California Agriculture

More than 2.4 million visitors participated in agritourism at California farms and ranches in 2008. They stayed at guest ranches in the foothills, picked peaches in the Sacramento Valley, played in corn mazes up and down the state, shopped at on-farm produce stands along the coast, held weddings in fields and vineyards from coast to mountains, and experienced myriad other agriculture-related tourism activities. The UC Small Farm Program conducted the first statewide economic survey of California agritourism operators to better understand their goals, needs and economic outlook. University researchers from several other states provided input and sample data from state surveys conducted between 2000 and 2007. This information will help to target outreach and address current and emerging challenges.

The United States and South Korea negotiated a bilateral trade agreement in 2007. After final legislative approval, likely later this year, high tariffs on exports of most California agricultural products to South Korea will be gradually eliminated. Already, with the tariffs in place, South Korea ranks among the top six destinations for many California agricultural exports. More-open access to the South Korean market will create significant opportunities for major commodities produced in California such as almonds and dairy products.

Over the past three decades, wineries in the western United States and sugarcane processing for ethanol in Central and South America have experienced problems related to the treatment and disposal of process wastewater. Both winery and sugarcane (molasses) wastewaters are characterized by large organic loadings that change seasonally and are detrimental to aquatic life. We examined the role of plants for treating these wastewaters in constructed wetlands. In the greenhouse, subsurface-flow flumes with volcanic rock substrates and plants steadily removed approximately 80% of organic-loading oxygen demand from sugarcane process wastewater after about 3 weeks of plant growth; unplanted flumes removed about 30% less. In field studies at two operational wineries, we evaluated the performance of similar-sized, paired, subsurface constructed wetlands with and without plants; while both removed most of the oxygen demand, removal rates in the planted system were slightly greater and significantly different from those of the unplanted system under field conditions.

Many California rice growers are now using foliar-active herbicides that require fields to be drained before application. Current regulations limit aerial herbicides and they must be applied by ground, requiring a soil surface dry enough to support application equipment. Our research showed that draining rice fields for a prolonged period early in the season led to a buildup of nitrate in the soil. About 60% of this nitrogen was lost when the field was reflooded, reducing nitrogen-use efficiency and uptake, and lowering grain yields. Nitrate-nitrogen accumulated at a rate of about 1.8 pounds per acre daily, and accumulation began about 4 days after the field was drained. During a typical drain of 10 to 14 days, about 20 pounds of nitrate-nitrogen per acre can be lost. Field experiments showed that incorporating fertilizer nitrogen into the subsurface soil increases nitrogen-use efficiency. Based on this research, we recommend that growers incorporate as much of their preplant nitrogen as possible below the soil surface and limit the drain period as much as possible.

Spray applications of pesticides to orchards are a common cultural practice; however, they present environmental concerns due to emissions of volatile organic compounds (VOCs), runoff that can allow pesticides to enter waterways, and spray drift onto nontarget areas. Advanced sprayer technology can address these concerns and improve application efficiency by reducing the amount of spray that does not reach the target. Target-sensing sprayers were evaluated in multiseason experiments. They reduced pesticide application rates by 15% to 40% and nontarget orchard-floor deposition by 5% to 72%, providing significant environmental and economic benefits.

A plant-based regulated deficit irrigation (RDI) experiment in the northern Sacramento Valley determined that crop consumptive water use and irrigation could be reduced without significant detrimental effects on almond production. Tree stress was measured by recording midday stem water potential, a direct measure of tree water stress. With a water stress level of −14 to −18 bars during the hull-split period, average annual water savings were about 5 inches. Over 5 years, no significant yield reductions were observed, although average kernel weight was slightly lower. The results suggest that water savings can be achieved without affecting yield, even in soils with low water-holding capacity.