Some plant nutrient relationships in the potato crop grown on a calcareous soil

Summary

A study of the chemical composition of various parts of the Russet Burbank potato grown on a well-drained Millville loam soil shows some interesting seasonal relations. A yield of 510 bushels per acre suggests that the crop was fairly well nourished.

The potato crop showed a seasonal decline in Thomas’ “quantity factor” for all tissues studied which agreed with his data for leaf analysis. However, the “quantity factor” is considerably below apparently desirable levels for the entire season. This combined with the seasonal behavior of quality factors” for nitrogen and potassium in tops, roots, and tubers, suggests the possibility of potassium deficiency. This conclusion is not indicated by leaf composition with respect to seasonal potassium “quality factor”.

The seasonal “quality factors” for nitrogen, phosphorus, and potassium show consistent disagreement when tops, roots, and tubers are contrasted with leaf tissue from the same plant.

The simple ratios N : K₂O; N : P₂O₅ and K₂O : P₂O₅, for tops, roots, and tubers indicate that nitrogen was in ample supply to this particular crop, and that potassium may have been somewhat limiting. This conclusion is not justified by these ratios in leaf tissue.

This study emphasizes the need for a re-examination of the theory (12-16) that “there is no fundamental physiological experimental basis to support the use of tissue other than the whole active leaf when one is trying to diagnose the mineral requirement of plants.”