Are Legume-Cereal Cover Crops a Good Fit in Organic Vegetable Production?.

Cover crops can provide important ecosystem services on farms and in surrounding areas and therefore are crucial in sustainable agriculture.  Legumes-cereal cover crop mixtures are often promoted because they combine the ability of legumes to add atmospheric nitrogen to the system through biological fixation in root nodules, and the ability of the cereals to scavenge nitrogen that is prone to winter leaching.  Efficient nitrogen use is especially pertinent in organic systems because the cost per unit of nitrogen in organic fertilizers is relatively high.  An important question to ask is whether or not legume-cereal mixtures are a good fit in tillage-intensive organic vegetable production systems?  To address this complex question, I will use data from a series of short-term component studies and a long-term organic vegetable systems study conducted during the past decade in the major region for high-value vegetable production in California.   This research has shown that the performance (i.e., biomass production, ground cover, weed suppression, potential nitrogen fixation) of cover crop mixtures can vary markedly between and within farms based on soil type, land history, cover crop management (i.e., seeding rate, planting method, planting date, mixture composition), and climate (i.e., winter rainfall and temperature).  A few typical scenarios will be used to illustrate how to make cost-effective decisions about when to use legume-cereal cover crops in rotations with high-value vegetables.  A novel and more interactive presentation style will be used… so come ready to participate.