Monday, August 6, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
With increasing plant diversity, there may be changes in ecosystem functions that result from differences in soil nutrient cycling, plant nutrition, and growth habits. Understanding the multifunctionality of biodiversity is necessary in agroecosystems for evaluating pros and cons of alternative management practices. At an organic farm, increasing plant diversity was expected to retain more nitrogen, reduce disease, create more resilience to stress, and increase yields. Plant diversity was manipulated temporally and spatially: mustard cover crop vs. no cover crop (fallow) in winter, and planting of mixtures with one, three or five tomato cultivars in summer, comparing a monoculture with the grower's best choice for a high-yielding cultivar with mixtures of it and other high-yielding cultivars in the region. Soil N, soil microbial biomass, crop nutrient uptake, canopy light interception, disease, GHG emissions, and biomass were measured. Preliminary results show that mustard reduced NO3- content in the soil through the winter and also during the tomato crop. There was a trend toward higher fresh weight in shoots and fruits biomass in fallow plots, but similar dry weight in shoots between fallow and mustard plots. Preliminary comparison of the cultivar mixtures indicates fairly similar yield and shoot biomass. Canopy cover and plant survival rate by treatment appeared to be higher in winter fallow plots. Further processing of data should provide more clarity on the multifunctionality of different types of biodiversity in this organic agroecosystem.
