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VALUE OF A BIOLOGICAL TEST FOR ESTIMATING THE INFLUENCE OF SOIL TYPE, PREVIOUS CROP AND SOIL STERILIZATION ON THE GROWTH OF PEACH AND APPLE
For each soil type, samples were taken from two different sites, each site being planted with two different crops: on the loamy soil apple or vine were grown, whereas the sandy soil was planted with peach or vine.
To study the effect of soil sterilization on soil sickness, seedlings were transplanted to non-sterile or autoclaved soil belonging to each of the above mentioned sites.
Results of this study demonstrate that:
- The influence of soil type on the growth of apple is predomimant, whereas on peach its influence is very weak.
- The previous crop does not affect the growth of apple seedlings whereas its effect on peach is very strong.
- Steam treatment stimulates the growth of peach trees, on apple its influence is slight or even negative.
The interactions between the three categories of treatment are sometimes strong and inpredictable, therefore it is imperative to take them into account for the correct interpretation of this type of experiment.
Among the eight criteria chosen to measure the growth rate of the trees the weight at the end of the experiment (6 months after transplantation) is the most sensitive for the peach and the number of leaves does not supply much information : it is exactly the reverse for the apple seedlings.
The height of the trees just before emergence of laterial shoots is a good criterium for the two plant tests allowing to give quick results (4 – 6 weeks after transplanting) thus allowing to conduct a greater number of tests in a limited space.