Richard A.I. Brathwaite

Compost and compost tea: Principles and prospects as substrates and soil-borne disease management strategies in soil-less vegetable production

Numerous studies have demonstrated the potential of composted organic wastes not only as substitutes for peat as a growth substrate but also to stimulate plant growth and suppress soil-borne diseases. The major impediment to the use of compost as substrates or biocontrol agents has been variation in physical and chemical characteristics and disease suppression levels across and within compost types, sources, and batches. Compost tea, a product of compost, has also been shown to suppress soil-borne diseases including damping-off and root rots (Pythium ultimum, Rhizoctonia solani, Phytophthora spp.) and wilts (Fusarium oxysporum and Verticillium dahliae). Although the mechanisms involved in disease suppression are not fully understood, sterilization of composts and compost teas has generally resulted in a loss in disease suppressiveness. This indicates that the mechanism of suppression is often, or predominantly, biological, although chemical and physical factors have also been implicated. The inoculation of composts with biological control agents, manipulation of compost tea production process, and the use of new techniques for organic matter characterization and microbial community profiling may improve the efficacy and reliability of disease control obtained.

Diallel study of open-pollinated maize varieties in Trinidad

SummaryIn Trinidad, maize (Zea mays L.) is primarily harvested in the immature stage as green ears for human consumption. The purchase of popular imported hybrid seed has become a substantial component of the economic inputs of maize production. The objectives of this study were to investigate combining abilities and heterotic patterns among available open-pollinated varieties and to assess correlations among five important traits: time to silking, plant height, grain yield, ear size, and marketable ears per hectare. General combining ability was significant for all traits. Specific combining ability was significant for all traits except ear size. Three intervarietal crosses showed moderate levels of heterosis (10–27%), and several yielded similarly to the control hybrids, Pioneer X304 and Pioneer 3078. The cross Acid Soil Tolerant 1991 SA-3 X ICTA Farm Corn was selected as the most suitable base population for mass selection. Phenotypic and genotypic correlations among the five traits studied were all positive and significant. Populations which flowered early were shorter and yielded less than the late flowering and taller populations and population crosses included in this study.

Effects and relationships of compost type, aeration and brewing time on compost tea properties, efficacy against Pythium ultimum, phytotoxicity and potential as a nutrient amendment for seedling production

Studies were undertaken to determine the effects and relationships of compost type, aeration, and brewing time on compost tea properties, phytotoxicity, and efficacy in inhibiting growth of Pythium ultimum in vitro. The effect of compost tea on dry matter of tomato and sweet pepper seedlings cultivated on compost-amended substrate was also investigated. Compost type, aeration, and brewing time significantly affected the microbial and chemical properties of compost teas made from banana leaf (BLC) and lawn clipping (LCC) composts. Both aerated and nonaerated compost teas made from BL and LC composts significantly inhibited mycelial growth of P. ultimum. However, growth inhibition (GI) levels were significantly higher in compost teas produced from LCC. Aerating compost tea (ACT) did not consistently result in higher GI levels across compost types. Neither did increasing brewing time beyond 18 h for ACT and 56 h for nonaerated compost tea (NCT). Across all ACTs, yeast population was positively related to GI whereas bacterial population had a positive relationship with GI across all NCTs. Evidence suggests that multiple groups of microorganisms contributed to GI through antibiosis and competition for resources. All compost teas stimulated seed germination of tomato and root growth in sweet pepper. However, NCTs brewed for 56 h using LCC or BLC, and ACT produced from BLC brewed for 18 h, significantly reduced seed germination of sweet pepper. Application of NCT brewed for 168 h made from BLC significantly increased total dry matter of tomato seedlings by 122% compared with the control.

Farmers' Attitude towards a Participatory Research Method Used to Evaluate Weed Management Strategies in Bananas.

Abstract In this study, farmers were engaged in a participatory research project and their attitudes evaluated. The purpose was to identify the characteristics of farmers who are favourably predisposed towards meaningful participation in the process. Several cover crops were tested for possible use in the management of watergrass (Commelina diffusa), a noxious weed in banana cultivation. Small, limited-resource farmers were exposed to the essentials of systematic research through a process of experiential learning using participatory techniques. Thirty-six farmers evaluated three cover crops against the current weed control practice of farmers, which served as the control. Farmers and researchers collaborated on the experimental design, treatment allocation, data to be collected and the form of the analysis. Summary data were subjected by the farmers to the Overlap Test to evaluate differences among the treatments. Results indicated that one cover crop, Desmodium heterocarpon, was better than the others in controlling watergrass. These results were confirmed by ANOVA. A Likert-type scale, used to assess farmers’ attitude, showed that overall, farmers were generally favourable towards the process. Differences in responses to attitudinal statements were based mainly on farmers’ differing education levels. Some level of attrition was experienced in this process, mainly by the older and more experienced farmers. The younger, less experienced farmers completed the trials to a large extent. The results provide useful information for the selection of farmers to be involved in future participatory technology development initiatives.

Modelling response patterns of physico-chemical indicators during high-rate composting of green waste for suppression of Pythium ultimum

High-rate composting studies on green waste, i.e. banana leaves (BL) and lawn clippings (LC), were conducted in 0.25-m3 rotary barrel composters to evaluate and model changes in key physico-chemical parameters during composting. Time to compost maturity and antagonistic effects and relationships of composts against Pythium ultimum were also investigated. Higher temperatures were achieved in LC compost (LCC), which did not translate to higher total organic carbon (TOC) loss but resulted in lower carbon to nitrogen ratio (C:N) and a more mature compost. With the exception of electrical conductivity (EC), net decreases were observed in pH, TOC and C:N across compost types. Total Kjeldahl nitrogen (TKN) showed a net increase in LCC and a net decrease in BLC. With the exception of TOC and pH, the results showed that compost type and time had a significant effect on the respective TKN, EC and C:N models. Compost temperature and TOC were best described by the critical exponential and rectangular hyperbola functions, respectively. Whereas TKN, C:N and pH were described using double Fourier functions and EC using Fourier functions. Composts achieved maturity within 19 days and significantly inhibited the growth of P. ultimum. Bacterial population was positively related to growth inhibition (GI) across compost types, whereas total microbial population had a positive relationship with GI in LCC. Evidence suggests that multiple groups of microorganisms contributed to GI through antibiosis and competition for resources. Composts were determined to be suitable for use as components of plant growth substrates based on compost maturity indices.

Assessing Maturity of Rotary Barrel Green Waste Composts for Use as Tomato and Sweet Pepper Seedling Starter and Transplant Growth Substrates

Maturity, which significantly affects the potential use of compost as a peat alternative substrate, or substrate component, is difficult to measure, and laboratory-based testing methods are generally unattractive to farmers, due to cost and time delays. The accuracy of relatively simple, quick, and inexpensive plant-exclusive and -inclusive methods for evaluating maturity of rotary barrel composted banana leaf (BL) and lawn clipping (LC) for use as seedling starter and transplant substrates for production of tomato (Solanum lycopersicum L.) and sweet pepper (Capsicum annum L.) seedlings were investigated. Nine substrates were tested: BL or LC compost mixed at rates of 20%, 50%, 80%, and 100% (by volume) with 0% compost; that is, PRO-MIX ‘BX’/Mycorise PRO (Premier Horticulture Ltd., Dorval, Canada) alone as the control. Compost rate affected substrate electrical conductivity (EC), which, in contrast to seedling emergence, survival, and aerial growth, increased with increasing compost inclusion rate. Compost maturity test methods produced no, low, and high levels of phytotoxicity results. Neither BL nor LC compost consistently had a greater phytotoxic effect; instead, the effect seemed to be crop specific. Leaf area was more sensitive to compounds present in the compost than root growth, and EC was the most important factor inhibiting seedling emergence, survival, and root length of tomato and sweet pepper. Microorganisms indigenous to LC compost likely suppressed the positive stimulatory effects of compost extracts diluted at 1:20 v/v on sweet pepper germination and root elongation. Solvita (Woods End Research Laboratory, Inc., Mt. Vernon, Maine), a rapid (4 h) compost maturity test, in combination with a seedling growth assay may be the simplest, least costly, and most useful method to evaluate compost use potential. PRO-MIX ‘BX’/Mycorise PRO amended with BL or LC compost at 1:5 v/v is a good alternative to peat-based substrates for use as a seedling starter and transplant substrate for production of sweet pepper seedlings.

Weed Management Challenges in Fairtrade Banana Farm Systems in the Windward Islands of the Caribbean

The banana (Musa sp.) is the foundation of the agricultural and rural-based community life of the Windward Islands where about 8000 farmers are involved in its production. Banana is primarily grown on small farms in hilly areas averaging two hectares in size, usually owned by local family farmers and exported mainly to Britain and Europe. These farmers have limited financial resources, farm part-time and grow other crops and/or livestock in their system of farming. With the loss of preferential European market arrangements and higher production costs than Latin America, many banana growers have turned to alternative marketing arrangements such as Fairtrade to maintain their profitability.

Commelina diffusa Population Dynamics in Banana and RuderalHabitats under Mechanical and Herbicide Management Regimes

Commelina diffusa is a colonising species of banana orchard habitats in St. Vincent in the Windward Islands of the Caribbean. In the present study, the population dynamics of C. diffusa were investigated in response to mechanical weed management with either a rotary string trimmer or glufosinate in ruderal and banana habitats. The study focused on density and size distribution of the weed over time and their response to two weed management strategies. The population dynamics of C. diffusa differed between the two habitats. Seedling establishment appeared to be an important factor influencing the dynamics of C. diffusa in banana orchards as there was little recruitment of seeds with less flower production compared with ruderal habitats where plants produced more flowers. Plants of C. diffusa in the banana orchard habitat had a longer growth cycle. In the banana orchard habitat, the C. diffusa population was greater and the plants were shorter with mechanical management than in areas treated with glufosinate. The results suggest that it is possible to manipulate the dynamics of C. diffusa in banana orchards as there is less chance of seed recruitment. Further research is necessary to refine an IPM approach for the management of C. diffusa.

Perspectives in Development for Maize Production in the Caribbean: A Case Study of Trinidad and Tobago

ABSTRACT The need to diversify out of sugar cane and to increase local food production resulted in the promotion of large-scale, input-intensive and mechanized grain maize (Zea mays L.) production for the Caribbean. This paper describes common problems encountered during large-scale development projects for the mechanized production of grain maize in Trinidad and Tobago. Farmers on small landholdings produce maize as a fast, easy and relatively profitable sideline vegetable. Development projects have not addressed the realities of this sector. It is unlikely that small-scale farmers will adopt grain maize production, as the production of green maize is more profitable.