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My research program covers a broad range of topics
dealing with nutrient management and soil quality in agricultural
and rangeland systems. I also have interests in remote sensing and
geographic information system (GIS) technologies as they apply to
studying soil processes at the landscape scale.
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Current Projects
Characterizing
Nitrogen Mineralization and Plant N Supply from Animal Manures
in Hawaii’s and Agricultural Soils |
| In order to improve the management of animal waste
materials as fertilizer materials in crop production systems we need
to understand nitrogen (N) mineralization rates in relation to plant
N requirements. If we can accurately predict the amount of plant
available N (PAN) from manure for a particular crop we can adjust
the application rates to produce good yields and minimize N losses
to leaching. Accurate estimates of PAN also allow us to predict residual
N from a single manure application and adjust subsequent manure application
rates to account for residual N. Currently, there is insufficient
field data to predict PAN form animal manures in Hawaii soils. Such
information is essential to assist farmers manage animal manures
as fertilizer materials in tropical cropping systems in ways that
maintain good crop production and minimize negative impacts on the
environment.
Nitrogen Mineralization Potential
in Important Agricultural Soils of Hawai‘i
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Soil organic matter management to improve
soil and crop quality on intensive vegetable farms in Hawaii |
| The goal of the research component of this project
is to develop sensitive, reliable and simple measures of soil biological
and physical properties that can be used to monitor changes in soil
quality due to organic matter inputs . Soil samples from some of
Hawaii’s intensive vegetable farms show significant decreases
in soil organic matter with negative impacts on soil and crop quality.
The importance of soil organic matter in crop production and the
maintenance of soil function and health is considered the single
most important indicator of soil productivity. A number of vegetable
farmers on Oahu, Maui, and Hawaii Island recognize that their conventional
soil management practices have had negative impacts on their soils,
but they are hesitant to adopt new management practices that involve
organic matter additions. A recent on-farm trial with compost showed
that compost additions had significant positive effects on both soil
and crop quality. Given the preliminary findings, we hypothesize
that improving overall soil health by using organic matter inputs
will lead to improved crop yields and quality. |
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Understanding Charcoal's Role in Improving
Soil Quality |
| Using charcoal as a soil amendment is currently being
proposed as an effective means to not only significantly increase
terrestrial C sequestration, but also increase soil fertility and
food production in the acid, infertile soils of the humid tropics.
Termed “Terra Preta nova”, this approach is modeled on
the C-rich anthropogenic soils known as “Terra Preta do Indio” (Indian
black earth) found in Amazonia and associated with habitation sites
of pre-contact Amerindian populations dating as far back as 7,000
cal yr BP. These soils are remarkable because they have remained
fertile and enriched in soil C compared with adjacent forest soils
despite centuries of cultivation. There are many anecdotal claims
indicating that adding charcoal to soils improves soil quality. The
reported results are highly variable because outcomes of such trials
depend on the nature of the soil and the type and amount of charcoal
applied. Would the result be the same if more or less of a different
type of charcoal of smaller or larger particle size were applied
to a different type of soil? We are currently studying the effect
of charcoal on soil properties and plant growth in the laboratory
and in greenhouse experiments.
Effects
of Flashed Carbonized© Macadamia Nutshell Charcoal
on Plant Growth and Soil Chemical Properties |
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Determining the Impacts of Water Pumping
and Alien Species Invasion Stream Flow for Sustainable Water Resource
Management in Makaha Valley, Hawaii |
| In this project I am collaborating with Dr. Miura
on evaluating the use of multi-spectral and hyper-spectral satellite
imagery to map the vegetation in Makaha Valley. We are interested
in seeing whether these satellite based sensors can be used to differentiate
invasive from native plant species with the intention of developing
vegetation maps characterizing the spatial distribution of invasive
and native plant species within the watershed.
Remote
Sensing of Invasive Species in Makaha Valley
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