Forage Mixtures to Minimize Deer Damage

The use of orchardgrass minimizes deer feeding and provides the greatest yields.
Forage Mixtures to Minimize Deer Damage - Articles

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Research Question

How much does deer feeding reduce yield and net economic return of forages under typical Pennsylvania conditions and can alfalfa-grass mixtures reduce the level of deer feeding associated with pure alfalfa?

Literature Summary

Alfalfa is a prime feed source for both dairy cows and non-domesticated, white-tailed deer in Pennsylvania. Damage to alfalfa by deer can be great. Numerous attempts have been made to deter deer from feeding on alfalfa and other crops but they have generally proven unsatisfactory because of high costs and/or ineffectiveness. Several researchers have reported that deer prefer alfalfa to forage grasses. However, the use of alfalfa-grass mixtures to deter deer from feeding on forage has been untested.

Study Description

Plots of alfalfa, timothy, orchardgrass, and alfalfa-timothy or orchardgrass mixtures in 3:1, 2:2, and 1:3 alfalfa to grass row arrangements were established within areas protected (with fencing) or unprotected from deer feeding. Forage from these plots was harvested three and four times in 1995 and 1996, respectively, and dry matter yield, percentage of alfalfa and grass, and forage quality were determined. Economic evaluation of each treatment was made based on the value of the harvested forage and the differential costs associated with production.

Applied Questions

To what extent do deer damage forages in central Pennsylvania?

Forages protected from deer feeding averaged 1660 lb/acre more DM yield than their unprotected counterparts (Table 1). The greatest amount of deer feeding occurred in pure alfalfa and the least in pure orchardgrass. Forage quality was not affected by deer grazing. Weeds began to invade the plots in the second year of the study and were more severe in the unprotected than protected plots. Deer feeding resulted in average economic losses of $80 and $28/acre for pure alfalfa and pure orchardgrass, respectively.

Table 1. Decrease in dry matter yield associated with deer feeding compared to no deer feeding on pure alfalfa, pure grass, or alfalfa-grass mixtures seeded in different row arrangements (mean of two locations for two years).
Grass speciesRows alfalfa:
rows grass
Reduced yield
alfalfa
lb/acre
Reduced yield
grass
lb/acre
Reduced yield
total*
lb/acre
*Reduction in alfalfa and grass yield combined. Weed yield is not included in total.
-4:0239202392
Timothy3:122291542384
Timothy2:212729262198
Timothy1:3900822
1722
Timothy0:4012301230
Orchardgrass3:117321341866
Orchardgrass2:210505681617
Orchardgrass1:36983941092
Orchardgrass0:40435435

Do deer selectively graze one forage species over another?

Deer selectively grazed alfalfa out of the alfalfa-grass mixtures and fed more on plots which contained timothy than those which contained orchardgrass. Averaged across all mixtures, alfalfa made up 35% of the total yield in the protected but only 19% in the unprotected mixed plots. Average yield reductions, as a result of deer feeding, were 1507 and 1102 lb/acre (excluding weed yield in 1996) for treatments containing timothy and orchardgrass, respectively (Table 1). Consequently, the economic losses associated with deer feeding were greater for mixtures containing timothy than orchardgrass (Table 2).

Table 2. Increase in dry matter yield and net income of pure grass and alfalfa-grass mixtures seeded in different row arrangements compared to pure alfalfa when both were exposed to deer feeding (mean of two locations for two years).
Grass speciesRows alfalfa:
rows grass
Compared to pure alfalfa
Increased yield*
lb/acre
Compared to pure alfalfa
Increased net return
$/acre
*Includes yield of alfalfa, grass and weeds.
Timothy3:191911
Timothy2:2155628
Timothy1:314960
Timothy0:41958-22
Orchardgrass3:1200241
Orchardgrass2:2284445
Orchardgrass1:3282526
Orchardgrass0:436406

In a field where deer generally feed, are particular forage species or forage mixtures better than others?

In areas unprotected from deer feeding, pure orchardgrass and alfalfa-orchardgrass mixtures had greater total yields than pure alfalfa (Table 2). Weed infestation in the second year of the study was greatest in pure alfalfa which had the greatest deer feeding and least in pure orchardgrass which had the least deer feeding in the first year of the study. Forage quality was not affected by deer feeding within the unprotected plots but was affected by the proportion of alfalfa to grass in the mixture. Alfalfa-orchardgrass mixtures had greater economic returns than pure alfalfa but only when alfalfa was seeded at 50% of the mixture (Table 2).

Recommendations

Deer feeding can greatly reduce forage yield. Deer selectively grazed alfalfa out of alfalfa-grass mixtures and showed a preference for timothy over orchardgrass. The use of orchardgrass alone or in a mixture with alfalfa minimizes deer feeding and provides the greatest yields. However, when deer feeding occured, net economic returns were greater for alfalfa-orchardgrass mixtures because of improved quality compared to pure orchardgrass.