Joint International Conference on Long-term Experiments ...

some pathogen agents, a chemical and thermic disinfection is necessary, with hot vapors
(150 o C), at 90 o -95 o C, for 6-7 hours, at 30cm deep.
The manure doses are 80-100t/ha once a year in greenhouses with older cultures and
twice a year (cycle I and cycle II) in new greenhouses (Davidescu D. and Velicica
Davidescu, 1992; Ciofu et al, 2003).
Composted birds manure can be also applied with 3 months in advance in doses of 15-
25t/ha and forestry composts from resins bark or beech (Rusu, 1993).
In greenhouse conditions, the mobility of nutritive elements from the organic manure is
more intense than at the same culture in the field, thus considering that for each 100t manure
in a vegetation cycle in the soil it is liberated in average: 250-300 kg N, 120-170 kg P2O5
and 350-450 kg K2O (after Davidescu D., 1992, cited by Avarvarei, 1997).
The technological steps for optimizing the content of organic matter (MO) is a
compulsory request for this technology, so that every interpretation and practical measure
takes into account this value of the organic component. An optimized agrochemical support
solves the nutrition effects and prevents or diminishes some disturbing factors (salinitysalinization,
acidity-acidification, toxicity of other ions, polluting effects) (Rusu, 1968,
1988).
2./ The agrochemical optimization of the reaction state and of the content of soluble
salts in the soil from the greenhouse at tomato culture
As regards the optimization of the content of soil in nutritive elements, the concentrations of
the nutritive ions have to be guided towards the levels of optimum sufficiency in soil, after
fertilizations.
The greenhouse soils are frequently prone to salinization and alkalization, following
the accumulation of soluble salts obtained from the fertilization with organic and chemical
manure, irrigation water, water from the phreatic layer and the process of chemical
alteration of the soil mineral fraction.
The soil disinfection using vapors in greenhouses has the effect of increasing
salinization due to the acceleration of the transforming process of the ammoniac azoth
(NH +
4 ), which inhibits the activity of nitrification bacteria. These two processes lead to a
temporary accumulation of NO2 (Davidescu D. and Velicica Davidescu, 1992).
Heavy irrigation water, as well as the superficial phreatic layer, constitutes a source of
enriching the surface soil layer with mineral salts (bicarbonate, carbonate, chlor, sodium
sulphate, magnesium).
Sweet irrigation waters (rain water) diminish the salinization effect with the dilution of
the soluble salts.
For this reason, shortly after being in use, the reaction of the greenhouse soil tends to
become neuter-alkaline or even alkaline, fact that has negative influences on the cultures
development.
The application of the amendments is imposed when the value of pH exceeds 8.5.
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