Articles
SOIL AND NUTRIENT AVAILABILITY UNDER PROTECTED CULTIVATION
Most of the fertilizer requirements are usually supplied by irrigation water which is often given by sprinkler and trickle systems of irrigation.
Base dressing of phosphorus and potassium are supplied under certain conditions.
In spite of the fact that plant development depends mainly on nutrient supplied with irrigation water, both of those nutrients added or found initially in the soil undergo various chemical reactions depending on the conditions prevailing in the soil.
The soil factors that may affect the nutrient availability to plants are: soil texture, pH, calcium carbonate content, E.C., organic matter, temperature and moisture content.
Nitrogen fertigation has received the greatest attention and is applied in the forms of ammonium, nitrate and urea.
These forms of nitrogen interact differently with soil.
In calcareous and alkaline soils, the use of ammonium has sometimes considerable advantages over the use of nitrate as the pH drops in the rhizosphere.
N2 and K achieve good movement and diffusion, they become more available for absorption in the active root zone.
On the other hand, P mobility in the soil is more limited but improves under fertigation.
Micronutrient deficiencies are common in the newly reclaimed sandy and calcareous soils, some alluvial soils are considered marginal with respect to Zn and Fe availability.
Both chelate and sulfate forms of Fe, Mn, Zn and Cu gave good results to cover deficiency when used with irrigation water.
Chelates are generally highly water soluble at a wide range of pH but inorganic forms may react with Oh, Co