Phytoavailability and extractability of potassium, magnesium and manganese in calcareous soil amended with olive oil wastewater

Abstract

Land disposal of olive oil wastewater using it as a soil amendment requires a knowledge of the effects that its application may produce on the status of the mineral nutrients in the plant-soil system. A pot experiment using calcareous soil was performed in a growth chamber to examine the effects of olive oil wastewater on the availability and postharvest soil extractability of K, Mg and Mn. The experiment included 6 treatments: two rates of olive oil wastewater, two mineral fertilizer treatments containing K (which supplied K in amounts equivalent to the K supplied by the olive oil wastewater treatments), a K-free mineral fertilizer treatment, and a control. The pots were sown with ryegrass as the test plant, harvesting 3 times at intervals of one month. Olive oil wastewater has demonstrated a considerable capacity for supplying K that can be assimilated by the plant, tending in fact to surpass the mineral potassium fertilizer tested. The application of olive oil wastewater tends to reduce the concentration of Mg in the plant, similarly to the effect of adding mineral potassium fertilizer. An enhancement of Mn availability takes place in the soil amended with olive oil wastewater, which on occasion has produced Mn concentrations in plant that could be considered phytotoxic or at least excessive. After harvesting, we observed an increase in the amount of exchangeable K in soil with added industrial wastewater. However, these increases are lower than those in soil treated with mineral potassium fertilizer. The levels of exchangeable, carbonate-bound, organic-bound and residual Mg in soil were higher in treatments incorporating olive oil wastewater than in those with added mineral K, with the opposite tendency occurring in the amount of Fe-Mn oxides-bound Mg in soil. Treatments based on olive oil wastewater, especially in high doses, increased the amount of exchangeable and carbonate-bound Mn in soil, in comparison with treatments adding mineral fertilizers with or without K. In contrast, the addition of industrial wastewater caused a drop in the amount of Fe-Mn oxides-bound and organic-bound Mn in soil.

Disposal of olive oil mill wastes in evaporation ponds: Effects on soil properties

“…Moreover, nitrate values were low probably due to the activity of heterotrophic denitrifiers [14] and, as has been shown in a series of incubation experiments, application of wastes to calcareous soils decreases NO 3 − production [60,35,61].…”

A review of the fate of potassium in the soil–plant system after land application of wastewaters

“…In contrast, the increases in potassium firmly bound in minerals and total potassium were not significant. Similarly, another study using olive mill wastewater on ryegrass [25] revealed a lower increase of the amount of exchangeable potassium with respect to soil treated with mineral potassium fertilizer. Differences reported in the fertilizer potential of the wastewaters are mainly derived from different initial quantities of OMWW and fertilizer applied, different environmental conditions and composition and quantities of soil clay minerals.…”

“…Wen et al [24] reported that potassium applied to crops of lettuce and snap beans was as equally available as inorganic fertilizer. Similarly, Gallardo-Lara et al [25] found that the application of OMWW significantly increased exchangeable potassium in the soil but the effect of wastewater was less than that of inorganic fertilizer. They found that the treatment significantly increased water-soluble and exchangeable potassium compared to a control treatment with potassium fertilizer.…”