A Pasture Response to Sodium Tungstate on a New Zealand Soil

Abstract

In an investigation of an apparent superiority of basic slag over superphosphate in stimulating pasture growth on a yellow-grey earth of the Warepa series (Otago Province), slag-treated plots were compared in 1951 with plots receiving superphosphate, (1) alone, (2) plus oz. sodium molybdate, (3) plus 2½ oz. molybdate and (4) plus 1 lb. ammonium metavanadate per acre. Molybdenum application at both rates markedly increased pasture production, notably through the clovers, while vanadium had no effect. In September 1953 sodium tungstate (molybdenum content < 0.1 p.p.m.) was applied over one block of the experiment at 1 lb./acre. The superphosphate plot with no applied molybdenum and that with vanadium responded greatly, particularly in white clover growth, that with oz. sodium molybdate responded slightly, while the plot treated with the heavier rate of sodium molybdate showed no additional effect from tungsten1. The implication was that tungsten could assume the role of molybdenum, presumably in nitrogen fixation by Rhizobia. A replicated trial studying the interactions of molybdenum, tungsten and vanadium, applied in proportion to their atomic weights (sodium molybdate 2½ oz./acre), has now been run on the same soil type. The trial was laid down on March 24, 1955. In the five yield cuts so far taken covering the period August 10, 1955–February 28, 1956, vanadium has had no influence either by itself or in conjunction with molybdenum or tungsten. It can therefore be disregarded in considering the molybdenum × tungsten interaction. Results are exemplified by data from the second yield cut in the tungsten × molybdenum interaction table (Table 1).