Enhancing Ecological Disease Management on Guam Through Building Agriculture professionals' Understanding of Soil Nutrients

View the project final report

• 2009 annual report

Commodities

• Vegetables: cucurbits, eggplant, tomatoes

Practices

• Crop Production: conservation tillage
• Education and Training: demonstration, extension
• Pest Management: cultural control, integrated pest management, mulching - plastic, row covers (for pests)
• Production Systems: agroecosystems
• Soil Management: soil analysis

Ecological management of plant diseases through soil nutrition is an area of agriculture production that Guam’s agriculture professionals require addition training in. The purpose of this project is to build agriculture professionals’ understanding of the role of soil nutrients in plant health and disease suppression. The training will cover the relationship between plant nutrition and overall crop production on Guam for the 13 essential elements as well as silicon in both conventional and organic farming systems. Although silicon is not considered an essential element for plants, it use on Guam holds a great deal of promise as it has been shown to enhanced the growth and the development of several monocots and dicots species. In addition to improving plant health silicon also has proved effective in reducing losses from both soilborne and foliar fungal diseases. Phase 1 Course Development: over the course of 18 months cucumbers, tomatoes, eggplant, and papaya will be grown and subjected to various nutrient regiments. Photos of plant symptoms as well as soil and plant date will be collected and developed into an instruction manual: Soil Nutrients and Disease Suppression on Guam. Phase 2 Instruction: for 4 months 10 agriculture professionals using material develop in phase one of the project will be instructed in diagnosis of plant nutrient problems. Visual as well as field equipment methods will be used. Phase 3 Field day and Evaluation: Agriculture professional trainees will host a field day for growers and the general public. Two months after the field day the agriculture professionals will meet and provide feed-back on the effectiveness of the project and to evaluate long term gains in their knowledge of plant nutrition and disease suppression.

The purpose of this project is to build agriculture professionals’ understanding of the role of soil nutrients in plant health and disease suppression and to assist agriculture professionals in passing their knowledge to growers. Guam’s agriculture professional are generally locally train with minimal exposure to the finer nuances of plant nutrition. Guam Cooperative Extension currently have production guides for both cucurbit and solanaceous crops (Yudin and Schlub eds., 1998, Schlub and Yudin eds., 2002), however, the majority of the information centers on N-P-K. It is believed that the soil fertilization sections of these guides need to be expanded into a new publication: Soil Nutrients and Disease Suppression on Guam. This guide would serve as this project’s training manual and would include discussions on plant nutrition of cucumbers, tomatoes, eggplant, and papaya with accompanying photographs of common nutrient deficiencies and excesses. The guide would also discuss the purchase and use of soil field test kits and equipment.

Phase 1 Course Development: The development of the guide will take 18 months and involve faculty and students from University of Guam Cooperative Extension and the University of Florida Institute of Food and Agriculture Sciences (IFAS). Of all the mainland US agriculture areas, Florida has the most in common with Guam with respect to climate, crops, diseases, and soils. During this phase of the project plants on Guam will be subjected to various soil nutrient regimes, which typifies Guam’s production. Symptoms will be photographed and field soil tests kits will be evaluate for Guam’s use. A farm survey of 10 farms will be conducted to evaluate current growers knowledge and farm practices. Crops will be evaluated for nutrient symptoms and soil tested for nutrient levels. A follow-up survey will be conducted on these same farms at the end of the project to evaluate the impact of the capacity building of Guam’s agriculture professional and the projects field day had on their knowledge and practices.
The guide will cover the relationship between plant nutrition and overall crop production on Guam for the 13 essential elements as well as silicon in both conventional and organic farming systems. Studies on the relationship between plant nutrition and overall crop production are common and the majority of the studies concentrate on improving the management of 13 essential elements (Savant et al., 1997; 1999). These include six macro-elements (N, P, K, S, Ca, and Mg) and seven micro-elements (Fe, Mn, Zn, B, Mo, Cl and Cu). These elements are considered essential because deficiency in any one of them adversely affects physiological plant function, resulting in abnormal growth and/or an incomplete life cycle. Historically, the relationship between nutritional deficiencies and crop health have been addressed by plant pathologists by identifying and studying them as “abiotic” or noninfectious disorders. When any of these micro- or macro- elements are present in the soil environment in amounts lower than the minimum levels required for normal plant growth, the plant becomes diseased and exhibits various external and internal symptoms (Agrios, 1997; Datnoff et al., 2005). The kinds of symptoms produced by the deficiency of a certain nutrient depend primarily on the functions of that particular element in the plant (Agrios, 1997). Because nutrients directly effect plant heath they also indirectly effect pathogen susceptibility. The reduced availability of nitrogen may increase the susceptibility of tomato to Fusarium wit and many solanaceous plants to Ralstonia solanacearum. Sigatoka disease of banana, increase in severity with increasing nitrogen fertilization.
Excesses of soil nutrients will also be discussed in the guide. The use of excess chemicals is always a waste of a growers financial resources and increases the risk in the environment from farming. In the Eggplant, Pepper, and Tomato Production Guide for Guam it was reported that no difference in the yield of tomato occurred when 60 lb N and 120 lb N/acres were used. In the same guide, cherry tomatoes in clay soil containing 75 ppm K2O, had the same growth response with 25 kg/ha as with 200 kg level. Excesses may also cause damages directly, high levels of available phosphorus may cause micronutrient deficiencies of Mg and Fe.
Silicon is considered a plant nutrient "anomaly" because it is presumably not essential for plant growth and development. However, soluble silicon has enhanced the growth and development of several plant species including rice, sugarcane, most other cereals, and several dicotyledons such as cucumber, watermelon, and pumpkin. Some researchers are beginning to explore the important and possibly essential role of silicon in plant growth, function and health (Datnoff et. al., 2001a). In native soils that are not limiting in available silicon, plants absorb the element and their silicon content may be of the same order of magnitude as that of the macronutrient elements such as calcium or magnesium (Epstein, 2001). The element silicon also has been demonstrated to reduce plant diseases in a number of crops, including rice, sugarcane, some vegetables and flowering ornamentals (Datnoff et. al., 2001a). In highly relevant work conducted in Florida, applications of silicon (calcium silicate) resulted in dramatic reductions of two foliar fungal diseases of rice (Datnoff et al., 1991). Although calcium silicate contains other nutrients, only silicon increased within plant tissues and correlated with disease reduction. In some cases, silicon use provided disease control equivalent to that of fungicides in both rice and turf (Datnoff et al., 2001b and Brecht et al. 2004). In addition, fungicide rates could be reduced when used in combination with this element. More recently, Seebold et al. (2000) and Rodrigues et al. (2001) demonstrated that host resistance of susceptible and partially resistant cultivars can be augmented with silicon to the same general level as those containing complete disease resistance.

Phase 2 Instruction: For 4 months 10 agriculture professionals using material develop in phase one of the project will be instructed in diagnosis of plant nutrient problems. Class will meet twice a month for three hour sessions. Participants from each of the agencies that advice farmers on soil nutrient issues will be selected: University Cooperative Service, Guam Department of Agriculture, National Resource Conservation Service, University faculty and staff. The pool of participants will be drawn from various disciplines: plant pathology, horticulture, agronomy, and 4-H. At least one of the participants will be from the private sector, an individual that is directly involved with application and evaluation of fertilizer requirements on a daily basis for clientele.
A holistic approach to instruction will be taken. First the instruction manual will be thoroughly studies. Students will be given hands on field experience and tested with real world problems. Finally at the end of the 4 month program the students will host a field day where they will have an opportunity to demonstrate their skills to the growers and the general public.
Visual diagnosis as well as field equipment methods will be used. Participants will develop, maintaining, and collected data on field demonstration plots that simulate real soil nutrition problems on Guam. Plots amended with various soil nutrients will be evaluate for crop health, symptoms, and plant diseases. These plots will be apart of field day demonstration, which the participants will host for growers and the public.

Phase 3 Field Day and Evaluation: Agriculture professional trainees will host a field day for growers and the general public. The inclusion of the field day into this project provides a form by which the agriculture professional demonstrate their new found knowledge and can begin the process of educating the farm community and the general public. The field day also provides the farm community a chance to see first hand the benefits and cost saving of proper soil nutrition. Funds will be dedicated within the project to bring one agriculture professional from Saipan and Rota, which are Guam’s largest two neighboring islands.
The project will be evaluated by means of a farm survey and testing of participating agriculture professionals. Two months after the field day a follow-up survey of the farmers visited during the course development phase of the project will be conducted to evaluate the impact of the capacity building of Guam’s agriculture professional and the projects field day had on their knowledge and practices. Also within this period of time the agriculture professionals will meet one more time to provide feed-back on the effectiveness of the program and to evaluate long term gains in their knowledge of plant nutrition and disease suppression.