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Soil samples were collected in the plots treated with : i) no input (CONTR); ii) fenamiphos (300 kg ha -1 )
(F.MPHOS); iii) raw sewage (80 mc ha -1 ) (R.S.); iv) exhausted pomace solid cake compost ( 20 t ha -1 ) (EOPC); v) fresh
pomace solid cake compost (20 t ha -1 ) (FOPC), after the treatments and harvesting to evaluate soil N-NO3, N-NH4
exchangeable, NaHCO3 - P (Olsen method), exchangeable bases, CEC, heavy metals concentration , total organic
carbon (TOC), total extracted (TEC) and humified carbon (humic and fulvic acids, C HA + C FA ) (Sequi et al., 1986;
Italian Ministry of Agricultural Resources, 1994). The degree of humification, DH% = (C HA + C FA )/TEC*100, the
humification rate, HR% = (C HA + C FA )/TOC*100, and the humification index, HI= NH / (C HA + C FA ), were also
calculated.
Data were statistically analysed by the analysis of variance and means compared by Duncan’s Multiple Range Test
(P=0.05).
RESULTS AND DISCUSSION
In the field experiment all the composts significantly increased the tomato yield compared to the untreated control,
but were statistically lower than chemical treatment (Table 1).
All the treatments significantly reduced the root infestation index and, with the exception of the lowest rates of raw
sewage and exhausted pomace compost, the soil nematode population (Table 1).
Results from this experiment and their comparison with those from the previous field experiments evidenciated that
incorporation of OMW into the soil could result in a suppression, but not in a complete eradication of phytoparasitic
nematode populations and, at low initial soil infestation, also in a crop yield increase. Therefore, the aim of soil
amendments with these materials should be a progressive reduction of infestation level under the tolerance limit of the
target nematode species (Sasanelli, 1994).
Table 1 - Effects of different olive mill wastes amendments on Meloidogyne incognita on tomato (cv. Tondino di
Zagaria).
Treatment
Dose
(t x
ha -1 )
66
Tomato
yield
(t x ha -1 )
Root gall index
(0 – 5)
Eggs and
juveniles/cm 3
soil
Untreated control - 25.4 a 4,5 b 19.8 d
Fenamiphos 0,3 40.5 e 2,7 a 10.6 abc
Raw sewage 4 32.3 bc 2,4 a 15.1 cd
8 29.0 b 2,5 a 5.2 a
Exhausted olive pomace compost 10 36.8 d 2,1 a 13.7 bcd
20 36.6 d 2,2 a 9.2 abc
40 36.3 d 2,2 a 11.2 abc
Fresh olive pomace compost 10 32.1 bc 2,8 a 5.3 a
20 33.7 cd 2,2 a 7.1 ab
40 35.8 cd 2,6 a 9.3 abc
Data are means of four replications; data followed by the same letter on the same column are not significantly
different according to Duncan’s Multiple Range Test (P = 0.01).
In the Figure 1 A can be observed a poor increasing trend of soil N-NO3 contents respectively for “R.S.”,
“EOPC”, “FOPC” treatments and lowest N-NO3 content in “fenamiphos-treated” plots.
Soil NaHCO3-P content was unaffected from experimental treatments, but soil exchangeable K showed higher
value in "fenamiphos-treated" plots (Figure 1A). On the contrary, in “FOPC-treated” plots higher “exchangeable-Ca”
content was recorded , while similar trends were observed in exchangeable Ca in “fenamiphos-”, “R.S.-”, “EOPC-
treated” plots. No differences were observed on exchangeable Na and Mg among treated plots compared with the
“control” (Figure 1 B ).
Among the heavy metals of the soil (Figure 1 C ), only Zn content was higher in “EOPC-“ and “FOPC-treated”
plots probably because during the composting processes of solid residual cake of olive milling ( fresh or exhausted ) a
Zn concentration could be verified.
Soil organic C (Figure 1 D) contents (total and extracted) seem lower in the plots treated with OMW (raw or
composted) in comparison to other treatments, because the incorporation into the soil of fresh organic matter improves
biological activity (Ocio et al., 1991). No variations were recorded on humified organic C, probably for the short period
of trial.
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