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Abstract
The effects of mixing lime and large quantities of phosphorus and potassium fertilizers with the subsoil were studied on 16 Maryland subsoils. These subsoils were covered with 10. cm of a fertile surface soil so the subsoils’ effect would be the major variable. Soybeans were grown on these soils in the greenhouse. These subsoils received 65.2 and 83.0 ug/g of phosphorus and potassium respectively. Two treated subsoils were also studied in the field. Simulated subsoiling in the field was accomplished by digging to a depth of 50.8 cm. Lime, 148 or 440 Kg P/ha, and 186 or 558 Kg K/ha were mixed with each 15 cm depth of subsoil. Soybeans and/or barley were planted on the field plots.
In general, the subsoils studied in the greenhouse indicated that the combined amendments of lime, phosphorus and potassium to the subsoils increased root production in the subsoil, nitrogen content in the soybean shoots, and yield.
First year field results on the Othello (Typic Ochraquult) soil indicated that soybean yields on treated subsoil plots were not significantly different from soil receiving the same surface applications of fertilizer. However the second year after treatment, the yields of double cropped soybeans and barley were increased by 706 Kg/ha (10.5 bu/acre) and 710 Kg/ha (14.4 bu/acre) respectively when compared to similar quantities of phosphorus and potassium applied to the surface soil of nonsubsoiled plots.
On the Monaouth (Typic Hapludult) soil, the first year yields of subsoil plots treated with lime, phosphorus, and potassium also failed to improve yields compared to surface application of the fertilizer. Lime, 440 Kg P/ha, and 558 Kg K/ha applied to the subsoil did significantly improve yields of full season soybeans over the untreated soil by 720 Kg/ha (10.7 bu/acre).