Improving the Nutrient Efficiency of Tree Crops

Introduction Essential mineral nutrients applied to crops are a cost to growers and, poorly managed, contaminate air and/or water resources. Over the past 30+ years, fertilizer costs (USDA, 2006) and evidence of the negative impact of fertilizer nutrient contamination of air and water resources have increased significantly (Tilman et al., 2002). Therefore, an increase in nutrient efficiency, measured as net income, plant yield, or nutrient absorbed or applied per unit available nutrient, should benefit the grower and the environment*. Of particular interest to California agriculture is tree crop nutrient efficiency, as perennial crops continue to replace annual crops in many regions of the central valley – a region of the state with rapid population growth and subsequent pressures on air and water resources. The purpose of this paper is a brief review of factors affecting tree crop nutrient efficiency with a focus on nitrogen (N), potassium (K), and zinc (Zn) – the nutrients most commonly limiting tree crop production in California. A review of past advances in tree crop nutrient efficiency and current challenges in tree crop and orchard nutrient efficiency will be presented.