LIBRO-CONGRESO-CITRUS

S10
and soil samples (0-10,10-20, 20-30 and 30-40 cm depth layers, along tree rows and between rows) were
collected from 2005 to 2009 for chemical analyses. Leaf Ca content was higher for the CM and for the
Cleopatra mandarin trees. Leaf K was higher for the MM and for the Rangpur ones. Ca and Mg in the 0-10 cm
soil layer between rows were higher for NT, and in the lower layers the contents were higher for CT. The MM
increased exchangeable K availability in all soil depths, and this management reduced the Ca content down to
the 30 cm depth layer. The establishment of orange orchards under the NT system did not cause detrimental
effects on soil fertility. On the contrary, it favored the increase of Ca and Mg in the top soil layer. The MM was
important not only for the maintenance of adequate K levels in the soil but also for the improvement of the
K recycling in the soil system.
S10P23
Response of clementine citrus to foliar potassium fertilization: Effects on fruit production and
quality
Hamza A1 , El Guilli M2 , Bamouh A3 , Zouahri A4 , Bouabid R5 , and Lfadili R6 .
1Institut National de la Recherche Agronomique (INRA), Agronomy, Morocco; 2Institut National de la Recherche Agronomique
(INRA), Phytopthology, Morocco; 3Institut Agronomique et Vétérinaire Hassan II (IAV Hassan II), Plant Production, Protection and
Biotechnology, Morocco; 4Institut National de la Recherche Agronomique (INRA), Soil Science, Morocco; 5Ecole Nationale d’Agriculture
de Meknès (ENAM), Soil Science, Morocco; and 6Institut Agronomique et Vétérinaire Hassan II (IAV Hassan II), Agronomy, Morocco.
hamza.abdelhak@gmail.com
Clementine “Cadoux” (Citrus reticulata Blanco) is a citrus fruit that is well appreciated by consumers. However,
this cultivar tends to produce fruits of small to medium size that are less accepted commercially. In this study,
we evaluated the effects of various rates and frequencies of foliar potassium fertilization, as either potassium
nitrate (KNO 3 ) or potassium sulfate (K 2 SO 4 ), on fruit production (fruit size, weight and yield) and quality
parameters (skin thickness, firmness, color index, maturity index, juice content, acidity and total soluble sugars).
Application rates of tested foliar fertilizers were 5% and 8% KNO 3 , 2.5% and 4% for K 2 SO 4 , applied either two
or three times during fruit growth on orchards of three planting densities (D1: 6 x 6 m, D2: 5 x 6 m and D3:- 6 x
3.5 m). The levels of potassium in leaves of clementine var. Cadoux increased by 40% two weeks after the last
foliar potassium application. Fruit weight increased with potassium application rate and frequency. Potassium
fertilization treatments in three foliar applications showed the best percentages of fruits of extra size class,
whatever the source of potassium (KNO 3 or K 2 SO 4 ) or plant density. Foliar applications of potassium increased
fruit color, firmness and rind thickness. Fruit juice content, acidity and total soluble sugars were slightly increased
by foliar potassium application. Raising potassium concentration and the number foliar applications increased
tree fruit production. In terms of efficiency of foliar potassium fertilizers, 4% K 2 SO 4 in three applications resulted
in a maximum gain of fruits per kg of foliar fertilizer.
S10P24
Impact of biostimulant substances on growth of Washington Navel orange trees
Mustafa N.S. 1 , and El-Shazly S. M. 2
1 National Research Center, Cairo (Citrus nutrition), Pomology, Egypt; and 2 Pomology Department, Faculty of Agriculture, Alexandria
University, Alexandria, Egypt. nabilhotline@yahoo.com
In a field experiment, Washington navel orange trees were treated with three biostimulants [potassium
humate, active dry yeast and amino green (amino acids mixture)] to study the effect of these substances on
vegetative growth and leaf contents of Na and Cl. Potassium humate was applied at 10 or 20 g/tree to the soil.
In addition, yeast extract at 0.2 or 0.4%, and amino green II at 0.25 or 0.5% were applied to the plant leaves.
The results showed that tree height, leaf area, leaf fresh and dry weights and volume index were positively
affected by the biostimulants treatments. Greater vegetative growth of trees was achieved with potassium
humate > active dry yeast > amino green. Data also demonstrated that biostimulant treatments significantly
decreased leaf Na and Cl contents compared to untreated control trees. Therefore, such substances (especially
potassium humate) can be used to reduce negative impacts of salinity in soil or irrigation water. In general,
biostimulants substances had a beneficial effect on growth performance and leaf contents of Na and Cl of
Washington navel orange trees.
170 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012