Managing Nutrient Flows in Forage Systems

One of the most beautiful things about well managed grazing systems is the establishment of strong and vigorous nutrient cycles.  Nutrients enter this cycle in the form of fertilizer, manure, hay, supplemental feeds, minerals, and nitrogen that is fixed from the air via the symbiosis between rhizobium bacteria and legumes (Figure 1).  Somewhere in the range of 80 to 90% of these nutrients are recycled in well managed grazing systems. This recycling occurs through the breakdown of plant residue on the soil surface and below ground roots that have died, and dung and urine that have been deposited by grazing livestock.  There are many macro and micro flora and fauna involved in this process including earthworms, insects, fungi, bacteria, and protozoa. 

Figure 1.  Nutrients enter grazing systems via feed and fertilizer and are recycled by grazing and deposition of dung and fertilizer and decomposition of plant residue and senesced roots. 

Grazing Redistributes Nutrients

In large continuously stocked pastures, animals will consume nutrients in form of forage and concentrate them around shade and water sources in the form of dung and urine.  One way to improve nutrient distribution in pastures is to subdivide and implement rotational grazing. 

Hay Removes Large Quantities of Nutrients

Every ton of hay produced removes approximately 40 lb N, 15 lb P2O5, and 50 lb K2O.  In a good year, approximately 120 lb N, 45 lb P2O5, and 150 lb K2O could be removed from each acre of hay ground. 

Moving Nutrients within Grazing Systems Using Hay

Hay feeding can be used to redistribute nutrients within a forage system.  Hay can be produced on paddocks or in fields that contain high levels of nutrients and then fed in areas that are low in fertility. 

Take Home Points

Although managing nutrient flows in forage systems can sometimes seem like a daunting task, remembering a few key concepts can help you develop a long-term strategy for nutrient flows in your grazing system.

· Rotational stocking improves nutrient distribution in pastures.

· Hay contains large quantities of nutrients. 

· Buying and feeding hay can be used to bring nutrients into grazing systems.

· Hay can be used to move nutrients within forage systems from areas of high concentration to areas of low concentration. 

· Spreading out hay feeding points improves nutrient distribution and increases the value of those nutrients. 

· Always feed hay on your poorest pastures.  

Read the full articles, including tables and graphics, in Cow Country News.

~ Chris Teutsch, for Cow Country News