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Alfalfa yield gap: Doing much more than average

Contributed by Michael Russelle Published on 27 February 2018
Alfalfa

We have suspected for a long time the average yield of alfalfa reported for U.S. farms is far less than what growers could produce. Is there a significant “yield gap” between these reports and reasonable yield goals?

Here’s the bottom line: The top 10 percent of producers in the 11 Western states harvest 2 or more tons per acre of irrigated alfalfa than producers in the middle of the pack. The “yield gap” under dryland conditions ranges from 1 to more than 3 tons per acre. Closing these yield gaps will mean more profit – pure and simple.

To draw these conclusions, I first asked forage experts for their estimates of reasonable yield goals. They agreed, in general, 8 tons per acre (13 percent moisture) was reasonable under irrigated conditions in the West, and 6 tons per acre was reasonable under rain-fed conditions in the East. To validate these estimates, I used data from cultivar trials, whole-field yield measurements and whole-farm yield estimates.

Cultivar trial evidence

Cultivar (variety) testing has become more difficult in recent years, but many states still conduct these independent trials of small-plot yields in primary alfalfa production areas. They typically are conducted over two or more production years to limit the effects of poor weather and receive all required inputs to minimize the effects of sub-par management.

Alfalfa dry hay yield (13 percent moisture) from cultivar trails across the continental U.S. were summarized over two or three production seasons, and the reported yields were reduced by 11.5 percent to account for typical harvest losses (Figure 1).

Yeild of irrigated and nonirrigated alfalfa in cultivar trials

Under irrigated conditions, which in these trials were designed to minimize yield limitations due to drought, nearly one-half of the trials produced yields exceeding 8 tons per acre. In every Western state except Montana and Wyoming, at least one location produced alfalfa dry hay yields higher than 8 tons per acre. At other sites, yields were lower due to growing season length, soil conditions and so on.

Small plots are not like whole fields. Cultivar trials are meant to do head-to-head comparisons under conditions as uniform and well-managed as possible. They provide an estimate of maximum yield based on the crop genetic potential. They often are conducted on good soils with excellent control of pests and pathogens. Irrigation is expected to be much more uniform than under farm field conditions.

Whole-field measurements

We know some producers have considerably higher yields than others. The best evidence of this is the multi-year, whole-field Wisconsin Alfalfa Yield and Persistence Program to determine actual yields of non-irrigated alfalfa over the age of the stand. Over a decade, the project followed 80 fields for one to four years, determining yield, moisture content and forage quality at every cutting. Field sizes have averaged 66 acres, ranging from 5 to 225 acres.

The top fields yielded 1.2 to 2.5 tons more alfalfa dry hay than the average of all fields. Ten fields in the study have been among the top four in two to three years, indicating soil, location and other site-specific conditions matter, but that year-to-year variations in rainfall, for example, can reduce or support yield.

These top-yielding fields generally declined only in the fourth year of production to average or 7 to 15 percent below the average yield across fields that season. The lowest-yielding fields were consistently below or within 4 percent of the average yield in other years. These results support the idea some fields are persistently yield-limited, where other fields support high yields unless weather, for example, intervenes.

Whole-farm estimates

What is missing from the normal agricultural statistics is the distribution of yield. The average yield for a state does not help us understand the range producers report.

I requested a special tabulation of the 2012 Census of Agriculture to provide the number of farm operations, acres and total production of alfalfa dry hay by state (Table 1). The results were provided for 1.5- tons-per-acre increments of yield up to 9 tons per acre and 3-tons-per-acre increments thereafter.

Average median and top 10% whole-farm yields of intirely irrigated alfalfa

The key take-home message from Table 1 is: The top 10 percent of farms in the 11 Western states apparently are achieving at least 30 percent to nearly 80 percent higher yields than the average state yield and 50 to 170 percent higher than yields on the “median” farm.

The yield gap between the top 10 percent and the state average is at least 1.7 to 3.2 tons per acre under conditions where the crop is entirely irrigated. (The yields shown for the top 10 percent are the lower limit for that group.)

From this specific dataset, we can conclude more than 1,100 farms are achieving considerably higher yields of alfalfa dry hay than most other operations.

Irrigation’s impact

In Figure 2, the three colored curves are for the indicated irrigation scenarios in Idaho.

Cumulative fraction of Idaho farms that reported dry alfalfa hay production

Median alfalfa dry hay yields were about 1.5 tons per acre for farms that did not irrigate alfalfa in 2012, 2.1 tons per acre for “partial irrigation” (where all alfalfa was partially irrigated or where some fields were irrigated and others on the farm were not) and 4.2 tons per acre for farms where all alfalfa fields were irrigated. In each case, one-half of the farms reported yields below these levels, and one-half reported higher yields.

Figures 3 and 4 also show data for entirely irrigated alfalfa. It is evident alfalfa dry hay yields at the lower end of the range differ greatly among the three Southwest states (Figure 3).

cumulative fraction of farms in the three Southwestern states

Very few farms reported yields of only 1.5 tons per acre in California whereas, in New Mexico, 30 percent of farms reported whole-farm yields of 1.5 tons per acre or less. Of course, the environmental conditions are generally much less extreme across the irrigated area of California, and if it were possible to have data from specific areas, we could compare “apples to apples,” as the saying goes.

At the other end of the range, 10 percent of the reporting farms in New Mexico achieved yields of at least 7.5 tons per acre whereas the top 10 percent in California and Arizona had yields of at least 9 tons per acre.

Yields of irrigated alfalfa in the three mountain states (Figure 4) were similar except for the lowest yield increment. In Colorado, whole-farm yields were 1.5 tons per acre or less on 28 percent of the operations but on only 17 percent of Montana operations. All were similar with respect to yields at the high end of the range.

Cumulative fraction of farms in the three Mountain states

In the remaining Western states (Figure 5), 10 percent or less of the farms reported alfalfa yields lower than 1.5 tons per acre. Otherwise, a greater percentage of farms produced higher alfalfa yields in Washington than the other states.

Cumulative fraction of farms in the five Pacific Northwest and Mountain states

Economics

In the 2010 California Alfalfa & Forage Symposium, Dan Putnam and his co-authors estimated the value of improved alfalfa cultivars based on yields in cultivar trials.

I use the same method here, recognizing the relatively minor increase in costs for seed ($60 amortized over a four-year stand life), acknowledging pest control expenses may be reduced with improved cultivars but are highly site- and situation-specific – and assuming no significant increase in marginal costs for greater yields. I, too, assume a hay price of $150 per ton.

The difference between the state average yield and the lowest yields for the top 10 percent of farms shown in Table 1 translates to an annual net return of $240 to $465 per acre. Compared to the median farms in each state, annual net returns are at least $285 to $690 per acre. Looked at another way, these are the net losses currently experienced because of inadequate management.

We do not know how many acres of alfalfa could be managed to produce at alfalfa’s genetic potential, but the story here is: The gap is large between what some producers achieve and what most do. Farm profitability would increase by closing the alfalfa yield gap. What’s holding you back?  end mark

PHOTO: Research looks at yield discrepancies to identify opportunities. Photo by Lynn Jaynes.

From proceedings of the 2017 Western Alfalfa and Forage Symposium, Reno, Nevada, Nov. 28-30, 2017.

Michael Russelle is a adjunct professor for the department of soil, Water and Climate with the University of Minnesota. Email Michael Russelle.

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