Studies in crop variation. III. An examination of the yield of dressed grain from Hoos Field

Extract

1. Of the three sources of supply of nitrogen, rape cake gave the highest mean yields in the absence of superphosphate; while nitrate of soda gave results significantly better than those obtained from ammonium salts.

2. Superphosphate is of importance to the barley crop, giving greatly increased yield when applied.

3. Sulphate of potash seems to have an adverse influence upon the barley yield.

4. The deterioration of the barley plots is much heavier than on the wheat plots. The convention of ascribing the whole linear term to deterioration may not be as true for some plots as for others. Part of the diminution in mean yield may be due to slow changes other than deterioration.

5. The mean annual percentage diminution is least on those plots in receipt of superphosphate and emphasises the importance of phosphoric acid not only in increasing the mean yield, but in maintaining the fertility of the soil.

6. Barley is more variable than wheat and is more subject to the influence of meteorological conditions.

7. The slow changes other than deterioration are relatively unimportant and seem closely connected with the manurial treatment. The cause of the slow changes is obscure, but there were probably special influences operating on certain of the plots.