PROJECT RESULTS

Enhancing Protein Content and Yield of Spring and Winter Wheat Through Innovative Use of Legumes in Rotation

Applicant: 

Dr. Martin Entz
Department of Plant Science
University of Manitoba
Winnipeg, Manitoba  R3T 2N2  Canada

Table of Contents:

• Background and Objectives
• Procedure and Project Activities
• Conclusions

ARDI Project:

#98-019

Project Status:

Completed May, 2002

Background and Objectives:

A considerable amount of research has been conducted on the role of perennial forages such as alfalfa and alfalfa/grass mixtures in cropping systems.  Perennial forages provide significant N and non-N benefits to the cropping system, however, growing perennial forages usually takes a commitment to livestock production.  The present research is aimed at developing legume-based cropping systems for Manitoba farmers who do not have livestock as part of their farming operation, and the focus was on how legumes affected wheat yield and wheat protein content.

Legume frequency has increased in rotations in western Manitoba, where drier conditions allow production of field pea and lentil, or in southern Manitoba where dry beans are well suited to the loamy and sandy soils in the area.  On the other hand, few grain legumes are currently grown in rotation in wetter areas of Manitoba.  Dry bean and pea crops usually fail when grown under conditions of excessive soil moisture.  One major objective of this research was to develop legume systems that would be compatible with wet soil conditions in eastern Manitoba.

Procedure and Project Activities:

Four different studies related to innovative use of legumes to boost the yield and protein content of Manitoba wheat crops were initiated in 1998 under this ARDI grant.

1. In study one the rotational yield and protein benefits of pulse grain crops were evaluated over three years.  Field pea consistently produced higher rotational N benefits than chickpea, dry bean or soybean.  Soybean showed almost no N benefits to following wheat crops, however, soybean grain yields averaged 2386 kg/ha (compared with 2284 kg/ha for field pea), indicating that soybean seed yields are adequate for commercial production in southern Manitoba.  Study 1 details.
    
2. In study two, rotational grain yield and N benefits of single-year, hayed forages and green manure crops were monitored in two sequential grain crops (wheat, then barley). Lentil and chickling vetch green manure crops produced the highest N benefits to sequential wheat and barley crops (80 kg N/ha contribution over two years) compared with single-year hayed alfalfa (45 kg N/ha contribution) followed by single-year hayed red clover (30 kg N/ha) and single-year hayed berseem clover (20 kg N/ha).  However, forage systems were much more economical than green manure systems, mainly because forage systems produced a marketable product in the first year.  Study 2 details.
    
3. In study three, a traditional Ontario practice (red clover relay cropped with winter wheat), plus similar treatments were tested for four site-years.  Results indicated that relay (red clover, alfalfa) and double (lentil, chickling vetch) cropped legumes with winter wheat and fall rye added an average of 35 kg N/ha to the following oat crop.  Study 3 details.
    
4. The final study, which is ongoing, considers the use of self-seeding legume cover crops in grain-based farming systems.  Thirty-three legume species were evaluated in Manitoba over two growing seasons.  A number of promising lines have been identified.  Based on ability of medic and subclover lines to produce seed (needed for regeneration), produce high levels of dry matter (needed for N contribution to soil), and to provide groundcover (important for weed suppression and soil erosion control), about 10 lines appear to have potential for production in Manitoba. Seedling recruitment dynamics of these annual self-seeding legumes is currently being investigated in trials located at Winnipeg, Carman and Indian Head, SK.  Study 4 details.    

Conclusions:

Potential Economic Impact for Primary Producers or the Agri-Food Industry

This research has identified the importance of both traditional and novel legume systems, and information from these studies will be of direct benefit to both primary producers and the agri-food industry as a whole.

Among the traditional systems (e.g. grain legumes in rotation with wheat), we clearly demonstrated that including field pea reduces N fertilizer needs in the following wheat crop by approximately 30 kg N/ha. Newer grain legume crops such as dry bean and chickpea also were found to contribute to the N economy of a following wheat crop, however the benefits of chickpea and dry bean were not as great as from field pea.  The magnitude of N fertilizer savings from these grain legumes was found to be less than 15 kg/ha.  Over the four site-years of trials, soybean was found to contribute no rotational N benefits to a following wheat crop.  Therefore, under the conditions of the present study (current soybean inoculation systems and cultivars), there appears to be little N benefit from including soybeans in crop rotations.  However, soybean is still a very good rotation crop, and among grain legumes, soybean has a high tolerance for wet soil conditions.  Information on the rotational benefits of grain legumes presented here will provide both farmers and the agri-food industry with a better picture of what can be expected when these crops are included in rotation with wheat.  Preliminary information from David Przednowek’s M.Sc. work indicates that including legumes in rotation improved the baking quality of wheat.

Novel legume systems included both annual forage legume hay crops as well as relay and double cropped legumes in combination with winter cereals.   It was discovered that under the conditions of the present study, growing annual forage legumes (alfalfa or red clover) for one year in a two-cut hay system was much more economical than growing a legume crop (chickling vetch or Indian Head lentil) strictly for green manure purposes. These results suggest that farmers in wetter areas of Manitoba will be further ahead financially by growing a single-year forage legume than by growing a green manure crop.  In fact, the annual net profit from single year forage crops was about $90/acre; similar to grain crop production. In drier areas of the province, such as the southwest corner, lentil and vetch green manures may be a better choice than forage legumes.  Information on the productivity of single year forage crops is important for farmers and for the forage seed industry.

Using a relay crop of alfalfa or red clover in a winter wheat or fall rye system provided significant amounts of N to a following cereal crop.  Maximum economic benefit of this practice was observed in the Red River Valley when alfalfa was relay cropped into winter wheat.  Therefore, winter wheat in combination with relay-cropped alfalfa offers farmers an opportunity to include short legume phases in the rotation, which benefits soil N status and helps to dry soils.  The seed industry is thus presented with a new opportunity to market appropriate forage seed varieties for the purpose of relay cropping with winter wheat.

Self-seeding annual legumes were evaluated over two field seasons under wet and dry soil conditions.  A number of promising lines were identified, and these are now being evaluated in long-term cropping systems in Manitoba and Saskatchewan.  Introduction of self-seeding medics into Manitoba cropping systems will directly benefit primary producers and the forage seed industry.

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