Reprinted from SOIL SCIENCE SOCIETY OF AMERICA PROCEEDINGS Vol. 30, No. 6, November-December 19661 pages 796-799 G77 South Segoe Road, Madison, Wisconsin 53711 USA Purchased by the U. S. Forest Service, for official use. Growth and Nutrient.Uptake of Irrigated Young Ponderosa Pine After Fertilizer Treatments• RoBERT F. TARRANT AND RoY R. SrLEN2 ABSTRACT pine seedlings grown for 1 year responded by increased top weight to N fertilizer alone and more so to combinations of N and P and N and S. In the current study, N and P fertilizers and supplemental water were applied to the soil beneath young ponderosa pine trees planted in a windbreak near a source of irrigation water. Objectives were twofold: (i) to determine effect of relatively heavy fertilizer treatments and irrigation on flower and cone production; (ii) to study growth and nutrient uptake after applying fertilizer to soil under conditions of substantial relief from moisture stress and competition. Interest in flower and cone production "ras aroused by observations of precocious cone bearing in 6-year-old planted trees. Flo\vering and cone production have been stimulated in a number of tree species by various cultural treatments, including irrigation and chemical fertilization (6, 12, 17). On the other hand, cultivating, \vatering, and fertilizing young western white pine did not substantially increase fl.o\vering or tree growth (2). Cone production in this study, even on fertilized plots, was. too lo\v to yield definite information. Even though the few cones produced were generally associated with N--fertilizer treatments, their distribution could have occurred by chance. The growth and nutrient uptake phase of the study was carried on over a 6-year period. Ammonium nitrate and treble superphosphate were applied to irrigated, 7-year old ponderosa pine (Pinus ponderosa Laws.) in a wind break planted on Deschutes sandy loam in central Oregon. Nitrogen was supplied at levels of 0, 200, and 400 lbI acre and Pat 0, 100, and 200 lb/acre in a factorial experiment. Fertilizer treatments application. were repeated two years after initial Over a 6-year period after first fertilizer treatment, tree growth was stimulated in relation to amount of N applied singly. When N and P were applied together in various combinations, growth was in some cases stimulated and in other cases reduced, according to the combination of the two elements. Foliage N concentration was not affected significantly by any treatment, but when P was applied at the 100-lb rate, addition of N treat­ ments caused a linear increase in foliage N concentration. With P at -200 lb, addition of N caused a linear decrease in foliage N concentration. At the conclusion of the study, N content of soils receiving the heaviest N fertilizer application was only about 11 % more than that of the controls. However, under heaviest P treatments soil P was more than five times that of unfertilized soils. PINE (Pinus ponderosa Laws.) is the most widely distributed species of its genus in North America. Because it occurs mainly in areas of comparatively low precipitation in the V\Testern USA, its growth is often Slow compared with that of many other commercial tree species. Thus, ponderosa pine- appears to be· a potentially rewarding tree with \Vhich to attempt stimulation of growth and perhaps cone, production, with chemical fertilizer. Many references are available on studies of the effect of chemical fertilizer on growth and nutrient uptake of various species of Pinus, but only a few are concerned with ponderosa pine. In one of these, nutrient uptake of ponderosa pine seedlings growing in Pacific Northwest tree nurseries "'as highest for N, intermediate for K, and lowest for P (19). When irrigation and N fertilizer treatments were applied to 90-year-old ponderosa pine, supplemental water had more effect in increasing diameter growth than N (13). Effects of N, P, and K fertilizer were studied in a 12-year-old plantation of ponderosa pine with an understory of naturally propagated western white pine (Pinus monticola Dougl.) and grand fir [Abies grandis (Doug!.) Lindi.] (10). Although understory trees responded to fertilizer with increased_ height- growth1 needle length, and foliage nutrient concentration, overstory ponderosa pine showed only slight gro"\'i'th increase and no change in foliage nutrients. In another study (20), ponderosa ONDJ<JROSA P STUDY PROCEDURES The study was begun in the spring of 1957 at tho US Forest Service tree nursery near Bend, Oreg., where 176 ponderosa pine trees were growing 6 feet apart in the outer row of a windbreak. All trees had been raised from seed of a single but unknown Northwest source and were outplanted when 2 years old. 'Vhen the study began, the trees were 7 years old, averaged 5.6 feet in height and 0.90 inch dbh. (diameter at breast height), and were free from major competition for light, water, and nutrients. The Bend Nrnsery is situated on a Brown soil of the Deschutes series, developed principally from windborne pumice sand derived from volcanic material erupted south of Bend. The soil has a loamy sand surface texture, is 18-24 inches deep, and overlies a fractured basalt substratum. Before the tree nursery was estab­ lished in 19461 the soil had been cultivated for a number of years. Topography is gentle with slope not exceeding 3 %. Native plant cover before cultivation included western juniper (Juniperus occidentalis Hook.), sagebrush (Artemisia tridentata Nutt.), and rabbitbrush (Chrysothamnus spp.). The po'nderosa pine timber type extends to \Vithin about 2 miles of the nursery site and is apparently limited only by low rainfall (about 10 inches) at this northern edge of an extensive commercial forest area. The row of 176 trees was divided into 3 blocks, \vithin each of which 9 plots of 3 trees each were randomly selected. An 18-foot buffer strip _separated plo.ts. Before fertilizer was applied, a deep-running colter was drawn between the pine rO\V and interior trees in the windbreak to reduce root competition from adjacent trees. On the outer side of the pine row, open ground \Vas disced and periodically hand­ ' hoed to eliminate grass and weeds. All -9 combinations of 0, 200, and 400 lb/acre of N (as ammonium nitrate) and 0, 100, and 200 lb/acre of P (as treble i Contribution from Pacific Northwest Forest and Range Experiment Station, Forest S_ervice, USDA, Portland, Oreg. Presented before Div_. S-7, Soil Science Society of America Nov. 18, 1963 at Denver, Colo. Received June 17, 1964. Approved July 7, 1966. superphosphate) were assigned randomly in each block and the broadcast fertilizer treatment was repeated in 1959 (per-acre fertilizer rates hereafter referred to as N-200, N-400, P-100, or ro P-200 ). During each year of the study, deep coltering between Principal Soil Scientist and Principal Plant Geneticist, re­ spectively, Forestry Sciences Laboratory, Pacific Northwest Forest and Range Exp. Sta. Corvallis, Oreg. 2 796 797 TARRANT AND SILEN: GROWTH AND NUTRIENT UPTAKE OF PONDEROSA PINE Table I-Average yearly height and diameter growth-effect of three levels of N fertilizer across each of three levels of P fertilizer. Phosphorus, lb/acre 0 200 Height Growth, 0 100 200 Probabilityt Nitrogen, lb/acre 1.51 1.42 1.67 1.60 1.74 1.49 400 PL 0.05* .47 .06 Location Average annual growth Age period of measurement* Height Diameter Years Feet Inches PQ feet 1.79 1.53 1.39 Table 2-Average annual growth of irrigated ponderosa pines co pared with that of unirrigated trees near Bend, Oregon 0.68 .04* .83 Bend nursery (irrigated) Lava Butte (not jrrigated) Racial studyt (not irrigated) 7-13 1.51 0.51 9-15 .87 .29 0-30 .55 .16 Diameter C.rowth, .inches 0 100 200 .51 .46 .49 .51 .54 .48 .53 .49 .43 .28 .17 .06 .63 .02* .25 *A value of 0.05 or less is considered evidence of significance. t Probability that the relationship between growth rates across three levels of N- fertilizer is either linear (PL) or quadratic (P Q) for a given level of P fertilizer. rows was done at the beginning of the growing season, side-ditch irrigation was applied several times during the growing season, and weeding was carried out within and adjacent to the plots. Initial height and dbh. of each tree was measured to the nearest 0.1 foot and 0.1 'inch, respectively, before growth began in 1957. Height growth, measured at the end of each growing season through 1962, \Vas selected as a criterion of response to treatment because the trees were free to grow. However, dbh. was measured at the end of the 1962 season to supplement height data. Foliage, sampled as a composite from the three trees on each plot, was analyzed for N concentration by the Kjeldabl method (1) and for P by an adaptation of the Fiske-Subbarow method (1) employing wet oxidation with nitric, sulfuric, and perchloric acids. Soil samples \Vere collected in 350-cc cylinders for bulk density determination and loose samples were taken for chemical analysis. Total N was determined by the Kjeldahl method (1) and P by extraction with NaHCOa· (14). Conelets and cones \Vere counted at the beginning and end of each growing season. Analysis of growth and foliage nutrient data indicated that magnitude of measurements differed signi­ ficantly between years but effect of treatment did not. Therefore, averages of yearly measurements of these factors are compared. RESULTS AND DISCUSSION *Years from planting 2-0 stock. t Largest one-third of trees of best growing source (16). meaningful, and ascribe growth rate reductions in this ca.se to a nutrient imbalance, as found by others (3, 8). The study site was some\vhat deficient in soil N for good ponderosa pine growth, as indicated by the, linear growth response \Vith incre8.'."ing amount of N fertilizer. Concentra­ tion of soil N averaged 0.093 in the upper 6 inches of un­ fertilized soil. Total weight of soil N was about 2,700 lb/acre to a depth of 18 inches over fractured basalt. Zinke (21) suggested a soil N content of about 3,000 lb/acre to a depth of 48 inches as a minimum requirement for good nutrition of ponderosa pine, an amount not greatly exceeding that found in the shallo\v soil of- the Bend Nursery site. Irrigation may have removed a great part of the limitation on ponderosa pine growth in the .study area. Irrigated trees measured as controls in this study grew much faster than unirrigated trees nearby (Table 2). Increased growth of ponderosa pine under irrigation has been noted also in two recent studies. Mosher (13) found diameter growth of 90­ . year-old ponderosa pine increased 1393 when he applied two 40-hour summer irrigations in north-central Washington, but only 293 when he applied fertilizer at the rate of 67 lb/acre elemental N without water. In Arizona, Water applied weekly a rates of 1 and 2 acre-inches increased diameter growth Of ponderosa pine 1.5 and 2 times, respectively, over that of unirrigated trees (11). Growth With no P fertilizer, height growth increased as the amount of N fertilizer was increased (Table 1). With N-200, height growth increased by about 6 o/0 over that of unfertilized trees. With N-400, height growth was almost 193 greater than that of controls. Diameter growth also tended to increase with increasing amount of N fertilizer, but differences were not statistically significant. When N-200 and P-100 were applied together, height growth increased about 153 and diameter growth increased about 63 more than unfertilized trees. When N-400 and P-100 were applied i_n combination, both height and diameter growth were less than values attained "rith N-200 and P-100 together, and we're little different from values obtained with unfertilized trees. With P-200 added to all levels of N, height and diameter growth rate tended to be reduced as the amount of N fertilizer was increased, although the relationship was not quite significant at the 53 level of probability. From a practical consi_deratibn, however, \Ve consider this ielationship to be Foliage Nutrient Content l\t1aximum differences in foliage N concentration averaged only 0.2% dry-weight basis, between treatments within years. In the absence of P fertilizer, foliage N concentration tended to increase as amount of fertilizer was increased, but differences were not significant (Table 3). When P-100 was applied, addition of N treatments caused a linear increase in foliage N concentration. Wi_th P-200, addition of N caused a linear decrease in foliage N concentra­ tion. The latter change in foliage nutrient content was the only one associated with a growth change, in this case a reduction. Maximum differences in foliage P concentration were also small, averaging only 0.053, dry-weight basis, between treatments within years. Increasing amount of N fertilizer had no significant effect on foliage P, either in the absence of P fertilizer or when P-200 was applied. With P-100, increasi:p.g N caused a linear decrease in ·foliage P concentration-an opposite effect of the same treatment on foliage N. 798 SOIL SCI. SOC. Al\1ER. PROC., VOL. 30, 1966 Table 3-Foliage nutrient concentration---eifect of levels o f fertilizer P across all levels o f fertilizer N (average of measurements 1, 2, 4, and 6 years after first fertilizer application) Phosphorus fertilizer, lb/acre Nitrogen, lb/acre Probabilityt 400 200 0 Foliage N Concentration, 0 200 400 1.63 1.59 1.63 Foliaoe 0 200 400 0.18 .20 .20 PQ 0.12 .01* .04* 0.13 .09 .45 3 1.69 I.75 1.55 1.61 1.62 1.61 PL SO IL N total lb/acre to 18 inc es NO FERTILIZER P Concentrr1tion, % 0.19 .18 .17 0.21 .19 .20 0.35 .04 .02 0.01* .79 .02* N 400 lb/acre twice • P 200 lb/acre twice • *Value of 0.05 or less is considered evidence of significance. t Probability that the relationship between. foliage N concentrationS across three levels of N fertilizer application is either linear (PL) or quadratic(P q) for a given level of fertilizer. Decreased foliage P concentration has also been found in a­ number of tree species other than poilderosa pine when substantial amournts of N fertilizer were applied (3, 5, 8, 18). A decrease in foliage P after N fertilization has been ascribed to an "antagonistic" effect between N and P. Whether results of the current study represent true "antagonism" or merely a dilution effect from increased foliage production is not kno'\\•n because absolute amounts of nutrients \Vere not foliage determined. Over all years of this study, foliage P concentration averaged 0.19% and ranged from 0.13 to 0.24%. These values agree closely with.those found for some other forest tree species (IO) and even with data from a study of 130 peach orchards in California in which foliage P averaged 0.19% and ranged from 0.14 to 0.27% (9). Poorest growth of peach trees was frequently associated with the highest soil P content and best growth with lowest soil P. Phosphorus fertilizer had only slight or no effect on growth of a variety of orchard trees _in several Western USA States (15). Foliage N/P ratio in Japanese larch (Larix leptolepis Sieb. and Zucc.) was correlated with growth (4, 8) and has also been suggested as a promising criterion for diagnosing N deficiency in Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] (5). In our study, however, there was no apparent relationship between foliage N/P ratio and growth, perhaps -because a wide range of foliage nutrient concentrations must be studied to obtain meaningful correlations between growth and foliage nutrient supply (18). 0 20 SO IL 40 60 BO !PO P total lb/acre to 18 inches Fig. 1-Soil N and P 6 years after fertilizer was first applied­ unfertilized plots vs. those twice receiving N at 400-lb. acre rate or P at 200-lb. acre rate. stantially greater soil N under heavy P fertilizer treatment, however, cannot be dismissed as readily. Although the study did not include analysis of soil microbial populations, a reasonable explanation for increased soil N in this case might be greatly increased nitrogen fixation by nonsymbiotic bacteria whose population growth was enhanced by favorable environ­ mental conditions under irrigation. Amount of N aHCOa-soluble P '\\'as not different between unfertilized soil and that receiving N-400 twice (Fig. 1). However, where P-200 had been applied twice, ainount of soil P was 91 lb/acre, more than 5 times that of the unfertilized soil which contained 17 lb/acre. -Residual soil P from the fertilizer applications is thus estimated at about 74 lb/acre, nearly 0.2 of the total amount applied. Soluble phosphate fertilizers may remain available for at least 7 years after application to Western USA soils (15). Most data indicate that residual soil P is directly related to amount of fertilizer applied. A relatively large amount of NaHCOa-soluble P remained in an eastern Oregon soil 6 years after P had been applied at the rate of 210 lb/acre (7). How­ ever essentially no residual P was found after 6 years when P had been applied at 53 lb/acre or less. This experiment, although conducted "'ith agricultural crops, included several of the factors dealt with in our study: an irrigated soil of near-neutral pH in eastern Oregon; application of treble superphosphate; and evaluation of residual P by Na0H3 Residual Soil N and P extraction 6 years ·after fertilizer was applied. Fate of applied nutrients is of special interest in this study By the end of 6 years, 49.3 lb of P were removed in crops-about 24% of the because as much"" 800 lb/acre N and 400 lb/acre P had been total P applied. added in the heaviest treatments. the end of 6 years) was 67 lb/acre, about 32% of the total P Six years after fertilizer was first applied, analyses were made of soil from unfertilized applied. Weight of NaHC03 (available P in soil at · plots and from plots that had twice received N-400 or P-200. According to -foliage analysis and growth data from our Soil that bad twice received N-400 contained only about 5% study, only a small part of the total fertilizer P applied might more N than unfertilized soil (Fig. 1). However, soil to which be accounted for as uptake by trees. Thus, physical and P-200 had twice been added, had about 11 % more N at chemical processes in the soil must be responsible for removing conclusion of the study. most of the added P from accountability by the NaHC03 Slightly greater N content of soil that had received heavy N fertilizer applications can be attributed to treat ent. Sub- extraction method. Reversion of added P to less available forms was probably a dominant process. High soil Ca content TARRANT AND SILEN: GROW'l'H AND NUTRIENT UPTAKE OF PONDEROSA PINE and near-neutral soil reaction suggest the possibility of formation of a considerable amount of relatively insoluble compounds of P. CONCLUSIONS On a Deschutes loamy sand soil in central Oregon, height and diameter growth of irrigated young ponderosa pine increased linearly as amount of N fertilizer was increased from 0 to 400 lb/acre. Addition of P fertilizer in various combina­ tions with N either increased or decreased tree growth depending on rates used. Ho\vever, even the unfertilized but irrigated trees, measured as controls in this study, grew much faster than unirrigated trees nearby. Concentration of N and P in tree foliage was not affected "'hen N fertilizer only was applied. When P fertilizer was added at the rate of 100 lb/acre with Nin increasing amounts, , foliage N concentration \'i'as increased and P concentration decreased. After 6 years, soil that had received heaviest N applications contained little more N than did unfertilized soil. Soil that had received heaviest applicaticins of P had about 11 % more N. The amount of P was not different between unfertilized soil and that receiving heaviest N treatment. However, in soil receiving heaviest P· treatments the amount of soil P was 91 lb/acre-:--more than 5 times that of unfertilized soil. LITERATURE CITED 1. Association of Official Agricultural Chemists. 1960. Official methods of analysis. 9th Ed. AOAC, Washington, D.C. 832p . 2. Barnes, B. V., S.nd R. T. Bingham. 1963. Flower induction and stimulation in western white pine. U.S Forest Serv; Res. Pap. INT-2 10 p. 3. Goor, C. P. _van. 1953. 'The influence of nitrogen on the growth of Japanese larch (Larix leptolepis). Plant Soil 5:29-35. 4. . 1955. De fosfaatbehoefte van bomen en de fosfaatbemesting in do bosbouw. (The phosphate require­ ments of trees and phosphate fertilizing in the forest.) Het Thomrumeel 11 :251-257 (Dutch.) 5. Heilman, P. E., and S. P. Gessel. 1963. The effect of nitrogen fertilization on the .concentration and weight of nitrogen, 799 phosphorus, and potassium in Douglas-fir trees. Soil Sci. Soc. Amer. Proc. 27:102-105. 6. Hoekstra1 P. E., and F. Mergen. 1957. Experimental induc­ tion of female flowers on young slash pine. J. Forest. 55:827­ 831. 7. Hunter, A. S., E. N. Hoffman, and J. A. Yungen. 1961. Residual effects of phosphorus fertilizer on an eastern Oregon soil. Soil Seil Soc. Amer. Proc. 25:218-221. 8. Leyton, L. 1957. The relationship between the gro\vth and mineral composition of the foliage of Japanese larch. II. Evidence from manurial trials. Plant Soil 9:31-48. 9. Lilleland, 0., and J. G.Brown. 1942. The phosphate nutri­ tion of fruit trees. IV. The phosphate content of peach leaves from 130 orchards in California and some factors which may influence it. Amer.Soc. Hort. Sci., Proc. 41 :1-10. 10. Loewenstein, H., and F. H. Pitkin. 1963. Response of grand fir and \Vestern \vhite pine to fertilizer applications. North­ west Sci. 37 :23-30. 11. Mace, A. C., Jr., and R. F. Wage. 1964. A measure of the effect of soil and atmospheric moisture on the growth of ponderosa pine. Forest Sci. 10 :454-460. 12. Maki, T. E. 1955. Stimulating seed production by fertiliza­ tion and girdling. In Proc. Third South. Conf. Forest Tree Impr. p. 74-80. 13. Mosher, M. M. 1960. A preliminary report of irrigation and ·fertilization of ponderosa pine. Washington Agr. Exp. Sta. Circ. 365. 5 p. 14. Olsen, S. R., C. V. Cole, F. S. Watanabe, and L.A. Dean. 1954. Estimation of available phosphorus in soils by extrac­ tion with sodium bicarbonate. USDA Circ. 939. 19 p. 15. Peterscin, Ii. B., L. B. Nelson, and J. L. Paschal. 1953. A review of phosphate fertilizer investigations' in 15 western states through 1949. USDA Circ. 927. 68 p. 16. Squillace, A. E., and R.R. Silen.1962. Racial variation in ponderosa pine. Forest Sci. Monogr. 2. 27 p. , 17. Steinbrenner, E. C., J. W. Duffield, and R. K. Campbell. 1960. Increased cone production of young Douglas-fir following nitrogen and phosphorus fertilization. J. Forest. 58:105-110. 18. Tamm, C. 0. 1956. Studies on forest nutrition. III. The effects of supply of plant- nutrients to a forest stand on a . Medd. Sogsforskn.Inst. 46(3). poor site. 19. Youngberg, C. T.1958. The uptake of nutrients by western conifers in forest nurseries.J. Forest. 56:337-340. 20. , and C. T. Dyrness. 1965. Biological assay of pumice soil fertility. Sol Sci. Soc. ·Amer. Proc. 29:182-187. 21. Zinke, P. J. 1960. Forest site quality as related to soil nitrogen content. Int.Congr. Soil Sci., Trans. 7th (Madison, Wis.) 3:411-418. .