April 18, 2023
Dickinson Research Extension Center Updates

Problems of Grazing Too Early





Llewellyn L. Manske PhD
Scientist of Rangeland Research
Dickinson Research Extension Center
701-456-1118
Preseasonality grazing of native grasslands during April and May prior to the new second year lead tillers reaching the three and a half new leaf stage are the previous years vegetative tillers that have survived overwinter on carbohydrate reserves that were stored by the tiller during the winter hardening process that occurs between mid August and hard frost. These carryover tillers are low in carbohydrate reserves that are inadequate to support root growth and new leaf growth. 
 
Partial defoliation by grazing is antagonistic to further tiller growth and to rhizosphere microbe activity. Spring growth depends on remaining quantities of carbohydrate reserves and on photosynthetic product from portions of previous years leaves that did not have cell wall rupture and regreened with chlorophyll. Additional leaf and root growth requires that the young lead tillers maintain adequate leaf area with a combination of carryover leaves and new leaves. 
 
At the time the new lead tiller has produced the third new leaf, the apical meristem would have produced 6 to 8 leaf buds and it stops producing leaf bud primordia and begins producing flower bud primordia by the three and a half new leaf stage. At this stage, the young lead tillers are nearly depleted of carbohydrates and the chlorophyll in the carryover leaves is senescing, and the tillers are capable of surviving removal of 25% of the new leaf growth but not removal of 50% of the new leaf area.
 
Defoliation of new young lead tillers prior to the three and a half new leaf stage terminates any beneficial activation of the four internal grass growth mechanisms, stops vegetative tillering mechanisms and prevents development of surplus short chain carbon energy from being exudated into the rhizosphere to stimulate microorganism activity and the ecosystem biogeochemical processes. The remaining new leaf area is unable to photosynthetically support additional active leaf growth. That tiller does not die but attempts to slowly produce leaf and root tissue at rates far below its potential rate and quantity of herbage production causing a great decrease in peak herbage biomass later in the growing season. 
 
Grazing that starts in early May on native grasslands results in a reduction of more than 75% of the potential herbage biomass. When grazing starts in mid May, from 45% to 60% of the potential herbage biomass is not produced that growing season.
 
For More Information Go To: 
 
NDSU Dickinson Research Extension Center logo
The NDSU Extension does not endorse commercial products or companies even though reference may be made to tradenames, trademarks or service names. NDSU encourages you to use and share this content, but please do so under the conditions of our Creative Commons license. You may copy, distribute, transmit and adapt this work as long as you give full attribution, don’t use the work for commercial purposes and share your resulting work similarly. For more information, visit www.ag.ndsu.edu/agcomm/creative-commons.

County commissions, North Dakota State University and U.S. Department of Agriculture cooperating. NDSU does not discriminate in its programs and activities on the basis of age, color, gender expression/identity, genetic information, marital status, national origin, participation in lawful off-campus activity, physical or mental disability, pregnancy, public assistance status, race, religion, sex, sexual orientation, spousal relationship to current employee, or veteran status, as applicable. Direct inquiries to Vice Provost for Title IX/ADA Coordinator, Old Main 201, NDSU Main Campus, 701-231-7708, ndsu.eoaa@ndsu.edu. This publication will be made available in alternative formats for people with disabilities upon request, 701-231-7881.