Nutrient Management Research Database

Availability of the macroelements N and P but not K was found to influence flowering intensity and fruit set of olive trees. Fruit load increased to a maximum as leaf N increased from 1 to 1.7% and then decreased as leaf N increased further. This trend indicates the negative influence of nitrogen over-fertilization on olive tree fertility. Negative effects of nitrogen on olive oil (Fernandez-Escobar et al., 2006) and flowering quality (Fernandez-Escobar et al., 2008) heave been previously reported. Total fruit load of olives increased appreciably as P in the leaves increased. Maximum fruit load corresponded to approximately0.2% P in the leaves. Regular P application of olive orchards is not common. The results of this study suggest that under intensive growing conditions P application might be beneficially.Potassium had little if any affect on tree vigor and productivity in spite of the large range of K supplied in the irrigation solution and found in the leaves. This suggests that irrigation lowers the olive tree’s demand for K, probably as a result of higher mineral availability. Thus, in regularly irrigated orchards, K fertilizer might be reduced without threatening productivity. As olive production advances into intensive cultivation practices, including season-long application of fertilizers in the irrigation water, management of nutrient application to optimize availability for maximum production is becoming a necessity. Further research is necessary to support this study's findings under field conditions. 

Olives trees were grown in containers filled with perlite and fertilized with a range of rates of N, P, and K.

N rates varied between 5 and 202 ppm, P rates varies between 0.2 and 20 ppm, and K rates varied between 10 and 200 ppm.

N was applied at 90% as nitrate and 10% as ammonium.

Irrigation was applied to achieve 30% drainage by volume.

Measurements included total leaf N, P, and K, flowering intensity, and fruit set.

Nitrogen

Flowering intensity was controlled by N concentration, with the lowest N rate showing extremely low flowering intensity. Maximum flowering intensity occurred when leaf N content was about 1.6%.

Fruit set was maximized at the 50 ppm N rate and decreased at higher N levels. Final fruit number per tree showed a similar pattern.

Phosphorus

All P additions increased flowering intensity. Fruit set increased with increased leaf P without showing any leveling off across the P levels tested. Total fruit number shoed a similar pattern.

Potassium

Flowering intensity had mixed results with K fertilization. In year 1 of the experiment, flowing intensity increased when K concentration increased from 8 to 81 ppm. In year 2, all K treatments had similarly high flowering intensity.

Fruit set was high for all K treatments and was not related to leaf K content. Fruit number was not increased by K fertilization above 8 ppm.