Student Research: Do Winter Annual Small Grains Reduce Perennial Grass Establishment?

Student Research: Do Winter Annual Small Grains Reduce Perennial Grass Establishment?

By Sarah Morton, Student in the Department of Agronomy and Horticulture, University of Nebraska-Lincoln
Advisors: Robert Mitchell, USDA-ARS Wheat, Sorghum, and Forage Research Unit; Daren Redfearn, Nebraska Extension Forage and Crop Residue Systems Specialist

Over the last 10 years, many acres of perennial grasslands have been converted to crop production. This has decreased available forage resources and negatively impacted sectors of Nebraska’s cattle industry. Due to their highly erodible nature, many of these converted acres are more suited for perennial grass systems; however, re-establishing perennial grasses comes with challenges. It has been shown that establishment may be improved by using residues from previous small grain crops.

Establishment of perennial species into small grain residue is not widely accepted, especially following cereal rye, primarily due to the possibility of allelopathic effects from the cereal rye on seed germination and seedling vigor of subsequent crops. In order to evaluate the possibility of negative allelopathic effects on perennial grass establishment a one-year study was conducted at the Agricultural Research and Development Center near  Mead.

Establishment Methods

In this study, three perennial cool-season grasses (smooth bromegrass, intermediate wheatgrass, and crested wheatgrass) and three perennial warm-season grasses (big bluestem, indiangrass, and switchgrass) were planted as monocultures into the residues of three small grain species (wheat, cereal rye, triticale, and oats). The cool-season perennial grasses were planted approximately three months after small grain harvest, while the warm-season grasses were planted approximately ten months after small grain harvest.

Stand Evaluation Methods

Frequency of occurrence of the perennial grasses was evaluated 30 days post-planting.  Both the cool- and warm-season grasses had typical emergence patterns that correlated with the emergence of weeds. Hence, high germination and emergence of the perennial grasses resulted in lower weed density, whereas lower germination and emergence of the perennial grasses typically had much greater weed pressure.  Intermediate wheatgrass and smooth bromegrass established well regardless of residue type with an establishment average close to 100%; however, crested wheatgrass plant frequency often averaged around 20%. 

As a group, the warm-season perennial grasses had poor establishment compared with the intermediate wheatgrass and smooth bromegrass. Frequency of occurrence for indiangrass averaged 50% when planted following triticale and wheat, but only 38% following oats and cereal rye. Big bluestem frequency of occurrence averaged 40% and switchgrass was found to average about 28%.


Planting perennial grasses into small grain residue after grain harvest had no effect on establishment. Generally, greater frequency of occurrence resulted in reduced weed cover for all cool-season perennial grasses.  Small grain residue may add the benefit of reduced weed competition, especially for species with increased seedling vigor. This data shows that planting perennial grasses into small grain residue will not adversely affect establishment when converting cropland into perennial pasture.

About the Author

Student researcher Sarah Morton
UNL agronomy student and researcher Sarah Morton examining perennial grasses.

Sarah Morton is a junior at the University of Nebraska-Lincoln majoring in agricultural education. She grew up on a family farm outside of Nehawka.

Support for this project was provided by a grant from the USDA NIFA FY15 Agriculture and Food Research Initiative: Education and Literacy Initiative–Undergraduate Experiential Learning Fellowships Program.

Find more stories about student research conducted through this project at Developing Undergraduate Research and Extension Expertise in Integrated Agronomic Systems.

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