Grass Growth and Pasture Management Part of the Ruminant Livestock: Facing New Economic Realities Meetings

Grass Plant Tillers Rhizome Tiller Crown Tiller Lead Tiller Seed head Source: L.L. Manske North Dakota State University

Grass Physiology Cool season grasses initiate flower buds on the crown when exposed to low temperatures and long nights. Carbohydrates are stored late in the growing season (fall management is critical). In the spring, new growth is initiated from the crown using carbohydrate reserves stored in the roots, rhizomes, stolens, and/or stem bases. As day length increases throughout spring, at some point a flowering response is triggered.

Grass Physiology Not all tillers produced by the plant are reproductive tillers, but… Because reproductive tillers grow taller than the vegetative tillers they shade out the vegetative tillers and in addition… As seed heads develop they produce plant hormones that retard the development of other vegetative tillers

Grass Physiology Removing the seed head by grazing or clipping will promote development of vegetative tillers Because most cool season grasses require cool temperatures and long nights to once again develop reproductive tillers, after seed heads are removed, vegetative growth is produced for the remainder of the year

UNDERSTANDING PLANT GROWTH Light Roots/Carbohydrate Reserves Temperature Water Fertility/Nutrients

PLANT REGROWTH AFTER HARVEST From Carbohydrates Produced by Remaining Leaf Area From Carbohydrate Reserves

Defoliation Stresses Forage Plants Reduces or eliminates photosynthesis Stops nutrient uptake from the soil In legumes, nitrogen fixation stops within hours of harvest

Leaf Removal vs. Root Growth % Leaf Removed Percentage Root Growth Stoppage Source: Crider, 1955

Grazing Principle For Rapid Regrowth: Take Half Leave Half (By weight/volume: recognize forage is denser towards base of plant)

What You Leave Behind… Affects re-growth rate Affects root growth Affects soil temperature Affects organic matter Affects water infiltration rate and water- holding capacity Affects nutrient cycling

Animal Intake and Pasture Residual Forage Systems Research Center work has found about 80% of the variation in grazing intake is correlated with post-grazing residual. When forage mass drops below a critical level, intake is restricted In other words, the reason the top end of graziers are getting better animal performance compared to lower end graziers is because they know when to get their livestock out of a pasture paddock.

Managing Grazing Heights: Pure or dominant grass stands SpeciesPre-graze inchesPost-graze inches Perennial Ryegrass6-73 Orchardgrass T. Fescue (E+) T. Fescue (E-) Brome grassPre or late jointing 2-3 TimothyPre or late jointing 4

Managing Grazing Height GrassLegumeMixtures SpeciesPre-graze inches Post-graze inches Bluegrass/w clover OG/L clover T fescue/L clover Alfalfa with grassbud2 - 3 Red clover with grass bud2 - 3

Grazing Principle Provide plants with adequate rest period to re-grow to correct grazing height

Relationship of rest period to pasture mass during periods of rapid vs. slow growth Period of fast plant growth (days) Period of slow plant growth (days) Lbs. DM / acre Optimum Rest Period Source: Craig Saxe, University of Wisconsin Extension

Rest Period Management Paddock number determines flexibility and the degree to which the grass plant can be managed. For example in a 4 paddock system if my goal is not to graze the new re-growth until 8 inches, then my rotation flexibility is days in the spring and 28 to 32 days in the summer In a 10 paddock system, rotation flexibility is 10 to 30 days in the spring and 50 to 70+ days in the summer More paddocks can result in higher utilization rates

MANAGEMENT TO OPTIMIZE PLANT GROWTH Avoid production of seed heads, keep the plant vegetative Maintain leaf canopy (residual management) Recharge plant root reserves Vary rest periods by season and rainfall Frequent shifts of short duration Provide adequate soil nutrients

Growing Season Management The reason behind using rest periods and residual management is to increase productivity and to put the grazier in the position to extend the grazing season through: Quicker green up in the spring Quicker recovery from drought Fall/Winter grazing?

Management Changes?