Plant Growth-Promoting Rhizobacteria and Chabazite Zeolite in the growth stimulation and protection of Sedum palmeri and Sedum sieboldii from aphid and red spider mite attack

Abstract

Research objective: The aim of this research was to evaluate the interaction that can develop between zeolite and microorganisms with beneficial effects on both the growth of Sedum palmeri and Sedum sieboldii and in the defence against Aphis sedii and Tetranychus urticae. Materials and Methods: The experiments, which started in January 2023, were conducted in the CREA-OF greenhouses in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E). The plants were placed in pots with a diameter of 12, 10 plants per 3 replications, for a total of 30 seedlings per experiment. The Sedum trial included the following theses (irrigated and fertilised): peat 70% + pumice 30% (CTRL); peat 70% + pumice 10% + chabazite natural zeolite 20%; peat 70% + pumice 30% + microorganisms (Azospirillum brasilense, Pseudomonas kilonensis and Bacillus aryabhattai), 1g/Kg of substrate at the time of substrate preparation; peat 70% + pumice 10% + chabazite natural zeolite 20% and micro-organisms (the same as those used in the thesis described above) in the same dosage. A second parallel experiment to control aphids and red spider mite involved: water treatment; treatment for aphids and red spider mite (soft potassium soap and azadirachtin 2.5 ml/l once a week; Kanemite 3 ml/l once a week); treatment for aphids and the alternative red spider mite (micronised zeolite 15g/l and microorganisms 1g/l, once a week). Plant height, leaves and flowers number, vegetative weight, root volume and length, microorganisms in the substrate, number of plants affected by aphids and red spider mite were determined on 15 September 2023. Results and Discussion: The experiment showed that the use of chabazite zeolite in combination with microorganisms can indeed significantly improve the vegetative and root growth of Sedum palmeri and Sedum sieboldii plants. Differences in growth between the use of zeolite and microorganisms and the untreated control are evident, with a significant improvement when the two theses are combined for all agronomic parameters analysed. In the substrate analysis, a greater presence of microbial biomass was found in the theses with zeolite, microorganisms and zeolite together with microorganisms than in the control theses, with a greater superiority of microorganisms in the substrate when zeolite and microorganisms are used in combination. The trial with micronised zeolite and microorganisms showed a significant result on the control of aphids and red spider mites, with data comparable to those of treatment with conventional chemical products. Zeolites are used successfully in the cultivation of many crops. Including cereals, vegetables, grapes and other fruits. By enhancing the absorption ability of soil, zeolite enhance the long-term quality of soil by retaining nutrients. Conclusions: For agricultural production, zeolites must have uniform properties and unique characteristics, such as cation exchange capacity and pH. Especially in agriculture and plant cultivation, zeolites improve their exchange capacity with the soil and plants through microbial activity. By lowering the pH of the substrate, microorganisms are able to solubilise the minerals retained by the zeolites, making them more available to the roots. Furthermore, zeolites, when micronised on the leaves, do a good job of protecting plants from insects and fungi, especially when used as a preventive measure. This can also ensure a significant reduction in synthetic chemicals and improve plant protection when these strategies are used in combination.