The following is from Grazing Bites and is used with permission.

by Victor Shelton, NRCS State Agronomist/Grazing Specialist

Yes, there is green grass.  Yes, both you and the livestock are more than eager to utilize it.  Yes, you both should wait before grazing it. 

It is one of the hardest times of the season for some people, me included.  We are tired of mud and tired of feeding hay.  There is an increasing amount of fresh new lush green grass beckoning to be grazed.  Why shouldn’t you allow the cows to partake in this new growth?  When is the ideal time to start grazing?

Let’s think this over a little.  What is the real problem with grazing too early?  Forages have just woken up from a long winter’s nap.  New growth comes from energy reserves stored in the roots and lower shoots; that early growth does not come from photosynthesis.  Plants must make their own food.  That process is called photosynthesis the production of carbohydrates from carbon dioxide, water and sunlight.  The process creates sugars and oxygen.  Early growth is not supported by photosynthesis; early growth comes from stored energy. 

You probably remember some past conversations we’ve had about not overgrazing last fall, especially before the forages went dormant.  That was a critical time for energy storage that is now expressed in the speed of new spring growth.  If reserves were withdrawn last fall, then it will take longer for plants to jump start this spring.  That last growth prior to going dormant is critical.  That particular solar panel is building reserves to sustain the plant over winter and providing energy for new growth in the spring.  If you turn around and let them graze it too early, especially if energy reserves are withdrawn last fall, then not only is spring production going to be reduced, total production for the whole year will be reduced.

If you either deferred grazing last fall until the plants were dormant or you stopped grazing once you reached appropriate stop grazing wintering heights (generally similar to stop grazing heights during the season, four inches for cool-season forages), then energy reserves should be decent and spring growth normally will be good.  Those reserves that were built in the roots and lower shoots last fall provide energy for quicker and more abundant growth in the spring. 

It’s not hard to notice the differences between two fields side by side, especially those managed so differently the past fall and early winter.  There is usually a remarkable difference in forage growth.  If you took clippings right now, you will often find a four to six-fold difference in forage present and I’ve seen even bigger differences. 

There are times when we want to slow growth in the spring, such as frost seeding legumes, so we reduce competition for those new seedlings.  Even under those conditions, we often see a slight reduction in total yield for the year, even with the benefits of the legumes and providing a little extra time for establishment.  A worse scenario is overgrazing in the fall with reserves not built and then turning around and initiating grazing too early in the spring or never removing them the entire time.  Energy reserves are grossly hampered in this situation and total yield potential for the season is quite often reduced by at least fifty percent.

I’ve heard people say, “The cows didn’t lose anything, they consumed it all.”  They consumed all that was grown, but the amount that was grown didn’t come close to the potential of the field.  It all boils down to, “it takes grass to grow grass.”

So, when should I initiate grazing in the spring?  Good question.  Fields that have good fast growth with reserves maintained over winter could be utilized for some grazing when forages are at least eight to ten inches tall.  Try and remove no more than one third of the forage and then move them on to the next field.  When forages are growing fast, rotate fast.  Try to never remove more than half of the entering growth amount or closer than the appropriate stop grazing height.  We’re talking cool season forages this time of year, so you can’t go wrong with using four inches as the stop grazing height.  Remember, stop grazing height is the shortest forages left standing, not the tallest.  If the pasture is rotated correctly it will have a fair amount of forage, between four and six inches left standing. 

Fields that were grazed hard last fall, especially prior to dormancy, could use a longer deferment prior to grazing this spring.  Those fields will need to first try to grow some solar panel off the reserve left, and then spend valuable time rebuilding roots and root reserves before allocating energy and resources to growing forage.  The plant is going to try and preserve itself and yield is the last thing on its mind; it’s thinking survival.  Quite often you will find these stands initiating reproductive stages quicker and earlier because of this survival mechanism.  In some cases, some anti-quality factors, such as alkaloids, may also be higher due to this.  In the long run, if you take care of the plant, the plant will help take care of you.  Unless you have run out of hay or are calving in mud, wait until the grass is ready.

If you haven’t taken any soil tests on your pastures recently, especially in the last four years, then now is a good time to do it unless you already did it last fall.  Fields that have any hay taken off them should be tested more often and at least every other year.  It is difficult to maintain a stand of quality forage that produces to its potential and provides nutritious feed without adequate fertility levels.  Systems that are rotated frequently, managed well, and don’t have any hay removed from them are generally a lot easier to maintain long term. 

If funds are limited, calcium is probably the first and best money spent.  Calcium and its relationship or ratio with magnesium have a major impact on the forage’s ability to extract nutrients from the soil and certainly the acidity or alkalinity of the soil which can dictate what will or can grow.  You should shoot for at least a 4:1 ratio of calcium to magnesium, or 5:1 if you are a dairy operation.  If you are really short on calcium and start fixing that problem, then you might find out that other elements start becoming more readily available. 

I’ll end today with a thought on magnesium.  It is a good idea to move to a high magnesium type mineral supplement (usually 10-20% instead of 1 or 2%) and continue with it until we are past the early flush of new forage.  The issue with insufficient magnesium is more of a problem where nitrogen and/or potassium has been applied recently or in excessive amounts.  For more detailed information about grass tetany, contact your local extension service or large animal veterinarian.

Keep on grazing!