Intercropping Should Replace Monocropping Once And For All
It’s time for some agro-justice in our fields
If you follow updates on environmental news, chances are you are familiar with the term monocropping in agriculture and the related debatable consequences it causes both at the field and the landscape level.
Or…was maybe monoculture the term you heard? Now, you may be wondering if there is even a difference between the two? Are they both equally impacting and, if so, what are the possible alternatives that could be implemented in our fields?
Monoculture or monocropping?!
To answer these questions, let’s make first a bit of order with the terminology here:
- Monoculture is the agriculture practice of growing a single crop in a field or farming system at a specific time (meaning that the next year I can grow something totally different). As a side note, monoculture is a technique used in both conventional and organic farming due to its unquestionable handyness during the farming operations of planting, weeding and harvesting: same type of crop to deal with, same type of machinery which is needed on the field.
- Monocropping is instead a continuous monoculture, meaning that the farmer keeps growing the same crop overtime on the same field.
Monoculture and monocropping are not the same thing and they do not have the same impact on the environment: monoculture’s negative effects can be counterbalanced by simply growing a different crop the following year (crop rotation), which does not happen in monocropping.
Monocropping is responsible for the well-known terrific effects at the environmental level, from soil fertility reduction, agro-biodiversity loss, ground-water contamination, soil erosion and loss of soil organic matter to ultimately the overtime decline in the crop yield, which is also the major concern of our irresponsible producers and likely the only thing that might make them think twice about what they are doing. The reason why monocropping has such detrimental effects lies not only in the fact that this agricultural technique is associated with an intensive use of agrochemicals but also because it depends on the use of agrochemicals to be a viable option.
Why monocropping sucks…
One of the reasons why monocropping is biologically unsustainable is the same why nothing, not even weeds, grows under a walnut tree: allelopathy.
Every plant produces biochemical compounds, named allelochemicals, which have a direct effect on the physiology, growth or behaviour of other organisms. Many types of allelochemicals are produced by plants to fight off pests or to inhibit the growth of other surrounding plants, in order to limit the competition in the quest for water, nutrients and light. Although not all allelochemicals are produced to harm or limit the growth of other organisms, most of these secondary plant metabolites can be considered as a sofisticated chemical weapon in the biological warfare going on in your field.
But what does it have to do with monocropping? If the same type of crop is grown repeatedly with no breaks (like in crop rotations) on the same field, the allelochemicals it produces will start building up in the soil, leading in some species (like wheat) to a self-inhibition: the plant will be stunting and less yielding. What does a stunting and less yielding plant need? Extra fertilization, especially of nitrogen, which is among the main macronutrients of plants. What happens when too much nitrogen is applied to the soil? We have nitrogen leaching into the groundwater or into the surrounding water bodies, causing eutrophication problems.
The problems do not end there though. A study reported that high rates of nitrogen fertilization leads to the formation in the soil of nitrosamines which
exerted strong phytotoxic, mutagenic, teratogenic and carcinogenic effects on micro- and macroorganisms (plants, animals and humans). They are strong inhibitors of DNA and RNA synthesis and block the transmission of genetic information connected with amino acid synthesis. — Byrnes et alt.
Under this scenario, it is easy to see how monocropping systems will lead within a short time a strong downfall of the agrobiodiversity of the field and to a destruction of the soil ecology. To cope with this, more agrochemicals inputs (pesticides to control insects no more limited by natural antagonists and fertilizers to make up for the loss in soil fertility) will be needed, creating a vicious cycle which will end when the soil won’t be able to bear the production anymore.
…and why intercropping rocks!
Now, we have seen what monocropping is and what are its effects. What can we do about it? The main alternative to monocropping are crop rotations. But here I would like to talk about a not so common practice in industrialized countries, but highly used in developing countries which can be an alternative to monocropping (and also used jointly with crop rotations): intercropping.
Intercropping consists in having multiple crop types grown simultaneously on the same field. There are three main types of intercropping:
- Row intercropping: several crops are grown on the field arranged in different rows based on crop type.
- Strip intercropping: an advanced version of row intercropping used in industrial agriculture, where a higher portion of the land (still subdivided in rows) is devoted to only one type of crop, next to another large row of a different type of plant.
- Mixed intercropping: this is a “vegetable garden version” of intercropping, where different crops are grown together in a mix on the field, without respecting any particular geometry.
What are the advantages of intercropping in comparison with monocropping? Many!
- Resource use efficiency. Over-yielding in intercropping systems have been attributed to a higher resource use efficiency, mostly related to a better exploitation of the water and nutrients allocated in the soil. Deep rooting crops can be associated with shallow rooting ones, leading to a complete absorption of the inputs across the whole soil profile.
- Different microclimate. Taller plants can provide shelter from wind or rain and shade to shorter plants, protecting them from solar radiation.
- Light interception. Intercrops composed on non-synchronous patterns of canopy development can exploit incoming sunlight in a much more efficient way than monocrops.
- Humidity. Relative humidity can be maintained at higher levels depending on the type of intercrop, reducing crops’ disseccation problems.
- Pest control. Pest management is also associated with higher yields in intercropping systems. Different plants can both offer shelter to pest antagonists. At the same time certain crops’ allelochemicals can be used as a beneficial weeding measure, if the plants are correctly intercropped taking care of their specific times of development.
Of course intercropping must be carried out carefully, as we have to keep in mind potential competition problems for water, light and nutrients (meaning that we cannot randomly put any crop together and expect to have a positive effect).
Think about it as a relationship or, better, as a symbiosis: each plant needs to be associated with its best partner in order to benefit it and benefit from it at the same time!
