Omission of nitrogen fertilizer on second rotation sites: effects on Pinus radiata growth in southern Australia

Abstract

Summary Four experimental areas near Mount Gambier were established each year for three consecutive years. Choice of twelve sites within these areas was based on the potential of newly planted radiata pine to respond to nitrogen fertilizer applied at the time of planting. Key soil and foliage chemicals were monitored along with cumulative rainfall at each site. Tree growth was measured annually. Results showed that there was no correlation between tree growth and any of the initial soil chemical values. Bracken fern inhibited tree growth on two sites and sand blasting damaged trees on a third. Regressions for growth vs cumulative rainfall showed there was a strong relationship between growth and total rainfall, with the two inland areas being significantly more productive. The four slopes of the linear plots of the regressions of growth vs cumulative rainfall were not significantly different. Application of nitrogen fertilizer provided no economic growth responses up to age 4 years. Only one area responded to applied nitrogen in this experiment. Copper deficiency symptoms were visible in one area a year after the application of nitrogen. There were significant differences in the foliar contents of many other nutrient elements depending on site and age.