Nitrate Leaching Mitigation Options in Two Dairy Pastoral Soils and Climatic Conditions in New Zealand

Abstract

This lysimeter study investigated the effect of late-autumn application of dicyandiamide (DCD), co-poly acrylic-maleic acid (PA-MA), calcium lignosulphonate (LS), a split-application of calcium lignosulphonate (2LS), and a combination of gibberellic acid (GA) and LS (GA + LS) to reduce N leaching losses during May 2020 to December 2020 in lysimeter field sites in Manawatu (Orthic Pumice soil) and Canterbury (Pallic Orthic Brown soil), New Zealand. In a second application, urine-only, GA only and GA + LS treatments were applied during July 2020 in mid-winter on both sites. Results showed that late-autumn application of DCD, 2LS and GA + LS reduced mineral N leaching by 8%, 16%, and 35% in the Manawatu site and by 34%, 11%, and 35% in the Canterbury site, respectively when compared to urine-only. There was no significant increase in cumulative herbage N uptake and yield between urine-treated lysimeters in both sites. Mid-winter application of GA and GA + LS reduced mineral N leaching by 23% and 20%, respectively in the Manawatu site relative to urine-only treated lysimeters, but no significant reduction was observed in the Canterbury site. Our results demonstrated the potential application of these treatments in different soils under different climate and management conditions.

Simulating Gibberellic Acid Effect on Pasture Yield on Naturally Deposited and Fixed Area Urine

“…On the other hand, the high rainfall events and intensity between June and September may have leached the GA into the soil. Similar results of GA showing a nominal reduction in NO 3 − -N leaching have been reported in other studies [11,16]. The authors demonstrated that application of urine + GA alone in mid-winter did not induce a significant reduction in mineral N leaching in lysimeter studies.…”

“…Three soil cores in each 0.2 m 2 urine patch were collected to 30 cm depth during harvesting at each experimental site using a stainless-steel corer with an internal diameter of 3 cm. Field moist soil cores from each treatment were composited and mixed manually before a 5 g sub-sample was extracted using 30 mL of 2 M KCl for mineral N (NH 4 + -N and NO 3 − -N) analysis on an end-over shaker for 1 h [11]. Extractants were analyzed for mineral N using the Technicon autoanalyzer [12].…”

“…Extractants were analyzed for mineral N using the Technicon autoanalyzer [12]. The autoanalyzer's functioning and chemicals used are explained by Matse et al [11]. In this study, soil mineral N refers to the sum of NH 4 + -N and NO 3 − -N.…”

“…The authors demonstrated that application of urine + GA alone in mid-winter did not induce a significant reduction in mineral N leaching in lysimeter studies. In order to increase GA's effectiveness in reducing mineral N leaching, Matse et al [11] proposed that GA must be applied together with an inhibitor. Similarly, Woods et al [7] reported that the application of GA to different forage species induced a nominal reduction in NO 3 − -N leaching.…”