Plantand Soil 175: 31---44,1995. (~ 1995 KluwerAcademicPublishers. Printedin the Netherlands.
Stem deformity in Pinus radiata plantations in south-eastern Australia. II. Effects o f availability o f soil nitrogen a n d response to fertiliser a n d lime
Peter Hopmans, Matt Kitching and George Croatto
Centre for Forest Tree Technology, Department of Conservation and Natural Resources P O. Box 406, Kew 3101, Australia Received 1 August 1994. Acceptedin revisedform7 January 1995
Key words: lime, nitrogen, phosphorus, radiata pine, soil acidity, stem deformity
Abstract Plantations of radiata pine (P. radiata D.Don) on soils previously under legume based pastures have a high incidence of stem deformity compared with forest soils. A comparison of soil properties and tree nutrition of 5 to 7 year-old radiata pine on former pastures in the first part of the study showed that stem deformity was strongly correlated with mineralisation of soil N and in particular with nitrification. Other soil properties that have changed as a result of pasture improvement, e.g. pH, available P and Mn, were only partially correlated with stem deformity. In the second part of the study, the role of N availability and other soil properties in the expression of deformity was further investigated in a separate field experiment on soils formerly under native eucalypt forest, tobacco cropping, and improved pasture. Young radiata pine plantings were treated with lime, phosphorus, and nitrogen applied as urea and sodium nitrate. Liming increased soil pH by around 1.5 units, raised exchangeable Ca 2+ and decreased available Mn. Soil mineral N content was only marginally affected by liming. Superphosphate increased soil available P and raised levels of P in foliage. Changes in soil pH, availability of P, Mn, and B did not affect growth or stem deformity at any of the sites. In contrast, application of N fertilisers at 200 and 600 kg N ha- ~ increased mineral N content and stimulated nitrification, particularly at the forest site. The high rate of N fertiliser increased basal area at the forest site by 45%, but also raised the level of stem deformity from 12% to 56%. At the tobacco and pasture sites, this treatment did not increase growth and did not significantly raise stem deformity above the already high basic level of deformity (63%). Implications of stem deformity in young plantations of radiata pine on potential utilisation later in the rotation are discussed. Introduction Plantations of radiata pine in south-eastern Australia have traditionally been established on land cleared of native eucalypt forest. Most of these plantations are nutritionally poor and fertiliser additions are generally needed to ensure satisfactory growth (Turner and Lambert, 1986). However, clearing of native forest for softwood plantations has been phased out over the last decade and new plantations are being established on land formerly used for agricultural production. While plantations on these generally fertile sites have high growth rates, a high incidence of stem and branch deformities is causing serious losses in mer-
chantable wood (Birk, 1992a; Birk et al., 1993; Carlyle et al., 1989). The deformities are characterised by loss of apical dominance, formation of numerous thick branches, angular kinking and distortions of branches, and kinking and twisting of stems. These symptoms have been named the Toorour syndrome (Carlyle et al., 1989) after the location where it was first described by Pederick et al. (1984). Although the symptoms are similar to those of copper deficiency in radiata pine (Turvey, 1984), our earlier work on stem deformity in radiata pine (Hopmans, 1990) showed that concentrations of copper in foliage of deformed trees exceeded deficiency levels, Cu/N ratios were well above those associated with copper deficiency, and furthermore,
32 application of copper fertiliser did not alleviate stem deformity. Unlike copper deficiency, stem deformity was not associated with low levels of lignin in woody tissues of radiata pine (Carlyle et al., 1989; Turvey et al., 1992). Comparison of radiata pine on former pasture and native eucalypt forest sites showed that the Toorour syndrome was associated with previous land use and high fertility of pasture soils (Carlyle et al., 1989). Pasture soils were shown to be more acidic with high levels of available manganese and high nitrate production compared with native forest soils. Nutrient status of deformed trees was generally satisfactory and it was concluded that this syndrome is unlikely to be the consequence of a single element deficiency. Similar symptoms reported for other conifers, variously described as 'crooked leaders' in Abiesfraseri (Hinesley and Campbell, 1992) and 'snake-tailed shoots' in P. caribaea and P. oocarpa (Zech and Drechsel, 1992), were observed in fast growing, healthy trees with a satisfactory nutrient status. These studies too indicated that the deformity was associated with high soil fertility and was not caused by a deficiency of any particular nutrient. A comparison of form of 20-year old radiata pine on a cleared native eucalypt forest and a former pasture site showed that the incidence of deformity increased with site fertility and was directly correlated with mineral N concentrations in soils (Birk, 1991). Application of N fertiliser at high rates to young radiata pine on coastal sands increased growth, but also induced deformity as observed by Smethurst and Nambiar (1989). These studies indicate that there may be a link between the Toorour syndrome and the availability and uptake of soil N.
l
.............^vondnle -
Victoria
Ca~b~or• Waffenbayne • Tolmte • ' Heyw~d
130 Nl
appmxkm 144 ~
E
IJ8 ~ E
Fig. 1. Locations of study sites in young radiata pine plantations in Victoria.
The present study followed on from our earlier work (Carlyle et al., 1989; Hopmans, 1990) and firstly investigates relationships between stem deformity in radiata pine and tree nutrition and soil properties, with particular emphasis on N availability, across a range of pasture sites. Based on the results of the first part of this study, a field experiment was carried out in the second part to determine the response of young radiata pine to lime, and fertiliser N and P at three sites with contrasting former land use, viz. native eucalypt forest, tobacco cropping and improved pasture.
Methods Survey of stem deformity on pasture sites A survey was carried out of 5 to 7 year-old radiata pine plantations on former pastures at 7 localities in Victoria (Fig. 1). Average annual rainfall ranged between 840 and 1164 mm for the inland sites, and between 700 and 980 mm for the coastal sites. At each site a randomised block of 9 plots of 20 m z 20 m was established. Height and diameter at 1.3 m over bark (DBHOB) were measured on all trees in each plot. In addition, stem and branch deformity of each tree was assessed on a scale of 1 to 6 of increasing severity using the scoring system of Pederick et al. (1984). Any visual symptoms related to specific nutrient deficiencies were also noted. Samples of 1 year-old needles were collected from the second major whorl in the upper crown of six randomly selected trees in each plot for nutrient analysis. These samples were dried at 80°C, bulked on an equal weight basis and milled prior to chemical analysis. N and P were determined colorimetrically on a sulphuric acid - hydrogen peroxide digest using a Chemlab 2 autoanalyser (Eastin, 1978; John, 1970), and K was determined by flame photometry on the same digest. In addition, Ca, Mg, Mn, Zn, Cu and B were determined by ICP-AES on a nitric -perchloric acid digest. Soil samples (0-10 cm) were taken from 12 randomised points within each plot and bulked on an equal volume basis. These samples were air-dried and sieved to pass 2 mm prior to chemical analysis. Soil pH was determined potentiometrically on a soil to 0.01 M calcium chloride mixture at a 1:5 ratio. Organic C was determined using the wet oxidation procedure of Walkley and Black as recommended by Nelson and Sommers (1982). Total N was determined using a micro- Kjeldahl digestion followed by steam distillation and titration (Bremner and Mul-
33 vaney, 1982). Ammonium (Nam) and nitrate (Nnit) were determined on 2 M potassium chloride extracts using steam distillation with MgO and Devarda's alloy followed by titration (Keeney and Nelson, 1982). Available soil P was estimated colorimetrically following extraction with acidified ammonium fluoride using the procedure described by Olsen and Sommers (1982). Exchangeable Ca, Mg, K and Na were determined using the procedure given by Gillman and Sumpter (1986). Concentrations of Ca, Mg, Na and K in the leachate were determined by AAS and flame photometry. Available Cu, Zn and Mn were estimated using the DPTA extraction method described by Baker and Amacher (1982). Concentrations of Cu, Zn and Mn in extractant solutions were determined by ICP-AES. Net nitrogen mineralisation potential of soils was determined using a procedure adapted from Stanford et al. (1974). Soil (20 g) was mixed with 30 g of acid washed sand and transferred to a 50 mL polyethylene syringe containing a glass wool pad. Inorganic N was removed with 5 additions of 20 mL, of 0.01 M calcium chloride at the start of the experiment, after 1 week of pre-incubation at 35°C, and again after 2 and 4 weeks of incubation at 35°C. Excess solution was removed under suction of approximately -80 kPa. Concentrations of inorganic N in leachates were determined using the same procedure as for extractable Nam and Nr~t. Net mineralisation potential of soils was estimated as the amounts of Nam and Nni t produced after 4 weeks incubation. Relative nitrification was calculated as the percentage Nni t in the total amount of N mineralised.
Fertiliser tr&ls Following on from the survey of plantations on pasture sites, trials were established near Myrtleford in northeastern Victoria (Fig. 1 ) in young radiata pine plantings on acidic red duplex soils derived from Ordovician shales and classified as a Dr 2.21 (Northcote, 1979). Annual rainfall measured at Buffalo Dam near the sites ranged between 908 and 1232 mm over the study period. Sites were selected to provide a strong contrast in former land use and included one site cleared of native eucalypt forest with debris windrowed and burnt one year prior to planting, one site with a history of tobacco cropping, and another site with a legume based pasture for grazing and hay production. Radiata pine was established on these sites after shallow ripping and pre-planting weed control using amitrol and atrazine. Regeneration of woody weeds at the forest site was
controlled by hand slashing. None of the plantings received any fertiliser prior to the establishment of the trials. In 1987, at the age of 2 years, treatments were applied to plots of 225 m 2 (30 trees in 5 rows by 6 trees) with 4 replicates in a randomised block at each site (forest, tobacco, pasture). These treatments included control (Nil), agricultural lime (L) broadcast at 12 tonnes ha - l , superphosphate (P) at I00 kg P ha - I , P plus L, P plus urea (AM) at 200 and 600 kg N ha 1 and P plus sodium nitrate (NT) at 200 and 600 kg N ha - l . The highest rates of N fertilisers were applied as split applications of 200 kg ha- 1 at the age of 2 years followed by 400 kg ha i one year later. All fertilisers were uniformly broadcast across the plots. It should be noted that all treatments with N fertilisers (AM and NT) were given a basal dressing of superphosphate at 100 kg P ha -1 to compensate for differences in the phosphate fertiliser history between the sites. Soil samples (0-10 cm) were taken from 20 randomised points within each plot (225 m2), bulked on an equal volume basis, air-dried and sieved to pass 2 mm prior to chemical analysis. Samples were collected from all plots prior to and again 30 months after treatment. These were analysed for pH, available E extractable Nam and Nnit, exchangeable Ca, Mg, K and Na, and DPTA extractable Cu, Zn and Mn. In addition, soil samples (0--10 cm) were collected, using the same procedure, from control, lime, and the highest rate of N fertilisers (AM 600 and NT 600) at 3, 6, and 18 months after treatment and analysed for pH, and extractable Nam and Nni~ only. Samples of I year-old needles were collected from the second major whorl in the upper crown of six randomly selected trees in each plot for nutrient analysis. Samples were collected prior to treatment at age 2 years, and annually thereafter to age 6 years. Heights were measured at age 2, 3, 4, 5, and 7 years. On each occasion, stem and branch deformity of new growth of all trees was assessed on a scale of 1 to 6 as mentioned earlier. Diameters were measured at 1.3 m over bark (DBHOB) at age 7 years. Effects of treatments on growth, stem form, tree nutrient status, and soil properties were tested using analysis of variance procedures. These analyses were carried out using the statistical software packages StatView® (Haycock et al., 1992) and SuperANOVA® (Gagnon et al., 1989). Where appropriate, means were compared using Fisher's protected LSD test at the 5% level of significance.
34 Table I, Growth and distribution of stem deformityin radiata pine plantations on former pastures Locality
Age (yrs)
Avondale Carboor Warrenbayne Tolmie Yarram Boolarong Heywood PLSDc
6 5 7 7 7 7 7
Height DBHOBa (m) (cm) 4.9 7.9 10.0 6.4 8.0 7.4 9.5 .5
9.4 12.1 16.4 11.5 15.5 15.8 13.1 1.2
Average Distributionof stem deformityb (%) stemform 1 2 3 4 5 6 4.7 2.8 2.3 4.4 1.5 1.3 1.4 .6
5 31 46 4 67 84 80
2 8 9 4 14 5 4
17 34 27 18 19 11 15
13 8 7 22 1
20 17 6 21 -
43 2 5 31 -
aMean diameter at 1.3 m over bark. bPercentage of trees in stem deformityclasses 1 to 6 (see text). CFisher's ProtectedLSD at p < 0.05.
Results Stem deformity on pasture sites The survey of 5 to 7 year-old radiata pine plantations on pasture sites showed that growth and stem deformity varied significantly between locations (Table 1). The effect of stem deformity on the potential yield of merchantable wood from these plantations is clearly shown by the distribution of stemform classes at each site. Trees in classes 1 and 2 can be expected to yield high quality sawlogs as well as pulpwood without any significant losses due to deformity. Trees in classes 3 and 4 are likely to give reduced yields of lower grade sawlogs and pulpwood. In contrast, trees in classes 5 and 6 are severely deformed (Hopmans, 1990), and are likely to provide a reduced yield of pulpwood only. Potential losses in high quality sawlogs due to severe stem deformity can be expected to range from 1 1 % to 63 % (trees in classes 5 and 6) at four locations in north-eastern Victoria. In contrast, stem deformity was low (Table 1) and potential losses due to severe deformity were considerably less in the three plantations at Yarram, Boolarong, and Heywood in the coastal region of Victoria. Average nutrient concentrations in the foliage of radiata pine (Table 2) differed only marginally between locations, and concentrations were generally well above levels considered necessary for satisfactory growth (Turner and Lambert, 1986). In particular, foliar concentrations of Cu were well above the critical range (2 to 4 mg kg -1) associated with Cu deficiency in radiata pine (Turvey, 1984).
The soil profiles were gradationai or duplex red and yellow (Table 3) based on the key for the description of Australian soils by Northcote (1979). In general, soils were acidic with comparatively high levels of organic C, total N and available P, typical of soils of improved pastures (Birk, 1992b; Russell, 1986). Organic C was significantly correlated with total soil N (R 2 = 0.63, p < 0.001) and C/N ratios ranged from 12 to 22. Incubation of soils at 35°C resulted in an initial flush of Nam after pre-incubation of 1 week. This was followed by a decline in Narn and an increase in Nnit during subsequent incubation. Relative nitrification (Nni t expressed as a percentage of total inorganic N mineralised) differed significantly between localities ranging from 2% to 35%. Stem deformity was generally well correlated with various forms of N in soils, but in particular with net mineralisation and relative nitrification (Fig. 2, R 2 = 0.96, p < 0.001). Correlations with other soil chemical properties explained less of the variability in deformity and with the exception of available P were not statistically significant. Fertiliser trials Differences in soil properties and tree nutrition between sites formerly under native eucalypt forest, tobacco cropping, and legume pasture are shown in Tables 4 and 5. Past agricultural land use and associated fertiliser practices were reflected in the differences in soil pH, exchangeable Ca and K, and extractable N and P between these sites. Soil pH was less acidic at the tobacco site, because lime is generally applied together with N, P, K fertilisers as a pre-sowing appli-
35 Table 2. Concentrations of nutrients in foliage of radiata pine on former pastures Locality
Avondale Carboor Warrenbayne Tolmie Yarram Boolarong Heywood PLSD a
N
P
18.8 19.8 19.9 17.9 18.7 17.3 16.0 1.7
2.1 2.0 2.1 2.5 2.0 1.9 1.6 0.4
K Ca ( g k g -~ ) 8.5 7.8 10.6 10.9 10.6 9.5 7.0 2.0
2.2 2.1 2.2 2.2 2.9 3,2 2.8 0.6
Mg
Mn
1.2 2.0 1.2 1.3 1.6 1.5 2.4 0.3
254 306 339 214 269 265 152 77
Zn Cu (rag k'g -~ ) 41 39 39 42 53 45 25 9
7.6 7.3 7,4 7.2 7.5 8.4 5.2 2.3
B
18 16 20 21 26 24 31 5
aFisher's Protected LSD at p < 0.05.
Table 3. Classification and chemical properties of soils (0-10 cm) of radiata pine plantations on former pastures Locality
Soil type a
pH b
Avondale Gn4.11 Carboor Dr4,21 Warrenliayne Gn4,11 Tolmie Gn4.31 Yarram Gn 3.91 Boolarong Gn 3.71 Heywood Dy4.51 PLSD a
4.32 4.24 4.29 4.93 4.69 4.31 4.80 .11
Org. Total C N (g k g - l ) 50 27 39 66 41 63 44 8
2.8 2,0 2,1 3.6 3.3 4.1 2.0 0.4
Extractable Net Min. c Extr. Nan Nnit Nan Nnit P (mg k g - l ) 33 46 32 45 28 60 16 13
12 6 4 4 5 6 2 2
28 27 35 45 88 107 9 14
15 5 3 12 4 2 <1 3
Exchange. cations Ca 2+ Mg 2+ K + Na + (cmol(+)kg- 1)
15 14 9 9 15 12 11 4
5.7 2.9 1.9 8.8 5.7 5,0 2.2 1.4
1.6 .7 .3 1.8 1.6 2.0 .7 .2
.95 .28 .38 1,3 .87 .46 .24 .28
.04 .06 .04 4.07 .15 .19 .12 .02
DPTA extr. Mn Zn Cu (mgkg -l ) 102 1.4 1.9 57 1.3 1.9 52 .9 1.0 .6 .9 115 130 5.6 5.8 27 1.5 1.0 ,4 .4 12 .6 1.1 22
'~Principal Profile Form according to Northcote (1979). bSoil to 0.01 M calcium chloride ratio of 1:5. CNet mineralisation of Nam and Nnit after laboratory incubation at 35°C for 4 weeks. dFisher's Protected LSD at p < 0.05.
cation for each crop. Likewise, legume based pastures are given regular applications of superphosphate, and fixation of atmospheric N by legumes increases soil N status (Bolan et al., 1991; Russell, 1986). Initial differences in extractable soil N, P and Mn at the forest, tobacco and pasture sites (Table 4) were also reflected in the levels of these nutrients in foliage ofradiata pine at these sites (Table 5).
6"
•~'~
5.
-~
4"
E ~
3
E
1
Growth and deformity Average stem form increased from 1.3 to 2.5 in response to N fertiliser applied at 600 kg N ha -t at the forest site (Table 6). Stem form ranged between 3.1 and 3.9 at the tobacco site and from 2.7 to 3.3 at the pasture site. This level of deformity is similar to that of several radiata pine plantations on pasture sites with medium to high deformity (Table 1) included in the
0
i
i
i
10
20
30
40
Relative nitrification (%)
Fig. 2. Relationship between stem deformity in radiata pine plantations on former pastures and relative nitrification in soils as determined by short-term, laboratory incubations (bars indicate standard deviations).
survey of the first part of the study. Average stem form of control plots at the forest site (Table 6) was the same
36
Table 4. Comparison and chemical properties of soils (0--10 cm) of radiata pine plantations on former native eucalypt forest, tobacco, and pasture sites before and 30 months after treatment with lime, phosphorus and nitrogen Soil/ Treat.
pH a Ca z+
Before treatment Forest 4.2 Tobacco 4.8
2.8 5.5
Exchange. cations Mg 2+ K+ Na + (cmol(+)kg- 1)
1.1 1.0
0.6 1.2
Extractable Nam Nnit
0.10 0.07
4.8 7.8
1.0 9.5
Extr. DPTA extr. F Mn Zn Cu (mg k g - 1)
5 133
16 16
0.8 1.3
1.3 1.5
Pasture
4.2
3.9
0.6
0.5
0.07
7.8
10.3
8
98
1.3
1.4
PLSD b
0.1
0.6
0.1
0.1
0.01
1.3
1.9
3
9
0.2
0.1
After treatment Forest Nil 4.2 P 4.5 L 5.7 PL 5.7 AM 200 4.4
2.2 4.8 15.7 15.2 3.7
1.0 1.2 1.3 1.1 1.1
0.62 0.86 0.72 0.68 0.71
0.07 0.08 0.07 0.07 0.10
10.1 14.1 9.5 9.5 10.9
0.3 0.2 0.4 1.2 0.7
7 41 9 48 46
36 63 32 20 53
0.6 0.9 0.5 0.6 0.9
0.7 1.1 0.7 0.7 0.9
4~5 4.6
4.7 4.8
1.1 1.2
0.78 0.75
0.11 0.19
13.9 11.0
3.1 0.5
50 47
50 73
0.8 0.8
0.8 0.7
NT 600
4.6
4.3
1.3
0.91
1.20
11.5
1.5
43
38
0.8
0.7
PLSD
0.3
2.5
ns
0.11
0.22
ns
1.9
16
24
0.2
ns
Tobacco Nil
4.9
6.4
1.4
1.02
0.04
8.3
5.9
100
41
1.3
1.4
P L PL AM 200 AM 600 NT 200
5.0 6.5 6.5 4.9 4.7 5.1
7.3 16.2 16.0 7.1 6.8 7.3
1.2 1.0 1.0 1.1 1.1 1.3
1.00 0.98 0.94 0.87 0.98 1.08
0.04 0.03 0.03 0.03 0.04 0.07
9.6 5.1 6.1 11.1 11.2 6.4
5.3 6.9 6.8 7.7 18.5 7.9
153 118 194 162 158 150
37 13 12 48 46 53
1,3 0,6 0.9 1.6 2.5 1.3
1.2 0.8 0.9 1.0 1.6 1,1
NT 600 PLSD
5.1 0.9
8.1 2.1
1.2 0.2
1.13 0.16
0.22 0.07
5.3 ns
12.7 4.9
145 33
36 12
1.4 0.5
1,1 0.5
9 43 12 51 45 42 44 41
112 127 70 49 135 143 123 128
1.1 1.3 0.7 0.8 1.3 1.2 1.5 1.5
0.9 0.8 0.7 0.7 0.8 0.8 0.7 0.8
22
35
0.5
ns
AM600 NT 200
Pasture Nil
4.5
5.9
0.9
0.62
0.02
13.2
10.0
P L PL AM 200 AM 600 NT 200 NT 600 PLSD
4.6 5.9 6.2 4.5 4.2 4.6 4.6 0.4
6.7 16.5 16.4 5.1 3.9 6.1 5.6 2.9
0.7 0.8 0.8 0.6 0.4 0.8 0.7 0.2
0.52 0.60 0.59 0.62 0.51 0.53 0.61 ns
0.03 0,02 0.02 0.02 0.02 0.04 0.31 0.07
11.1 6.7 7.7 9.7 12.1 7.6 6.1 ns
6.3 8.1 9.4 7.2 18.7 10.0 13.7 7.3
aSoil to 0.01 M calcium chloride ratio of 1:5. bFisher's Protected LSD at p < 0,05; differences between means not significant.
37 Table 5. Concentrations of nutrients in foliage of radiata pine on former native eucalypt forest, tobacco, and pasture sites before treatment Site
N
S
P K (gkg -1 )
Forest
16
1.1
1.7
Tobacco
18
1.3
2.5
Pasture
18
1.2
2.0
PLSD a
1
0.1
0.1
Ca
Mg
AI
Fe
Mn Zn (rag kg -~ )
Cu
B
9
1.8
1.3
480
56
142
39
6.1
9
12
1.9
1.0
480
61
198
43
6.0
12
10
2.1
0.9
490
53
356
49
6.9
11
1
0.2
0.1
ns
4
30
4
0.4
2
'~Fisher's Protected LSD at p < 0.05; ns, differences between means not significant.
Table 6. Height (H, m), basal area (BA, m2 ha - l ) and average stem form (SE average score on a scale of I to 6 of increasing deformity) of 7-year-old radiata pine 5 years after treatment with lime, phosphorus and nitrogen on former native eucalypt forest, tobacco, and pasture sites Treatment
Forest H
Tobacco
BA
SF
H
BA
Pasture SF
H
BA
SF
Nil
8.4
8.3
1.3
10.6
26.6
3.2
12.1
27.3
2.7
P
7.7
6.6
1.5
10.7
25.1
3.1
12.2
27.4
2.9
Lime
8.3
8.3
1.4
10.9
25.0
3.2
12.2
29.8
2.7
Lime + P
8,9
I0.1
1.4
11.1
28.5
3.3
12.2
28,8
2.9
AM 200
8.3
8.2
1.8
10.5
25.3
3.5
12.3
28,8
2.9
AM 600
9.3
12.0
2.5
10.2
27.2
3.9
12.0
26.2
3.0
NT200
9.1
10.0
1.6
10.9
28.4
3.1
12.4
28.9
2.7
NT 600 PLSD '~
9.0 ns
11.3 2.1
2.0 0.5
10.6 ns
28.3 ns
3.4 ns
12. l ns
26.7 ns
3.3 ns
aFisher's Protected LSD at p < 0.05; ns, differences between means not significant.
as that observed in plantations with a low incidence of deformity (Table 1). The incidence of stern deformity (percentage of trees in classes 3 to 6) in control plots was low at the forest site (12%) compared with the tobacco (64%) and the pasture sites (62%). Stem deformity reached its peak at age 4 to 5 years (Fig. 3). At the forest site, application of N fertilisers significantly increased stem deformity from 12% to 38% and 56% for urea at 200 and 600 kg N ha -t, and to 23% and 40% for sodium nitrate at 200 and 600 kg N ha- 1, respectively. In contrast, application of N fertilisers resulted in only minor increases in the already high levels of deformity at the tobacco and pasture sites. Liming and P fertiliser did not affect stem deformity at any site (Fig. 3). Tree height was not affected by either lime, E or N fertilisers at any site (Table 6). However, significant differences in height growth between sites became apparent during the study (Fig. 4). Average height at age 7 years ranged from 8.6 m, to 10.7 and 12.2 m
at the at the forest, tobacco and pastures sites, respectively. At the forest site, application of N fertilisers at 600 kg N ha-I in combination with superphosphate increased basal area (BA) at age 7 years from 8.3 to 11.3 and 12.0 m 2 ha -~ for sodium nitrate and urea, respectively (Table 6). However, BA was not affected by lower rates of N fertiliser or any of the lime or P treatments. Growth at the tobacco and pasture sites was not significantly affected by any of the treatments. Soil
Over a period of 18 months after treatments commenced, average mineral N content of the soil increased to 76, 102, and 100 mg kg- l for the highest rate of urea, and to 44, 75, and 73 mg kg-1 for the highest rate of sodium nitrate at the forest, tobacco and pasture sites respectively (Fig. 5). Application of urea stimulated nitrification as indicated by the high levels of soil nitrate (Fig. 6), in particular at the forest site,
38
AM600
ml r~
o
Forest Tobacco
•
0
2
3
4
5
7
Aiv1200
MVL600
60 "~
Pasture
~
~
NT200
m
o
2
3
i 4 Age
h 5 (yrs)
i 6
i 7
Fig. 4. Height growth of radiata pine established on former native eucalypt forest, tobacco, and pasture sites. Bars indicate standard errors.
~
40
140
Forest
120"
g 2
3
4
5
Z:
7
10o 80"
Ill Nil g~ Lime AM600 H NT600
60" E
40" 20~ 0
0 AM200 AM600 NT 200 Yr600
6
18
140
30
Tobacco
120 ~
o 4°la 2o
~.
0
g
100 ~
7
80"
2
3
3
4 Age
5
Nil Lime [] AM600 Et NT 600
•
60" 7
(yrs)
z~
40" 20"
Fig. 3. Changes in stem deformity (percentage of trees in stem form classes 3 to 6) in response to N fertilisers applied to young radiata pine on land previously under native eucalypt forest, tobacco cropping, and improved pasture. Bars indicate standarddeviations.
0 0
3
6
18
140
30
Pasture
12o: ,.~
where nitrate increased from less than 1 mg k g - z to 44 mg k g - l after 18 months. Levels of ammonium in fertilised plots declined rapidly to those in control plots, however, nitrate was still higher in most plots treated with N at 600 kg ha-~ after 30 months (Table 4). Exchangeable Na + increased following applications of sodium nitrate (Table 4). Superphosphate increased extractable P levels by approximately 50 mg kg-1 (Table 4). It also increased exchangeable Ca 2+ and DPTA extractable Mn and Zn at the forest site. Liming increased soil pH by around 1.5 units and also increased exchangeable Ca 2+ at all sites (Table 4). In addition, it decreased DPTA extractable Mn and Zn at all sites, and Cu at the tobacco site. Lime did not appear to affect the mineral N content of soils at 3, 6, 18 and 30 months except for a temporary increase at the tobacco site (Fig. 5).
Z
I00"
80'
• I~ D []
6o 2
Nil Lime AM600 NT600
r20-
o 0
3
6 Months
18
30
Fig. 5. Changes in extractablesoil N following application of lime, urea and sodium nitrate to young radiata pine plantations on former native eucalypt forest, tobacco, and pasture sites. Bars indicate standard errors.
Tree nutrition Application of N fertilisers at the rate of increased levels of N in foliage of radiata pine from 14 to 20 g kg-1 at the forest site and from 17 to 20 g kg - I at the tobacco site. At the pasture site levels of N in foliage ranged from 18 to 21 g kg -~ , and levels were not significant-
39 Forest
100
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i -
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Ammonium Nitrate
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,~
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m
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Fig. 6. Extractable ammonium and nitrate in soil 18 months after application of lime, urea and sodium nitrate to young radiata pine plantations on former native eucalypt forest, tobacco, and pasture sites. Bars indicate standard errors.
ly affected by applications of N fertiliser. In general applications of N did not significantly affect foliage concentrations of other nutrients with the exception of B. Levels of B in foliage were generally marginal (between 8 and 12 mg kg -1 ) at all sites, and there was evidence of B deficiency in several trees at the forest site. Application of sodium nitrate stimulated uptake of B, particularly at the forest site where concentrations in foliage increased from 9 to 22 mg k g - 1 after 4 years for the highest rate of N (Fig. 7). In contrast, urea did not affect the uptake of B. There was no indication of a decline in Cu in foliage in response to application of N except at the tobacco site, where sodium nitrate reduced Cu in foliage to around 3 mg kg- t. Application of superphosphate increased foliar levels of P from 1.3 to 1.9 g kg -l at the forest site, from 2.5 to 3.5 g k g - 1 at the tobacco site, and from 2.0 to 2.8 g kg -1 at the pasture site. Treatment with superphosphate or lime also raised levels of Ca in foliage from 1.6 to 2.5 g kg -1 at the forest site, from 2.0 to
Age (yrs)
Fig. 7. Changesin levels of B in foliage of radiatapine following application of urea and sodium nitrate at 600 kg ha-l on former native eucalyptforest, tobaccoand pasturesites (bars indicate LSD values).
3.0 g kg-l at the tobacco site, and from 2.1 to 3.2 g kg-t at the pasture site. Superphosphate also increased the levels of Zn in foliage from 20 to 35 mg kg-l at the forest site. Levels of Zn at the other sites ranged between 35 and 55 mg k g - l but differences between treatments were not significant. Application of lime caused a decline of Mn in foliage from 190 to 110 mg kg -1 at the forest site, from 300 to 140 mg kg -I at the tobacco site, and from 540 to 370 mg kg-1 at the pasture site. Levels of other micronutrients were not significantly affected. Although liming decreased the level of DPTA extractable Zn in soils (Table 4), there was no commensurate decline of Zn concentrations in foliage. Liming resulted in a slight decrease of 0.5 g kg -1 in levels of N in foliage at the forest and tobacco sites but only for two years after treatment.
40 Discussion Deformity on pasture sites
In south-eastern Australia pasture improvement with legumes and regular fertiliser additions have increased soil organic matter and availability of N and P (Birk, 1992b; Carlyle et al., 1989; Russell 1986). In addition, introduction of legumes in pastures has generally changed the nitrogen cycle in favour of nitrification; this has caused significant acidification in pasture soils in south-eastern Australia (Bolan et al., 1991; Helyar et al., 1990). The survey of young radiata pine plantations on pasture sites showed that stem deformity was positively correlated with net N mineralisation and in particular with nitrate production in soils (Fig. 2). The incidence of stem deformity was low on soils with high levels of mineral N but with a low capacity to nitrify. The nutrient status of trees was generally satisfactory, and it is unlikely that stem deformity was associated with a specific nutrient deficiency. These findings are consistent with the correlation between deformity in 20-year old radiata pine established on former pastures and total mineral N in soils reported by Birk (1991). The incidence of stem deformity in plantations on pasture sites in north-eastern Victoria was high with up to 63% of trees severely deformed. This can be expected to have a significant impact on potential utilisation of these stands. Although the study showed a decline in deformity of new growth with time (Fig. 3), severe deformity at an early age affects the lower and most valuable part of the stem and this is likely to result in a downgrading of that section from a high quality sawlog to pulpwood, or the log is rejected altogether when sinuosity exceeds the limits for mechanical debarking and processing. Moderate deformity is likely to result in downgrading of sawlogs to pulpwood. Average potential loss in merchantable volume due to culling of severely deformed trees was estimated at 36% (range 11% to 63%). This represents a significant increase in loss of merchantable wood due to defects compared with plantations on former native forest sites in the same area. A study of the impact of defects on merchantable volume of 17 year-old radiata pine plantations on cleared native eucalypt forest by Wright et al. (1967) showed that 14% of trees had moderate to severe stem deformity in plantations on lower slopes; this compares with an average of 36% of severely deformed trees in the present study. Wright et al. (1967) reported a loss in volume due to culling of
deformed trees of 4.2 m 3 ha- ~ (1.2% of total volume) and a downgrading of sawlogs to pulpwood of 42 m 3 ha - l (11.3% of total volume). A more recent study of the effects of previous land use on merchantable volume by Birk et al. (1993), showed a significant reduction in the yield of sawlogs in a 21 year-old plantation established on a cultivated pasture in New South Wales. Severe deformity early in the rotation of this plantation resulted in a significant reduction in merchantable volume at age 21 years. Trees with stem defects increased from 45% on a former native forest site to 88% on a former cultivated pasture. This increased volume loss due to culling of trees with severe deformities from 10% to 27% and decreased sawlog volumes by 50% due to downgrading of deformed trees to pulpwood. Clearly, deformity of radiata pine occurring early in the rotation on pasture sites can be expected to decrease the value of wood produced and increase the amount of waste. The survey of pasture sites clearly showed a strong link between deformity and relative nitrification in soils (Fig. 2), however, other soil properties such as pH, available P and Mn may still be implicated in the expression of the Toorour syndrome. The hypothesis put forward from this survey, that deformity is due to soil N mineralisation and nitrification, was further investigated at three sites with contrasting former land use in the second part of this study. High rates of N fertiliser were used in this second part of the study to stimulate soil N mineralisation and to assess its effects on growth and deformity of radiata pine. In addition, the effects of fertiliser P, and liming on growth and stem form of radiata pine and soil properties were also examined. Soil properties of sites formerly under native eucalypt forest, tobacco cropping, and improved pasture selected for the trial were typical of the agricultural land used for establishment of pine plantations in south-eastern Australia with elevated levels of available N (mainly as nitrate), extractable P, and exchangeable cations (Table 4). These changes in soil properties due to previous land use have resulted in elevated levels of N, P, K, Ca, Mn, and Cu, but decreased levels of Mg in foliage of radiata pine (Table 5). Similar changes in nutrient status of radiata pine on former pastures compared with forest sites were reported by Birk (1991) and Carlyle et al. (1989). Height and basal area at the age of 7 years at the three sites of this study were within the range for fast growing radiata pine plantations in Australia (Birk, 1992a; Snowdon and Benson, 1992) and New Zealand (Hunter et al., 1987; Madgewick et al., 1977). Growth
41 40
30
•
~.,k
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•
o
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o
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o
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o oo
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o ~
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,
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Fig. 8.
Relationships between basal area of radiata pine at age 7 years and levels of N in foliage at age 4 years, 2 years after application of lime, N and P fertilisers on former native eucalypt forest, tobacco, and pasture sites.
at the tobacco and pasture sites was not affected by N fertiliser, lime or superphosphate. In contrast, the combined application of N (600 kg ha-l), either as urea or nitrate, and P (100 kg ha - t ) as superphosphate increased basal area by 45% at the forest site. Growth response to N applied at the lower rate was not significant, presumably due to immobilisation of fertiliser N at the forest site. Likewise, growth responses to superphosphate without N and lime were negligible, indicating that the response was mainly due to improved availability and uptake of N. At the forest site, plot basal areas at age 7 years were correlated (R 2 = 0.44, p < 0.01) with levels of N in foliage at the age of 4 years (Fig. 8) indicating that the response was mainly related to tree N status. There was little change in basal area when N levels exceeded 17 g kg - t . In contrast, basal area was not correlated with N in foliage at the tobacco and pasture sites where levels were generally above 17 g kg -1 indicating that availability of N at these sites was probably in excess of tree requirement. These findings are consistent with the strong correlation between growth and N content of foliage following application of N to young radiata pine in New Zealand (Hunter et al., 1987). Average stem form (Table l) in the survey of pasture sites, based on a scale of 1 to 6 of increasing deformity, ranged from 1.3 (low deformity) to 4.7 (severe deformity). Average stem form of untreated radiata pine was 1.3 at the forest site, and 3.2 and 2.7 at the tobacco and pasture sites (Table 6). The latter sites are representative of plantations with intermediate to high deformity in the survey of former pasture sites. The incidence of stem deformity (in unfertilised trees was low (12%) at the forest site compared with the tobacco (64%) and pasture (62%) sites. The basic level of deformity at the forest site is consistent with the
incidence of stem kinks (14%) in radiata pine plantations on lower slopes around Myrtleford reported by Wright et at. (1967). The lower rate of N fertiliser at the forest site did not improve growth, but increased stem deformity to 38%. The highest rate o f N fertiliser increased basal area significantly, but also increased stem deformity to 56%, similar to the level of deformity at the tobacco (64%) and pasture (62%) sites. There was little difference in response to N applied as urea or sodium nitrate except that deformity was somewhat less for nitrate treatments at the forest site (Fig. 3). This response to fertiliser N is consistent with the relationship between stem deformity and availability of nitrate (Fig. 2) from the survey of pasture sites in the first part of this study, because applications of urea induced strong nitrification resulting in higher levels of mineral N and nitrate in soil compared with applications of N as sodium nitrate (Figs. 5 and 6). Application of N increased mineral N in soils at the tobacco and pasture sites, but increases in stem deformity were small and generally not significant indicating that detbrmity was already at a maximum on these sites. Stem deformity was assessed on new growth since the previous assessment, and results showed a maximum deformity of around 63% between age 4 and 5 years followed by a decline. This also showed that approximately 37% of trees retained good stem form irrespective of the increase in available soil N. Radiata pine planted on the study sites originated from open pollinated seed orchards in Victoria, and is representative of the genetic material currently used to establish second rotation plantations on former native eucalypt forest sites. This indicates a considerable tolerance of some trees to high N supply; therefore genotypes of radiata pine selected for straightness from progeny trials on pasture sites are likely to maintain good form on soils with a wide range of available N as nitrate. These results support the findings of Bail and Pederick (1989) that the expression of deformity in response to high availability of soil nitrate appears to be under strong genetic control. This has made it possible to select and propagate genotypes with straight stems and light branching for establishment of plantations on these nitrifying pasture soils. While this provides a practical solution to the problem of poor form in new plantings on pastures, there remains the potential risk of inducing poor form with N fertilisers applied to existing young plantations on less fertile sites. The majority of 1st and 2nd rotation plantations in south-eastern Australia are on former native lbrest sites. There is considerable scope for improving the productivity of these plantations through more inten-
42 sive site and nutrient management (Flinn and Turner, 1990). However, the present study indicates that applications of N early in the rotation may not just improve growth, but also increase deformity in young trees. Strong genetic variation of radiata pine in the expression of the Toorour syndrome inspired further work to define differences between genotypes. Nutritional physiology and structural and anatomical characteristics of straight and deformed trees were investigated in a separate study at the pasture site (Turvey et al., 1993). However, comparison of nutrient concentrations in meristematic tissues, as well as wood density, tracheid length, and microfibril angle of leaders showed little difference between straight and deformed trees. So far these results have indicated little difference in nutritional physiology or anatomical features between straight and deformed genotypes of radiata pine. A similar investigation of 'crooked' leaders in Abiesfraseri showed no consistent difference in nutrition of trees with straight and deformed shoots, except that foliar nitrogen concentrations tended to be higher in deformed trees (Hinesley and Campbell, 1992). Likewise, Zech and Drechsel (1992) found that deformity in new growth described as 'snake-tailed shoots' in P. caribaea and P. oocarpa was not associated with a specific nutrient deficiency or an imbalance of nutrients. These findings are consistent with results from the present study which showed that stem deformity in radiata pine was not associated with a specific nutrient deficiency, but was due to high N mineralisation and nitrification. Furthermore, deformity was induced with N fertiliser. While our study showed a strong link between N supply and deformity, further work is needed to investigate the physiological processes of stem deformation of radiata pine in response to nitrification using 15N tracer studies. This technique could be used to identify differences in uptake and assimilation of 15N labelled nitrate between straight and deforming genotypes of radiata pine. Applications of sodium nitrate plus P increased basal area as well as stem deformity at the forest site, but did not affect either growth or deformity at the other sites. This treatment also did stimulate the uptake of B at all sites (Fig. 7) and therefore raised concentrations of B in foliage from marginal to satisfactory levels. Concentrations of B continued to increase well after the decline in soil mineral N to pre-treatment levels (Fig. 5) and it is suggested that availability and uptake of B improved due to applied sodium rather than nitrate. This is consistent with the observation that B in foliage was not affected by N applied as urea, although this
treatment did induce significant nitrification. Likewise, treatment with P alone did not significantly increase levels of B in foliage. On sites with chronic B deficiency, an improvement in B levels of radiata pine can be expected to alleviate die-back symptoms and increase growth (Hopmans and Clerehan, 1991; Lambert and Turner, 1986). Concentrations in foliage were generally above the level associated with B deficiency in radiata pine (5 mg kg- l), and although levels of B in foliage increased from marginal to satisfactory levels, there was no evidence to indicate that this improved growth or reduced deformity at any of the sites in this study. This is consistent with earlier work by Hopmans and Clerehan (1991) which showed that borax applied to B-deficient radiata pine on former pastures decreased die-back symptoms but did not affect stem deformity. The increase in growth and decline in stem form was due to fertiliser N (as sodium nitrate) rather than an improvement in the uptake of B. The combined application of N (as urea) plus P maintained B in foliage at similar levels to those of control treatments. Application of N alone could have resulted in a decline in B levels and induced B deficiency as shown in other studies (Arronsson, 1983; Stone, 1990). Regular applications of P fertilisers are a common practice for tobacco cropping and maintenance of legume-based pastures in Australia. High availability and uptake of P is therefore common in plantations of radiata pine established on such agricultural sites compared with plantations on cleared forest sites (Birk, 1991; Carlyle et al., 1989). These studies showed that stem deformity was associated with high soil P status. In the present study application of superphosphate increased soil P levels by around 50 mg kg -1 raising P levels in foliage from marginal (I .3 g kg- l ) to satisfactory (1.9 g kg -1) at the forest site and to very high levels (3.5 g kg - l ) at the tobacco site. This raised the P status of trees at the forest site to the same level as unfertilised trees at the pasture site, but did not induce stem deformity. This shows that while high P status is often characteristic of plantations on sites formerly under agricultural land use, increased availability and uptake of P does not cause stem deformity in radiata pine. Previous work showed that pasture soils were more acidic with higher levels of extractable Mn than soils under native eucalypt forest (Birk, 1991; Carlyle et al., 1989). Elevated levels of Mn in foliage of radiata pine were found to be associated with tree deformity on former pastures (Birk, 1991). This raised the question of the role of soil pH and Mn in the process
43 of deformity on these sites. In the present study lime was applied to change soil pH sufficiently to have a significant impact on soil properties and tree nutrition, and to determine the effects on tree growth and deformity. Liming changed soil pH by 1.5 units, increased exchangeable Ca 2+ and decreased extractable Mn and Zn. This raised Ca and decreased Mn in foliage at all sites, but levels of Zn were not affected. Although levels of Mn in limed, deformed trees at the tobacco site declined to the same level as in untreated, straight trees at the forest site, this change in Mn status did not reduce stem deformity. While there was a substantial decline of Mn in foliage following liming, concentrations remained well above the critical level (10 mg kg - l ) normally associated with Mn deficiency in radiata pine (Turner and Lambert, 1986; Will, 1985). Results of the present study showed that stem deformity in radiata pine was not affected by substantial changes in soil pH or Mn. In general liming of these young plantings did not increase mineral N content of soils (Fig. 5) and only raised nitrate levels marginally at the tobacco and pasture sites (Fig. 6). Liming has been shown to temporarily increase nitrate in soil solutions in P sylvestris forests, mainly because of stimulation of biological activity in the litter layer. This increased nitrate leaching and reduced levels of N in foliage (Arnold et al., 1993; Marschner et al., 1989). In the present study lime was applied at the age of 2 years, prior to the development of a litter layer, and although liming may have stimulated nitrification, there was little change in total mineral N content of soils. Because changes in soil N were comparatively minor, stem deformity was not affected by liming.
and 56% respectively. Deformity increased when N was applied either as urea, which stimulated nitrification, or as sodium nitrate. This raised stem deformity to a similar level as observed at the tobacco and pasture sites (63%). Soils at the latter sites were already nitrifying and while application ofN fertiliser stimulated further nitrification, this did not increase deformity significantly above 63%. This indicated that deformity had already reached its maximum at these sites. Previous studies have demonstrated that agricultural land use not only changes soil N mineralisation, but also pH, availability of P and micronutrients. The impact of these factors on radiata pine were also examined and it was shown that soil pH, availability of P, Mn, and B did not directly affect stem deformity. It is therefore concluded that stem deformity of radiata pine is induced by soil nitrification. Further work is required to define the physiological processes involved in the expression of stem deformity in response to uptake and assimilation of nitrate. There is strong genetic variation in the expression of the Toorour syndrome, and while attempts to define differences between straight and deforming genotypes ofradiata pine have not been successful so far (Turvey et al., 1993), tracer studies using ~SN may be needed to define functional differences. At present, the use of N fertilisers to stimulate growth of young plantations on forest soils is likely to induce poor form to a similar level as observed on the more fertile pasture sites. This is likely to reduce expected gains in merchantable wood (Birk et al., 1993). However, future planting of forest sites with genotypes of radiata pine specifically selected for straightness and light branching on nitrifying pasture soils (Bail and Pederick, 1989) would allow the productivity of these sites to be increased with N fertilisers and would minimise losses due to stem deformity.
Conclusions A survey ofradiata pine on former pasture sites showed considerable variation in stem deformity between sites. Deformity was not associated with any specific nutrient deficiency, but there was a strong correlation between soil N mineralisation, particularly relative nitrification, and stem deformity in these young plantations across a range of pasture sites. The hypothesis that deformity was due to nitrification was tested on three sites with contrasting former land use (eucalypt forest, tobacco cropping, and pasture). Application of N fertilisers at rates of 200 and 600 kg ha-~ increased stem deformity in young plantings on former eucalypt forest site from a comparatively low incidence (12 %) to 38%
Acknowledgements The authors thank the Victorian Plantations Corporation for providing financial support for this study. We also thank Ross Bickford and John Collopy for carrying out the tree measurements at age 7 years, Melissa Flatman and Debbie Smith for assistance with the collection and chemical analysis of foliage and soils, and Richard Stokes for assistance with drafting of figures. The authors also thank Dr David Flinn for his encouragement throughout the project and Dr Elaine Birk for her constructive comments on the manuscript.
44
References Arnold G, van Diest A and Sweers I L 1993 Response of a Scots pine (Pinus sylvestris) stand to application of phosphorus, potassium, magnesium and lime. II. Soil solution composition. Neth. J. Agric. Sci. 41,267-289. Arronson A 1983 Growth disturbances caused by boron deficiency in some fertilized pine and spruce stands on mineral soils. Commun. Inst. For. Fenn. 116, 116--122. Bail I R and Pederick L A 1989 Stem deformity in Pinus radiata on highly fertile sites: expression and genetic variation. Aust. For. 52, 309-320. Baker D E and Amacher M C 1982 Nickel, copper, zinc and cadmium. In Methods of Soil Analysis, Part 2. Ed. A L Page. pp 323-336. American Society of Agronomy Inc., Madison, WI. Birk E M 1991 Stem and branch form of 20-year old radiata pine in relation to previous land use. Aust. For. 54, 30-39. Birk E M 1992a Biomass and nutrient distribution in radiata pine in relation to previous land use I. Biomass. Aust. For. 55, 118-125. Birk E M 1992b Nitrogen availability in radiata pine plantations on former pasture sites in southern New South Wales. Plant and Soil 143, 115-125. BirkE M, Bowman V J, Fulton J A and Hides 11993 Merchantability of Pinus radiata in relation to previous land use. Aust. For. 56, 157-164. Bolan N S, Hedley M J and White R E 1991 Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures. Plant and Soil 134, 53-63. Bremner J M and Mulvaney C S 1982 Nitrogen - Total. In Methods of Soil Analysis, Part 2. Ed. A L Page. pp 595-624. American Society of Agronomy Inc., Madison, WI. Carlyle J C, Turvey N D, Hopmans P and Dowries G M 1989 Stem deformation in Pinus radiata associated with previous land use. Can. J. For. Res. 19, 96-105. Eastin E F 1978 Use of an autoanalyser for total nitrogen determination in plants. Commun. Soil Sci. Plant Anal. 9, 107-113. Flinn D W and Turner J 1990 Opportunities for increased softwood production through intensive site and nutrient management. In Prospects for Australian Plantations. Eds. J Dargavel and N Semple. pp 225-240. Australian National University, Canberra, Australia. Gagnon J, Roth J M, Carroll M, Hofmann R, Haycock K A, Plamondon J, Feldman D S Jr and Simpson J 1989 SuperANOVA. Abacus Concepts Inc., Berkeley, CA, 316p. Gillman G P and Sumpter E A 1986 Modification to the compulsive exchange method for measuring exchange characteristics of soils. Aust. J. Soil Res. 24, 61-66. Haycock K A, Roth J M, Gagnon J, Finzer W F and Soper C 1992 StatView. Abacus Concepts Inc., Berkeley, CA. 466p. Helyar K R, Cregan P D and Godyn D L 1990 Soil acidity in New South Wales - Current pH values and estimated acidification rates. Aust. L Soil Res. 28, 523-537. Hinesley L E and Campbell C R 1992 Crooked leaders and nutrition in Fraser fir christmas trees. Can. J. For. Res. 22, 513-520. Hopmans P 1990 Stem deformity in Pinus radiata plantations in south-eastern Australia: I. Response to copper fertiliser. Plant and Soil 122, 97-104. Hopmans P and Clerehan S 1991 Growth and uptake of N, P, K and B by Pinus radiata D. Don in response to applications of borax. Plant and Soil 131,115-127.
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