on cropping farms PAANZ Workshop Technology to reduce N leaching - - PowerPoint PPT Presentation

The New Zealand Institute for Plant & Food Research Limited

Rootzone reality – a fluxmeter network to measure and manage N leaching losses

• n cropping farms

PAANZ Workshop – Technology to reduce N leaching Paul Johnstone, Plant & Food Research

The New Zealand Institute for Plant & Food Research Limited

A rapidly changing farming landscape

» Goal of farmers hasn’t changed – Farming for profit while minimising losses » Period of regulatory change – intent vs demonstrate » Rise of tools for predicting whole farm outcomes and setting associated policies

» Model vs measure » Recognition that farming systems are complex!

The New Zealand Institute for Plant & Food Research Limited

Plugging a gap – ‘Rootzone reality’

» Provide growers and regional authorities with robust measurements of N and P leaching losses from cropping farms across sites and seasons under GMP’s » Why?

» Need more measured data for discussion » Need an idea about whether GMP’s have the desired impact » Need to do it together to inform models and policy

Overview:

» Summary of network and sites » Year 1 findings » The role for precision technologies?

The New Zealand Institute for Plant & Food Research Limited

Measuring losses - tension fluxmeters

» Why use tension fluxmeters?

» Permanent and non-intrusive » Capture complete drainage events » Cost-effective approach

» What is a tension fluxmeter?

» PVC pipe that intercepts drainage (stores ~14 L) » Silica sand and DE reduce sediment transfer » Passive wick » Drainage pumped to surface through plastic tubes

150 mm 50 mm 1000 mm 200 mm 150 mm

The New Zealand Institute for Plant & Food Research Limited

Context - installing and testing fluxmeters

» Installation process

» Representative areas of fields, not extremes » Hole augured, unit lowered, soil carefully repacked » Top of fluxmeter is at a depth of 1.0 m

» Testing performance

» Disturbed soil needs to settle » Soil water balances to look at inputs (irrigation + rainfall) and outputs (drainage)

The New Zealand Institute for Plant & Food Research Limited

The fluxmeter network

» Network design

» Four monitor regions » Three sites per region » 12 fluxmeters per site (144 units)

» Sites

» Commercial fields » Range of soils, climates and management practices » Avoided high water tables, artificial drainage and stones

The New Zealand Institute for Plant & Food Research Limited

Key measurements

Soil fertility (N, P, C…) Crop biomass (DM, N uptake, export) Drainage (volume, NO3, NH4, DRP, Total P)

The New Zealand Institute for Plant & Food Research Limited

Drivers of nutrient losses – loading and drainage

Implication: manage soil fertility and drainage

Low drainage High drainage Low soil fertility Low loss Low loss High soil fertility High risk High loss

The New Zealand Institute for Plant & Food Research Limited

1 2 3 4 5 6 7 8 9 10 11 12 100 200 300 400 1 2 3 4 5 6 7 8 9 10 11 12 100 200 300 400

Measured loading – soil nitrogen

High Moderate Mineral N (kg/ha, to 1 m depth) AMN (kg/ha, to 1 m depth) High Moderate Low Low

Canterbury Manawatu Hawke’s Bay Waikato/Auckland N available today… N available soon…

The New Zealand Institute for Plant & Food Research Limited

1 2 3 4 5 6 7 8 9 10 11 12 50 100 150 200 250

Measured loading – soil phosphorus

Optimum Olsen P (mg/kg, to 0.2 m depth)

Canterbury Manawatu Hawke’s Bay Waikato/Auckland

Above

• ptimum

The New Zealand Institute for Plant & Food Research Limited

1 2 3 4 5 6 7 8 9 10 11 12 250 500 750 1000 1250 1500 500 1000 1500 2000 2500 3000

Drainage Rainfall Irrigation Long term average rainfall 13 12 12 11 12 5 13 12 13 5 7 6 NR NR No result

13 12 12 11 12 5 13 12 13 5 7 6

Measured drainage

Rainfall and irrigation (mm)

Canterbury Manawatu Hawke’s Bay Waikato/Auckland

Drainage (mm) Monitoring period (months)

The New Zealand Institute for Plant & Food Research Limited

Measured nitrogen losses

Cumulative mineral N losses (kg/ha)

Canterbury Manawatu Hawke’s Bay Waikato/Auckland

What represents an acceptable environmental loss? What represents an acceptable economic loss?

The New Zealand Institute for Plant & Food Research Limited

Measured phosphorus losses

Cumulative Total P losses (kg/ha)

What represents an acceptable environmental loss? Not an economic driver

Canterbury Manawatu Hawke’s Bay Waikato/Auckland

The New Zealand Institute for Plant & Food Research Limited

Overall synthesis from network to date

» Key stats since installation and October

» Captured drainage ranged from 0.3 to 611 mm » N losses ranged from 0.2 to 226 kg N/ha » P losses ranged from 0.01 to 0.56 kg P/ha

» Winter and spring losses dominate

» Rainfall is a key driver; reduce loading? » Irrigation not resulting in significant drainage during summer

» High soil N and P levels = high risk » Value of data increases with long-term trends…

The New Zealand Institute for Plant & Food Research Limited

Implications for precision technologies?

» Tight management of water and nutrients is important to limit losses

» GMP’s are working » Precision technologies can also help

» Likely to require different solutions

» mapping, sensing, VRI, VRN…

» How to decide what to use and when?

The New Zealand Institute for Plant & Food Research Limited

Acknowledgements

Grower collaborators Project managers: Diana Mathers (FAR) and Angela Halliday (Horticulture NZ) PFR team: Matt Norris, Shane Maley, Mike George, Gina Clemens, Steve Thomas, Steve Green, Carlo van den Dijssel, Paulo Zuccarini, Nathan Arnold, Adrian Hunt, Christina Finlayson, Glen Clark and Peter Wright.

The New Zealand Institute for Plant & Food Research Limited

Paul.Johnstone@plantandfood.co.nz