Growth and nutritional responses of containerized sugar and Jeffrey pine seedlings to controlled release fertilization and induced mycorrhization

Two controlled release nutrient formulations, Sierra 17-6-10 + Miners and H igh N 24-4-8, and ectomycorrhizal inoculation with palletized basidiospores of Pisolithus tinctorius (Pers.) Coker sr Couch were evaluated for their e ffects on containerized sugar pine (Pinus lambertiana Dougl.) and Jeffrey p ine (Pinus jeffreyi Grev. & Balf.) seedlings. Low, medium, and high applica tion rates of each amendment formulation were tested. Peters 20-10-20 water soluble nutrients, also applied with three rates, plus unfertilized and un inoculated seedlings of each species provided for comparison of treatment e ffects on growth and nutrition. Shoot growth in both sugar and Jeffrey pine , as indicated by dimensions, volume, and mass, increased with amendment ap plication rate, and the response to controlled release nutrients exceeded t hat to the water soluble formulation. Jeffrey pine root growth, in terms of mass and total length, paralleled that of the shoots, but in sugar pine, t he three fertilizers produced comparable root growth that did not increase with application rate. For both species, however, the Sierra formulation pr oduced the greatest specific root lengths among fertilized seedlings. Inocu lated sugar pine seedlings generally exhibited smaller dimensions and volum e and less shoot and root mass than uninoculated sugar pine. Jeffrey pine w ith induced mycorrhization were also generally smaller in shoot dimensions and volume but had greater shoot and root mass than uninoculated seedlings. Total root length and specific root length were increased substantially in both species by mycorrhizal inoculation. The Sierra formulation applied at the high rate resulted in the most FI tinctorius mycorrhizae in Jeffrey pi ne, but in sugar pine, mycorrhizal counts and the percentages of root lengt h colonized declined as fertilization rates rose although nutrient addition s increased both relative to that found in unfertilized seedlings. Foliar a nalysis for a broad array of macro- and micronutrients revealed a coupled i ncrease in nutrient concentrations, notably of N but also P and S among oth ers, and amendment application rates in sugar and Jeffrey pine, which at le ast in part probably explains the growth responses to fertilization noted a bove. The High N amendment, which excelled in elevating N uptake, also had a propensity to depress P concentrations in both species, however. Inoculat ed sugar pine had higher foliar N and K but lower Ca and Mn overall than un inoculated seedlings, while inoculated Jeffrey pine had higher K and Zn but lower N, P, Ca, Mg, and S than their uninoculated counterparts. In the lat ter species, however, the depressed macronutrient uptake in inoculated seed lings was frequently offset by fertilization with specific formulations and /or application rates. Overall, these results indicate that the high rate o f the Sierra amendment produced the most favorable array of attributes in b oth sugar and Jeffrey pine, but that P. tinctorius is likely a more promisi ng mycobiont for inoculation of the latter species than the former. (C) 200 1 Elsevier Science B.V. All rights reserved.