Show LOSS OF VIRGIN FERTILITY sufficient quantities of neo essary in soils to maintain Product Ivene to maintain the productiveness of 0 a soil it Is necessary to preserve within the soil sufficient quantities of avII available abt plant food at it least to the yield from falling on off after a period of cropping hundreds of field experiments have demonstrated that thai tile the best soils will anvill gradually lose their virgin fertility unless more aban ordinary care Is given to the cropping cropp ln system aud and the return of plant foods |