United States 

Depart me nt of 

Agriculture 

Forest Semi ce 

Southeastern Forest 

Experiment Station 

A Loblolly Pine 

Management Guide 

When and Where to 

Apply Fertilizer 

Carol Wells and Lee Allen 

General Technical 

Report SE-316 

Carol Wells, Research Soil Scientist 

Southeastern Forest Experiment Station 

Research Triangle Park, North Carolina 

and 

Lee Allen, Assistant Professor 

Forestry Department 

North Carolina State University 

Raleigh, North Carolina 

A Loblolly Pine Management Guide 

Mhen arid Where to Apply Ferti 1 izer 

KEY POINTS 

If you are growing loblolly pine in plantations and you 

are looking for attractive investments in increased 

wood production, consider forest fertilization. 

- Planning for fertilization requires months of lead time 

to obtain soils information, to take foliage samples, 

and to have them analyzed. 

Results of foliar analysis are key indicators of needs 

for soil nutrients, and special procedure for collecting foliage samples must be followed. If a reyenerat?on cut is planned, foliage samples can be taken from 

the stand before harvest to determine the need for 

phosphorus application before a new stand is pi anted. 

Applying 50 pounds of phosphorus per acre increases 

lob101 ly pine site index (age 25) by 10 to 15 feet 

on typical very poorly, poorly, and somewhat poorly 

drained soils on the Lower Coastal Plain. 

A needle phosphorus content of less than 0.10 percent 

indicates a need for soi 1 phosphorus. The growth response to phosphorus fertilization increases as the 

need1 e phosphorus content without fert i 1 i zat ion 

decreases from 0.10 to 0.06 percent. 

In we1 1 -stocked (but not overstocked) stands, 5-year 

volume increment can be increased by 200 to 300 cubic 

feet per acre by applying 150 pounds of nitrogen per 

acre, plus 25 pounds of phosphorus per acre if both are 

needed. 

Responses to nitrogen fertilization are best on soils 

where nutrient supplies are limiting growth but misture conditions are Favorable. Highly responsive 

stands have basal areas of 70 to I20 square feet per 

acre, foliar nitrogen contents less than 1.2 percent, 

and site indexes (age 25) between 50 aqd 75 feet. 

*a In selected stands, investments in forest fertilizat-ion 

can be expected to yield returns of 10 to 28 percent ~f 

increases in product value are taken into account. 
The notion of improving plant growth by increasing the supplies of soi 1 nutrients is very 

074 hut its application in the forests of the 

Southern United States is rather new, In principle, fertilizer application ivproves growth if 

the rlutrients that are appl i ed were st~fficiently 

scarce to limit plant growth, In practice, fertilizer application is profitable if the improvement in growth more than pays the costs of treatment. Research results in recent years show that 

fertilizing loblofly pine stands can often he 

profitahle, and avai lable records show that ferti - lizer had heen applied to some 875,000 acres of 

lohlol ly pine by 1982, The trick for a forest 

manager is to determine when and where opportunities to profitably fertiliz~ exist. This guide 

is meant to assist in that process, 

Promi si ng Research Results 

The first formal studies of forest fertilization in the Southeastern IJnited States were with 

phosphorus (P) on slash pine in 1945, and with 

nitrogen (N) and phosphorus on lohlolly pine in 

the 1950's. Large increases in growth were observed when phosphorus was applied to wet, phosphorus-deficient soi 1s of the Lower Coastal Plain. 

Benefits from N application were also observed, 

but the results were not as spectacular as those 

from P. These early results led to the formation 

of cooperatives at the lini versity of Florida and 

at North Carolina State IJniv~rsity to work with 

forest industry in the development of forest fertilization technology, 

The North Carolina State Forest Ferti 1 i zation 

Cooperative has primarily investigated loblol ly 

pine, the sp~cies discussed in this publication, 

Recommendations presented here are based largely 

on the results of a large number of fertilizer 

trials conducted by that cooperative and the 

Southeastern Forest Experiment Station, 
On many wet soils on the Lower Coastal Plain, 

application of P dramatically improves lohfolly 

pine growth. On three such soils, application of 

P at 50 pounds per acre at planting time improved 

1 oh1 01 1y pine growth sufficiently to increase the 

estimated site index (age 25) hy 15 to 17 feet 

(table f). 

Table 1.--Hei ght, projected site index, and projected yield for lohlo1 ly pine on three soils fertilized with 50 pounds of phosphorus per acre and not ferti 1 i zed 

Soi 1 Projected volume at-- 

and when Ag Height Site index 

treatment measured (age 25) 

Age 25 Age 40 

Years - .. - Feet - - Cubic feet per acre 

Leon 

None 9 16 (35 1,500 2,200 

5 0 9 22 5 0 2,350 3,150 

Woodi nqt on 

None 13 2 4 42 1,600 2,600 

50 13 34 59 3,600 4,700 

Leaf 

None 15 4 3 6 7 4,022 4,884 

5 0 15 5 4 84 6,200 8,000 

Among the three soils, the percentage gain in 

site index was largest on the poorest one, the 

Leon, The projected volume increases at ages 25 

and 40, however, were greater for thp Woodington 

and the Leaf soils, which were of higher quality 

before treatment, The manager must he concerned 

primari ly with the prospective incr~ase in yieldl 

Consider the example of the Woodington soi 1, 

The estimated increase in volume per acre attrihrttable to P application was 2,000 cubic feet at 
0 

L 

a! 

111 

E 

'r- 

-I--' 

3 

rrj 

0 

ail 

a 

P-- 

1- 

* P-" 

3 

c2 

Ti. 

a 

m 

r-i 
In 15- to 25-year-old stands on th~ Piedmont, 

N a1 one produced about "c~ same yield increases as 

N, P, and K (potassium) together. In 4- to 10- 

year-old stands in the same region, there as some 

advantage to adding P along with N (table 3). In 

the Lower Coastal Plain and to a lesser extent in 

the Upper Coastal Plain, P mixed with N was henpficial for trees in both age groups. 

Tahte 3.--Eight-year gross volume mean response to ni tr;.cjen 

plus phosphorus in 4- to 10-year-old lohlolly pine stands 

moderately deficient in phosphorus 

Fertilization Lower Upper Piedmont 

treatment Coastal PI ai n Coastal Plain 

(lblacre) 

----- -Cubic feet per acre - - - - - - 

Number of studies indicated in parentheses. 

Growth rates in areas fertilized with N generally return to prefertilized levels in 5 to 8 

years. In the interim, effects amount to an accelerati on of stand development. Results of many 

studies show that N ferti 1 ization advances stand 

development by changing di ameter di st ri but i ons, 

mortal i ty , and domi nant hei ghts. The average advance in stand development from 100 to 151) pounds 

per acre of N is equivalent to almost 1 year in 

the 5 years after application. More responsive 

stands gain considerably more than the average* 

Consideration of stand development is important 

because volrlme added to large trees is more valuable than that added to smaller ones, and fertilization increases growth of largo trees more than 

srnall~r ones in a stand, 
Reliable data on growth responses of stands 

over age 25 come from only seven studies--two in 

the Lower Coastal Plain, one in the Upper Coastal 

Plain, and Pour in the Piedmont, The 5-year volume increases from 100 pounds of N and 50 pounds 

of p per acre averaged 166 cubic Feet per acre for 

four stands age 26 to 30, and 206 cubic feet per 

acre for three stands 35 to 36 years old, No 

increase in diameter growth was detectable 3 years 

after 200 pounds per acre of N was applied to a 

stand over 50 years old on a high-quality site on 

the Piedmont PI ateau. 

Those results indicate a smaller increase in 

volume after treatment for stands over 25 than for 

7 5- to 25-year-old stands, The greater wood value 

i n trees 25 to 40 years old, however, should make 

treatment of the older stands cost effective, 

Lohlol ly pine wi 11 respond to N applications 

from the time of planting if competition is control led, and some very good growth responses have 

been obtained in 5- to 10-year-old stands, From 

an economic point of view, however, returns from 

treatments in young stands are less attractive 

than those in older stands because investments in 

young stands must be carried for longer periods. 

The only fertilizer elements currently known 

to produce economical ly attractive growth increases in lob101 ly pine are N and P. K, and possibly other elements, limits growth on some sites, 

but further research will be needed before their 

appl i cation can be recommended . 

Determi ni ng Ferti 1 i zer Needs 

The kinds of yrowLh responses we have described, and the attractive investment opportunities they imply, are not avai 1 ah1 e everywhere. 

The prudent manager must learn to identify the 

ci tas v~her~ grointti.; resp~nses wi 11 he sati sfactory. 
Money spent on this identification process will be 

saved many times over 3y avoiding waste of fertilizer. We recommend foliar analysis for identifying sites to fertilize. Even where such techno1 ogy i s used, the predict iorl of responses wi l 1 

be less than perfect, hut this technology wi 11 improve the prohability of success* 

- Phosphorus 

The selection of sites for P application 

should be based on soi 1 type, soi 1 drainage, 

current tree performance, and fol i ar tests. 

Stands on very poorly to somewhat poorly drained 

clays and sands (Aquults, Aquents, and Aqt~epts) on 

the Lower Coastal Plain generally respond we1 1 to 

additions of P, If the stand that is being harvested from such a wet soil has a site index (age 

25) helow 60 feet or if the existing stand is not 

vigorous, P fertilization should he considered. 

Site identification can be further refined by 

analyzi ng sampl e needl es from 1-year-01 d or ol der 

stands. Methods for col lecti ng samples are 

described later in this publication. The total P 

concentration in ovendried needles is the best 

indicator of the need to fertilize, Guidelines 

for P fertilization based on foliar P concentrations for loblolly pine are: 

Percent 

concent ration -- .- - .- - - -- - - -- Interpretation -- - - -- 

< 0.10 Deficient , high probabi 1 i ty 

of response 

0.10-0.12 Critical range, general iy 

responsive in comhi nati on 

with nitrogen 

General ly not responsi vn 
Nitrogen (Ui th and Without Phosphorus) ----------------- ---- - 

Selection of stands for N application depends 

on stand stocking and tree size as well as site 

factors. Stocking must be considered beca~~se it 

determines how fully the stand will utilize the 

added resource. Tree size is important in determining the economic value of a stand's growth 

response, 

Recogni ti o~ of stands with M deficiencies 

from their soil and site characteristics is, at 

best, iwxact. The objective, of course, i s t o 

find stands where a lack of N alone or in combination with P is limiting tree growth. There is 

no point , for example, in adding N to a site where 

there is not enough soil moisture to permit a 

large increase in tree growth. Sdte index can be 

an indicator of nutrient deficiency, but it integrates other factors as we1 1, i~cluding soil moisture and other environmental resources. As with 

P, we have found that N deficiencies are most re1 i ably determined through fo1 iar analysis. 

We have a1 so developed general guide1 ines for 

i dent i fyi ng promising sites for N appl i cati on. 

With these guidelines, many sites can be categorized as likely to be very responsive, moderately 

responsive, or weakly responsive: 

Very responsive. This category includes 

sites where insufficient nutrient supplies are 

limiting growth but moisture availability and 

other site factors are favorable. Examples include most clayey upland Piedmont soils (e.g., 

Ceci l and Davidson), poorly to moderately drai ned 

sandy Coastal Plain soils (e.g., Chipley, Ocilla, 

and Pactol us ) , and mderatel y we1 l -drai ned soi l s 

with relatively deep spodic horizons (e.g., Centenary and Echaw), 

Moderately responsi ve. Thi s group incl udes 

a broad range sf soi 1 and site conditions typified 
by moderately we1 1 "L owe1 1 -drained upland loamy 

so-ils (eeg., Orangebug, Norfolk, and Ruston), On 

these sites, insufficient mi strrre may restrict 

fertilizer response during some partion of the year, 

Weakly responsive, On many sites in this 

group, nutrient limitations are overshadowed by 

gross deficiencies in other envi ronmental factors, 

like moisture availability and soil rooting volume- Many we1 1 -drained upland soi 1s must be 

placed in this category because insufficient 

moi sture wi 11 1 i mi t response to fert i 1 i zer 

appl ication during most years. Certainly, this 

condition exists in soils with a sandy surface 

horizon more than 40 inches deep (e.g., Troup and 

Lakeland). Rooting volume restrictions occur in 

soi 1 s with thick spodic horizons occrlrring near 

the soil surface (e.g., Murvil le and Lynn Haven) 

and in soils with shallow bedrock or a fragipan 

(e.g., Lax and Talladega). Also included in the 

group of nonresponsive soils must he those that 

a1 ready have sufficient nutrients present, Such 

sites wif 1 normally be the very best--those with 

site indexes at age 25 of more than 70 feet. Typical members of this group are mineral soi Is with 

a thick organic matter accumulation at the surface 

which have been art-ificially drained arld fertilized with P (e.g., Bayboro and Pantego). 

After promising sites have been identi fiecl in 

the way just described, the fol lowing guide1 ines 

should be used in selecting stands to treat: 

1. Stand stocking should be moderate 

(70-120 square feet per acre of 

pine basal area). 

2, The N concentration of ovendried 

sample needles should be less than 

3.2 percent. If the P concent ratf on 

is less than 0J.2 percent, P should 

be applied along with N, 
3. Treat 5 to 8 years before the 

pl anned harvest, 

4. The site index for age 25 should be 

between 50 and 75 feet. 

On the sites identified in this manner, N at 

150 pounds per acre should be applied. Where P 

also is needed, apply 25 pounds per acre. At 

least 75 percent of the stands identified in the 

manner described should respond to treatment in an 

economically attractive way if there is a market 

for mixed wood products. 

The potential for overstocked, stagnated natural stands to respond to fertilization is questionable. If foliar tests in such stands indicate 

a need, P application may be effective, but N appl ication should probably be delayed unti 1 the 

stand is thinned, 

Nitrogen ferti 1 i zati on can he economical ly 

attractive in 3- to 10-year-old stands in the 

Lower Coastal Plain if the stand also has severe P 

deficiency. Where P must be applied, the cost of 

applying N as well is little more than cost of the 

additional fertilizer. 

Fertilizers and Methods for Applying Them 

Inorganic Ferti 1 izers --.- - - -- 

Phosphorus may be applied as triple superphosphate (TSP) (20 percent P) , di ammoni um phosphate (DAP) (18 percent N, 20 percent P), or fineground rock phosphate (GRP) (9 to 13 percent P). 

The first two are highly soluble, whereas the 

last is only slowly soluble. Although long-term 

comparisons on loblolly pine have not been made, 

TSP and GRP appear to be equally effective, When 

a source of GRP is nearby, its cost is usually 

lower per pound of P than is TSP. The cost of 
applying GRp may he hi g%r, however, hec-iirse it 

is harder to spread than TSP and because iriore of 

it must be applied to add a given amount of P. 

DAP is an option where both N and P are needed, 

Uhere a P deficiency has heen identified, apply sufficient ferti 1 izer to add 411 to 50 pounds 

of P per acre, Apply at the time of planting or 

as soon after as practical. The season of application has no important effect on the pine response. 0n stands age 3 or older, OAP can he 

applied to add N as well as P if an N deficiency 

is suspected. The additional cost of DAP over TSP 

is relatively small and permlts an economical aplication of a small amount of N, 

Ammonium nitrate (33 percent N) and urea (46 

percent N) are the most common fertilizers used to 

add N to forest soi 1s. Some of the nitrate fa in 

ammonium nitrate can he lost in leaching if heavy 

rains follow application. Some ammonium N can he 

lost from urea as NH3 gas passed to the atmosphere. 

Since neither source has proved superior for application to southern pine, the choice should be 

based on the comparative local costs per unit of 

N applied. 

In general, an application rate of 100 to 150 

pounds of N per acre is likely to be most attractive economically. Additional growth stimulation 

can he achieved by applying 200 to 251) pounds of N 

per acre, but that additional growth is seldom 

sufficf ent to justify the cost of applying the 

additional 100 pounds of N. 

Several application methods have been successful in the South, P has been broadcast before 

disking or bedding, handed prior to bedding and 

incorporated into the soi 1 during bedding, and 

broadcast from the air or ground or sidedressed 

after planting, Since no consistent difference in 

growth has been associated with the method of 
appf icati oq, the cheapest nethod wi tfi the equipment at ?and should be favored, 

Ni t rogen has been appl i ed from he1 i copters 

and fi xed-wi ng ai rcraft with good success. Where 

ground equipment can be used, however, ground 

application is probably cheaper, 

Sewage Sludge ------- 

Sewage sludge is often an effective source of 

N, P, and other elements for trees, 1t-i 8- and 

27-year-old lob101 ly pine stands, 400 pounds per 

acre of highly avai lable N in sewage sludge has 

been as effective as commercial fertilizer, A 

sludge in which the N was in a less available 

form produced a smaller immediate growth increase 

when the equivalent of 600 pounds per acre of N 

was applied. The benefits of this treatment, however, may be expressed for a longer period. That 

study is sti 11 in progress, 

There are several important factors to consider when application of sewage sludge is contemplated, First, the cost of the material is 

likely to be low, but the cost of application may 

be quite high. Second, sludges vary widely in 

their contents, The candidate material must be 

carefully analyzed, and pilot tests of its effects 

are advisable hefore large-scale appl icatioqs are 

begun, Finally, the approval of heatt3 authorities is required in most States before sewage 

sludge can be applied. 

PJi t rogen-Fi xi ng Pl ants -- --4- - -- 

The culture of nitrogen-fixing pla~ts in 

forests may he considered an indirect form of N 

fertilization. Leguminous plants established in 

lohlolly pine plantations at planting or 1 to 2 

years after planting add several nundred pounds of 

N per acre to the soil before they arc shaded out 

by the pine* Growtt.1 increases of 7091 07 1y pine 
have been obsewed 3 or 4- years c?ff'er the pl dntl'ng 

of lespedeza species in y-otrng stands, Tire duration of the increases is not yet known, and the 

technology for use of nitrogen-fix-ing plants in 

forestry is still being developed. Use of such 

plants is promisiay, Rut only pilot testing is 

recommended before attempting a large project, 

Fire and Fertilization --- ---.- - -- 

Burning should be a~oided in lnhlolly pine 

stands immediately before and for a few years 

after N applications. Although little research 

has been done on effects of fire on fertilization 

results, some general effects are known. If urea 

is applied over the alkaline ash that is present 

for a few months after a fire, some of the ferti 1 izer kJ wi '9 i be lost to the atmosphere as ammonia@ Furthesmore, burning within 3 to 4 years 

after N application is likely to volatslize N from 

whatever ferti l izer sti 1 f remai ns and from the 

nitrogen-rich litterfall that fol lows feti 1 i zation. Pc avoid such losses, avoid burning for 6 

months prior to application and for 4 years after 

application of N fertilizer. 

Envi ronmental and Other Side Effects 

Forests produce more than trees, and foresters will want to know the effects of fertilizing on the entire forest ecosystem, Perhaps the 

1 argest current concerns are with water qua1 i tye 

Results from the Piedmont and Coastal Plain show 

little or no measurable increases in N or P in 

streams after fertilization of pine stands- Increases do occur when ferdi 1 i zer inadvertent 1 y 

falls on open water, bud movement frorn the land 

to the water appears to be slow and smallE When 

parts of watersheds have been fertililzed, applying material only where it is needed, no changes 

in water quai i 1 ty have been detected, 
Fertilizing loklolly pine increases growth 

of understory plants, adding soi 1 protection and 

improving wildlife habitat, Specific data for 

these benefits are lacking, but the increase in 

understory growth is easi ly observed. Ferti 1 izing 

increases the nutritional content as well as the 

volume of understory plants, making them more 

valuable as wildlife food. Particularly on phosphorus-deficient soi 1 s, application of ferti 1 izer 

can be expected to significantly improve deer 

habitat. 

Lohlol ly pine is relatively efficient at 

taking up nutri ents that are in short supply. It 

survives in soils that are too deficient in nutrients for survival of many native species. 

Thus, applying fertilizer to such soi 1s in sufficient quantitites to improve pane growth can be 

expected to benefit other plant species even more. 

Increases in severity of fusiform rust have 

been reported in loblol ly pine stands ferti 1 ized 

at the time of planting, The increases, however, 

do not appear to have been sufficient to negate 

the benefits of fertilizing. 

Nitrogen ferti 1 izi ng of pine increases fol i - 

age and branch weights. In stands that have recently been thinned to correct severe overstocking, the additional branch and foliage weights may 

increase the risk of ice breakage. This risk can 

be reduced by thi nni ng before overstocki ng becomes 

severe, and by delaying fertilization for a year 

or two after thinning. 

Fol i age Sampl i ng 

The recommendations presented in these guidelines cannot be followed without the results of 

foliar analyses. In this respect, fertilizer 

prescriptions in forestry differ from those in 

agriculture, where prescriptions are usually based 
on soi 1 analyses. Efforts are underway to arrange 

for re1 i able, low-cost fol iar analyses for 

forestry. 

A separate foliage sample is reqrli red for 

each unit that differs appreciably in soil type 

or stand growth. If both soil and foliage Sampl es are bei ng c o l l e c t e d , they should represent 

the same management units or areas. Low concent rations of avai lable phosphorus in soi 1 tests 

are not reliable indicators of the need for P, 

but hi gh test values show phosphatic or hi ghly 

fertilized soils and rule out the need of ferti1 ization* 

Needles are easy to remove from seed1 ings and 

saplings, but special equipment is needed for 

larger trees, Pole pruners are useful in collecti ng needles from trees up to about 35 feet tall. 

A gun is best for sampling foliage in taller 

trees. A 12-gauge shotgun on ful l choke does the 

job quite we1 1 when loaded with number 4 shot. 

The foliage sample for each area or unit 

should be a composite collected from a minimum of 

15 (and preferably more) dominant and codominant 

trees selected at random from the area* For experimental plots (0.05 to 0.25 acres), a composite 

sample from 7 to 10 trees is usually adequate, 

Four rules must be followed: 

1. Collect samples in December through 

March. 

2. Collect a primary lateral branch 

from the upper one-half of the 

dominant or codominant tree* At 

the point of collection, the crown 

should be essentially free of competition for light. 

3, Take needles only from the first 

flush of growth from the previous 
growing season on the primary 

lateral branch, The needles should 

he representative of the upper crown 

and largely Free of disease or insect damage. The first flush is 

usually the largest, and it often 

follows a small flush of short 

needles (fig, 1). 

4. Carefully label the samples to be sure 

you know what area they came from. 

The composite sample sent to the laboratory 

should consist of at least 200 needle fascicles 

that are free of soi 1 and other contamination, 

Within 12 hours of collection, the samples 

must he refrigerated, stored on ice, or placed 

in a drier. Dried samples are preferable for 

transporting to the laboratory. Drying is best 

done in a forced-air oven at temperature of 140 

to 160 OF, (60 to 70 "C) for 24 to 28 hours, 

Sample last fully mature flush, 

Figure PI--Fol iage sampling position, 
Economi cs of Forest Fert i 1 i zati on 

There is nothing unique about forest ferti - 

1 ization as a business investment. Even the uncertainty of yield increase is common with other 

practices. Ferti 1 ization involves the out1 ay of 

cash today with the expectation of generating a 

return over and above cost at some point in the 

future. Forest ferti 1 ization must compete successful ly for funds that can he invested in other 

ways. Computation of the return on investment 

(ROI) is one way to compare forest fertilization 

with other investment opportunities. That procedure has been followed in the examples provided 

here. 

In the simple cash-flow patterns typical of 

forest fertilization, ROI can he interpreted as 

the ear~ing rate for invested capital after taxes 

are taken into account. 

We present two examples to i 11 ustrate the 

economic returns from fertilization. One is for P 

appl i cat i on at pl anti ng or a few years thereafter. 

The second is for appl ication of N and P at stand 

age 20. There is no thinning, and the stands are 

clearcut at age 25. These examples were selected 

because experimental data were avai 1 able to esti - 

mate the changes in yield associated with the 

treatments. 

In taxing timber income, ferti l ization costs 

may he capitalized, expensed, or amortized upon 

negotiation with the Internal Revenue Service. In 

our examples, the cost of fertilizing at planting 

time was capitalized, and the cost of fertilizing 

5 years before harvest was amortized over the 

5-year period, These choices were arbitrary and 

rfo not represent recommendations of costing 

procedu res . 

In addition to tax treatment, four other 

factors --product mi x, stumpage prices, treatment 
costs, and growth responses--are important in 

determining the profitabi 1 ity of a ferti 1 izing 

operat i on. 

In our analysfs, the product: mix included 

pulpwood (to a 4-inch top), chip'n'saw wood (to 

a 6-inch top), and saw logs (to a 9-inch top). 

Stumpage prices were $1 5 per cord for pulpwood, 

540 per cord for chip'n'saw wood, and $150 per 

thot~sand hoard feet for saw logs. It was assumed 

that stumpage prices would increase at a real rate 

of 2 percent a year. On a high site (70 feet at 

age 25), 10 to 15 percent of the volume would be 

in saw logs, 55 percent in chip'n'saw wood, and 

the remainder in pulpwood. 

Costs for the fertilizer and its application 

were assumed to he $30 per acre for applying 40 

pounds P at planting and $60 per acre for applying 150 pounds N and 50 pounds P 5 years before 

harvest. 

Applyi ng Phosphorus at Pl anti ne 

Responses to P application at planting time 

were estimated by projecting volume and value 

gains over a 25-year rotation where site index 

(25 years) was improved by 5, 10, and 15 feet. 

Volume gains for these improvements were estimated 

over a range in initial site indexes for unthinned 

lob101 ly pine plantations. A planting density of 

700 trees per acre was assumed. Volume gains are 

presented in table 4, and after-tax ROI in table 

5 e 

The long-term improvements in site make ferti 1 i zing of phosphorus-defi cient soi 1 s economi - 

cal ly attractive* Estimated KO1 ranges from 9.0 

to 15.6 percent. These estimates are probably 

conservative because they do not reflect the increased opportunities for midrotation thinning 

to incredse cash flow or for M fertilization to 

i ncrease fi nal yields 
Tahle 4.--Vo11!~e yalrts over a 25-year rotstlor? 3n op+-i^;7r~s~i 

stands where phnsphnri~s ferti 1 szatlon jncrecises 2S-;~$r s: te 

index by 5, 10, and 15 feet 

Initial Site index improv~ment 

25-year 

site index 

(feet ) 5 feet 10 feet 15 feet 

- -- 

---- - Cuhic feet per acre - - - - - 

510 I, 053 1,625 

Tahle 5.--After-tax returns on invecrt%ents over a 25-y?ar 

rotation in unthinned stands where phosphows fertiljzation 

increases 25-year site index by 5, 10, and 15 feet 

Initial Site index improvement 

25-year 

site index 

(feet) 5 feet 10 fect 15 feet 

--..---- - Percent - - - - - - - 
Preharvest Fert i 1 i zat i nn 

Responses to fertilizing 5 years before harvest nsre based on estimated changes in stand 

diam~ter distri hution after the application of 100 

pounds N and 50 pounds P per acre. The 5-year 

vol tlme increases on moderately responsive sites 

were estimated for a range of initial stand densitips and site indexes (fig. 2). Value and ROI 

estimates (tahl~ 6) were calct~lat~rf assurni ng that 

the volume and value gaiqs would h~ obtained at 

the end of the 5-year respon ;P period. 

Volume Gain I 

4 5 55 65 75 

SITE INDEX CLASS ( 25 years 1 

Figure 2,--Fi ve-year vuiume rescsnse to appi jcat~orr of bOO pounds 

njlrogen and 50 pounds phosphorus per acre in untkinned loblolly 

pine stands at age 20. 
Tab1 e 6.--After-tax returns on investment for 

costs amortized over 5 years with wrchandised volume gains from N + P fertilizer response (as per figure 3) 

Site index class (25-year) 

Initial 

density 

(t reeslacre 1 45 55 65 75 

..--- -Percent - - - - - 

A1 t hough the vol ume gains are re1 at ively 

modest (about 240 cuhi c feet per acre), they combine with shifts in diameter distribution toward 

larger trees to produce attractive ROI. The estimated ROI values range up to 17.3 percent, and 

the values shown in table 6 are quite conservative 

for several reasons. Fi rst, the growth increases 

are based on observed responses to 100 pounds N 

and 50 pounds P, while the treatment costs are 

based on application of 150 pounds N and 50 pounds 

P. k few studies indicate that it is advisable 

to apply 150 pounds N, but growth data are insufficient to reliably estimate the response to the 

additional N. Second, the growth responses indi - 

cated can be obtained on many sites by applying N 

alone. Third, expensing of the fertilizer cost 

worrld have increased the ROT values. 
The conservati ve procedures we fol lowed in 

the economic analyses leave little doubt about one 

primary conclusion: Ferti lization provides very 

attractive investment opportunities for managers 

of loblolly pine forests. Fertilization also offers strategic opportunities to increase supplies 

of southern pi ne--a major objective of forest products manufacturers who grow much of the timber 

they process. As prescription technology is more 

finely tuned, risks associated with ferti 1 izer 

appl i cat i on wi 11 be reduced and fi nanci a1 returns 

will become even more attractive. 
Addi t .l' anal Rea.di ngs 

Ailer, H, lee; Ballcrcf, Russ. F;lr*.;t f~~t~i~~i?ti~" fl ?w'071; ;jVl;tl. 

if.: LoLili:liy pirrp e;3sy~t~~ S~T~[~CSIU;~I; 1987 DPCP~~!~~~ ?-lij; i~\i;7~;i1~i;, 

NG, Ralejgtl: North Carolina State versl ty, Scho-11 Forest 

Resources; 1983: 163-181. 

Gent, J.A., Jr. ; A1 len, H. t, ; Csnpbell , R.G. ; We1 t s, C.G. "agn? t ~de, 

@brat1 on, arid ~~onoti~~t analysr s of 'ioblol ly p?ne growth 

foilow-ing beddlng and phosphorus fert~lization. In: Phosphorus fertilrzation in young loblolly pine stands. NCSFFC Kpp. 17. (North 

Carol I na State Forest Ferti 1 ~zation Cooperat] ve. 1 Kaler gtj, NC: North 

Carol r na State Un1 versi ty, School of Forest Resourc~s; Ir"134: 1-18, 

Gent, James A*, Jr.; A1 len, H. Lee; Campbell, Robert G. Phosphorus and 

nitrogen plus phosphorus fertilization in loblol ly plne stands at 

estahl i shmerlt. NCSFt-C Rep. 17. (North Carolina State Forest Fert-r - lization Cooperative.) Raleigh, NC: North Carol~na Stat,& Univers~ty, 

Schlx~l of Forest Resources, 1984: 19-28, 

Jorgensen, Jacques R. ; A1 len, H. Lee. So1 1 amendments to rnalntai or 

enhance site prodtlctiv~ty. In: Ellwood, E.C. ; Ross, E.W., eds. 

Ya~ntai ni ng forest site productivity. Proceed1 nqs 1st regional 

techpi ca l conference; 1983 January 27-28; Myrtle Beach, SC. Appa1 acli-ian Society of American Forest~rs, SAF 83-09. Rethesda, MD: 

-Coc?oty of Arnerlcan Foresters; 1983:59-76. 

Kush?a, J.D. ; Fisher, R.F. Pr~dictinq sf ash pine response to ni tr3gen 

art,? ~hosphorus fert~ 1 i zati on. Soi 1 Science Soc~ ety American Journal 

c416): 1303-1306. 

Tlar-ks, A.E.; Shoulders, E. Effects of shallow water tables on he? ght 

growth and phosphorus uptake by lob101 ly and slash pines. Res. Note 

Sii-285. New Orleans, LA: U.S. Departrnert of Agriculture, Forest Serv~co, Socithern Forest Eupprimprl* St;tion; 1952. 5 pp. 

We1 Is, Carol G. ; Crutchf~eld, D.M. Fol'ar andlys~s for ?red;ct~ng 105- 

lolly pine response to phosphorus fert~li~ation on wet sltes. Kes. 

Note SE -128, As+evj 1 le, NC: U.S. Department of Agr? cul ture, Forest 

Service, Southeastern Forest Experiment Stat~on; 1969. 4 pp. 

Wells, Carol G.; Crutchfield, D.M.; Berenyi, N.M.; Davey, C.B. Soi 1 

and fol iar guide1 ines for phosphorus ferti 1 izatinn of lob101 ly pine. 

Res. Pap. SE-110. Ashevi 1 le, NC: U.S. Separtrne~t of Agriculture, 

Forest Service, Southeastern Forest Experiment Stati OR; 1973. 15 pp. 

We? Is, Carol : :tiler, Lee* Where and whe~ to apply Fertilizer. A lohlnlly p7np management guide, Gen, Tech. Rep. SE-30. Ashevtlle, NC: 

U, S, Depa rtrneqt of Agri cui ture, Forest Servl ce, Southeastern Forest 

Experiment Station; 1985, 23 pp. 

Growth rates 10 loblolly pine ( L,) stands can often be 

increilcod markrri'iy by apply?rig qitrogen, or nitrogen 

a?d pksphsrvs ferti 1 i aers. On -deficie~t Lower Coastal 

bla'ln sltes, tkle grourtl: improve 

KEYWORDS : Pi nu< taeda, econcmi c returns, nitrogen, phosphorus, 

fol lage anXjGSs7 

Wei 15, Carol ; A1 len, t~e. Where and whel to apply fertilizer. A lohlo2 ly pi~e management gu?de, Gen, Tech, Rep. SE-36. Ashevf l le, NC: 

U,S, Department of Agr~ CUT ture, Forest Service, Southeastern Forest 

Exprrirqertt Station; 1985, 23 pp. 

Growth rdtes in loSlolfy pine (P~nus taeda L,) stands can often be 

increased markedly by applying FSphK nitrogen, or nit rogerl 

and pbosphorus fertjlizers. On p5csp+or~s-deficio?t !.ower Coasts1 

PI ai n s~ tes , the growth improvement from phosphorus ferti I izat ?on of 

Ioblolly pine often amounts to an increase in site index (age 25) of 

15 feet. Nitrogen and nitrogen plus phosphorus ferti 1 ization produces 200 to 250 cuh~c feet of addittonal wood in the 5 pars after 

application mostly on larger diameter trees, 

YEVWPRDS: Pinus ta~da, economic returns, nitrogen, phosphorus, 

fol iap an-57 
NOTES 
NOTES 
NOTES 
NOTES 
NOTES 
December 1985 

Southeastern Forest Experiment Station 

200 Weaver Boulevard 

P.O. Box 2680 

Asheville, North Carolina 28802 
The Forest Service, U.S. Department of Agriculture, is dedicated to the principle of multiple 

use management of the Nation's 

forest resources for sustained 

yields of wood, water, forage, 

wildlife, and recreation. Through 

forestry research, cooperation 

with the States and private forest 

owners, and management of the 

National Forests and National 

Grasslands, it strives-as directed by Congress-to provide 

increasingly greater service to a 

growing Nation. 

USDA policy does not permit discrimination because of 

race, color, national origin, sex or religion. Any person 

who believes he or she has been discriminated against in 

any USDA-related activity should write immediately to 

the Secretary of Agriculture, Washington, D.C. 20250.