Nitrogen Fertilizer Options for Cannabis Production

Nitrogen Fertilizer Options for Cannabis Production

Nitrogen Fertilizer Options for Cannabis Production

Professor DeBacco

Effects of Nitrogen Fertilizer Rate Timing
Nitrogen can be found in either organic or inorganic forms in the soil.
Organic forms of nitrogen are found when plant and animal material decomposes and releases proteins and amino acids back into the soil as part of the nitrogen cycle.
When organic materials are broken down by bacteria they form inorganic nitrogen as ammonia, in a process called ammonification (Murphy, 2007).
Inorganic nitrogen includes nitrates (NO3-), nitrite, (NO2-), ammonium (NH4+), and dinitrogen gas (N2).
European research had indicated hemp cultivars did not need as much nitrogen compared to wheat (Ranalli, 1999).

Research from Canada Hemp Response to Nitrogen Fertilizer
Research in Canada demonstrated that hemp responded to nitrogen up to 120 kg N/ ha (110 lb N / Acre) when soils were deficient, by increasing seed and biomass yield (Vera et al., 2009).
Research in Saskatchewan showed a positive response to fertilizers, with nitrogen rates up to 150 kg N/ ha (130 lb N / Acre) being optimal (Vera et al., 2009).
In Quebec, Canada, additions up to 200 kg N/ ha (180 lb N / Acre) showed a positive response with no plateau observed (Aubin et al., 2015).
Summary:
Nitrogen rates of 120 kg N/ ha (110 lb N / Acre) to 200 kg N/ ha (180 lb N / Acre) shoul dbe the target range
Ideal target should be around 150 kg N/ ha (130 lb N / Acre)

Nitrogen Transformations
All major soil nitrogen transformations are mediated by various soil microorganisms. Also, the fate of any fertilizer nitrogen source will be subject to the following:
1) Mineralization: conversion of organic nitrogen to inorganic nitrogen by microorganisms
2) Nitrification: conversion of ammonia nitrogen into nitrate
3) Denitrification: conversion of nitrate into a nitrogen gas
4) Ammonia volatilization: loss of ammonia nitrogen as a gas
5) Leaching of nitrates: caused by over-irrigation, especially in sandy soils
6) Immobilization: conversion of inorganic nitrogen into an organic form
7) Ammonium fixation on certain types of clay

N Conversions and Impact on Root-Zone pH
Plants take up ammonium and other positively charged cations by releasing one hydrogen ion (H+) into the medium solution for each ammonium ion absorbed. Over time, ammoniacal nitrogen uptake increases hydrogen ion concentration thereby lowering the growing medium pH.
The uptake of negatively charged anions such as nitrate is most often accomplished by releasing hydroxide ions (OH-). In the medium solution, hydroxide and hydrogen ions combine to form water (H2O). Over time the reaction of hydroxide and hydrogen ions decreases hydrogen ion concentration and increases the medium pH

Impacts of Different % of Ammonium on Root-Zone pH
Rose plants were grown hydroponically in a nutrient solution containing different percentages of ammonium
These effects are much more dramatic than what would occur in a commercial growing medium as it is somewhat buffered due to its chemical properties and added limestone.

Organic Matter and Nitrogen
Soil organic matter will mineralize about 20-40 pounds of nitrogen/acre/year.
95% or more of total N in surface soils is present as organic nitrogen.
Under normal growing conditions, when soils are warm, moist, and well-aerated ammoniacal nitrogen (i.e., ammonium plus ammonia) converts to nitrate in 2-3 weeks, making nitrate the most abundant inorganic form of nitrogen

Chemical Nitrogen Fertilizer Options
Advantages
Quickly available
Contains known and defined amounts of nitrogen
Disadvantages
Can have short residual times requiring repeated applications

Organic Nitrogen Fertilizer Options
Advantages
Often a free source of nitrogen
Material can also have other soil property benefits
Disadvantages
Can also come with other nutrients that may not be needed

Organic vs Synthetic Fertilizers

Link to Lecture Slides: https://drive.google.com/file/d/1jmQXmUtlNdy9iikyeTTgI29oLi8BN1cX/view?usp=sharing

*Due to the description character limit the full work cited for “Nitrogen Fertilizer Options for Cannabis Production” can be viewed at… https://drive.google.com/file/d/1I_WzKUAzkJ2-BCGna0xsBRaSih6G6ZRV/view?usp=sharing