Nutrient Management Research Database

http://ucanr.edu/sites/Nutrient_Management_Solutions/files/212700.pdf

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.

This paper presents a review of tree crop nutrient efficiency research with a focus on nitrogen, potassium and zinc.  It also includes a section on current challenges in tree crop and orchard nutrient efficiency.  

This paper presents a review of literature on nutrient efficiency in tree crops.  First, nutrient use efficiency is defined as unit of nutrient absorbed by the plant per unit of nutrient available.  Then, results of research focusing on nitrogen, potassium and zinc are presented. 

In discussing nitrogen (N), the review suggests that an efficient nitrogen management program synchronizes N fertilizer applications in amounts that is biologically feasible for a tree to take up, with periods of elevated N use in the tree, and times fertilizer application to minimize losses of N from the root zone.  Soil N and tree N status are integral in creating such a program.  Yield/crop load is also extremely important in determining application rates that lead to high N efficiency. Timing of irrigation and timing of fertilizer injection in a drip fertigation system are also key factors in achieving high N use efficiency.  

Potassium(K) is less studied, but the author suggests that fertigation of K can improve efficiency when compared to banding, calcium can be used to move K further into the soil, and foliar applications of potassium nitrate may deliver K efficiently.

The final nutrient reviewed, zinc, is only needed in small quantities, is immobile in the soil, and for these reasons foliar applications are commonly used in the fall or during dormant periods.