Chris Teutsch: Managing Nutrient Flows in Forage Systems

Managing Nutrient Flows in Forage Systems

Chris Teutsch UK Grain and Forage Center of Excellence, Princeton, Kentucky

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 (Whitehead, 2000). 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. To learn more about this complex cycle, take a look at the Soil Biology Primer from the Soil and Water Conservation Society (2000). The objective of this article is to provide some practical tips for improving the distribution and flow of nutrients in your forage system.

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 (Figure 2). Overtime, this redistribution of nutrients can be significant, resulting in nutrient deficiencies in some areas and excessive levels in others. One way to improve nutrient distribution in pastures is to subdivide and implement rotational grazing (Figure 3). Confining livestock to smaller areas for short periods of time significantly improves dung and urine distribution. In a study done at the University of Missouri, they found that it would take 27 years to deposit one dung pile per square yard in a continuously stocked system versus 4 to 5 years when animals were rotated twice a week (Lory and Kallenbach, 1999).

Hay Removes Large Quantities of Nutrients

Every ton of hay produced removes approximately 40 lb N, 15 lb P2O5, and 50 lb K2O (Table 1). In a good year, approximately 120 lb N, 45 lb P2O5, and 150 lb K2O could be removed from each acre of hay ground. To maintain productivity in hayfields, these nutrients must be replaced. The best approach is to establish and follow a fertilization program that is based on regular soil testing.

This month’s FEATURED VIDEO is is Approaches to Managing Nutrient Distributions within Forage Systems. This video can be seen at https://youtu.be/IW8InN9v1fg

This month’s FEATURED PUBLICATION is “Soil Biology Primer” by A.J. Tugel, A.M. Lewandowski, and D. Happe-vonArb. Soil and Water Conservation Society, Ankeny, IA. It can be accessed at https://bit.ly/3jT2uRi

FENCING TIP

Use high quality temporary fencing. Temporary fencing comes in a number of styles including polywire, electric tape, electric braid, and polyrope. Electric tape should be used where high visibility is needed. Polywire is most commonly used by graziers since longer runs can be held on reels. When selecting polywire products, chose products that contain more strands of wire and for loner runs, choose products that contain wire made of mixed metals. Polywire containing mixed metals are about 40 times more conductive.

FORAGE MANAGEMENT TIPS

• Don’t graze cool-season pastures closer than 3 to 4 inches. This will help to lower crown temperature and reduce moisture loss from the soil. • Graze summer annual and perennial pastures to allow cool-season pastures to rest and to avoid toxic tall fescue. • Plant winter annuals after the first good rain in August. • Plant alfalfa and other perennial cool-season grasses after the first good rain in August. • Exclude livestock and apply 60 lb N/A in mid to late August for stockpiling. • Use UKY variety testing results to select varieties that will be planted in the fall. • If drought occurs, confine animals to one pasture and feed hay.

Importing Nutrients into Grazing Systems with Hay

In most cow-calf operations in Kentucky, hay is fed between 120 and 150 days, depending on stocking rate. The amount of hay fed and the corresponding value of the nutrients in this hay for various herd sizes are shown in Table 2. The ACTUAL value of these nutrients will depend greatly on how this hay is fed. If hay is fed in one paddock, these nutrients will be of little value since they are NOT distributed evenly across the pasture area (Figure 4). To capture the MAXIMUM value of these nutrients, hay should be fed at various points across the landscape. This will greatly improve nutrient distribution (Figure 5). While there are several approaches to accomplish this, bale grazing may be the most practical. In this scenario, hay bales are set out in pastures in late fall or early winter and livestock access is limited to several bales at a time using temporary electric fencing. More information on bale grazing can be found in a video on the Virginia Forage and Grassland Council’s YouTube Channel.

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. Overtime nutrients can be transferred from areas of high concentration to areas of low concentration (Figure 6).

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. 1. Rotational stocking improves nutrient distribution in pastures. 2. Hay contains large quantities of nutrients. 3. Buying and feeding hay can be used to bring nutrients into grazing systems. 4. Hay can be used to move nutrients within forage systems from areas of high concentration to areas of low concentration.

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

6. Always feed hay on your poorest pastures.

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

Figure 2. In a large continuously stocked pastures, grazing livestock will move nutrients from grazing areas and concentrate them around shade, water, and feeding areas

Figure 3. Subdividing large continuously grazed pastures improves nutrient distribution by forcing animals to deposit nutrients in the form of dung and urine in the same paddock where they were consumed as forage

Crop

Alfalfa Tall Fescue Orchardgrass Bermudagrass Sorghum-Sudan

N P2O5

lb/ton

K2O

56 15 60 39 19 53 50 17 62 43 10 48 40 15 58

120-day Hay Feeding Period

25 45 1,800 675 2,250 $2,068 50 90 3,600 1,350 4,500 $4,136 75 135 5,400 2,025 6,750 $6,203 100 180 7,200 2,700 9,000 $8,271

150-day Hay Feeding Period

25 56 2,250 844 2,813 $2,585 50 113 4,500 1,688 5,625 $5,169 75 169 6,750 2,531 8,438 $7,754 100 225 9,000 3,375 11,250 $10,330

Assumptions: Hay needed is 30 lb/cow/day • Hay contains 40 lb N/ton, 15 lb P2O5/ton, and 50 lb

K2O/ton • Fertilizer prices were $0.54/lb N, $0.49/lb P2O5, and $0.34/lb K20 Table 2. Quantity and value of nutrients contained in hay for herd sizes ranging from 25 to 100 brood cows with hay feeding periods of 120 and 150 days

Figure 4. Hay is commonly fed in areas that are easily accessible during the winter months. This is normally in pastures that are located adjacent to roads and lanes that have hardened surfaces

Figure 5. Spreading feeding points out provides a more uniform distribution of the nutrients contained in hay. This increases the value of those nutrients