Theodore J.K. Radovich

Effects of Vermicompost Tea (Aqueous Extract) on Pak Choi Yield, Quality, and on Soil Biological Properties

This study investigated the effects of vermicompost tea (aqueous extract) on yield and chemical quality of pak choi (Brassica rapa cv Bonsai, Chinensis group) grown in three media (two soils and a peat-perlite medium) under two fertilizer regimes (compost and synthetic fertilizer). The impacts of tea application on the chemical and biological properties of the growth media were also investigated. Vermicompost teas were prepared using various extraction methods (non-aerated, aerated, aerated with additives) with 1:10 (v:v) chicken manure-based vermicompost to water dilution and applied weekly at the rate of 200 mL plant−1 for 4 weeks. Application of vermicompost tea increased plant production, total carotenoids and total glucosinolates in plant tissue. This effect was most prominent under compost fertilization. Total phenolic was lower in vermicompost tea treated plants compared to those treated with only mineral nutrient solution and the water control. Vermicompost tea improved mineral nutrient status of plants and media, and enhanced the biological activity of the media. Variability in yield and chemical quality of plants across treatments was explained largely by variability in tissue N uptake and dry matter accumulation. Dehydrogenase activity and soil respiration of vermicompost tea-treated growth media were approximately 50% higher than untreated media. This study confirmed that vermicompost tea can positively influence plant yield and quality and increase soil biological activity in multiple soil types.

Important Cabbage Head Traits and Their Relationships at Five Points in Development

We set out to document events and relationships among key traits throughout cabbage head formation, particularly in early stages, in order to help develop and implement efficient strategies to increase crop yield and quality. Head traits used as indicators of horticultural maturity and crop quality were documented at five stages of development in 3 commercial fresh market/slaw and processing cabbage cultivars grown in 2001 and 2002 at The Ohio State University, Ohio Agricultural and Development Center in Wooster, Ohio. Seedlings containing 2–4 true leaves were planted in June of both years. Trait measurement began 35 days prior to the estimated market maturity date for each cultivar and continued weekly for five weeks. Harvest timing affected all head traits evaluated. Head weight, diameter, volume, and density and core volume generally increased with harvest date, while the ratio of head polar to equatorial diameter and the percent of head volume occupied by the core decreased. A strong curvilinear relationship between head mean diameter and head weight was found. Developmental changes in head density, in contrast to weight and size, were found to be largely independent of thermal time. Information gained in this study adds to our understanding of cabbage crop development. It also strongly suggests that accurate assessments of developmental stage during the scheduling of harvest are required to maximize head quality. The results also indicate that head growth and maturation should be viewed as separate and distinct concepts in discussions of head development.

Nitrogen Release Patterns of Some Locally Made Composts and Their Effects on the Growth of Chinese Cabbage (Brassica Rapa, Chinensis Group) When Used as Soil Amendments

ABSTRACT. Due to strong demands from organic farmers, landscapers, and home-gardeners, production and utilization of composts have rapidly increased. So, there is the need for their characterization (compost quality evaluations, particularly their nutrient releasing characteristics). In this study, three vermi-composts, six thermo-composts, and a green manure were incubated at 10 g/kg with a Mollisol and an Oxisol at room temperature. Unamended soils served as controls. Nitrate (NO3-N) was extracted and measured at 3, 7, 14, 21, 28, 42, and 56 days during the incubation. The results showed that the potentially mineralizable N (referred to as N0) varied widely among the composts, but the mineralization rate (k) remained nearly constant, ranging from 0.02 to 0.03/day, suggesting that approximately 2 to 3% of N0 was transformed into NO3-N per day. Cumulative NO3-N release was linearly related to the square root of the total N in the composts. Relative absorbance at 260 nm of a 0.01M NaHCO3 extract failed to predict N0, but could clearly separate vermi-composts (low absorbance readings) from thermo-composts (high absorbance). A subsequent greenhouse experiment using pak choi (Brassica rapa, Chinensis group, cv. Bonzai) as the test plant grown on the same two soils amended with 10 g/kg composts or green manure demonstrated the beneficial effects of the organic inputs when compared with the control (soil alone) or a complete mineral fertilizer treatment (providing 80 mg N/kg as 16-16-16 commercial fertilizer with 0.5% micronutrients). Organic amendments provided more benefits to cabbage growth in the infertile yet better drained Oxisol than in the fertile but poorly drained Mollisol.