Nguyen Hue

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Verified

Nguyen verified their affiliation via an institutional email.

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• Ph.D.
• Professor at University of Hawaiʻi at Mānoa

Past use of arsenical pesticides has resulted in elevated levels of arsenic (As) in some Hawaiian soils. Total As concentrations of 20-100 mg/kg are not uncommon, and can exceed 900 mg/kg in some lands formerly planted with sugarcane. With high contents of amorphous aluminosilicates and iron oxides in many Hawaii's volcanic ash-derived Andisols, a...

Arsenical herbicides were used extensively for emergent weed control in Hawaiian sugar cane cultivation from 1913 to about 1950. As a result, surface soil arsenic concentrations average 280mgkg(-1) across more than 60km(2) of former sugar plantation land in the eastern portion of the Island of Hawaii. This study was conducted to elucidate the relat...

Soil acidity, which is characterized by mainly aluminum (Al) toxicity and often calcium (Ca) deficiency, is a serious constraint for crop production. To separate these two factors and to alleviate the acidity problem using organic materials instead of lime, a greenhouse experiment was conducted on two acid soils of Hawaii. Eight treatments were est...

A local biochar was made from invasive tree species, mainly leucaena (Leucaena leucocephala L.) with the highest temperature around 350-400 o C. Subsequently, two types of compost were prepared with and without 5% biocchar and were amended to a nutrient-poor weathered soil in Oahu, Hawaii. Sweet corn (Zea mays L.) was grown as a test crop. Our prel...

The magnetized water treatment can significantly increase root mass, sprouting rate (16% vs. 4.5%), and lower lodging rates (0% vs. 9%) relative to the non-magnetized water control. The north-seeking pole notably enhances both sprouting speed and shoot growth while the south-seeking pole exposure has more obvious effect on root development compared...

Hawaii is known for its diverse micro-climates, making the evaluation of varieties at different locations an important strategy to determine the best varieties for each climate zone. Demand for dry beans in Hawaii has been rising due to the increase in production of value-added goods made from legumes. Initial field trials in 2017 were conducted to...

Soil, like human, must have good health to function well. This condition can only be achieved when its biological, chemical, and physical aspects are in their optimal capacity and in balance. And if the soil is sick (i.e., contaminated), remediation should be timely taken. Such requirements could be partially met by using biochar as a soil amendmen...

State of Hawaii and the University of Hawaii at Manoa (USA)

Rapid increases in population have led to a higher demand for food. Meeting this demand, as demonstrated by the Green Revolution in the 1960s, has necessitated the use of chemical fertilizers.

Phosphorus (P) is essential to all living organisms and a major nutrient for the successful crop production in organic farming. Organic production guidelines ban the use of highly soluble, manufactured P fertilizers, thus P sources for organic farming must come from P rock, green or animal manures, compost, and biofertilizers. In this article, we f...

Soil remediation is the act of removing or reducing the availability of contaminants from soil. In the case of agriculture, soil remediation targets the removal of pollutants, including residual pesticides/herbicides, hydrocarbons, and toxic heavy metals. This is often done by chemical treatments with multiple washes or excavation of soils, which a...

Maintaining soil fertility and obtaining good crop yields in highly weathered tropical soils through organic practices–without chemical/synthetic inputs—requires a scientific approach and skillful managements, especially for phosphorus (P) nutrient. Our objective was to find a combination of lime and rock phosphate additions that made soil pH low e...

Soil acidity is a serious problem worldwide. Its causes can be both natural and anthropogenic. Natural processes involve a) leaching losses of base cations such as calcium (Ca 2+), magnesium (Mg 2+), potassium (K +), and replacing with proton (H +) and aluminum (Al 3+) on the surface of soil particles wherever rainfall is substantial; b) weathering...

Many Hawaiian agricultural soils are acidic with low-nutrient retention; therefore, organic soil amendments are often used to improve soil properties and increase yields. Amendments can be incorporated for annual crops, but perennial orchards need surface application to avoid damaging surface roots. Pot trials compared responses to incorporated (IB...

Soil, like human, must have good health to function well. This condition can only be achieved when its biological, chemical, and physical aspects are in their optimal capacity and in balance. Such requirements could be partially met by using biochar as a soil amendment. More specifically, biochar is a solid material, high (>50%) in organic carbon (...

One application of biochar, at the recommended application rates, can last in the soil for over a decade, since biochar does not decompose easily. Five leafy green varieties, Hatakena, Mizuna, and three varieties of Komatsuna, were evaluated for yield and biomass production under two application rates of biochar (0 and 10 ton/ha) at Kula Agricultur...

Soybean is also known with other names worldwide, such as: Soya bean, daizu (Japanese), dadou (Chinese), and kong (Korean). Soybean days to harvest are between45-65 days for fresh pods or seeds and 70-90 days for dry seeds. Soybean plant population is recommended to be around 6 plants/foot and 30 in between rows. However, smaller row spacing (4-5 p...

Highly weathered soils in Hawai’i are low in fertility, negatively affecting plant growth. The potential of biochar for improving soil nutrient availability to crops is promising, and prompts this study. Two biochars at 2% (w/w) made of lac tree (Schleichera oleosa (Lour.) Oken) wood and mixed wood (scrapped wood and tree trimmings) with and withou...

Biochar, a product of biomass that is heated in a limited oxygen environment (pyrolysis), has been reported to improve soil quality and increase plant growth. To quantify and further characterize such roles of biochar, three experiments were conducted: (1) a greenhouse trial on an acidic tropical Ultisol, which evaluated the aluminum (Al) detoxifyi...

Highly weathered soils in the tropics are low in fertility, negatively affecting plant growth. The potential of biochar for improving soil nutrient retention is reportedly promising, triggering this study to assess the nutrient retention capacities of two biochars when applied at 2% in combination with two composts also applied at 2% to an Ultisol...

A poster presentation at Our Farms, Our Future Conference. The conference was sponsored by SARE/ATTRA. From April 3-5, 2018 at Hyatt Regency Hotel in St. Louis, MO. USA. The poster represented some of the results rom different projects/grant awards from the Western SARE, Hawaii Department of Agriculture, HATCH, and the USDA.

Innovative Waste Management Strategies: Utilizing Locally Produced By-Products as Organic Amendments for Crop Production in Hawaii. Our Farms, Our Future Conference.

Organic farming has become a popular and important aspect of sustainable agriculture in many countries, particularly in tourism oriented, densely populated areas, such as Hawaii. Yet, the resources for improving the soil and enhancing the crop’s growth, that are acceptable to organic farmers, are regulation-imposed, and thus less available as compa...

An introduction to the Univ. of Hawaii at Manoa

Arsenic chemistry, toxicity, and remediation

The application of locally available invasive algae biomass as a fertilizer for crop production in Hawaii is being investigated as a substitute for imported chemical fertilizers. Three closely related greenhouse trials were conducted to determine if the algae served as a source of potassium (K) on growth, yield, and K mineral nutrition in pak choi...

Nutritional status of vegetable crops is often monitored by analysis of dried plant tissues, which is costly and often time consuming. Two greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon facilities , to evaluate the portable cardy ion meter (CIM) in determining potassium (K +) status in fresh petiole sap of pak choi a...

Biochar is a promising soil amendment for sustainable agriculture, including the amelioration of soil acidity. To assess the liming potential of biochars, two field experiments were conducted in West Java, Indonesia with different of soil acidity levels. Lac tree (Schleichera oleosa) wood and ricehusk biochars at 4% and 8% alone or in combination w...

Biochar, due to its porous nature, calcium carbonate (CaCO3) equivalent, surface functional groups, and other properties, could serve as an acid soil amendment. To investigate the liming potential of biochars, laboratory characterization, greenhouse and field experiments were conducted in Hawaii, USA and West Java, Indonesia, respectively. Six wood...

Nutritional status of vegetable crops is often monitored by analysis of dried plant tissues, which is costly and often takes time. Two greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon facilities, to evaluate the portable cardy ion meter (CIM) in determining potassium (K+) status in fresh petiole sap of pak choi as comp...

Soils rarely have sufficient nutrient for crops to reach their potential yield. Applying organic fertilizers without prior knowledge of their properties may cause yield decline under low application or pollute the environment with excessive application. Under‐ standing the nutrient variability and release pattern of organic fertilizers is crucial t...

Highly weathered soils in the tropics are poor in nutrient and hardly support the plant growth. The capacity of biochar to improve soil nutrient retention is recently recognized. The objective of this study was to assess the nutrient retention capacities of two biochars when applied in combination with two composts to two highly weathered soils of...

Amendments are usually needed to support crop growth in highly weathered soils. Two biochars (0, and 2%) and composts (0, and 2%), were applied to two tropical soils of Hawaii (Leilehua series, Ultisol and Wahiawa series, Oxisol). Chinese cabbage (Brassica rapa cv. Bonsai) was used as the test plant in two greenhouse trials. The experimental design...

The application of locally available invasive algae biomass waste as a fertilizer for crop production in Hawaii is of great importance to substitute the commercial chemical fertilizers and to reduce the cost of production and increase grower profitability. Three greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon faciliti...

In Hawaii, there are many small farm holders. Intercropping may increase diversity of farm products, reduce input costs, and increase farm profitability. Two field experiments were conducted in Hawaii to study the effect of three legume species intercropped with sweet corn (Zea mays L.) on the growth, relative chlorophyll content, biomass, and yiel...

Highly weathered soils, mainly Oxisols and Ultisols, in the tropics, including those in Hawaii, are poor in nutrients due to leaching and therefore hardly support good crop growth. Biochar reportedly has a great capacity to retain nutrients due to its numerous small pores and large surface area/charge. Our research showed that nutrients from compos...

Cover crops are the backbone of sustainable cropping systems: as they can prevent soil erosion, reduce nutrient leaching, add organic matter, improve soil health, fix nitrogen, suppress weeds, and reduce insect pests and diseases. In addition to these well-established benefits of cover cropping, leguminous cover crops can contribute significant amo...

Due to strong demands from organic farmers, landscapers, and home-gardeners, production and utilization of composts have rapidly increased. So, there is the need for their characterization (compost quality evaluations, particularly their nutrient releasing characteristics). In this study, three vermi-composts, six thermo-composts, and a green manur...

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j h a z m a t h i g h l i g h t s • Former sugarcane plantation soils contain elevated total and in vitro bioaccessible arsenic from historical herbicide application. • Iron amendments effectively reduce arsenic bioaccessibility. • Phosphate additions to iron treated an...

Arsenic-based pesticides were prevalent in Hawaii during the 1920s to 1950s to help manage weeds in sugarcane fields. Since then, Hawaii soils have accumulated high amounts of arsenic, which have the potential to damage human health. Health risks include: skin lesions and hardenings, cancers, and neurological disorders. Many of these sugarcane land...

Manure applications can change soil porosity, bulk density, hydraulic conductivity, and nutrient availability, thus affecting root growth and distribution. Information on root distribution is important to developing more efficient irrigation strategies that meets crop water requirement and reduce excess irrigation. Two field experiments were conduc...

Former sugar cane lands on the Island of Hawaii have elevated soil arsenic (As) from historical use of arsenical pesticides. The bioaccessible fraction of total As (AsTOT) is a measure of the potential for human As uptake by incidental ingestion of soil, and is used in the assessment of human health risk and the need for remedial action. Ferric chl...

Due to strong demands from organic farmers, landscapers, and home-gardeners, production and utilization of composts have been rapidly increased. So is the need for their characterization. Thus, three vermi-composts, six thermo-composts and a green manure were incubated at 10 g/kg with a Mollisol and an Oxisol at room temperature. Unamended soils se...

Biochar is a stable form of charcoal produced from heating organic materials in a high temperature and low oxygen process. Due to its porous nature, surface functional groups, and other properties, biochar could serve as a beneficial soil amendment. To investigate this potential of biochars, six wood-derived biochars were characterized, and then am...

As a result of increased population, improved standards of living, and strict environmental laws, biowastes have been generated in huge quantities. Thus, land applications of these wastes are desirable, or even necessary, to keep the environment healthy and to conserve natural resources. Yet, the success of such uses requires knowledge of complex b...

Extension agents brought forth concerns that a strange phenomenon was affecting multiple crop types in central Oahu. A multi-disciplinary team of specialists at the College of Tropical Agriculture and Human Resources (CTAHR) studied the incident called "Yellowing Problem" and ruled out disease and pesticide damage as the causal agent, leaving soil...

Reducing grower reliance on off-island inputs to promote plant nutrition has been identified by industry as a high priority in efforts to improve agricultural sustainability in Hawaii. A variety of knowledge gaps exist that prevent producers from using more locally produced amendments in their fertility program. This presentation will focus on rece...

Greenhouse experiments were conducted to evaluate the effects of different concentrations of vermicompost water extracts (teas) and seed soaking duration on germination of tomato (Solanum lycopersicum) and lettuce (Lactuca sativa) seeds. In the first experiment, tomato and lettuce seeds were soaked in vermicompost teas prepared from chicken manure-...

Two field experiments were conducted to evaluate the use of relative chlorophyll content (RCC) in sweet corn leaves as an indicator of nitrate concentration in soil. Study objec-tives were (1) to evaluate the effect of manure types (chicken and dairy), rates (0, 168, 336, and 672 kg ha −1 equivalent N), and application frequency (one and two applic...

This study investigated the links between variability in compost quality, the biochemical characteristics of their extracts (compost tea) and plant growth indicator through a series of experiments. Five different commercially produced composts were selected for quality evaluation. They were: (i) chicken manure-based thermophilic compost (ii) green...

Variability in compost stability and maturity limits utilization of these potentially beneficial plant growth promoting local amendments by Hawaii growers. Lab incubation and greenhouse experiments were conducted to screen locally produced composts for their nitrogen release and plant growth response in different soils. Eleven different composts we...

This study investigated the effect of vermicompost tea on the germination of tomato and lettuce seeds. Greenhouse experiments were conducted twice during September to December, 2010. Aerated vermicompost tea was prepared by extracting commercially produced chicken manure-based vermicompost in water at 1:10 dilution rate (vermicompost to water ratio...

Previous work has demonstrated the potential of compost tea to enhance plant growth and nutritional status.One factor thought to contribute to variability in the efficacy of compost tea is the amount of compost per unit volume of water. To address these gaps in our understanding, two greenhouse trials and two field trials were conducted to investig...

Two greenhouse trials and two field trials were conducted to investigate the effects of vermicompost tea (aqueous extract) on growth, tissue N and phytonutrient content of pak choi (Brassica rapa chinensis), and on soil biological properties. In the greenhouse experiments, plants were fertilized with chicken manure-based thermophilic compost. In th...

Changes in soil properties and vegetable growth were quantified on a low-fertility tropical soil. Four treatments (two composts, urea, and control) were applied to an Oxisol (Rhodic Haplustox, Wahiawa series) in a field on Oahu, Hawaii. Chinese cabbage (Brassica rapa, Chinensis group) and eggplant (Solanum melongena) were grown sequentially as test...

This study investigated the effects of vermicompost tea (aqueous extract) on yield and chemical quality of pak choi (Brassica rapa cv Bonsai, Chinensis group) grown in three media (two soils and a peat-perlite medium) under two fertilizer regimes (compost and synthetic fertilizer). The impacts of tea application on the chemical and biological prope...

Soil acidity is a serious constraint for crop production in many regions of the world, Hawaii included. Liming is the conventional remedy, yet lime is costly and may not be available in some places. Our research showed that biochar, a by-product of bio-fuels production, could replace lime, at least partially, in alleviating soil acidity. A combinat...

Why Compost? • US garbage: 200 + million tons/yr or 5 lbs/person/day • Costs of disposal • Regulations • Good organic fertilizers • Soil amendments

Tea Time for the Garden Water based extracts of compost (compost tea) have a relatively long history in agriculture. This is not sur-prising since they are simple to make by soaking compost in water and agitating by stirring, aeration or other methods. Scientific investigations of claims of the benefits of compost tea are much more recent. Study re...

Application of aqueous extract of vermicompost has been shown to improve plant health, yield and nutritive quality. Few studies have been conducted to determine the effect of vermicompost extract on soil biological properties. The objective of this study was to evaluate the independent effects and interaction between vermicompost extract and soil t...

There is growing evidence that compost extract can benefit plant health and yield but a consistency of the effect is a concern. Compost quality plays a major role in extract quality; however, little work has been done to evaluate the effect of compost sources on compost extract quality and subsequent plant response. The objective of this study was...

Past use of arsenical pesticides has resulted in elevated levels of arsenic (As) in some Hawaii soils. Total As concentrations of 50 -100 mg/kg are not uncommon, and can exceed 900 mg/kg in some former sugarcane lands. Given the high content of amorphous aluminosilicates and iron oxides in many Hawaii Andisols, a high proportion (25 – 30%) of soil...

Phosphorus (P) is an essential nutrient for plant growth and reproduction. One of the tasks of soil testing is to identify whether the soil P level is sufficient to meet crop requirements, and if not, to provide an estimate of the quantity of P that must be added for good growth of a given crop. Data for 12 soils (11 series) from Hawaii were used t...

BACKGROUND: Multiple studies have been reported on the effect of compost tea on suppression of certain plant diseases. However, relatively little work has been done to investigate the effect of vermicompost tea on yield and nutritional quality of vegetable crops. In this study, experiments were conducted to determine the effect of extraction method...

Multiple studies have reported on the effect of compost tea on suppression of certain plant diseases. However, relatively little work has been done to investigate the effect of compost teas on yield and nutritional quality of vegetable crops and even fewer studies have addressed the relationship between extraction methods, chemical and biological c...

Proteoid roots are reportedly an adaptation to soils with either low phosphorus (P) or iron (Fe) or both. Since macadamia (Macadamia integrifolia, a member of the family Proteaceae) is an important crop in Hawaii, a factorial experiment with soil P levels of 0, 150, and 500mg/kg and Fe levels of 0, 5, and 10mg/kg was conducted to evaluate the effec...

Soil amendment with organic materials (crop residues animal manure, and green manure) reportedly has positive effects on soil properties, from acidity to plant-nutrient availability. To examine that hypothesis, an incubation study was conducted to assess the changes in some chemical properties of three different tropical soils (Andisol, Ultisol, an...

Soil acidity is a serious constraint to crop production and ecosystem health. Acidification can occur naturally via the formation of carbonic acid (CO2 + H2O ΠH2CO3 ΠHCO3 - + H+) and subsequent leaching of basic cations or through man-made processes. These include the formation of sulfuric and nitric acids by coal burning, automobile exhaust emis...

Arsenic (As) is widely known for its adverse effects on human health, affecting millions of people around the world. In Asia the consumption of groundwater (through wells) in an attempt to replace polluted surface water supplies has resulted in widespread As poisoning. Both, the United States Environmental Protection Agency (US-EPA) and the World H...