His land was originally purchased by his father in 1909 and, with the exception of one trial application back in the 1960s, no commercial fertilizers have been used on the farm since it was acquired. Instead, Lambert relies on green manures to ensure the health and fertility of his soils, and as a result he achieves yields nearly equal to his neighbors' at less cost.
Green manures are crops grown strictly for soil conservation and improvement.
Crops such as oats, Austrian winter peas, annual rye, vetch, lupine, sweetclover, and buckwheat may be used. Legumes are especially useful because they have the capacity to fix atmospheric nitrogen in the soil. Green manures draw nutrients from the subsoil and, in the process, they improve soil structure, stimulate biological activity, provide organic matter, and reduce nutrient leaching, while suppressing weeds and diseases. Wheat and peas are Lambert's commercial crops, but he balances his exports with the periodic return of green manures to continually renew his soil. In Lambert's crop rotation, winter wheat is followed by green peas.