both species occurred in soils collected from chemically fallowed fields.  P. smithii did not produce reproductive structures at the time of harvest for this study.  Organic fields contained significantly more organic matter than soils receiving herbicides (mean 1.33% and 1.03%, respectively), but both had less than the 1.50% observed in native prairie soils; organically farmed soils had the greatest cation exchange. Despite having no fertilization treatment, nitrate, phosphorus, and potassium levels were highest in organically farmed soils.  Results from our study contribute to a growing body of research on the negative effects of repeated herbicide application and chemical fallow management practices.  In addition, results suggest organic methods as a viable alternative to chemically managed farming.

1 - Montana State University Northern, Biology, 300 13th Street West, Havre, MT, 59501, United States
2 - Montana State University Northern, Biology, 300 13th Street West, Hagener Science Center 205, Havre, MT, 59501, United States

chemical fallow
Vida wheat

Presentation Type: Poster
Number: PCW004
Abstract ID:331
Candidate for Awards:None

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