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  4. »eUpdate 439 January 31st, 2014»Winter/spring fertilization of tall fescue and smooth bromegrass pastures

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Department of Agronomy

Kansas State University

1712 Claflin Rd.

2004 Throckmorton PSC

Manhatan, KS 66506

785-532-6101

agronomy@ksu.edu

Extension Agronomy

Winter/spring fertilization of tall fescue and smooth bromegrass pastures

Much of the nitrogen (N) applied to tall fescue and smooth bromegrass hay meadows and pastures goes on in January or February in eastern Kansas. The amount and timing of N depends on whether the field is hayed or grazed; how much, if any N was applied in the fall; the price of N and hay; and the growing conditions since last fall.

While January and February is normally the driest time of the year, there is still adequate moisture most years to move the N down into the root zone and stimulate early season growth of tall fescue and smooth bromegrass.

Hay

Normal N fertilization rates for established fescue and bromegrass hay fields are 90 to 120 pounds actual N per acre, or about 30 pounds of N per ton of expected yield. A recent summary of fescue and bromegrass N response data shows that across nearly 100 experiments, the average yields for unfertilized plots was 1.35 tons of hay per acre, while maximum yields averaged 3.15 tons of hay with 140 pounds of N.

N Rate

(lbs N/acre)

Hay Yield

(tons dry matter/acre)

Hay Yield Increase

From 20 pounds N

(tons dry matter/acre)

0

1.35

-------

20

1.80

0.45

40

2.20

0.40

60

2.52

0.32

80

2.78

0.26

100

2.97

0.19

120

3.10

0.13

140

3.15

0.05

160

3.14

-0.01

 

Doing some simple cost-and-return calculations, using a long-term average value of $60 per ton as the value of the hay produced and $0.50 per pound of N, the normal rates of N mentioned above (90 to 120 lbs/acre) are appropriate to maximize profit in most years. It will be important to watch N costs, however, as they continue to be volatile.

The other issue is hay price and supply. With the extended drought through 2012 in many parts of the state, prices for grass hay were considerably above the long-term average of $60 per ton. With the good hay yields in the eastern half of the state in 2013, and the production of significant acreage of annual forage hay, such as forage sorghum or sudan grass, hay prices in many areas have returned to more traditional values.  If that is the case, applying normal N rates  in the 90- to 120-pound range should be most profitable. 

One issue these calculations don’t consider is hay quality. Protein levels will be increased at the higher N fertilizer rates, assuming timely harvest. So in cases where producers are relying on high-quality hay as their primary protein source, they may want to push N rates a little higher, or add supplemental protein to rations at the lower N rates.

Pasture

Under normal conditions, tall fescue and smooth bromegrass pastures that are grazed in both spring and fall should receive about 100 pounds total N per acre, with 60% applied in the winter or early spring and 40% in late August or early September, along with any needed P and K. So producers should plan on applying 60 to 70 lbs N per acre in winter or early spring, starting as early as January or February.

In any type of fertilizer management program for tall fescue and smooth bromegrass, for best results, needed phosphorus and potash should be applied in the late summer, along with a light application of N.  P and K rates should be based on soil tests. Phosphorus will help the grass develop a good root system for the winter, and develop buds for new tillers the next spring. P and K applied in winter or early spring won’t provide the same benefits.

Other considerations

One additional nutrient producers should consider watching for tall fescue and smooth bromegrass pastures or hayfields is sulfur (S). If the pasture or hayfield is receiving adequate nutrients and precipitation, but is dropping off in production, it could be deficient in S. Sulfur deficiency will cause a general reduction in forage production long before it results in visual deficiency symptoms. An application of S to a tall fescue or smooth bromegrass pasture or hayfield that is deficient in S can result in forage yield increases of as much as 500 to 800 lbs per acre.

To determine whether P, K, S, and lime are needed on tall fescue and smooth bromegrass fields, producers should consider soil sampling. The best time to sample is 30 days prior to fertilizer application. Samples for a P and K soil test should be taken to a 6-inch depth. A profile S test to a depth of 24 inches should be used to evaluate S needs.

 

Dave Mengel, Soil Fertility Specialist
dmengel@ksu.edu