Use of Commercial Humates in Agriculture

A special issue of Agronomy (ISSN 2073-4395).

Deadline for manuscript submissions: closed (31 August 2016) | Viewed by 17081

Special Issue Editors

School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
Interests: plant nutrition; plant physiology; plant breeding; abiotic stress; phenotyping; cereals

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Guest Editor
Research Fellow, Discipline of Plant & Food Science, School of Agriculture, Food & Wine, University of Adelaide, Waite Campus, Glen Osmond 5064, South Australia

Special Issue Information

Dear Colleagues,

Humic substances are natural organic compounds, which are sourced from plants, peat, soil, and coals, such as lignite and leonardite. Humates are salts of humic acids, the most active component of humic substances, which are more soluble and, thus, more reactive in soil.

There is a range of humates available commercially for use in agriculture, e.g., potassium, calcium, boron, and sodium, usually used for the purposes of 1) increasing production on soils with heavy metal contamination, salinity, sodicity, extreme pH, low water content, adverse temperatures, and low organic matter; and 2) increasing the efficiency of inorganic fertilizers. However, there are few rigorous studies, which have investigated the effectiveness of commercial humates, and findings are variable. The industry relies largely on anecdotal case studies to promote these products to farmers. Given recent increased interest, it is timely to review current status and future opportunities for research and application of commercial humates in agriculture.

We take this opportunity to welcome the submission of research articles, and communications on this topic with particular reference to abiotic stress tolerance.

Dr. Yusuf Genc
Dr. Graham Lyons
Guest Editors

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Keywords

  • Commercial humates
  • Humic acids
  • Soil conditioners
  • Soil fertility
  • Microbial activity
  • Abiotic stress tolerance
  • Organic matter
  • Plant growth
  • Yield
  • Crops

Published Papers (2 papers)

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Research

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663 KiB  
Communication
Replenishing Humic Acids in Agricultural Soils
by Michael Susic
Agronomy 2016, 6(4), 45; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy6040045 - 28 Sep 2016
Cited by 23 | Viewed by 7706
Abstract
For many decades, it was commonly believed that humic acids were formed in soils by the microbial conversion of plant lignins. However, an experiment to test whether these humic acids were formed prior to plant matter reaching the soil was never reported until [...] Read more.
For many decades, it was commonly believed that humic acids were formed in soils by the microbial conversion of plant lignins. However, an experiment to test whether these humic acids were formed prior to plant matter reaching the soil was never reported until the late 1980s (and then only as a side issue), even though humic acids were first isolated and reported in 1786. This was a serious omission, and led to a poor understanding of how the humic acid content of soils could be maintained or increased for optimum fertility. In this study, commercial sugar cane mulch and kelp extracts were extracted with alkali and analyzed for humic acid content. Humic acids in the extracts were positively identified by fluorescence spectrophotometry, and this demonstrated that humic acids are formed in senescent plant and algal matter before they reach the soil, where they are then strongly bound to the soil and are also resistant to microbial metabolism. Humic acids are removed from soils by wind and water erosion, and by water leaching, which means that they must be regularly replenished. This study shows that soils can be replenished or fortified with humic acids simply by recycling plant and algal matter, or by adding outside sources of decomposed plant or algal matter such as composts, mulch, peat, and lignite coals. Full article
(This article belongs to the Special Issue Use of Commercial Humates in Agriculture)
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Review

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211 KiB  
Review
Commercial Humates in Agriculture: Real Substance or Smoke and Mirrors?
by Graham Lyons and Yusuf Genc
Agronomy 2016, 6(4), 50; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy6040050 - 28 Oct 2016
Cited by 31 | Viewed by 8785
Abstract
Soil humic substances (HS) are known to be beneficial for soils and plants, and most published studies of HS and humates, usually conducted under controlled conditions, show benefits. However, the value of commercial humate application in the field is less certain. This review [...] Read more.
Soil humic substances (HS) are known to be beneficial for soils and plants, and most published studies of HS and humates, usually conducted under controlled conditions, show benefits. However, the value of commercial humate application in the field is less certain. This review attempts to answer the question: How effective are commercial humates in the field? Commercial humates, especially K humate, are used widely in agriculture today as “soil conditioners”. A wide range of benefits is claimed, including growth of beneficial soil microbes; deactivation of toxic metals; improvements in soil structure including water retention capacity, enhanced nutrient and micronutrient uptake and photosynthesis; resistance to abiotic stress, including salinity; and increased growth, yield and product quality. Despite this, there is a surprising lack of solid evidence for their on-farm effectiveness and findings are often inconsistent. The industry relies largely on anecdotal case studies to promote humates, which are often applied at unrealistically low levels. It is recommended that products should be well characterised, physically and chemically, and that careful field studies be conducted on foliar humate application and pelletised humates at realistic rates, targeted to the seedling rhizosphere, for a variety of crops in a range of soils, including low C sandy and saline soils. Full article
(This article belongs to the Special Issue Use of Commercial Humates in Agriculture)
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