1 research outputs found
Prediction of soil Olsen P through mixed pasture leaf tissue biochemical and biophysical properties, topography and farm management in New Zealand hill country : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agricultural Science at Massey University, Turitea, New Zealand. EMBARGOED until 1 January 2024.
Embargoed until 1 January 2024In New Zealand hill country, soil Olsen Phosphorus (P) is a key piece of information used to
decide rates, products and areas to which aerial applications of phosphate fertilisers are made.
Laboratory based soil Olsen P measurements are made on bulked soil cores collected along
transects, laid out across slope faces. On most hill country farms, aerial fertiliser applications
are applied uniformly over large blocks or the whole property. Accurate, detailed soil maps are
scarce, but essential for site specific nutrient management. Current soil sampling techniques
provide spatially sparse information and attempts to interpolate point measurements of soil
properties in hill country, have not been successful.
The potential improvement in nutrient use efficiency would lead to increases in pasture
production and quality, and an increase in production of meat and wool produced off the same
land area. As sheep and beef production is forced from more productive land into more
marginal areas by other land uses, managing hill country landscapes efficiently will become
critical for the sheep and beef industry. Increases in global food demand, a growing interest in
product origins and production practices by the consumer, and tightening of environmental
regulations will further put pressure on these systems. Appropriate soil and fertiliser
management has suffered from a lack of information to make sound decisions. Maps of soil
Olsen P are a first step, with much potential in the applications of hyperspectral imaging yet to
be discovered.
The objective of this thesis was to develop a model that could be applied to readily available
data layers, to make continuous predictions of phosphate availability in the soil (Olsen P)
across New Zealand hill country farms. This research was one part of a larger project that
firstly aimed to derive estimates of pasture parameters from hyperspectral imagery. This
information could then be used in conjunction with ancillary data to determine soil nutrient
status. Finally, this information would be used to inform variable rate fertiliser applications
through a prescription map loaded into a computer controlled aerial top dressing system.
A multi-site, multi-seasonal database from eight commercial hill country farms incorporating a
range of leaf tissue nutrient concentrations, pasture biophysical properties, and topographic,
soil and farm management information was built up alongside soil chemical properties. Model
development was based on in-situ measurements and laboratory analysis of leaf tissue and soil
samples collected on 0.5m x 0.5m plots. A total of 3,030 plots were sampled in the autumn
and spring.--Shortened abstrac