Effect of annual weeds on water and nitrogen availability to Pinus radiata trees in a young plantation

• Published in: Forest ecology and management 1992, Vol.48 (1), p.145-163
• Main Authors: Woods, P.V., Nambiar, E.K.S., Smethurst, P.J.
• Format: Article
• Language: English
• Subjects: ABSORCION DE AGUA; ABSORCION DE SUBSTANCIAS NUTRITIVAS; ABSORPTION D'EAU; ABSORPTION DE SUBSTANCES NUTRITIVES; Agronomy. Soil science and plant productions; ANNUAL WEEDS; AZOTE; Biological and medical sciences; Chemical control; Fundamental and applied biological sciences. Psychology; MALEZAS ANUALES; MAUVAISE HERBE ANNUELLE; NITROGEN; NITROGENO; NUTRIENT UPTAKE; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; PINUS RADIATA; WATER UPTAKE; Weeds
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/0378-1127(92)90127-U

The importance of competition between trees and annual weeds for nitrogen (N) and water was evaluated in a Pinus radiata D. Don (radiata pine) plantation between two and three years of age growing on a sandy podzol in the southeast of South Australia. Increasing the width of the weed-control strip spanning the tree row had little effect on tree water status, but increased the uptake of N by trees. Application of N fertilizer alleviated N deficiency and tree growth suppression induced by weeds, suggesting that when N supply is high (e.g., on fertile sites) intense weed control is unnecessary in plantations beyond two years of age. On the other hand, competition for N by weeds would seriously aggravate N deficiency in young pine trees grown on low-N soils. When N fertilizer was applied, weeds rapidly absorbed mineral N from the soil, and within three months, the N content of weeds was 10.2 g N m −2 greater than in the unfertilized control. This represents 68% of the amount of N applied in fertilizer. Weeds therefore increased the uptake of fertilizer N by plant biomass, and thereby improved N retention on site. Tree growth increased with N fertilizer at all levels of weed control and responses to weed control and N fertilizer were additive. The growth of weeds increased the soil organic carbon status and the rate of N mineralization. The presence of weeds reduced the incidence and severity of stem deformation, which was exacerbated by N fertilizer application and complete weed control. In general, strip weed control may be a better option than complete weed control in managing weeds in young P. radiata plantations.