Application of a glass fertilizer in sustainable tomato plant crops

Glass frits with a P₂ O₅ /K₂ O ratio equal to 0.65 and different concentrations of SiO₂ (6.5-56.0 wt%), CaO (0-5.1 wt%) and Al₂ O₃ (0-14.6 wt%) have been prepared and analysed as potential glass fertilizers (GF).

P₂ O₅ and K₂ O were leached primarily within the first 5 days but the total amount was dependent on the SiO₂ /Al₂ O₃ ratio of the glass frit. Sustained P₂ O₅ and K₂ O leaching for more than 40 days could be obtained if the glass frit contained more than 7% Al₂ O₃ . A final glass frit composition (29% SiO₂ , 5% CaO, 7% Al₂ O₃ , 30% P₂ O₅ , 25% K₂ O) was selected and used in an experimental tomato crop of 1 ha area, where one half was fertilized with an NPK conventional fertilizer and the other half with the GF fertilizer.

After harvesting the tomato crops, the GF fertilizer was found to result in a higher yield than the NPK conventional fertilizer: 59980 kg and 74 360 kg for NKP and GF, respectively. The general characteristics of the harvested tomato fruits and leaves were similar in the two cases and the differences fell within statistical error. No differences in any of the soil characteristics were detected as a result of the use of GF. © 2018 Society of Chemical Industry.