The Problem How do we manage our grasslands for maximum production and while maintaining sustainability?
Student Learning Objectives To identify how grasslands have come to be as they are. To differentiate types of grasslands and categories of prairies in the United States. To calculate stocking rate and animal equivalency units. To distinguish the categories of grassland forages. To identify management practices for utilizing grasslands that promote sustainability.
Is there a difference? Grassland Pastureland Rangeland Cropland
Terms Grassland- Any plant community in which grasses and/or legumes make up the dominant vegetation. Pastureland- Land devoted to the production of native and introduced forages that are harvested by grazing. High economic inputs. Rangeland- Land that is devoted to the production of natural species. Less intensively managed. Hayland- Land which primary purpose is to harvest forage. Cropland- Land devoted to the production of a cultivated crop and is harvested for livestock feed.
The Grasslands Types Tallgrass Prairie Transition Prairie Shortgrass Prairie Grasslands used to comprise 25% of U.S. land area Now ≈ 17%
Tallgrass vs. Shortgrass Prairie Tallgrass Prairie Used to cover the area from Indiana to central Nebraska. Up to 6 ft in height. Some of the richest soil in the world Became cropland Shortgrass Prairie Stretch from the Rocky Mountains to the central panhandle of Nebraska. Areas of lower annual precipitation More exist because they are in a less productive area of the nation.
Nearly all of the tallgrass prairie has been converted to farm production or other human developments. (Irrigation is not usually necessary) All shortgrass prairie requires irrigation to make cultivated farming possible. Less desirable for cultivation
Vegetative Community Climax Community (Vegetation) The stage of succession in which an area has reached its most natural state. Some theorize that forestland was the climax community of the tallgrass prairies Fires caused by lightning and the Native Americans may have destroyed the forests and became grassland Early Native Americans hunted on foot and utilized fire as a weapon against bison Today we calculate climax community by determining range condition.
Vegetative Community Types of vegetation Grasses Grasslikes Forbs Shrubs All compete for resources for maximum growth Grazing rates affect the relative amounts of each
Management Techniques Objective = long-term maximization of livestock productivity from managed rangeland. Do not damage the capacity for grass production Treat grasslands that are not at their max potential Control soil erosion and depletion Avoid depleting the groundwater supply Utilize the appropriate grazing pressure Control undesirable vegetation
Management Techniques Evaluating Carrying Capacity (Grazing Capacity) Types of vegetation present Growth rate of desirable species Effects of grazing Climate Soil type Slope Precipitation
Management Techniques Grazing capacity determines stocking rate Stocking rate is expressed as animal equivalent units (AEU) (AU) 1 AEU is equal to the amount of forage required for a 1,000 lb animal for a given amount of time. Time will generally be expressed in months 1 AEU for one month is an animal unit month (AUM) Equivalencies 1 cow/calf pair = 1.2 AEU 1 weaned calf= 0.5 AEU 1 yearling calf= 0.67 AEU 1 steer = 1AEU 5 goats/sheep= 1AEU 1 horse/bull= 1.25 AEU 1 elk= 0.67 AEU 4 deer= 1 AEU
What we want to know…. I have a pasture which I want to run cattle on. What is the greatest amount of cattle (stocking rate) I can run on the ground to achieve maximum profit yet avoid overgrazing?
To calculate stocking rate… Stocking rate = suggested initial rate x adjustment factor (table 6)(chart) What is the suggested initial stocking rate for a sandy site in vegetative zone I? 0.5 AUM/Ac What is the suggested initial stocking rate for a limy upland site in zone IV? 0.9 AUM/Ac If the previously mentioned sandy site is determined to be at 65% range condition, what is the adjustment factor? 0.8 What is the stocking rate for the sandy site in zone I? 0.5 AUM/Ac * 0.8= 0.4 AUM/Ac
How many cow/calf pairs could this 400 acre sandy site with a stocking rate of.4 AUM/Ac pasture for 5 months? 0.4 AUM/Ac * 400 Ac= 160 AUM 160 AUM / 5 M = 32AU/1.2AU= 26.6 = 26 pairs
400 acres; 5 months; 65% range condition; saline subirrigated site in zone IV
Farmer Lloyd in Crofton, Nebraska wants to start pasturing yearling steers on his recently purchased 450 acres of silty overflow land. The pasture season is 5 months. The NRCS came out and sampled his pasture and discovered it is at 55% range condition. (This means it is producing at 55% of it’s potential at climax community) How many steers could Farmer Lloyd pasture for the given period of time?
What if I I’m given all the necessary information including the number of animals but want to discover how many acres I need in order to successfully graze those animals?
10 deer; 12 months; Range Site II; Saline subirrigated site at 60% range condition Figure AU’s Multiply by months to calculate AUM’s. Use the reciprocal of AUM/Acre for Ac/AUM Multiply AUM by Ac/AUM
Vegetative Community (Grasses) Grasses Complex root system that holds soil in place and preserves soil moisture High source of nutrition for grazing animals Light grazing benefits grass “Graze half, leave half” If all of the leaves are consumed, recovery of grasses takes longer
Decreaser- Varieties of grasses that are easily damaged with even light grazing. Increaser- Varieties of grasses that thrive under heavier grazing. Adaptations that allow them to access resources more efficiently Often unpalatable and therefore are avoided by herbivores Invader- Plants that move into an area after it has been badly overgrazed. Occasionally will move into areas that are badly undergrazed Vegetative Community (Grasses)
Management Techniques Undergrazing and overgrazing are detrimental to the plant community Discourages growth of desirable grasses Promotes growth of invaders Most animals do not graze uniformly on their own Concentrate themselves near water or salt/mineral areas Separate salt/mineral locations from water sources to promote more even grazing Grazing management systems promote even grazing
Grazing Management Systems Continuous Grazing Livestock are left in one area year-round and allowed to graze at will Uneven grazing will occur Less work and expense
Grazing Management Systems Deferred-Rotation Grazing Pasture is divided into two or more grazing areas (paddock) Livestock are moved periodically to allow grass recovery time
Grazing Management Systems Management Intensive Grazing Grazed at a high stocking rate for a very short period Promotes the growth of increasers Higher quality forage may improve gains Increases utilization of available forages including those which have low palatability. Increased labor requirements More water sources required
Range Restoration Controlled grazing is the first step of restoration If seeding is required, grazing must be withheld until grasses are re-established Eliminate vegetation if the area is overgrown by invaders In less severe cases, controlling grazing may be adequate to restore rangeland Light overseeding and fertilization may speed the process
Summary Much of the United States grassland has been depleted over the years due to conversion to cropland or urban structures. Prairies are divided into two main categories- Tallgrass in the east and shortgrass in the west. Transition prairies are between the two Stocking rate can be calculated by evaluating a pastures grazing capacity and figuring an animals AEU’s Grassland forages are divided into grasses, grasslikes, forbs, and shrubs. The most important management factor is to properly manage grazing of grasslands.