Analysis of short portions of curves relating yield and uptake of phosphorus in glasshouse experiments

Abstract

It was shown that pot experiments with considerable variation between yields of replicate phosphate treatments can still give valuable information when the dry weights of the plant tops are plotted against their P uptake. This applies only to young plants that are genetically stable. The position of the lines relating yield and P uptake is subject to many factors which include the super-imposing of a fertiliser on the applied phosphates, structure of the soil, placement of the phosphate in the soil and attack of an insect.
The graphs show that there are two kinds of yield variation between replicate phosphate treatments. The first provides points along, the second points away from the yield-P uptake line. Yield variation between replicate treatments can be tolerated if yield-P uptake points are near to the line. Short portions of yield-P uptake lines can be considered to be regression lines. The position of yield-P uptake regression lines in the coordinate system and the residual variances about these regression lines can be used to explain the effect of soil treatments.