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The effect of nitrogen and sulphur application rates and sulphur source on the nutrition and growth of lodgepole pine (E.P. 886.10)

Last updated on August 22, 2023

Introduction

Extensive research has been undertaken to determine the nutritional status of lodgepole pine in western Canada and to document the effectiveness of fertilization in improving the growth of immature stands. Nitrogen (N) deficiencies, and responses to N fertilization, have been well documented. On some sites, however, sulphur (S) deficiencies may be induced or exacerbated by N additions. Growth responses have been enhanced on many sites by combining S with N in fertilizer prescriptions. A N+S blended fertilizer is currently used in most large-scale aerial fertilizer operations in the interior of British Columbia.

Extensive research has documented the effectiveness of various forms and application rates of S fertilizers on stimulating S uptake and growth of agricultural crops. However, very little similar research has been undertaken in conifer forests. The preliminary results from E.P. 886.09 reported superiority of ammonium sulphate (AS) over S0 - sodium bentonite prills in terms of S uptake and fascicle weight response of lodgepole pine one year after treatment. Oxidation of the S0 was apparently too slow to increase S uptake, at least during the 1st growing season. However, previous investigations with different S0 products have found that the rate of oxidation of S0 varies considerably depending on size and (or) composition. The large differences in rates of release from various S0 products can be attributed largely to differences in particle size and dispersion, which affects the amount of surface area available for microbial attack. Finely divided S powder, fine S0 held in urea pellets, and S0 suspensions are often oxidized relatively quickly following application. Therefore, preliminary reported results from the AS and S0 comparative study for lodgepole pine (E.P. 886.09) may have been different if S0 had been applied in a more readily oxidizable form and if tree growth had been monitored for a longer period.

This study was initiated in 1990 as a follow-up to the earlier E.P. 886.09.

Objectives

The objectives of this study are to: i) determine the response potential of young lodgepole pine to different rates of N and S fertilization, ii) determine the relative effectiveness of elemental and sulphate sources of S, and iii) investigate the nature of N rate x S rate x S source interactions.

Treatments

Fertilizer treatments consist of two N application rates (200 and 400 kg/ha) applied alone, and in combination with two S sources (S0 and sulphate S) and two S application rates (50 and 100 kg/ha). An additional unfertilized treatment served as a control.

Each of the 11 treatments was randomly applied to 15, "single-tree" plots at each of two study locations. Fertilizer was applied by hand to a 5m radius area surrounding each selected "plot" tree.

At the time of establishment and again after 3, 6 and 9 years, the dbh and height of all 165 "plot" trees at each study site were measured. Foliar nutrient data were also obtained from all treatment plots prior to fertilization and at the time of each re-measurement. Soil sampling was undertaken to determine the treatment effects on soil S cycling.

The study is now inactive.

Publications

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