Further studies on the placement of fertilizer for potatoes

Summary

The efficiency of a potato fertilizer depends not only upon its composition, the rate at which it is applied, but also upon where in the furrow there was only a slight difference in yield as compared with complete fertilizer applied at each side of the seed piece.

The main implication suggested by the results is that potato fertilizer may be rendered more efficient by applying it not as a complete fertilizer but by what might be termed a differential placement. In view of the fact that superphosphate is believed to promote root development the placement of this constituent in contact with the seed piece, especially as it exerts no appreciable injurious action when applied at normal rates, would appear desirable. As certain nitrogen materials when in contact with the seed piece cause the most injury it would seem desirable that they be placed on each side of the seed piece in combination with the potash materials not only to avoid injurious effects but to promote the efficiency of the potato fertilizer as much as possible. From a yield standpoint the divided placement, over the two-year period, (Treatment 6), gave a yield that was 27.5 bushels greater than that obtained when the complete fertilizer was applied in a band on each side of the seed piece (Treatment 2).

The results presented herein, although obtained over a two-year period on one soil type, suggest strongly that all the ingredients of a potato fertilizer do not necessarily render their greatest efficiency when applied as a complete fertilizer even though the method of application, side placement, is known to be favorable to emergence, stand and yield.

Finally, it should be considered that the only phosphati material used in the present study was ordinary superphosphate, containing 18 per cent P₂O₅. Just how other phosphates, such as ammonium phosphate, would have behaved, if similarly applied, was not determined.