How fully productive olive trees (Olea europaea L., cv. 'Chondrolia Chalkidikis') manage to over-satisfy their P nutritional needs under low Olsen P availability in soils?

The Crucial Role of Soil Organic Matter in Satisfying the Phosphorus Requirements of Olive Trees (Olea europaea L.)

“…The application of Spearman correlations indicated that acid and alkaline phosphatases followed the same pattern, showing a negative correlation to Pext (Figure 5a,b). These results are in agreement with those of Song et al [40], who also found a negative correlation between acid and alkaline phosphatase activity with available P, thus indicating that Pext estimation may depict only the current status of available P but not the latent capability of the system to release P through phosphatase activity [21]. However, they found a positive correlation between phosphatase activity and organic P and suggested that organic P fractions may be more useful tools to evaluate phosphatase activity and the capacity of the system to obtain labile P. In our study, inorganic fertilization inputs in the LOM plots possibly suppressed the activity of phosphatases.…”

“…This means that foliar nutrient determination may be a more representative procedure than soil analysis to evaluate the nutritional status of olive trees. These results are in accordance with those of Ferreira et al [7] and Chatzistathis et al [21] and verify the second objective of the study, suggesting that soil analysis is not sufficient to provide reliable results about proper fertilization guidelines.…”

“…Since LOM and MOM fields received external inputs of inorganic P fertilizers, which is a direct way to increase the available P pools, Pext was expected to be higher in these than HOM, where only organic inputs were applied. Chatzistathis et al [21] also studied the response of olive trees to P mineral fertilization and found that inorganic and total P, as well as Pext, were significantly increased compared to the non-fertilized trees. The foliar analysis (Figure 4) showed that the trees grown in HOM fields presented over-sufficient P concentrations, similar to those found in the LOM and MOM sites.…”

“…Although the influence of P application/fertilization on olive trees' nutrition and physiology has been studied extensively [7,19,20], no attention has been paid to the combinational effect of soil organic matter content and irrigation on the satisfaction of the P nutritional needs of olive trees. According to our knowledge, only Chatzistathis et al [21] indicated the beneficial influence of organic matter on the satisfaction of P nutritional needs in fully productive olive trees; however, in their study, the effect of irrigation on foliar P nutrition was not included, and different SOM levels were not included. Thus, the novelty of this study consists of the combinational investigation of three organic matter levels (low, medium and high) and irrigation on soil and foliar P in mature olive trees.…”

“…Irrigation was performed with a drip irrigation system (with approximately 300-500 mm water, in five equal doses, during the period from May to September). Furthermore, weed cut and pruning material was left on the soil surface to enrich organic C and nutrient recycling [21,22]. The altitude of the experimental groves varied from 0 to 600 m above sea level.…”