Abstract
This review covers most of the published literature on potassium (K) fertilization in bareroot seedbeds with the intent to concentrate on the southern United States. The timing and rates of K fertilization for bareroot seedlings are often based on logic and myths and, as a result, K recommendations vary considerably. Some recommend bareroot pine seedlings be fertilized with twice as much K as nitrogen (N) while others apply less than 100 kg ha-1. It was determined that several long-held claims about K fertilization are invalid. Nursery seedbeds do not need to contain four times as much available K as N and the belief that extra K fertilization will increase freeze tolerance or drought resistance of non-deficient seedlings is invalid. There are no data to support the claim that K fertilization increases root growth or assists in the formation of terminal buds. For sandy seedbeds, there is no need to apply K before sowing. Adding extra K during the fall does not increase seedling morphology or seedling performance when loblolly pine seedlings, at lifting, have more than 0.5% K in needles. A reduction of K fertilization can be achieved by reviewing foliar tests prior to K top-dressings.
Highlights
In some low-fertility soils, fertilization with potassium (K) will sometimes increase the growth of eucalyptus and pine plantations (Stoeckeler and Arneman 1960; Baule and Fricker 1970; Shoulders and Tiarks 1987; Almeida et al 2010; Carlson et al 2014; Bassaco et al 2018)
Did others assume this study proved K fertilization increased drought tolerance? A trial at a Wisconsin nursery found no improvement in drought tolerance when seedlings were treated with 134 kg ha-1 of K (Stoeckeler and Arneman 1960)
1) For bareroot seedbeds, there is no need for the soil to contain four times as much K as N. 2) There is no need to apply KCl or K2SO4 before sowing pines or hardwoods
Summary
In some low-fertility soils, fertilization with potassium (K) will sometimes increase the growth of eucalyptus and pine plantations (Stoeckeler and Arneman 1960; Baule and Fricker 1970; Shoulders and Tiarks 1987; Almeida et al 2010; Carlson et al 2014; Bassaco et al 2018). Many soil types have adequate levels of K and adding additional K to soil at these locations does not improve plantation growth. For this reason, many loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) stands are fertilized only with nitrogen (N) and phosphorus (P) (Albaugh et al 2018). Much is known about the effects of N and P fertilization on seedlings growth and development, information about positive effects of K fertilization on bareroot seedlings is limited For this reason, a literature review was undertaken to establish what is known about K fertilization practices in bareroot nurseries in southern states. This review addresses nursery literature from the 20th century since most of the fertility research after 2000 deals with N and P applications for container nurseries
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