Thesis (M.S.)--University of California, Davis, 2009
The nutritional information provided by the University of California established critical values for almonds may be outdated and insufficient. In December 2006, researchers at the University of California, Davis conducted focus groups with a sample of almond growers, nutrition consultants, farm advisors, and representatives from the California Environmental Protection Agency, the California Air Resources Board, and the Almond Board of California. The focus groups were designed to collect information relating to factors affecting growers' nutrition decisions, priorities in education and research relating to plant nutrition, and expected consequences of environmental regulation to the almond industry. Stakeholders identified numerous problems with the UC critical values, including the short window of time in which tissue samples can be collected, difficulty in collecting tissue samples that account for spatial variability across a field, and dissatisfaction with the values' reliance upon average nutritional status. Participants were also concerned that critical values may be over-simplified, failing to account for complex interactions occurring on orchards. Some growers respond to uncertainties about the critical values by applying large amounts of fertilizer in order to obtain nutritional values well about the UC-recommended values. Many stakeholders voiced concern about the future of the almond industry in light of impending environmental regulations, since there is a lack of good data on which to base nutritional limits. Stakeholders identified university research as a way to protect the industry from over-regulation and described their priorities for research topics. Based on the focus group results, researchers surveyed 1800 randomly-selected almond growers in June 2007 about their plant nutrition programs in order to assess the nutrition practices of the industry, identify opportunities for improvement, and target research and extension needs. Analysis of the survey data demonstrates that the majority of respondents, and particularly those respondents with large almond acreage, use fertigation to apply nitrogen, apply nitrogen coincident with periods of maximal plant demand, and collect annual tissue samples. While these results suggest compliance with best available management practices and are likely to result in good nutrient use efficiency, survey results also suggest that growers are uncertain about current practices used to monitor orchard nutrient status and would value additional information to enable greater precision in rate and timing of fertilizer application
