Does Sainfoin Need Phosphorus At or After Establishment?

Sainfoin (Onobrychis viciifolia Scop.), an introduced perennial forage legume, can be considered for use as a good alternative to alfalfa.
Sainfoin is well adapted to calcareous soils (i.e. high calcium and high pH) with low phosphorus. It has excellent drought tolerance and very good cold hardiness, but poor tolerance to poor drainage and high acidic soils (low pH). It is very comparable with alfalfa, especially for quality and animal performance; however, hay yield may be slightly lower than alfalfa, depending on the location. It is very palatable and nutritious, and is preferred over alfalfa by cattle, sheep and deer. Some important advantages with sainfoin are that it does not cause “bloat” problems in cattle and has no or little insect pests. Some cultivars of sainfoin (e.g. ‘Shoshone’) are resistant to alfalfa stem nematode. Although sainfoin seems to perform well in low phosphorus soils, anecdotal evidence suggests that sainfoin may positively respond to high phosphorus.

Do we have enough evidence in Wyoming that would support the above statement of phosphorus requirement in sainfoin? The UW Department of Plant Sciences has recently initiated a study at the Powell Research and Extension Center that aims to answer the question. The overall goal of the study is to determine appropriate dose response of sainfoin to added phosphorus and to establish management strategies.

To accomplish this goal, the sainfoin cultivar Shoshone was established in 2007 at the Powell Research and Extension Center. Five phosphorus levels (0, 20, 40, 60 and 80 pounds P2O5 per acre) were applied on May 6, 2009 and the whole set of treatments was repeated four times to obtain accurate response. The same phosphorus treatments were also applied on a newly established (2009) sainfoin plots to understand whether sainfoin responds to added phosphorus when sainfoin is already established.

Different growth information, especially forage yield and quality, are being continuously monitored and recorded. No differences were observed among the treatments for forage yield in 2007?planted sainfoin; however, numerically the highest yield was obtained in 2009?planted sainfoin with phosphorus treatment of 60 pounds P205 (5-6 tons per acre from two harvests).  

Likewise, no differences were observed in forage quality among different phosphorus treatments indicating that phosphorus does not alter or change forage quality. Old sainfoin stands and surface application of phosphorus may have contributed to this non?significant result. In 2011, a new stand of sainfoin was established and phosphorus treatments were incorporated into the established plots.

It is early to conclude or provide specific recommendations for phosphorus requirement in sainfoin from this study; however, the preliminary results indicate that sainfoin may have positive response to added phosphorus, especially if phosphorus is incorporated properly into the soils. It is anticipated that the study will provide useful information for producers in the region.

Anowar Islam is an assistant professor and the UW Cooperative Extension Service Forage Agroecologist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or mislam@uwyo.edu.