Winery and distillery derived materials as phosphorus source in calcareous soils

- The effect of winery-distillery wastes addition on soil P availability was studied.
- Two calcareous soils typical from the grape-growing areas were used.
- Available P in soil increased regardless of the amount of P applied.
- Modification of soil pH and organic matter dynamics could also affect these changes.
- P released in excess is accumulated in soil as poorly soluble calcium phosphates.

The depletion of phosphate rock reserves makes necessary the finding and characterization of new phosphorus (P) sources to ensure a sustainable P fertilization. This research deals with the effect of the application of organic materials derived from the winery and distillery industries on P availability in two calcareous soils. Soils were treated with five organic materials providing different amounts of P: two raw wastes (exhausted grape marc and grape stalk) and three composts made with different proportions of these materials or including cake lees as well. The soils were incubated for 16 weeks determining soil pH, dissolved organic carbon and Olsen P in five samplings with time. At the end of the incubation, inorganic P was fractionated to NaOH-NaCl-P, citrate-bicarbonate-dithionite-P (CBD-P), and HCl-P and the P sorption index (PSI) was also determined. The increment in Olsen P was firstly positively related to the amount of P applied, being higher in the composted materials, but along time the effect of other factors such as the organic matter incorporation influenced these changes. After 16 weeks of incubation, the enhancement of Olsen P produced by the different materials equalized (8.9 mg kg− 1 on average), despite of the different amounts of P applied with each one. Increasing the P applied with the organic materials in these soils enhanced P retained in the sparingly soluble P fraction (HCl-P) whereas the addition of raw materials slightly released P from this fraction, recovering more P in the most labile pool (NaOH-NaCl-P). It can be concluded that the winery and distillery derived materials had a positive effect on soil P availability and that P in excess would be retained due to the calcareous nature of these soils, avoiding contamination risks.