76 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, I

The main points which are to be observed in the data presented are :—

    (i) There is a well defined seasonal tide in the variation of all the consti-
      tuents, and the tide was almost identical during the seasons 1929 and
      1930, though the magnitude of the variation was slightly different, pro-
      bably because the seasons differed slightly.

    (ii) The nitrogen and phosphoric acid content curves had a striking paral-
      lelism, almost throughout the experimental period.

    (iii) The calcium content varied practically inversely as the phosphoric acid
      and nitrogen.

    (iv) The potash content had a tide similar to that of nitrogen and phosphoric
      acid, but the peak values were not contemporaneous, the two latter
      constituents showing a lag of a month.

    (v) The nitrogen value had its peak coincident with that of the rainfall curve,
        the peak being at the time of the flowering of the grass and the lowest
      value at a time of dry weather when there was little or no fresh growth.
      The variation in the nitrogen being not due wholly to seasonal factors
      but to the stage of growth.

    (vi) The pastures investigated showed no definite sign of being deficient in any
      of the minerals though a shortage of calcium and phosphate are indicated
      at certain seasons.

                                DISCUSSION OF RESULTS.

The herbage of the pastures under investigation, it must be remembered,
represented a pure culture of Spear grass (Andropogon contortus). There was no
leguminous plant growing along with the grass and hence any variation in the
mineral content represented a change in the chemical composition and was not due
to there being differential amounts of legumes and non-legumes in the herbage.
In temperate regions the growth of leguminous plants affects the composition
of the herbage, and much of the work done on the question of variations in the
mineral content of pastures is strictly not comparable with that under report now.
The results now presented show that even for pure culture grass grown under non-
intensive conditions in a tropical climate, the seasonal variation in the mineral and
nitrogen content of the herbage of grasses is very similar to that recorded in tem-
perate regions.