Daniel C. Olk
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View article: Can adoption of multispecies cover crop mixtures improve soil water movement in fragipan soils of southern Illinois?
Can adoption of multispecies cover crop mixtures improve soil water movement in fragipan soils of southern Illinois? Open
Crop production on fragipan soils can be severely limited due to restrictive root growth and perched water table. We hypothesized that roots of multispecies cover crop mixtures containing annual ryegrass (ARG, Lolium multiflorum L .), hair…
View article: Investigating the nature of soil carbohydrates and amino compounds with liquid chromatography
Investigating the nature of soil carbohydrates and amino compounds with liquid chromatography Open
Carbohydrates, amino acids, and amino sugars are constituents of soil organic matter (SOM) that are involved in the dynamics and transformation of soil carbon and nitrogen. Moreover, their quantification can shed light on either their plan…
View article: Introduction of a Fallow Year to Continuous Rice Systems Enhances Crop Soil Nitrogen Uptake
Introduction of a Fallow Year to Continuous Rice Systems Enhances Crop Soil Nitrogen Uptake Open
Rice grown in California constitutes 20% of total U.S. rice production and is typically grown in a continuous rice monoculture system. In recent years, growers have been forced to fallow their lands often due to winter droughts leading to …
View article: Influence of Annual Ryegrass (Lolium multiflorum) as Cover Crop on Soil Water Dynamics in Fragipan Soils of Southern Illinois, USA
Influence of Annual Ryegrass (Lolium multiflorum) as Cover Crop on Soil Water Dynamics in Fragipan Soils of Southern Illinois, USA Open
Fragipans are dense subsurface soil layers that severely restrict root penetration and water movement. The presence of shallow fragipan horizons limits row crop production. We hypothesized that the roots of cover crop might improve soil ph…
View article: Maize Growth Responses to a Humic Product in Iowa Production Fields: An Extensive Approach
Maize Growth Responses to a Humic Product in Iowa Production Fields: An Extensive Approach Open
Field evaluations of commercial humic products have seldom involved replication across location or year. To evaluate the consistency of humic product efficacy in field conditions, we determined the effects of a humic product on maize ( Zea…
View article: Maize Growth and Grain Yield Responses to a Micronized Humic Product Across Soil Types and Annual Weather Patterns in Central Iowa, United States
Maize Growth and Grain Yield Responses to a Micronized Humic Product Across Soil Types and Annual Weather Patterns in Central Iowa, United States Open
Despite growing interest in humic products as crop amendments, very few field evaluations have considered environmental factors of humic product efficacy. We determined the spatial and temporal variability in the efficacy of a micronized h…
View article: Tree Species of Wet Tropical Forests Differ in Their Tissue Biochemistry and Effects on Soil Carbon Dynamics
Tree Species of Wet Tropical Forests Differ in Their Tissue Biochemistry and Effects on Soil Carbon Dynamics Open
Given the hypothesized effects on soil organic matter (SOM) of polyphenols in plant tissues, differences among tree species in their biochemical composition could influence the turnover and accrual of SOM in various ways. The extent to whi…
View article: Using Humic Fractions to Understand Natural Organic Matter Processes in Soil and Water: Selected Studies and Applications
Using Humic Fractions to Understand Natural Organic Matter Processes in Soil and Water: Selected Studies and Applications Open
Natural organic matter (NOM) plays key environmental roles in both aquatic and soil systems. A long‐standing approach for evaluating NOM composition and activity is to extract soils with alkali solutions to obtain humic substances, namely …
View article: Developments in Agricultural Soil Quality and Health: Reflections by the Research Committee on Soil Organic Matter Management
Developments in Agricultural Soil Quality and Health: Reflections by the Research Committee on Soil Organic Matter Management Open
The North Central Education and Research Activity Committee (NCERA-59) was formed in 1952 to address how soil organic matter formation and management practices affect soil structure and productivity. It is in this capacity that we comment …
View article: Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters
Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters Open
J. Environ. Qual. 48(2):217–232 In Table 2 of this article, the phrases “2004 humic acid” and “2004 fulvic acid” were inadvertently switched in the far-left column. Reversing their order then provides the proper data matrix. We provide the…
View article: Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems
Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems Open
The possibility that N fertilizer increases soil organic matter (SOM) mineralization and, as a result, reduces SOM stocks has led to a great debate about the long-term sustainability of maize-based agroecosystems as well as the best method…
View article: Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters
Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters Open
To study the structure and function of soil organic matter, soil scientists have performed alkali extractions for soil humic acid (HA) and fulvic acid (FA) fractions for more than 200 years. Over the last few decades aquatic scientists hav…
View article: Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized
Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized Open
Nitrogen fertilization is critical to optimize short-term crop yield, but its long-term effect on soil organic C (SOC) is uncertain. Here, we clarify the impact of N fertilization on SOC in typical maize-based (Zea mays L.) Midwest U.S. cr…
View article: Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers’ fields
Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers’ fields Open
In tropical deltas, intensive monoculture with three rice crops per year (RRR) has been the standard for decades. However, in recent years some farmers have started rice-based rotations with one or more upland crops per year. The trends fo…