Optimizing the Efficacy and Use of Vermicasts Dr. Lord Abbey, P.Ag; Cert. Ad. Ed. Instructor/Researcher, Hort. Production Assiniboine Community College, Brandon, MB Presented at the 23 rd Annual National Compost Conference, Sept 11-13, 2013, Toronto, ON
Overview Background information Objectives of the study Experiments: Drying of vermicasts Rehydration of dried vermicasts Comparison of nutrient contents: FMV vs ODV Nutrient-release profiles of FMV vs ODV Seedling growth following medium amendment Summary/questions/discussion
What is vermicasts? Vermicast is fine textured, pure excreta eliminated from the digestive systems of worms Vermicasts contain macro- and micro-nutrients Vermicasts contain organic compounds collectively termed humic substances i.e.: Humins Humic acid Fulvic acid PGHs & PGRs
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Importance of vermicasts: Vermicasts improve soil structure & nutrient content It improves soil water & nutrient retention through its hydrophilicity & improved soil structure It also improves plant tolerance to biotic and abiotic stresses Ultimately, it enhances plant growth, yield & quality These suggest that vermicasts have significant potential for commercialization
Limitations to the use of vermicasts: Non-adaption to mechanization in their moist and friable state Production, storage and application are not standardized Variations in bulk density (0.16 0.5 g/cm 3 ) Variations in moisture content (13-78%) Unknown shelf-life Often unattractive
Objectives of study: To determine the rehydration pattern of ovendried vermicasts (ODV) To compare nutrient-release profiles and efficacies of fresh, moist vermicasts (FMV) and ODV on the growth of seedlings
Experiments Drying of vermicasts: To determine drying curve characteristics 100-g samples (n=4) of FMV were dried Static-bed oven-dryer @ 75 o C Equilibrium moisture content (EMC)=2hrs Moisture factor (MF)=1.6 w/w
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Micropores 140 120 100 80 60 40 20 Macropores EMC 0 0 30 60 90 120 150 180 210 240 Drying time (min)
Rehydration of oven-dried vermicasts: To determine water re-absorption pattern 20 g of ODV was tied in a cheese cloth This was put in a 2-L polyethylene bag Covered with moist potting mix at 75% field water-holding capacity The cheese cloth and the vermicasts were weighed before and after different time intervals
Micropores Saturation phase Macropores Crevices Wetting
Nutrient content: Table 1: Comparative analysis of nutrient content of FMV and ODV Moisture content DM content Bulk density EC Total N Total P 2 O 5 Soluble K 2 O Treatment (dwb) (%) (g/cm 3 ) (µs/cm) (g/kg) (g/kg) (g/kg) FMV 42 58 0.48 5300 8.05 4.65 5.51 ODV 2 98 0.55 5400 14.01 7.72 10.01
Nutrient-release profile: Comparative analysis of bioavailability 48 g of FMV or 30 g of ODV (MF=1.6) was wrapped in a triple layer cheese cloth and tied Each was separately immersed in 400-mL distilled water The solution was stirred prior to recording the salinity and electric conductivity (EC)
Rapid release Saturated layer & water entry into core of granule
Effects on seedling growth: To determine effect on plant growth Test plant: Collards (Brassica oleracea var. Acephala cv. Champion) Treatment: Mix of 800 g coir and 68.5 g of FMV or 42.8 g ODV 800 g of coir alone (control) CRD with five replications Final harvest was done 5WAS
Table 2. Effect of FMV vs ODV on growth of collards seedlings Length of Stem dia Stem FW Trt #Leaves/plnt leaf blade (cm) (mm) length (cm) (g) Control 2.0b 0.73b 1.02b 2.33b 0.07b FMV 3.5a 7.48a 2.38a 6.48a 1.63a ODV 3.8a 7.70a 2.40a 5.93a 1.91a Mean 3.1 5.3 1.93 4.91 1.2 Means with the same letter within a column are not significantly different at α=0.05, Least significant difference (LSD)
Summary: Quality characteristics of ODV is retained suggesting potential use on commercial scale Vermicasts at an initial MC of 42% can be oven-dried @ 75 o C for at least 2 h to attain EMC Heat treatment increased bulk density, %DM and nutrient content There was similarity in the efficacies of FMV and ODV in terms of nutrient-release and nutrient available for plant uptake Reference: Abbey et al. (2013). Drying and rehydration of vermicasts do not affect nutrient bioavailability and seedling growth. American Journal of Plant nutrition and fertilization Technology, 3(1):12-21.
Thank You!! Contact: abbeyl@assinibpone.net