Monitoring report on plant nursing

The results clearly showed that plant variety did not influence the characteristics of the substrates, since the same trend of chemico-physical and biological parameters was observed in both cultivars in both countries. On the other hand, the plant species seemed to affect the micro and macro element behavior. In fact, they increased at the end of the vegetative cycles of strawberry and lettuce, suggesting a release and a low plant adsorption; on the other hand, they decreased in the pomegranate trials probably for a higher pomegranate absorption. This trend was in accordance with that of biochemical activities, since in strawberry and lettuce they remained constant or decreased over the time probably due to the sufficient nutrient content and a probably inhibition by their specific products. In pomegranate, enzyme activities generally increased over the time, suggesting an activation of microbial population that could be due to a development of roots, surely more significant than in the other plants (strawberry and lettuce). However, in all the substrates, a low organic matter mineralization, due to the stability of the substrate and a reduction in heavy metals (absorbed by plants), in particular in sediment substrates (TS 50-TS100), was found. Also an increase over the time of N-NO3 was generally detected, indicating an improvement of physical characteristics and a better oxygenation of these substrates. In conclusion, it can be affirmed that the agronomic and functional properties of all the substrates were probably acceptable for plant growth and development also in the substrate prepared just with sediments. Of course, the chemical and biochemical results of the agronomic substrates should be compared and discussed with the results of plant growth and physiology. Through the cultivation in two different environments (Italy and Spain) the possibility to cultivate the selected model food plants in containers using sediment-based substrates was assessed; the very low or absent mortality rate in lettuce, strawberry and pomegranate gave evidence of this. Strawberry, pomegranate and lettuce plants grew well on sediment-based substrates, nevertheless some observations need to be done. Lettuce heads grew well on TS50 sediment-based substrate, but slower than in TS0; on TS100 growth was very slow and the final lettuce heads weight was lower if compared to that of TS0 and TS50. Main differences which could be observed between lettuce heads grown in the 3 substrates regareded leaf colour, size of leaves, head diameter, fresh and dry weight of heads (relevant differences at same date, ranging from about 100 g per lettuce head in TS100, 135 g in TS50 and about 200 g in T0). The latter differences tend to be less evident if lettuce heads on TS50 and TS100 are grown for 7-15 days longer. Sediment based substrates, at all sediment concentrations, have shown to be good for pomegranate plants development and no cultivar effect was observed; the null mortality and a similar growth of trunk and tree height, indicated that the different substrates did not affect the vegetative growth of pomegranate. The size of the tree was significantly higher in the TS0 treatment, although neither the production nor the size of the fruit was affected in the TS50 treatment compared to the control, but they were affected in the (TS100) and values were lower. Surprisingly, in Spain pomegranates produced fruits at the second year of cultivation also in TS100. After two years of cultivation fresh and dry weight (whole plant, aerial part and root), root length and heavy metal and nutrient presence from destructive analysis were also recorded; no dead plants were found, and all growth parameters resulted similar. Strawberry plants grew well on sediment-based substrates but a relevant cultivar effect was noticed; dealing with sediment concentration in the substrate no relevant differences were observed between TS50 and TS0 performances; in general, TS100 affected negatively plant growth and the related parameters remained below to the other two treatments. Furthermore, the use of treated sediment-based substrates affected fruit production and size of fruits, mainly the TS100 treatment. Furthermore, the sediment-based substrates allowed to save water for irrigation: between 6% (TS50) and 28% (TS100) of the volume of water applied to the control (TS0) in strawberry and between 13% (TS50) and 26% (TS100) of the volume of water applied to the control in pomegranate. The use of a substrate made of only sediment could be used only for the cultivation of some species (i.e. it should be possible cultivate pomegranate); decreasing the sediment percentage in the substrate to 50% or less could allow crop growth and productivity very similar to those obtained using a common peat based commercial substrate. It would be advisable to fine-tune the optimum mixing percentage since the results for this have been quite promising. Moreover, it would reduce the peat consumption for food crops cultivation in container and the volume of water applied for irrigation. As a final statement, we can say that the three treatments obtained a similar vegetative growth, although regarding the production and morphology of the fruit, the TS100 treatment was below the other two treatments (TS0 and TS50) in some measured parameters. It would be convenient to study other percentages of sediments in the substrate between TS0 and TS50 and between TS50 and TS100, to optimize the results. Decreasing the sediment percentage in the substrate (< 50%) could allow crop growth and productivity very similar to those obtained using a common peat based commercial substrate.