College of Agricultural Sciences—Cooperative Extension
May 5, 2009
G RAZING IN B ERKS
1238 County Welfare Road, Suite 110, Leesport, PA 19533-9709 Phone 610-378-1327 Fax 610-378-7961
K E E P I N G Y O U R W AT E R W O R K I N G F O R Y O U
T
he three primary ingredients for making meat, milk, and fiber are solar energy, water, and soil minerals. We’re emphasizing how to manage these resources to create wealth with the least amount of iron and oil between the raw resources and your finished product. Water can be thought about from two very different aspects of pasture-based livestock production. The first is water that makes plants grow while the other viewpoint is from the animal’s drinking perspective. This article will discuss water for plant growth Fresh plant growth may be over 90% water so it is obviously a key component for pasture growth. Rarely does the water level in a healthy plant drop below 60-70%. While a small amount of water does enter the plant through the plant leaves, the vast majority of that water must enter through the root system. There must be water in the soil for the roots to absorb. Without water in the soil, there is no plant growth. In some parts of the country, rain water falls wonderfully from the sky on a fairly regular basis. This is another free input we need to capitalize on in our production systems. We cannot affect how much rain falls on our pasture, but there are a number of things we can do in our everyday management that can affect what happens to rain water once it reaches the pasture surface.
Let’s follow the possible paths for a band of raindrops as they fall to the earth.
FOLLOW THE RAINDROPS
In a pasture that has been rested, the drop will likely be intercepted by plant leaves. Some drops will be held on the surface of the leaves while others fall through all the living plant material to reach the ground surface. A bit of the water held on the leaves actually enters the plant while most of it runs down the leaves to the stem channeling its way down to the ground surface. All along the route, some is likely to be dripping off. If it is relatively warm, some of the rain water may evaporate from the leaf surface before it ever reaches the soil. If it is relatively cool, very little evaporates until the end of the rain storm. The water running all the way down the stems meets the soil surface near the crowns of the plants. For bunch grasses in semi-arid rangelands, this is a means for the plant to concentrate water near its root zone. Trees do the same thing by channeling water from throughout the canopy to the trunk. The better job a plant does of selfishly capturing falling rain, the greater its odds of survival. If the soil surface is covered with plant litter, a great deal of water can be held in this litter layer and then more slowly enter the soil.
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College of Agricultural Sciences
Penn State, U.S. Department of Agriculture, and Pennsylvania Counties Cooperating
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G r a z i ng i n B e r k s
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If the soil surface is bare, the soil will only absorb water at a rate equal to the saturation potential of the surface layer. Once the surface layer is saturated, any additional water reaching the soil surface is repelled. If the land is sloping, the water runs downhill, which is a basic law of nature. If there is nothing to stop the flow of water on your property, you have lost that free resource. If the ground has no slope, the water pools there and has the opportunity to either infiltrate the soil when the surface layer drains to deeper layers or it can evaporate away. If it evaporates away, that free resource is gone from your property. Infiltration rate depends on soil type, structure, and organic matter content. You can’t do very much to change your soil type other than selling out and moving somewhere else. You can significantly affect both soil structure and organic matter content through grazing management. Compacted soils do not infiltrate or hold water very well. Low organic matter soils do not hold water very well. Let’s summarize what we have just observed: Taller plant canopies break the fall of a raindrop so when it does reach the soil surface, it is trickling—not pounding. Plant structure can channel and concentrate water near their root systems. Rested pastures can capture more water. Yes, it also transpires and uses more water but they also reduce runoff potential. In short grazed pastures, more raindrops directly hit the soil with greater impact.
This results in a more compacted surface layer, more disturbed soil from impact and greater erosion potential. Properly rested pastures grazed to an appropriate residual will always have some plant material left behind that becomes the litter layer that protects the soil surface. A chronic symptom of pastures grazed too short is the near absence of litter on the soil surface. Without litter to break raindrop impact, hold water in a sponge-like manner and insulate the soil, both runoff and evaporative losses are accelerated. Short-grazed pastures have restricted root systems which lead to less soil structure and great propensity towards soil compaction, both of which result in increased runoff and decreased infiltration. There is less water entering the soil with a shallower root system that cannot utilize deeper water reserves. Less water entering the plant and a shallower root system means less opportunity for the plant to utilize mineral nutrients held in deeper soil strata. All of the above affects the productivity of the pastures. Water is a critical ingredient for making meat, milk, and fiber. Our choices in grazing management have a tremendous impact on the effectiveness of the precipitation or irrigation that falls on our pastures. We can choose to have healthy productive pastures or we can choose to create a drought. The choice is yours to make. Reprinted with permission from The Stockman-Grass Farmer.
G r a z i n g i n B er k s
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SMALL GRAIN SILAGE OR BALAGE
S P R I N G F E R T I L I Z AT I O N OF FORAGES
S
ilage is an excellent way to utilize small grain crops used in companion cropping programs or grown to supplement forage supplies. Harvesting cereals as silage can also salvage a crop that has been damaged by hail, frost or insects. Cereal silages should be harvested in the milk to soft dough stage to maximize the yield of energy per acre. As cereal grains mature from the boot to the dough stage, the protein level drops while the energy value increases. Dairy producers can maximize protein content by harvesting cereals in the boot stage. Little wilting is necessary when harvesting at the early dough stage. Approximate feeding values for commonly grown cereal crops are shown below. Feeding values of small grain and corn silage.
Crop Dry Matter 38.8 39.4 40.2 39.8 37.3 Crude Fiber Crude Protein TDN
H
ow much nitrogen to apply to a forage crop this spring will depend on the use of the forage to your operation. Pasture N Application Healthy grass stands have a huge capacity to respond to nitrogen additions. However, if the result of N application is pasture growing faster than the livestock can eat it, then the nitrogen has been wasted. Also, nitrogen is recycled through the urine and manure deposited by the grazing animals so optimum rates will be about one-third less than in stored feed systems. Increase nitrogen rates slowly over time until the forage supply and stocking rate are in balance. There is also some opportunity to modify the timing of nitrogen application. Lower rates could be applied in the early spring rather than later in the season in order to match livestock demand. The success of this approach will be limited by the amount of rainfall during the summer.
Pennsylvania Forage and Grassland News
Barley Wheat Oats Rye (wilted) Corn
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Source: Virginia Polytechnic Institute and State University
Sincerely,
Mena Hautau Extension Educator, CCA Email: mmh10@psu.edu
Morgan Firestine Extension Educator Email: maf5002@psu.edu