『Abstract
This work aimed to evaluate the impacts of the organic fertilization
and the use of green manure (GrM) on the different soil P fractions
in areas under organic agriculture in the municipality of Ubajara,
state of Ceara（後のaの頭に´）, Brazil. The work
was carried out in an organically cultivated farm situated in
the Ubajara municipality, state of Ceara（後のaの頭に´）,
Brazil. Soil samples of a sandy soil were collected at the 0-
to 50-, 5- to 10-, 10- to 20-, 20- to 40- and 40- to 50-cm layers
in areas of Caribbean cherry with (+) and without (-) previous
incorporation of GrM in the rows (+GrMr and
-GrMr) and between-rows (+GrMb-row
and -GrMb-row). Area under natural vegetation
(NV) was also sampled and considered as reference. P fractionation
was performed by using a sequential extraction scheme adapted
from Hedley. The cultivated systems presented higher P contents
than NV, mainly in the most labile P pool (res-Pi
+ NaHCO3-P), indicating that organic management
favoured greater P cycling of this fraction. In the cultivated
areas labile P pool accounted for 20, 17, 21 and 27％ of sum of
soil total P in the -GrMr, -GrMb-row,
+GrMr and +GrMb-row,
respectively. There was an increment of 86％ in the organic P pool
in the organically cultivated areas in relation to the NV. The
organic management promoted an increase on the available-P forms
by avoiding and/or decreasing the rate of transformation of the
Pi in more stable P forms, enhancing the
P cycling. The use of green manure promoted increase on the most
labile P pool (Resin-P + NaHCO3-P) and seems
to contribute to the P incorporation into biological cycle. On
the other hand, the risks of P losses in the organically managed
areas should be considered and suggest a scientific remark to
farmers for a better management of organic farming in sandy soils.
Keywords: C and P pools; Green manure; Compost; P leaching』
1. Introduction
2. Materials and methods
2.1. General description of the study site
2.1.1. Caribbean cherry with green manure (+GrM)
2.1.2. Caribbean cherry without green manure (-GrM)
2.1.3. Natural vegetation (NV)
2.2. Sampling and P fractionation
2.3. Statistical analyses
3. Results and discussion
3.1. Soil P fractionation
3.2. Soil P movement
4. Conclusions
Acknowledgements
References