The effects of subsoil loosening and deep incorporation of nutrients on yield of broad beans, cabbage, leck, potatoes and red beet

SUMMARYExperiments were made on a sandy clay loam soil with five crops to determine the effects of thorough loosening of the subsoil and deep incorporation of nutrients on yields during the subsequent 4 years.Loosening to 0·9 m increased fresh-weight yields by between nil and 95% depending on the crop and season. Responses were still considerable 4 years after the initial loosening and there was no evidence of any decline with time. Deep incorporation of nutrients did not improve yields.Loosening gave a durable increase in the volume of coarse pores and decreases in bulk density and penetrometer resistance. It also nearly doubled the rate of root extension when estimates were made for one crop, consistently increased water extraction from below 30 cm and, on occasion, reduced plant water stress.It is concluded that most of the benefits from deep loosening resulted from improvements i the rate at which plants could extract water rather than nutrients from the subsoil.