Organic Farming

Abstract: In Tanzania, seed infection by bacterial leaf spot (BLS) pathogens (Xanthomonads) causes yield losses up to 45% in the tomato (Lycopersicon esculentum L.; Solanaceae family). Several studies have been conducted and wedged ecological organic agriculture (EOA) technologies (i.e., on botanicals/ biopesticides) which are significant to organic farmers in Tanzania. Nevertheless, these studies have been conducted in laboratory and screenhouse conditions, hence the technology cannot be disseminated to organic farmers for application before being validated. The current study was laid out as a 2x3 factorial experiment with five replications. Factor A was two common tomato cultivars “Rio grande” and “Malkia F1”, while factor B was seed treatment with three levels of crude plant extracts namely A. vera, C. arabica, and A. vera + C. arabica, and untreated control. Tomato seeds were soaked in the ready-made extracts for 12 hrs, then air-dried for 1 hr before sowing. The collected data were subjected to analysis of variance using Genstat 16^th edition software and means were separated using Tukey’s Honest Test at (α = 0.05). The highest efficacy against the pathogen (Xanthomonas perforans) causing bacterial leaf spot (BLS) was obtained from a combination of extracts from A. vera + C. arabica hence, recommended for seed treatment. Organic tomato farmers need to adopt seed treatment practices that ensure seedlings’ start-up and enhance crop growth and productivity. Although the results of validation comply with the recommendations from previous research findings, further study is needed to evaluate the effectiveness of plant extracts subject to seasonal variability among the production areas. Also, the bioactive fractions from the plant extracts and their mechanisms of action need to be evaluated comprehensively.

Abstract: Several scientific reports indicate lower as well as higher relative yield stability in organic and conventional (chemical) agriculture systems.   This study present results of on-farm trials conducted on leafy vegetables grown in in organic and conventional management systems. Four leafy vegetables collard green (Brassica oleracea cv. acephala), kale (Brassica oleracea cv. sabellica), lettuce (Lactuca sativa) and swiss chard (Beta vulgaris L. cv. cicla) were grown in organic and conventionally managed plots in the spring 2018 and 2020. United States Department of Agriculture (USDA), National Organic Program (NOP) standards were followed for cultural and management practices in organically managed experimental field plots. Synthetic chemical inputs (seeds and fertilizer) were applied in the experimental field plots managed in conventional production system. Data on plant height, leaf number and total fresh weight of leafy vegetables were measured at the end of the experiment. Results showed that maximum fresh weight per plant was obtained from conventionally grown kale and the lowest was recorded in conventionally grown lettuce. The fresh weight of collard (344.1 g/plant) and kale (475.6 g/plant) was significantly higher in conventional system relative to the organic management system in collar (184.9 g/plant) and kale (242.3 g/plant). In contrast, for lettuce, significantly greater fresh weight was obtained in the organic (266.5 g/plant) compared to conventional (189.3 g/plant). No difference recorded in fresh weight of swiss chard grown in organic (222.0 g/plant) and conventional (263.7 g/plant) production systems. No difference observed in plant height and number of leaf count between the two production systems. Findings suggest that growth and yield responses in organic and conventional production systems can vary with the individual crop species. Results presented could be helpful to growers in planning for the organic production of leafy greens vegetables.

Abstract: Organic certification, especially for smallholders, often uses group certification procedures. An internal control system (ICS) visits all farmers, and then the external certification body (CB) inspects a sample to assess the ICS' performance. Harmonised methods for measuring the ICS' reliability are missing so far. Here, we define criteria of "ICS performance", propose a new procedure for quantifying this performance and, based on this procedure, suggest that the sample size can be determined using classical statistical methods for survey sampling, instead of using the square root or a percentage of group size as in current practice.