A comparison of three nitrate leaching mitigation treatments with dicyandiamide using lysimeters

摘要

The effect of three surface applied nitrate leaching mitigation treatments 3,4-dimethylpyrazole phosphate (DMPP), sodium chlorate (ClO3-) and a combination of Gibberellic acid and Lignosulphonate (GA + LS) at two levels (R1, R2) were compared to a single level of dicyandiamide (DCD, 10 kg ha(-1)) in lysimeter field sites in Canterbury and the Manawatu, New Zealand. All treatments were applied as surface sprays 24 h following urine application to simulate a practical application timing in a grazed pasture. In the Canterbury site, on a stony Lismore soil the treatments were ranked in order of significance (P > DMPP (R2, 29), GA + LS (R2, 25), ClO3- (R1, 25; R2, 23) > DMPP (R1, 13) >> GA + LS (R1, -18), while in the Manawatu site with a volcanic pumice soil the rankings were: ClO3- (R1, 41; R2, 37), DMPP (R2, 32) GA + LS (R2, 15) > DMPP(R1, 18) >> DCD (4), GA + LS (R1, -3). The results showed that the efficacy of GA + LS increased with application rates while the increase in rate for the chlorate (ClO3-) produced no further reductions in nitrate leaching.