Intercropping still as effective as ever

Intercropping has improved plant production from centuries ago and is still effective to this day. Intercropping is one of the traditional farming systems that has been practiced by farmers for more than 2000 years.

Pasture Scientist at Mabalengwe Agriculture Nolubabalo Tshwati says this traditional method has been practiced for ages in South Africa since time immemorial.

Previous studies have also shown that intercropping enhances not only crop productivity but also the efficient utilisation of resources, both above-ground and below-ground.

Recent research efforts have made progress towards a better understanding of intercropping.

In 2016, the Chinese Journal of Eco-Agriculture reviewed the potential of intercropping to strengthen ecosystem services and functions at the agroecosystem level, propose research directions and highlight practical uses in modern agriculture.

They found that Intercropping increased biodiversity, productivity and stability of the agroecosystems.

“In addition, intercropping enhanced water use by separating in time the maximum water requirements for the different species and by separating spatially their hydraulic lift. The enhancement of nitrogen (N) acquisition was attributed to niche differentiation of N resources, in which cereals acquired more mineral N from the soil while legumes fixed more N from air N2: cereals were more competitive than legumes in uptaking N, fostering symbiotic N2 fixation in legumes,” reported the publication.

It further reported that some species facilitated the conversion of unavailable P into mobilized P, benefiting themselves and the neighboring species.

“For instance, the roots of fava beans released carboxylates or protons to help dissolving P compounds. Also, the roots of chickpeas released phytase or phosphates to decompose organic P in the soil, increasing P availability. There were inter-specific facilitations of iron (Fe) and zinc (Zn) when intercropping dicotyledonous or non-graminaceous species (with strategy I for Fe acquisition and non-Fe or Zn mobilization) and graminaceous monocotyledonous ones (with strategy II for Fe acquisition and Fe or Zn mobilization).

“This benefited micronutrient availability in intercropped non-Fe mobilizing or Zn-mobilizing species.” In the paper, they also identified some important research directions for the future of intercropping research and its practical uses.

Research directions include crop diversity and agricultural sustainability, signal-controlled interspecific interactions between intercropped species, linking those interactions to above- and below-ground diversity and functional, structural and empirical models for intercropping. Intercropping can be used to develop ecologically intensive agriculture and organic farming, enhance fertilizer recovery and enrich edible crop parts with micronutrients.

Finally, they identify the need to develop suitable machinery and to breed new crop varieties for intercropping.”

Another traditional example of intercropping is found in Malawi, where pigeon pea is generally intercropped with the staple food crop, maize. Pigeon-pea is a grain legume crop that can be a very important crop in the rural areas where it can be grown for human consumption and supplement the range of food crops available. Pigeon pea has multiple uses for grain, fuelwood, livestock feed and to mark field boundaries and to improve soil fertility.

This combination works perfect because the slow growth of pigeons in the early stages offers little competition to the companion maize crop. Thus, maize yields are the same as in sole crops. After maize harvest, the pigeon peas grow at a faster rate well into dry season using residual soil moisture. As rooting characteristics of pigeon pea and maize are different there is very little underground competition during the maize growth and the deep rooting system of pigeon pea allows it to use moisture left deep in the soil when maize is harversted. Growing pigeon pea is then a bonus crop which costs the farmer little extra in labour. They are well adapted to soils of poor quality and respond little to fertilizers. This means that the fertilizer used should be that required by the main crop.

According to the Agricultural Research Council (ARC), pigeon-pea is a grain legume crop that can be a very important crop in the rural areas where it can be grown for human consumption and supplement the range of food crops available. The ARC states that the introduction of this crop in the rural areas will help alleviate poverty by providing a source of food.  In South Africa, this crop is not grown as a field crop. Long-duration unimproved pigeon-pea is grown as shade plants in home gardens, where only a few long rows are planted.

Pigeon-pea has the ability to survive and give good economic returns when planted under dryland conditions. Because this is a legume crop, its root nodules enrich the soil by adding about 40kg of nitrogen per hectare. It can be planted commercially, because its production requires low farming inputs. It is a drought-tolerant crop, and can therefore, be planted under dryland production conditions. After harvesting, it can be used as fodder for feeding animals.

Tshwati said intercropping has always been part of planting, even at home gardens. “During rainy season or planting season, we knew that in our home gardens when our parents planted, they used more than one crop at the same time – that is intercropping. This is done by planting more than one plant in one line or alternative lines. Our forefathers knew the benefits of doing that and this practice has many advantages,” said Tshwati.

 Tshwati shared the advantages of intercropping with Mzansi Agri Talk:

  • Diversity and stability of fields
    As the structure of the soil is essential to its function (including delivering critical ecosystem services, such as nutrient cycling, carbon storage and flood prevention), this represents a significant gap in understanding. It is especially important to investigate this connection because soil degradation is affecting one-third of the earth’s soils and is largely due to deterioration in soil’s physical structure.
  • Reduction in chemical/fertilizer application
    This is very much cost effective because the price of fertilizers is very high. Why use an expensive fertilizer when you can improve the problem of soil fertility by intercropping?
  • A complementary sharing of plant resources, such as Nitrogen from N fixing plants
    It is so much advisable to intercrop with plants that can fix their own nitrogen and other nutrients back to the soil, the few examples of these plants include beans. Some cover crops directly add nutrients to the soil by fixing nitrogen at their roots. Examples include winter field beans and peas, clover and vetch. These are all types of legume and are a great choice for sowing before nitrogen-hungry brassicas such as cabbage.  Some plant roots influence soil structure in many ways, for example, by binding and compressing the particles in soil to make it stronger, and forming pathways for water to flow through soil, which helps reduce run-off, thereby reducing flooding.
  • Weed suppression, and a reduction in susceptibility to insects and disease
    Intercropping and cover cropping are practices that increase diversity in the cropping system and enhance the utilization of resources such as light, heat and water. These practices can also help to suppress weeds and increase the likelihood of being able to reduce herbicide use in the cropping system. Alternatively, in organic or other systems where herbicides are not used, intercropping and cover cropping can reduce the yield loss potential and provide stability in the system.
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