PHOSPHATIC MANURES

Waipa Post, Volume 45, Issue 3251, 5 November 1932, Page 5

PHOSPHATIC MANURES

EXPERIMENTS AT ROTHAMSTED Phosphates- unlike the nitrogenous fertilisers, increase the proportion of clover in the herbage, and so add greatly to its protein content. This increase is not confined to the spring months, as happens With nitrogenous fertilisers; it is maintained through the season, and is continued in the next. The gain in protein may be considerable—much greater than the gain in dry matter. But quite a number of Waikato farmers are convinced that though phosphatic manures stimulate growth they take too much out of the ground in doing so, and if a season's dressing is missed the pasture rapidly deteriorates. In the first year after application water soluble phosphate is most effective, so that superphosphate comes out best. Citric soluble phosphate comes next, hence high soluble basic slag is second. . Mineral phosphate and low soluble basic slag are less effective. The value of mineral phosphate as compared with the others changes a good deal according to soil and season. In the drier conditions of Hertfordshire and the Eastern counties, under investigation by the Rothamsted Experimental Station, it came a long way behind high soluble slag and was very similar to low soluble slag; in the moisten- warmer conditions of Devonshire it acted more like high soluble slag and was much superior to the low soluble slag. I» the second year the high soluble basic slag did better than superphosphate at several of the centres, both on the hay land and on the grass repeatedly mown, though it had not then caught up with superphosphate. At the Devonshire centre mineral phosphate acted as well as high soluble slag, though it was still behind on the two years' programme, but the low soluble slag showed no sign of improvement. The experiment is being continued by the Rothamsted authorities to see what happens in the third and fourth years.