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WP 3: Screening of species and genotypes

The overall aim of this work package is to identify potential new genotypes and species for use as cover crops (CC) or living mulch (LM) in order to improve the balance between main crops and subsidiary crops, fill niches in crop rotations and thus, to improve soil conditions.Cover Crops should be fast growing and highly productive and fit in the off-season between main crops.

In contrast, a Living mulch should not be too competitive and it should be complementary with the main crop, i. e. occupying niches not used by the main crop.Both types of crops should contribute to soil fertility and soil health as much as possible and potentially generate additional income from the farming system.While perennial and annual legumes are of high interest due to their N-fixing ability, non-leguminous species may have beneficial effects on soil health and quality and general biological diversification.

For many cover crops, species mixtures (e.g. legumes and grasses) are the rule rather than the exception, adding to biodiversity and system stability. Since there is no cash crop to be produced, both LM and CC should be designed as much as possible as species mixtures to enhance biological diversity in general. The specific objectives of the WP are:

  • To identify new species of interest as LM or CC, both legumes and non-legumes as single species and mixed species stands.
  • To identify genotypes of currently used perennial T. repens, T. subterraneum and other legume species better adapted for use as LM.
  • To identify genotypes of annual self-reseeding species adapted for use as LM and to cold winters.
  • To develop a simplified and sustainable seed production system for subterranean clover, in order to allow seed production in European conditions and on relatively small scale
  • To assess potential alternative uses of new species – e.g. value as livestock feed or for industrial processing

Plant Material

There is a vaste resource of potentially adapted specieas among the annual legumes; most of them are originating from the Mediterranean area. Many of them, especially Trifolium  and Medicago species are cultivated as pasture crop in areas with dry summers. Their number is increasing, since, especially in Australia and in the Mediterranean countries, new species are continuously introduced as forage crop. However, little is known on their suitability as cover crops or living mulches

Subterranean clover and White clover are the the species most used as living mulch.However, the commercia varieties have been selected as forage crops, and are therefore relatively aggressive. On the other hand, it isknown, that genotypes with lower groth habit, lower competitivity, early ripening and, (in the case of white clover) minor vegetative activity in the summer, but these properties have never been selection criteria for these species.

Non legumes: Beside the legumes, which are in the focus of the screening programmes, approx. 20 different species of non-legumes, promising to be adapted as living mulch or cover crop in mixtures with legumes will be tested.

 

 


Experimental sites

The first steps of the screening programmes wlll be performed in two Mediterranean (Central Italy and Morocco) and one temperate environment (Southern Germany). Further Evaluation of selected accessions will be will be done in 6 environments, ranging from Northern Germany to Southern Brazil.

View interactive map of the evaluation sites


Overview over the screening programmes

Screening procedures and criteria

Step one: pre-selection: In the first year, single unreplicated rows will be planted either in Morocco or in Germany. The aim of these trials are Seed propagation and the assessment of: Morphological traits (growth habit, plant height, density, position of the pod); Phenology (time of flowering and ripening, determinedness of the development cycle); Seed production (a first estimate of the productivity for seed in the respective environment); Seed shattering behaviour; Nodulation and the need for special rhizobium inoculum; and Resistance to frost (in Germany). Since the heritability of these traits is high, they can be assessed on a few plants without replication. In Morocco, seed will be propagated in the field and in Germany in the greenhouse. The assessments will enable us to distinguish the following categories of species: Species of limited interest in general or for the respective environment, which will be eliminated from further screening. Species potentially suitable as LM, with prostrate growth habit, early maturity and senescence preferably determinate growth cycle and good potential for seed production. Species potentially suitable as CC or green manure, with high biomass and competitive ability, and also good potential for seed production. A second cycle will be started in the second year, in order to test higher numbers of genotypes of the most promising (or most diverging ) species.

Step two: Evaluation. In the second year, species and accessions suitable as LM or CC will be tested in separate experiments .

  1. Species potentially suitable as CC will be tested as sole crops. The assessments comprise biomass determination, determination of N content and N yield.
  2. Species potentially suitable as LM will be tested in small split plots with three compartments:

    • only the LM,
    • LM + a cereal as main crop,
    • only the main crop. With this experimental design as well the competitive pressure exerted by the LM on the main crop, the complementarity of the two components, i.e. their capacity to use different ecological niches, can be determined.

In the 3rd year evaluations will be continued with fewer genotypes and larger plots, including quantitative determination of effects of competition and main crop grain yields.


Possibilities of combined use of legume biomass

Additional uses of Subsidiary crops

Though the legumes in the studied systems have mainly ecological functions, their biomass may in part also be grazed or harvested and used as forage, as substrate for biogas production or as basic material for industrial use (“green chemicals”).

An additional harvest may be performed e.g. of the regrowth of a living mulch in autumn after harvesting a cereal, of whole-season CC (which might be necessary in climates with very short vegetation periods) or using perennial or self-reseeding legumes alternately as living mulch and as sole crop for biomass production during the rotation.Harvesting may have a negative impact on the ecological services, but could also stimulate N fixation, because N-rich materials are kept away from the soil.

Energy production is possible using fresh material or silage as fermenting substrate for biogas production.However, less than 50 % of the total energy content of green matter can be transformed into biogas and less than 30% into electricity in this way. Alternatively, the fresh material may be pressed and the dehydrated material used for direct combustion. The liquid phase may be used as fermenting substrate.

On the other hand, legume green matter contains approx. 17-22 % of proteins, which, in contrast to that of most grain legumes, are of high biological value. Extraction of proteins from lucerne leaves have been already realised on industrial level; several protein extracts are commercially available. Beside Proteins they contain various amounts of poly-insaturated fatty acids, minerals and vitamins. An Increasing demand for agricultural products and effects of scale may make such products more competitive in the future.

The Protein budget of the EU is currently negative (-70%), which is compensated by importations of products like soybean or fish meal, with doubtful impact on global sustainability. Possibilities to increase production of proteins of high value are therefore of high interest while energy production from agricultural products has to be valuated critically, if this is paid with higher imports of proteins.

Several legumes, especially Medicago spp. have been shown to produce isoflavones, flavones, and saponins. These compounds have attracted great interest for certain health-related issues such as anticancer activity or phytoestrogen production, among others, but also as potential adjuvant or even ecological insecticides.

Therefore, both well-established, and newly identified crop species and genotypes, will be analysed for the most interesting secondary metabolites to determine potential additional uses besides feed and energy. We will therefore valuate the new legume species to be used in combined systems, where proteins and other products of high value are extraxted, and only the vastes used for energy production.