Issue 28, December 2019
This issue of Soil Horizons explores soils and their influence on water from micro-scale to farm- and national-scale, and ways to improve the management of our soil resource. We present key research findings on the importance of soil health, finite high-class soils, improving S-map to aid the management of irrigation and erosion control, soil ecological guidelines for trace elements, and new soil monitoring and management tools.
In this issue
Targeting smarter erosion control with new research
A new 5-year (2018–2023) MBIE funded programme ‘Smarter Targeting of Erosion Control’ (STEC) is now well underway, exploring cost-effective ways of targeting land-based erosion control in the hope of slowing the damage and improving water quality. The programme is led by Manaaki Whenua – Landcare Research in collaboration with NIWA, Massey University, Waikato University, international researchers, programme partners Whanganui iwi (Tamaūpoko Community group) and Rangitāne o Manawatū, as well as several regional councils.
Identification of high-risk agricultural activities: national mapping of winter forage cropping and intensive grazing on hill country land
Winter forage cropping and grazing practices in New Zealand hill country can result in severe de-vegetation and erosion, and therefore have a significant negative impact on downstream water quality. Research has shown that sediment and nutrient losses from winter-grazed hill country pasture are greater with increased slope and increased percentage of bare ground associated with soil damage from treading.
Soil Matters: Whakahirahira te mana o te oneone
Through our MBIE Endeavour funded programme Soil health and resilience – oneone ora tangata ora we are exploring the concept of ‘soil health’ and what it means across New Zealand society using both a conventional science and a mātauranga Māori approach.
The case of the finite soils – making their value visible
Urban encroachment onto versatile land is a growing concern across New Zealand with agricultural and horticultural land being lost to urban development. This led to the National Policy Statement for Highly Productive Land being proposed in August 2019.
Reducing water use and nitrogen loss under irrigated cropping
Soil physical properties, such as profile available water, are key influences on irrigation management, while others influence environmental outcomes, such as soil drainage and nutrient loss. Soils can be spatially variable, with varying capacity for water storage.
Managing irrigation and harvest intensity of lucerne to increase soil carbon stocks
There is growing recognition of the need to increase soil carbon stocks to improve soil fertility, enhance the sustainability and resilience of productive systems, and sequester carbon dioxide from the atmosphere to offset greenhouse gas emissions. While international initiatives, such as the 4 per 1000 Initiative Soils for Food Security and Climate call for action for countries to achieve increases in soil carbon stocks, this is particularly challenging for New Zealand where soil carbon stocks are already high and grazed grassland is the dominant agricultural practice. A direct sampling approach requires a statistical sampling design within a spatial framework that samples the expected spatial variability and detects changes in soil carbon stocks within specified uncertainty limits over a period of about 5 years.
A national soil carbon monitoring system for agricultural land in New Zealand
Manaaki Whenua – Landcare Research has received funding from The New Zealand Agricultural Greenhouse Gas Research Centre (NZAGRC) and the Ministry for Primary Industries (MPI) to commence the first phase of a new nationwide baseline soil carbon measurement study. This study will improve New Zealand’s ability to report greenhouse gas emissions and removals under international climate change agreements and satisfy a growing desire by primary industry organisations and individual farmers to know how New Zealand’s soil carbon stocks might be changing.
Soil specific surface area can be measured cost effectively by water adsorption
Soils can store large amounts of soil organic carbon (SOC) because carbon can be shielded in organo-mineral complexes that form on mineral surfaces and protect organic molecules from microbial decomposition. Some soils have very large mineral soil surface areas, in the order of hundreds of square meters per gram of soil, that make them biochemically reactive and can lead to the protection of large amounts of SOC. Sandy soils, on the other hand, have much smaller mineral surface areas, in the order of tens of square meters per gram of soil. This gives sandy soils little capacity to protect and store significant amounts of SOC.
Recent progress in soil spectroscopy
Sustainable land management requires reliable information about a wide range of soil properties, but the cost – both financial and in terms of time – of direct measurements for those properties, can be a burden. Proximal sensing technologies can offer an alternative to the reference laboratory methods: sensors exploiting different parts of the electro-magnetic spectrum can provide estimates for some of those key soil properties faster, and often cheaper. Soil spectroscopy has been an area of research for the Manaaki Whenua pedometrics research team for a number of years now.
Cloud-connected, smartphone-driven infiltrometer network
One of the key soil information requirements for smart agriculture and storm water management is how fast water infiltrates into the soil at various antecedent soil moisture conditions. Infiltration data are the most important factors for estimating run-off of water applied at a known rate. Storm water generated from a catchment can be appropriately routed if the portion of the rain that contributes to the run-off is properly estimated.
Progress on enriching S-map soil information to enable better decision-making across New Zealand
The S-map NextGen programme is a 5-year MBIE Endeavour funded programme focussed on the science that underpins S-map, New Zealand’s national soil map. The programme’s major focus is to create a step-change in the quality of soil hydrological information S-map supplies to a wide range of end-users, for the diverse range of soils that occur across New Zealand (Figure 1). The third year of the programme has been completed, and some of the highlights are summarised below:
What are “Soil Guideline Values” and which should I use?
Soil guideline value (SGV) is a generic term used to collectively describe different criteria that typically identify concentrations of substances such as nutrients and contaminants in order to manage soil quality.