A tuber of potato and two-three seeds of peas are put in one pit (furrow) at joint cultivating of potato and peas. The greatest crop is got on plots with friable fertile soil (mineral and organic fertilizers well introduced). Even in the absence of fertilizers such combination of cultures will not cause a strong exhaustion of soil on a plot. Peas itself enrich soil with nitrogen, thanking to root nodule bacterium which settle on its roots and acquire nitrogen from air. It is necessary to "infect" seeds of peas or a plot with the root nodule bacterium. For this purpose handful of the soil, taken from a field where peas grew, is put in every pit, or seeds are processed with the Nitragin preparation. One bottle of this preparation is enough to process seeds for 1hectare.