Agriculture Reference
In-Depth Information
Adapted from University of Idaho guidelines
Nitrogen
Nitrogen is essential to plants and is the nutrient most often deficient in
orchards. In conventional orchards, nitrogen is easy to add in the form of
rapidly available industrial fertilizers, and it is seldom added before plant-
ing trees unless soil concentrations are very low. The situation for organic
orchardists is less clear because many organic nitrogen fertilizers become
available to plants relatively slowly. In some organic orchard trials, the es-
tablishment and growth of trees in organic plots treated with organic ni-
trogen fertilizers was very poor when compared with adjacent conventional
treatments. The problem has likely been due to low amounts of available soil
nitrogen and the inability of growers to rapidly increase available nitrogen
to the newly planted trees using slow-release, organic materials.
Compounding the problem is that the nitrogen cycle in the soil is very
complex, and nitrogen is constantly shifting from one chemical form to an-
other as it moves through micro- and macroorganisms and plants. Rather
than simply looking at nitrogen (NH and NO ) concentrations in a soil test
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report, a better guide to available nitrogen for a planned orchard is to look
at the soil test results for organic matter. As organic matter decomposes in
the soil, it adds nitrogen that is available to the plants.
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