George S. Abawi

Farmer-oriented assessment of soil quality using field, laboratory, and VNIR spectroscopy methods

Soil quality and health are terms describing similar concepts, but the latter appeals to farmers and crop consultants as part of a holistic approach to soil management. We regard soil health as the integration and optimization of the physical, biological and chemical aspects of soils for improved productivity in an economic and sustainable manner. This paper describes the process used for the selection of soil quality/health indicators that comprise the new Cornell Soil Health Test. Over 1,500 samples collected from controlled research experiments and commercial farms were initially analyzed for 39 potential soil quality indicators. Four physical and four biological indicators were selected based on sensitivity to management, relevance to functional soil processes, ease and cost of sampling, and cost of analysis. Seven chemical indicators were also selected as they are part of the standard soil nutrient test. Soil health test reports were developed to allow for an overall assessment, as well as the identification of specific soil constraints. The new soil health test is being offered on a for-fee basis starting in 2007. In addition, visible near infrared reflectance spectroscopy was evaluated as a possible tool for low-cost soil health assessment. From preliminary analyses, the methodology shows promise for some but not all of the soil quality indicators. In conclusion, an inexpensive soil health test was developed for integrative assessment of the physical, biological, and chemical aspects of soils, thereby facilitating better soil management.

Diversity and Aggressiveness of Rhizoctonia solani and Rhizoctonia-like Fungi on Vegetables in New York

Vegetable growers in New York, especially those growing table beets, have recently observed that the corn rotation is no longer effective in suppressing diseases caused by Rhizoctonia solani and Rhizoctonia-like fungi. To investigate this problem, 68 isolates of Rhizoctonia solani and Rhizoctonia-like fungi infecting vegetables in New York were isolated, characterized, and their pathogenicity on corn determined. Sequence analysis of the rDNA internal transcribed spacer region inferred 26 isolates to belong to R. solani anastomosis group (AG) 2-2 and 19 isolates to belong to AG 4. Remaining isolates belonged to AG 1, AG 2-1, AG 5, AG 11, Ceratobasidium AG (CAG) 2, CAG 6, and Waitea circinata var. zeae. This is a first report of AG 11 and W. circinata var. zeae recovered from naturally infected vegetables in New York. Pathogenicity tests on corn showed that the majority of isolates are pathogenic on corn, and isolates belonging to AG 2-2, AG 5, and AG 11 exhibited high aggressiveness. These results suggest that certain strains of R. solani and Rhizoctonia-like fungi infecting vegetables in New York have acquired the ability to infect corn. In addition, snap bean was inoculated with seven isolates exhibiting low to high aggressiveness on corn, and a correlation between aggressiveness on corn and snap bean was observed.