Is the future of agriculture perennial? Imperatives and opportunities to reinvent agriculture by shifting from annual monocultures to perennial polycultures

Abstract

Non-technical summaryModern agriculture is associated with numerous environmental predicaments, such as land degradation, water pollution, and greenhouse gas emission. Socio-economically, it is characterized by a treadmill of technological change, increased mechanization, and economic consolidation, while depressing economic returns to farmers. A root cause is the dominance of annual plants cultivated in monocultures. Annual crops require the yearly clearing of vegetation resulting in soil erosion and other forms of ecosystem degradation. Monocultures are susceptible to agricultural pests and weeds. By contrast, perennial polycultures informed by natural ecosystems, promise more sustainable agroecosystems with the potential to also revitalize the economic foundation of farming and hence rural societies.

Roadmap for Accelerated Domestication of an Emerging Perennial Grain Crop

“…Furthermore, in the beginning of the growth season, the shallow root systems are inefficient at taking up water and nutrients, which is a major cause of ground and surface water pollution by nitrate leaching. A perennial grain crop that does not need to be sown every year would develop a long-lived deep root system ( Figure 1A) that sequesters carbon and takes up nutrients and water efficiently [7,8]. This crop could be intercropped with perennial legumes to provide additional ecosystem services such as nitrogen fixation [9].…”

Harnessing local knowledge for scientific knowledge production: challenges and pitfalls within evidence-based sustainability studies

“…Before the introduction of modern inputs such as synthetic fertilizers and fossil fuel-based machinery, the sustainability of agriculture was secured through the photosynthetic conversion of solar energy, and this provided food for people and feed for domestic animals. It was simply a thermodynamic necessity for more food calories to be produced on farms than the farmers had invested in growing the food (Crews et al 2018). Key to successful agriculture, under such conditions, was the maintenance of soil fertility through various practices whose effect was to circulate nutrients from harvested crops, via people and livestock, back into the soil.…”

“…Most of these practices relied entirely on knowledge acquired through practical experience by generations of farmers rather than scientific knowledge: the early scientific inputs to agriculture, such as stump-pullers, improved ploughs, and threshing machines were almost exclusively mechanical, rather than biological or chemical (Huffman and Evenson 2008). Today the priorities have changed, and we are in a situation where seeds and agrochemicals dominate the scientific inputs to agriculture, most of which are detrimental to the long-term integrity of agro-ecosystems (Foley et al 2011, Crews et al 2018 The potential pitfalls of taking practical experience into account are, of course, to some extent, the very flaws that prompted the evidence-based movement to begin with (Munro 2014):…”

Comparative analysis of seed size, germination, and vegetative allocation in annual and herbaceous perennial crops and their wild relatives inLupinusandPhaseolus(Fabaceae)

“…Herbaceous perennial species have been proposed as key components of ecological intensification (Jordan & Warner, 2010; Ryan et al, 2018). Longer-lived species have deep, persistent root systems that mitigate erosion and enhance nutrient uptake, they produce perennating shoots which reduce yearly planting costs, and have a longer photosynthetically active growth period, allowing for high biomass production each year (Cox et al, 2006; Crews et al, 2018). Due to their ability to tolerate stressful, resource-poor conditions, herbaceous perennial crops also have applications in arid lands unsuitable for annuals (Cox et al, 2006).…”

“…Due to their ability to tolerate stressful, resource-poor conditions, herbaceous perennial crops also have applications in arid lands unsuitable for annuals (Cox et al, 2006). Further, multiple perennial species grown together in polyculture have the potential to increase pest resistance, inhibit weeds, and foster a diverse and healthy soil microbiome (Crews et al, 2018). However, only a few perennial seed crops (principally cereals, oilseeds, and pulses) have entered the domestication process, and we know relatively little about how artificial selection for increased seed production will impact the rest of the perennial plant.…”