an introduction to intercropping

Intercropping is a growing method rooted in ecological diversity. In intercropped systems, two or more component crops are grown together for a given growing period. There are currently four types of intercropping systems:

  1. Strip: crops are grown simultaneously in independent rows within the same field
  2. Row: crops are grown together simultaneously and a minimum of one crop is planted in a row
  3. Mixed: there is no specific order to the crops
  4. Relay: the growing system is dependent on the lifecycle stage of the intercropped plants. Typically, the second crop in the intercropping schedule is planted after the first crop reaches the reproductive stage and before it reaches peak maturity
types-of-intercropping
Types of Intercropping, Source: own, Adapted from Mousavi and Eskandari (2011)

Regardless of the intercropping pattern selected, the plants grown together should be complementary in nature in that they have different “rooting abilities, canopy structure, height and nutrient requirements” which produce a yield advantage. This occurs when resources that could not be utilized by a single crop are utilized by an additional crop growing in the same space.  One of the best-known examples of intercropping is the three sisters method developed by Native Americans in the United States, where Maize, pole beans and winter squash are grown together. The Maize provides a form for the beans to climb and shades the squash. The beans stabilize and fix nitrogen for the Maize plants. The squash provides ground cover, effectively maintaining moisture levels and suppressing weeds.

In order to develop an advantageous intercropped system, five fundamental principles must be adhered to:  

  1. A detailed plan must be developed, including an understanding of the characteristics of the component crops
  2. Crops must be timely sown
  3. Adequate fertilizer must be applied at the appropriate time
  4. A weed and pest strategy must be in place
  5. Harvesting must be efficient

If the wrong types of plants are grown together or the spacing is incorrect, the output will decrease.  To determine whether an intercropped system is effective, the land equivalent ratio [LER] is typically used, where:  (INTERCROP 1 / PURE YIELD 1) / (INTERCROP 2 / PURE YIELD 2). Results > 1.0 indicate an advantageous pairing. Results < 1.0 indicate a disadvantageous pairing.

sources:

Lithourgidis, A.; Dordas, C.; Damalas, C. A.;  Vlachostergios, D.N. (2011, April) Annual intercrops: An alternative pathway for sustainable agriculture. Australian Journal of Crop Science, 5(4) Retrieved from https://www.researchgate.net/publication/224934832_Annual_intercrops_An_alternative_pathway_for_sustainable_agriculture
Mousavi, S. R.; Eskandari, H. (2011, January). A General Overview on Intercropping and Its Advantages in Sustainable Agriculture. Applied Environmental Biological Sciences. 1(11). Retrieved from https://www.researchgate.net/publication/220000362_A_General_Overview_on_Intercropping_and_Its_Advantages_in_Sustainable_Agriculture
Sullivan, P. (1998, November). Intercropping Principles and Production Practices. Agronomy Systems Guide.  Retrieved from http://www.iatp.org/files/Intercropping_Principles_and_Production_Practi.htm
Wiley, R.W. and Rao, R.M. (1980, April) A Competitive Ratio for Quantifying Competition Between Intercrops. Experimental Agriculture, 16(02). Retrieved from https://www.researchgate.net/publication/231898671_A_Competitive_Ratio_for_Quantifying_Competition_Between_Intercrops

Zeman, F. (2012) Metropolitan sustainability: understanding and improving the urban environment. Oxford, Cambridge, Philadelphia, Delhi: Woodhead Publishing Limited