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

ABSTRACT

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 < 0.1) and % reduction (as indicated in the brackets) in nitrate leaching from dairy urine patches (600 kgN ha⁻¹): DCD (63%) >> 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.

KEYWORDS:

• Gibberellic acid
• lignosulphonate
• DMPP
• chlorate
• nitrate leaching
• dairy

Acknowledgements

We would like to acknowledge funding from Ballance Agri-Nutrients, Pastoral Robotics Limited and Callaghan Innovation.

Disclosure statement

No potential conflict of interest was reported by the author(s).