Use of different spent oyster mushroom substrates as soil amendment on the establishment and growth of Spinacia oleracea L. and Beta vulgaris L.

MSc (Agriculture (Crop Science), North-West University, Mafikeng CampusSpent mushroom substrate (SMS) refers to the residual substrate that remains after mushrooms have been harvested. SMS is known to improve the ecological soil status such as improved microbial and biochemical activities when employed as an amendment. A pot experiment was carried out to investigate the growth response of Spinacia o/eracea and Beta vulgaris to three types of spent oyster mushroom substrates and these were; Urochloa panicoides; Zea mays and 0atura stramonium. Soil amendments were carried out in the proportion of 60 soil: 40 substrate (v/v) for each of the respective substrates. Three seeds of S. o!eracea and B. vulgaris were directly planted in each respective pot (25cm in diameter) and grown for a period of 12weeks. The experimental treatments were generated from mixtu res of soil and SMS of different plant species as follows: (i) U. panicoides; (ii) Z. mays; (iii) 0. stramonium; (iv) Substrate mix and (v) Un-amended soil (control) for each vegetable type and these were replicated eight times making a total of forty (40) experimental units for each respective vegetable type. The experimental units were arranged in a Complete Randomized Design (CRD). For both vegetables, results indicated significant differences of different growth media on seedling emergence, seedling height and total root biomass (PS0.05). First seedling emergence of Spinacia oleracea was observed eight (8) days after planting (OAP) and reaching full emergence on the seventeenth (17) OAP. S. o/eracea seedling emergence percentages for all four respective amended soils ( U. panicoides, Z. mays, 0 . stramonium and substrate mix) was 100% and the un-amended soil had 91 .75%, thus were found not significant at PS0 .05 . Similarly B. vulgaris also had 100% emergence for seedlings grown on the four amended soils. U. panicoides and un-amended soil had 87.63% and 95.87%, respectively and were statistically significantly different (PS0.05). The different SMS had a statistically significant influence on seedling height of S. o/eracea (PS0.05). The growth assessments from the respective treatments were as follows: Z. mays (27.26cm), 0. stramonium (25.09cm), substrate mix (21 .2cm), un-amended soil (16.53cm) and U. panicoides (13.83cm) was the lowest. A similar trend was observed on B. vulgaris seedlings; however, the lowest was observed on seedlings grown on un-amended soil (12 .06cm). Various SMS had a significant effect on the total dry root biomass of S. oleracea and B. vulgaris seedlings. The highest total dry root biomass recorded was 8.519-1 for S. o/eracea seedlings grown xv on Z. mays amended soils and the lowest was seedlings grown on un-amended soil (0 .209-1 ) . For 8. vu/garis, the highest dry root biomass recorded was on seedlings grown on D. stramonium (12 .919-1 ) and seedlings grown on un-amended soil had the lowest root biomass (0.599-1 ). The in-vitro investigation on the suppressive effects of SMS on commonly occurring soilborne pathogens, such as Rhizoctonia solani and Fusarium oxysporum was evaluated by assessing the mycelial growth of the two respective pathogens in a PDA infused with respective substrates extracts. The study indicated that mycelial growth of R. solani and F. oxysporum on Z. mays extract infused PDA had the lowest mycelial growth recorded (16mm and 16.2mm). This was probably an indicative of antifungal properties which better inhibited the growth of both R. solani and F. oxysporum in PDA infused with Z. mays extract. The following mycelial diameter growths of R. solani were recorded : unamended soil 72mm; U. panicoides 37.25mm; D. stramonium 46.50mm and Substrate mix 38mm. Similar results were also noted on mycelial growth of F. oxysporum. The findings of this study have shown that use of spent mushroom substrates as a soil conditioner for horticultural plants improved plant growth and also had suppressive effect on soil-borne pathogens. It was also noted that there was variation between the different substrates in their effect as crop growth enhancement and disease management. It is therefore recommended that different biomass found in various respective farming areas should be evaluated and assessed for their performance as soil amendments and as suppressant for soil-borne pathogens.Master