EFFECT OF CHLORIDE AND NITRATE SALTS ON GROWTH AND MINERAL COMPOSITION OF AVOCADO AND CITRUS ROOTSTOCKS

This investigation was carried out during two successive years (2000 & 2001)
in an orchard for sub-tropical fruits located in Abou-Rwash district, Giza Governorate,
Egypt. Two rootstocks of avocado (Persea americana Mill.), the salt-tolerant "Hass"
and the salt-sensitive "Duke" and two rootstocks of citrus, the salt tolerant "Rangpur"
lime (Citrus limonia) and the salt-sensitive "Volkamer" lemon (Citrus votuemerene;
were grown in a sandy soil and irrigated daily with nutrient solutions containing
various chloride concentrations. Increasing the concentration of chloride resulted in elevated chloride levels in
avocado leaves, and toxic symptoms that were more pronounced in the "Duke" than in
the "Hass" avocado rootstocks. When leaves of both rootstocks had accumulated
similar chloride levels and showed scorching damage, the leaves of "Hass" abscised,
while those of "Duke" did not. High chloride reduced the total dry matter yield of the
root more than that of the leaves. Addition of nitrate to the irrigation water reduc~d chloride accumulation in the
leaves and alleviated its adverse effects. High nitrate reduced phosphorus levels and
caused chlorosis in young leaves. Citrus rootstocks responded similarly, but leaves of
the chloride-sensitive "Volkamer' accumulated more chloride than "Rangpur". Nitrate
reduced chloride accumulation and toxic symptoms in the leaves of the two citrus
rootstock.