. Fertilisers and manures. d by the Soil—Soils appropriate to Superphosphate—Fate of Superphosphate applied to the Soil—Soils appropriateto Basic Slag—Neutral Phosphatic Manures for light Soils—Comparison of Bone Meal with other Phosphatic Fertilisers. Before considering the question of the relative fertihs-ing value of the different phosphatic manures and theirapplication in practice, it will be necessary to get someidea of the function of phosphoric acid in the nutritionof the plant. Just as nitrogen delays maturity by promotinggrowth, phosphoric acid has an opposite effect; it is insome way
. Fertilisers and manures. d by the Soil—Soils appropriate to Superphosphate—Fate of Superphosphate applied to the Soil—Soils appropriateto Basic Slag—Neutral Phosphatic Manures for light Soils—Comparison of Bone Meal with other Phosphatic Fertilisers. Before considering the question of the relative fertihs-ing value of the different phosphatic manures and theirapplication in practice, it will be necessary to get someidea of the function of phosphoric acid in the nutritionof the plant. Just as nitrogen delays maturity by promotinggrowth, phosphoric acid has an opposite effect; it is insome way closely bound up with grain formation, beingalways found in greater proportions in the reproductiveparts of the plant than elsewhere. This ripening actionis very clearly seen in the Rothamsted experiments onbarley ; the plots without phosphoric acid being as arule about a week behind those which receive thisfertiliser. This effect is brought out in the diagrams, Fig. 3, N. of whole content pr-esenl in the July 4- Fig. Curves showing the effect of Phosphoric Acid in hastening the formationof Grain of Barley, and the Migration of Nitrogen to the and 4 with Phosphoric AciJ. I and 3 without PhosphoricAcid. [To face page 137 CHAP, v.] RIPENING ACTION OF PHOSPHORIC ACID 137 which show the results of certain determinations madeupon barley cut at regular intervals during the develop-ment of the grain from some of the Rothamsted barleyplots in 1904. The two lower curves show the rate of the formationof the grain week by week, calculated as percentages ofthe weight of the whole plant, for the two plots whichreceive phosphoric acid and for the corresponding plotswithout, both series being similarly treated as regardsnitrogen and potash. It will be seen that the formationof grain begins earlier where phosphatic fertilisers havebeen used, and even at the end is more , the two upper curves show the migration ofthe nitrogen to the grain, agai
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