What is intercropping?
Intercropping is considered as the practical application of ecological principles such as diversity, crop interaction and other natural regulation mechanisms. Intercropping is defined as the growth of two or more crops in proximity in the same field during a growing season to promote interaction between them. Available growth resources, such as light, water and nutrients are more completely absorbed and converted to crop biomass by the intercrop as a result of differences in competitive ability for growth factors between intercrop components. The more efficient utilization of growth resources leads to yield advantages and increased stability compared to sole cropping.
Furthermore, the multifunctional profile of intercropping allows it to play many other roles in the agroecosystem, such as resilience to perturbations, protection of plants of individual crop species from their host-specific predators and disease organisms, greater competition towards weeds, improved product quality and reduced negative impact of arable crops on the environment.
Nitrogen fixing legumes can be included to a greater extent in arable cropping systems via intercrops. Legumes contribute to maintaining the soil fertility via nitrogen fixation, which is increased in intercrops due to the more competitive character of the cereal for soil inorganic N. This leads to a complementary and more efficient use of N sources. Intercropping of grain legumes and cereals therefore offers an opportunity to increase the input of fixed nitrogen into agroecosystems without compromising cereal N use, yield level and stability.
Despite all its advantages, the agricultural intensification in terms of plant breeding, mechanisation, fertiliser and pesticide use experienced during the last 50 years has lead intercropping to disappear from many farming systems.
Methodology in intercropping
The agronomic advantages of intercropping are the result of differences in competitive ability for growth factors between intercropped components. In terms of competition, this means that the components are not competing for the same ecological niches and that interspecific competition is weaker than intraspecific competition for a given factor. The fact that the crops involved may have different resource requirements as well as different growth patterns makes it more complicated to define a proper methodology for the study of intercrops compared to studies involving one species – sole cropping.
The interpretation of interactive effects between intercrop components activities and soil processes is extremely complex. For example, specific crop growth affects soil shading and light interception and therefore also temperature, plant water uptake changes soil water content in the rhizosphere which effects microbial decomposition rates, decomposition rates affect soil texture, water retention characteristics, rooting profiles and nutrient availability to the crops. Experimentally it is very difficult to disentangle these processes. Thus, to really interpret all these processes at once and under variable and interacting conditions, dynamic simulation models of these systems are valuable.
Extent of intercropping in Europe and worldwide
Intercropping was a common practice in Europe before mechanisation, plant breeding and use of synthetic fertilizers and pesticides was implemented in a more intensified the agricultural production starting in the 1950ties. Intercrops of clover and grasses in pastures are still widely used in European agriculture, but arable intercropping (cereals, grain legumes, oil seeds) for feed and human consumption is presently not so common.
It has been scheduled that the entire animal feed sources in organic farming should be of organic origin from 2005 in the EU (EU Commission (EC) No. 1804/1999). This will require a major increase in organic cereal and grain legume (protein) crop production, to balance the European organic deficits. As an example, the French deficit for organic feed protein, considering complete organic feed supply, was 9000 tonnes in 1999.
In this context, intercropping can be adopted for modern European organic farming systems as a practical alternative to existing mainly sole-cropping strategies. Intercropping perspective in arable systems and the potential area for intercrops in organic farming is large considering the possible economic benefits and future legal requirement in feed and food industry.
Re-introducing intercropping in European organic agriculture to a greater extent should not be reversion to old methodology, but rather considering the usefulness of this old and sustainable cropping practice in a modern, innovative and technology-oriented organic agriculture. Furthermore, intercropping constitutes a concrete means to increase the diversification of agricultural ecosystems, for which there is a worldwide appeal.
The importance of agrobiodiversity encompasses socio-cultural, economic and environmental elements. All domesticated crops and animals result from human management of biological diversity, which is constantly responding to new challenges to maintain and increase productivity. Biodiversity provides not only food and income but also raw materials for clothing and medicines, among others. It also performs other services such as maintenance of soil fertility and biota, and soil and water conservation, all of which are essential to human survival.
There is a growing awareness that the variety of landscapes and the related biodiversity shaped by agriculture over centuries could be harmed by the continued intensification. Intercropping is planned biodiversity, and it is thought that planned diversification will increase associated biodiversity, and in this way contribute to conserving biodiversity in the open agricultural land and associated ecosystems.
Organic farming and intercropping
Organic farming is a steadily increasing production form in European agriculture. It is environmental friendly, due to low input of nutrients and no use of pesticides, and it contributes to the production of food without pesticides and antibiotic residues. A further expansion of organic farming is needed to meet consumers worldwide having an increasing demand for products, which are healthy, safe, and of high quality and produced with consideration for animal welfare and the environment. European organic farming and research within this area are in the forefront internationally and offers the opportunity of a food production, which could strengthen the competitiveness of EU agriculture. Intercropping is of special relevance and importance in future organic farming systems, because it offers a number of significant enhancements of both the net productivity of organic farming and the ecosystems in farming regions as a result of the increased diversity of the cropping system.
Intercropping is a method for simultaneous crop production and soil fertility building and it may also contribute to the prevention of nitrogen leaching risks sometimes observed from sole crops such as grain legumes due to changes in incorporated residue chemical quality involving nutrient turnover. It is also an ecological method to manage pests, diseases and weeds via natural competitive principles that allow for a more efficient resource utilisation. This same competitive principles also contribute to an improved quality of intercrop products. The inclusion of N2 fixing crops in an intercrop leads to the utilisation of the renewable resource of atmospheric nitrogen which increases the sustainability of the agroecosystem. Intercropping can also be regarded as a practice to increase the production of less stable crops such as grain legumes and hereby contribute to lowering the protein deficit in EU at lower risk for the farmer.
All these potentials strongly comply with the guidelines set up in Agenda 2000 and including ‘the European model of agriculture’, emphasising the production of healthy, safe and high quality food considering animal welfare, and environmentally sound production, especially in relation to reduced nitrate leaching from agricultural land. The project also relate to the Community policy of new preventive methods for improving plant health, since the diverse crop community in an intercrop may prevent the rapid spreading of diseases and pests. Intercropping is also relevant for integrated and conventional agriculture aiming at reducing the input of resources in plant production.
If you want to know more…
Association Européenne des Protéagineuses
Convention on Biological Diversity
European Union. Quality of Life Program
National Sustainable Agriculture Information Service (ATTRA)
Organic Agriculture at FAO (Food and Agriculture Organization)