A longstanding question in agriculture is whether ecologically-friendly farming methods can achieve the same yields as industrially-farmed fields.
The answer, according to a new study, is at least a partial yes. Combining the right mixture of nature-based and traditional farming measures could generate the same yields, while using significantly less synthetic fertilizer.
Looking at a mass of data gathered through more than 30 long-term studies of nature-friendly farming measures across Europe and Africa—some of which ran for decades—researchers determined that measures including the diversification of crops, growing nitrogen-fixing plants like legumes, and spreading waste manure over soil could replace a chunk of the artificial fertilizers that are applied across global farmland to produce high yields.
These measures fall under a farming approach with growing traction called ‘ecological intensification’. It describes a set of natural processes to “complement or substitute for the role of anthropogenic inputs in maintaining or increasing yields,” the researchers write. One researcher, quoted in the new study, describes these measures as “sustained by nature and sustainable in nature.”
The aim is to keep food yields high, while reducing the impacts on the surrounding ecosystem—a large share of which in traditional agriculture come from synthetic fertilizers, which causes significant soil, water, and marine pollution and whose production also emits large quantities of greenhouse gas.
Until now, no one has really investigated how much ecological intensification works to increase yields, across different farming contexts. So, combining the robust data gathered from the 30 studies, the researchers built a model that could tease out these various measures and compare and contrast their effects.
The dataset also included several farm trials that combined ecological intensification measures with varying levels of synthetic fertilizer application. This allowed the researchers to also examine how well nature-friendly approaches worked alongside more traditional yield-enhancing tactics, and investigate potential synergies there.
What this trove of data revealed is that across a wide range of regions and farming contexts, ecological intensification can be a significant substitute for synthetic fertilizers. Incorporating nitrogen-fixing plants like legumes on farmland keeps nitrogen locked in the soil, supplying plants with these nutrients naturally. Adding waste manure from livestock to the soil, meanwhile, can provide nitrogen, phosphorus and potassium to boost yields. And diversifying crops with cover species boosts soil fertility and makes fields more resilient to pests and disease.
But the researchers uncovered a complication in this relationship: the positive impact of ecological intensification is limited by the amount of synthetic nitrogen fertilizers farmers apply to the soil. Where regular levels of synthetic fertilizer are showered across fields, the benefits of more nature-friendly measures are canceled out. For example, adding nitrogen-fixing legumes only increases yields when small amounts of synthetic fertilizer are applied to the land; these benefits are drowned out when nitrogen fertilizer is widely-applied. Similar findings were made for manure application and crop diversification.
Meanwhile, in cases where no nitrogen fertilizer was applied to farmland at all, the researchers found that nature-based methods failed to achieve the same yields as traditionally-fertilized crops. It’s all about finding the sweet-spot, they say: “Thus, using [ecological intensification] in combination with some [nitrogen fertilizer] may best reduce the trade-off between input use and the land required to produce a given yield.”
Boiled down, this means that nature-based methods can supplement a large share of the synthetic fertilizer needed to achieve regular yields in most farming contexts—reducing the requirement for this polluting input. It’s a powerful justification to cut back on fertilizer where we use too much.
In fact, the researchers calculate that in most farming contexts fertiliser use could be reduced to around 100 kg of nitrogen per hectare without adversely affecting yields, if nature-based methods are applied as well. That’s significantly less than the estimated global average of about 140 kilograms, and a decline that would represent a dip in the emissions, groundwater and marine pollution associated with this overused commodity.
The researchers are careful to point out that fertilizer is unequally distributed around the globe, and in many regions, it’s actually the case that more is required to grow crops and improve food security. To this end, the findings could also be used to justify sharing it around more equitably: if we can rely more on ecological intensification to cut back on fertilizers where it’s being excessively-applied, then we can divert the surplus to parts of the world where it’s truly needed to give crops a boost.
“Widespread uptake of [ecological intensification] practices could therefore contribute to a more equitable global distribution of fertilizer,” the researchers say.
MacLaren et. al. “Long-term evidence for ecological intensification as a pathway to sustainable agriculture.” Nature Sustainability. 2022.
Updated: 12 July 2022 at 10:38am MST.