M. Tagliavini et al., Agronomic means for the control of iron deficiency chlorosis in deciduous fruit trees, J PLANT NUT, 23(11-12), 2000, pp. 2007-2022
Iron deficiency induced chlorosis represents the main nutritional disorder
in fruit tree orchards grown on calcareous and/or alkaline soils. Until roo
tstocks tolerant to Fe deficiency chlorosis are available for most suscepti
ble fruit species, the agronomic means of preventing or curing Fe deficienc
y chlorosis will be considered of utmost importance by fruit growers. Chlor
osis of fruit trees has been successfully controlled through foliar or soil
applications of Fe chelates, which are expensive and have to be applied an
nually. In this paper results of research carried out within an EU joint re
search project are reported, where the effectiveness of alternative, low-in
put, environmentally friendly management techniques to control Fe deficienc
y chlorosis has been tested in established kiwifruit, peach and pear orchar
ds located in the Po Valley (Italy), in the Ebro Valley (Spain) and in the
area of Imathia (Greece). Iron sulphate supply to the soil proved to be eff
ective only if applied together with high amounts of organic matter such as
compost or manure, Promising results in preventing chlorosis were obtained
by sowing a mixture of graminaceous species along the tree row and supplyi
ng them with Fe sulphate. Laboratory tests indicated that long lasting decr
eases of pH in calcareous soils are difficult to achieve. We have also foll
owed two approaches using foliar sprays: 1) testing a variety of compounds
which may activate the Fe pool likely present in chlorotic leaves (citric,
sulphuric, ascorbic and indole-3-acetic acid) and 2) applying Fe sources al
ternative to synthetic Fe chelates. Sprays aiming to activate the Fe pools
in a chlorotic leaf were generally effective, although rarely caused a full
recovery. This suggests that inactivation of Fe occurs outside the mesophy
ll cells. Sprays of Fe sulphate in all the crops tested showed similar or e
ven higher regreening effect than FeDTPA.