The effects of soil compaction and fertilizer application on the ...

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The effects of soil compaction and fertilizer application on the establishment and growth of. Pinus radiata. R.C. Simcock, R.L. Parfitt, M.F. Skinner, J. Dando, and ...
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The effects of soil compaction and fertilizer application on the establishment and growth of Pinus radiata R.C. Simcock, R.L. Parfitt, M.F. Skinner, J. Dando, and J.D. Graham

Abstract: Ground-based harvest operations in planted forests can adversely affect the soil and subsequently the productivity of the plantation. This study examined the effects of compaction, site preparation, and fertilization on soil physical and chemical properties and tree growth in a trial established at a second-rotation harvest on an imperfectly drained clay loam located in the North Island, New Zealand. Treatments were installed following harvest of Pinus radiata D. Don. There were four physical treatments: no treatment, compaction in rows by skidder, site preparation (rip and disk), and compaction followed by site preparation; the three nutrient treatments included no fertilizer, nitrogen (N), and N plus phosphorus (P). Response of P. radiata was studied for the first 4 years of growth. Compaction reduced survival of P. radiata at planting and during the first year of growth as the result of an increased oxygen deficit, caused by a reduction in macropore volume, and a shallower depth to the perched water table. Site preparation improved both survival of the seedlings and growth over 4 years. There was an initial growth response to N, but fertilizer did not increase survival of the seedlings. After 4 years, both site preparation and N plus P treatments gave approximately 10% extra growth, suggesting that N plus P may have been as effective as site preparation for improved growth of the trees that survived the first 2 years. However, since survival of seedlings is important to the economics of plantations, especially where planting densities are low, site preparation of soils with low macropore volume should be considered as a management tool. Résumé : Les opérations forestières qui se déroulent sur le terrain dans les plantations peuvent être néfastes pour le sol et, subséquemment, pour la productivité de la plantation. Cette étude examine les effets de la compaction, de la préparation de terrain et de la fertilisation sur les propriétés physiques et chimiques du sol et sur la croissance des arbres dans un essai établi lors de la récolte après deux révolutions sur un loam argileux mal drainé situé dans l’île du Nord en Nouvelle-Zélande. Les traitements ont été mis en place après la récolte de Pinus radiata D. Don. Il y avait quatre traitements physiques : aucun traitement, compaction dans les sentiers de débusqueuse, préparation de terrain (fragmentation et disquage), compaction suivie par la préparation de terrain; il y avait trois traitements avec des nutriments : aucun fertilisant, avec d’azote (N) et avec N plus phosphore (P). La réaction de P. radiata a été étudiée pendant les quatre premières années de croissance. La compaction a réduit la survie de P. radiata au moment de la plantation et durant la première année de croissance à cause de l’augmentation du déficit en oxygène causé par une réduction du volume de macropores et une moins grande profondeur de la nappe suspendue. La préparation de terrain a amélioré la survie et la croissance des semis sur une période de 4 ans. Il y a eu une réaction initiale de la croissance à N mais la fertilisation n’a pas augmenté le taux de survie des semis. Après 4 ans, la préparation de terrain et les traitements avec N plus P ont procuré environ 10 % de croissance supplémentaire, ce qui laisse croire que la fertilisation avec N plus P a pu être aussi efficace que la préparation de terrain pour une meilleure croissance des arbres qui ont survécu pendant les deux premières années. Cependant, comme la survie des plantations est importante pour l’économie des plantations, particulièrement où la densité des semis est faible, la préparation de terrain sur les sols avec un faible volume de macropores devrait être considérée comme un outil d’aménagement. [Traduit par la Rédaction]

Simcock et al.

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Introduction Ground-based harvesting of plantation forests can result in soil compaction and disturbance, leading to reduced soil

quality and loss of production of subsequent tree crops (Bockheim et al. 1975; Rab 2004). Compaction often causes a reduction in soil porosity and increased soil bulk density (Gent et al. 1983). The recovery of soils from compaction

Received 21 June 2005. Accepted 9 January 2006. Published on the NRC Research Press Web site at http://cjfr.nrc.ca on 11 April 2006. R.C. Simcock. Landcare Research, Private Bag 92170, Auckland, New Zealand. R.L. Parfitt1 and J. Dando. Landcare Research, Private Bag 11052, Palmerston North, New Zealand. M.F. Skinner. Kaska Road, RD2, Rotorua, New Zealand. J.D. Graham. Ensis, Private Bag 3020, Rotorua, New Zealand. 1

Corresponding author (e-mail: [email protected]).

Can. J. For. Res. 36: 1077–1086 (2006)

doi:10.1139/X06-009

© 2006 NRC Canada

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Can. J. For. Res. Vol. 36, 2006

Fig. 1. Site location, plot location, and experimental design. Each plot is 40 m × 40 m. Fertilizer treatments are shown with shading (none, nitrogen (N), and N plus phosphorus (P)). Physical treatments: O, control (uncompacted, no site preparation); C, compaction; R, site preparation (rip and disk); CR, compaction plus site preparation. Blocks are 1–4. Block 1, high disturbance; 2, medium disturbance, 3, low–medium disturbance; 4, low disturbance.

may be slow and can take more than 20 years, since it involves climatic processes and biological activity (Dickerson 1976; Jakobsen 1983; Rab 2004). The Montreal Process requires forestry production to be sustainable (http://www. mpci.org), and further information on the sustainability of forests after soil compaction during harvest is required. In northern New Zealand, highly weathered, clay-rich Ultisols are used for production forestry. However, since these soils have low iron oxide content and shallow topsoils over low-permeability subsoils, they are vulnerable to loss of soil quality during harvest operations (Hewitt 1998). These soils are particularly vulnerable to loss of macropore volume. They also have relatively low total phosphorus (P) content (