I recently had the honor and pleasure of spending a weekend at a retreat that involved many great people, including Wes Jackson of The Land Institute. One of the highlights for me was when Wes displayed a life-size image comparing two plants, both grasses with edible seeds.
This one image explains why Farmland LP uses pasture in rotation to ensure soil fertility, and provides a glimpse into the cutting edge of plant breeding for sustainable agriculture.
Wes Jackson (on right) displays life-size images of a wheat plant (left) and a variety of perennial grain named Kernza (right) currently being developed by plant breeders.
One of the missions of The Land Institute is to develop edible seed crops, including grain varieties, harvested from perennial plants. Why? Just look at the difference in the root structure between wheat and the plant on the right. Because wheat is an annual plant, it only grows roots for less than a year before producing seeds and dying. This means root depth is shallow, and another crop of wheat requires a new cycle of planting.
By contrast, the perennial grain plant has roots several times deeper than the annual plant, and needs no replanting each year. The root depth is what I want to highlight. Roots draw minerals and water from the soil and bring them to the leaves where they are combined with air and sunlight to produce new biomass. Perennial plants have access to vastly greater volumes of soil than annuals. Whereas annual plants need constant inputs of fertilizer to maintain topsoil nutrient levels, perennials tap into soil depths and actually replenish the topsoil by relocating minerals to the surface. Perennials also protect the land from erosion, which is currently depleting precious soils and causing water pollution.
In the future, it will be great to have perennial seed crops to massively reduce the need for soil tillage, irrigation, and fertilizer inputs. As I explain in a previous post, for now we can use rotation between pasture and annual seed crops as a way to enhance soil fertility with fewer outside inputs. This picture does an amazing job of showing why that works.