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  4. »eUpdate 552 February 26th, 2016»Winter/spring fertilization of tall fescue and smooth bromegrass pastures and hayfields

K-State Agronomy eUpdates

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 and hayfields

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, but there is still time to apply it now. 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.

 

Figure 1. Grazing tall fescue pasture. Photo by Lyle Lomas, K-State Research and Extension.

 

N for 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 summary of K-State N response data shows that across nearly 100 experiments, the average yields for unfertilized brome and fescue 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 $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 both hay price and N costs, however, as both can be volatile. Hay price varies considerably with weather and supply, and N prices can move substantially from year to year.

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 will want to push N rates to the upper end of the recommended range.

Another consideration is when N is applied. While most growers apply all the N and any needed P and K for hay production in a single application in the spring, research in Kansas has shown that applying all the fertilizer in the fall will normally result in slightly higher yields, though the protein values will normally be slightly lower. Fall applications of N and P stimulate root growth and produce more tiller buds, resulting in more stems the following spring.

N for 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% of the N along with any needed P and K in late August or early September. So producers should plan on applying 60 to 70 lbs N per acre in late winter or early spring, starting as early as January in southeast Kansas or February in the central and northern parts of the state.

P and K fertilization

Both smooth bromegrass and fescue are efficient users of soil P and K. One of the reasons for this is the dense root system -- two to three times more roots per unit of soil volume than corn or soybeans. As a result these crops can grow and thrive at lower soil test levels than other crops commonly grown in Kansas. But both smooth bromegrass and fescue do remove about 12 pounds of P2O5 and 40 pounds of K2O per ton of hay, which will lower soil test values. Thus, these grasses will respond to P and K fertilization on soils with low or very low soil test levels. Recent work in northeast Kansas has shown response to applied P at soil test levels below 12-15 ppm. P and K application rates should be based on soil tests, as with most crops.

In any type of fertilizer management program for tall fescue and smooth bromegrass, whether for hay production or grazing, needed phosphorus and potash should be applied in the late summer or fall for best results, along with a light application of N. Research with smooth bromegrass and fescue production has shown that fall applications of N and P, while these cool-season grasses are still actively growing, 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 late winter or early spring won’t provide the same benefits.

One option for hay production not widely used is to apply all the N, P and K needed for the following year in late fall, rather than early spring. Research has shown that the yields from a late- fall application are actually higher than from an early spring application, but the protein levels in the hay are slightly lower (a dilution of the N due to higher biomass production). The increased production from a late fall application is due to the stimulation of root growth and production of additional tiller buds.

 

Other considerations

One additional nutrient producers should be aware of 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.

Sulfur is taken up by plants as sulfate. If a sulfur application is needed to correct a deficiency in a growing crop, a sulfate-S source should be used, such as ammonium sulfate or gypsum. Elemental sulfur sources can be used if applied far enough in advance of crop uptake needs to allow soil organisms to oxidize the S to sulfate. This will normally take several weeks to months, depending on soil temperature and moisture.

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 in the fall, 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

Dorivar Ruiz Diaz, Nutrient Management Specialist
ruizdiaz@ksu.edu

Stu Duncan, Northeast Area Crops and Soils Specialist
sduncan@ksu.edu

Doug Shoup, Southeast Area Crops and Soils Specialist
dshoup@ksu.edu