N-leaching in hill country; farmer led research

Abstract

There is scant information on nitrate-N leaching in East Coast hill country. Castlepoint Station, a focus farm in the Wise Use of fertiliser Nitrogen (N) project and in the face of potential restrictions on fertiliser N use, ran a 3 year trial focused on the impacts of N fertiliser on pasture and animal production as well as nitrate leaching.

Effects of closing date on seeding and hardseededness of balansa, gland, Persian and arrowleaf clovers on East Coast dryland

“…Rainfall falls mainly over the late autumn and winter, with occasional summer rain events. Very regular and high wind run occurs during spring and early summer that constrains pasture growth (Crofoot et al 2010). A 16.6 ha steep north facing paddock (CPS-H) with a resident pasture of crested dogstail (Cynosurus cristatus), rat's tail (Sporobolus africanus) and danthonia (Danthonia sp.)…”

The effects of pastoral hill country natural landscape features and land management practices on nitrate losses and its potential attenuation for improved water quality

“…Nitrate leaching from applied N fertilisers in pastoral hill country depends on several factors, including fertiliser application rate, timing, weather, slope and soil properties. However, linear increases in N leaching with increased N fertiliser application rates have been reported across NZ hill country farms (Crofoot et al, 2010; Hoogendoorn et al, 2017; Morton & Stevens, 2023). Hoogendoorn et al (2017) estimated an increase of 11%–29% in nitrate leaching at a fertiliser application rate of 20–50 kg N ha −1 , which are rates commonly applied across NZ hill country farms.…”

“…The accumulation of nutrients, runoff and seepage water on flat (low) slopes makes them CSAs with greater potential for nitrate leaching, due to their accumulation and rapid transport processes. For instance, Crofoot et al (2010) found higher nitrate‐N leaching at low (0–12°) and medium (13–25°) slopes compared with high (>25°) slope in a hill country farm in the Wairarapa region of NZ. Similarly, consistent with the higher soil nitrification potential observed at low slopes (Devantier et al, 2012; Letica et al, 2006), Hoogendoorn et al (2016) reported greater nitrate‐N leaching on low (68 kg ha −1 ) versus medium (5 kg ha −1 ) slopes at Ballantrae Research Farm in NZ.…”

“…Given that land management significantly influences nitrate losses to freshwaters, it is important that adequate and sustainable practices are adopted to limit nitrate losses from hill country farms. One such practices is precision fertiliser application, which is supported by the body of literature on the impact of fertiliser application on nitrate losses (Crofoot et al, 2010; Hoogendoorn et al, 2017; Morton & Stevens, 2023). Variable rate fertiliser strategies help achieve precision fertiliser application by first identifying the production potential of hill country Land Units (LUs), assessing the soil characteristics/fertility of the LUs (via soil and herbage sampling), and then applying the appropriate fertiliser rates to obtain an economic optimum soil fertility based on the identified production potential (White et al, 2017).…”