LIBRO-CONGRESO-CITRUS

S10
on gray upland soil were used. Phosphate and potassium fertilizers were applied at rates of 0% (PK0), 50%
(PK1), and 100% (PK2), with respect to the conventional amount of fertilizers (P 2 O 5 : 120 kg ha -1 , K 2 O: 240 kg
ha -1 ). Reduction in the rate of application of phosphate and potassium fertilizers had no influence on the
sugar and acid contents of the fruits. In addition, reduction in the rate of phosphate application had no
influence on the available phosphoric acid content in the soil. Phosphorus concentration in the leaves of PK0
was lower than that of PK1 and PK2; however, the concentration was within the standard range for nutritional
diagnosis- The exchangeable potassium content in the soil of PK0 was lower than that of PK2. Potassium
concentration in the leaves showed no change in all the treatments. These results show that reduction in the
rate of phosphorus fertilizer application is possible in Satsuma mandarin orchards to prevent accumulation
of available phosphoric acid in the soil. Since the level of exchangeable potassium in the soil decreased, it is
necessary to judge the reduction in the rate of potassium fertilizer application by performing soil diagnosis.
S10P28
Potassium leaching from young lysimeter-grown orange trees
Boman B. J. 1 , and Battikhi A.M. 2
1University of Florida (UFL), Indian River Research and Education Center, USA; and 2University of Jordan (UJ), Soil Science, Jordan.
bjbo@ufl.edu
A study was conducted at University of Florida Indian River Research and Education Center to determine the
effects of different fertilizer forms on the leaching of potassium to groundwater in the sandy soils common
to the area. Lysimeters constructed from polyethylene tanks were filled with Oldsmar fine sand soil. A single
‘Midsweet’ orange on Carrizo citrange rootstock tree was planted in each lysimeter. Fertilization treatments
included conventional applications of dry-soluble fertilizer at 6-week intervals, weekly fertigation applications,
and single annual applications of two different controlled release materials. Irrigation (by microsprinklers) and
drainage volumes measured with totalizing flow meters were collected weekly for two and a half years. Trees
fertilized with controlled release products achieved equivalent growth to trees fertilized by the dry soluble
materials and to those fertigated, even though the controlled-release treatment trees received only 44% of N
and K as the other treatments. The amount of K leached averaged 39% (fertigated), 45% (controlled release),
and 56% (dry soluble) of that applied. The total K leached with the controlled release fertilizer treatments
was approximately one-half that of the fertigated trees and one-third that of the dry broadcast treatments.
Leaching of K was found to be directly related to the weekly rainfall rate.
S10P29
Effect of organic fertilization on soil organic matter and on root apparatus of citrus trees
Trinchera A. 1 , Torrisi B. 2 , Allegra M. 2 , Rinaldi S. 1 , Rea E. 1 , Intrigliolo F. 2 , and Roccuzzo G. 1
1 Centro di ricerca per lo studio delle Relazioni tra Pianta e Suolo (CRA-RPS), ITALY; and 2 Centro di ricerca per l’Agrumicoltura e le
Colture Mediterranee (CRA-ACM), ITALY. francesco.intrigliolo@fastwebnet.it
The aim of this work was to verify the effect of organic fertilization on soil organic matter and on root apparatus
of mature orange trees [Citrus sinensik] ValenciaeLate, grafted on C. aurantiu., in citrus orchard organically
managed for 15 years. In a randomized block experimental design, compost from “pastazzo” (mixture of
citrus pulp and skin), poultry manure, bovine manure, compared to a mineral fertilizer, were applied yearly to
the soil (the same N/plant/year). For each plant, an equal volume of soil was sampled at the same distance
from the trunk determining, in the sampling areas, the root density (roots weight/soil volume). The root
biomass was then separated into primary and secondary roots, calculating the related fresh weight and dry
matter. Representative young roots were selected and analyzed by electron scanning microscopy (SEM). As
far as soil characterization concerns, the TOC%, TEC%, HA% and FA% were determined and then the related
HR% and DH% were calculated. Results showed that organic fertilization, when compared to the mineral one,
determines not only an improvement of soil organic matter content and humification parameters, but also
an increase of root biomass. The SEM analysis evidenced that organic fertilizers induced the appearance of
adventitious buds on the terminal portions of the roots, an improved regularity of the elongating meristematic
cells an, an increase of the production of root mucigel.
172 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012