Responses to nitrogen, phosphorus and sulphur applications to aPinus radiatastand in the Tumut region, New South Wales

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Abstract
Two experiments, one in an unthinned stand and one in a thinned stand, both testing the effects of nitrogen, phosporus and sulphur on the growth of 16-year-old Pinus radiata in the Tumut region of N.S.W. are described. In both experiments the only growth responses were to applied nitrogen. In the unthinned stand there was little response in basal area to application of 100 kg N/ha but there was a response to 400 kg N/ha. In the thinned stand there was a large response in basal area at the lower rate of application of fertilizer but little additional response at the higher rate. However, stand form factor increased at the higher rate with the consequence that there was a substantial increase in volume increment due to the higher rate of addition of nitrogen fertilizer. The basic density of wood produced after application of fertilizer was only 5% lower than in non-fertilized stems. Foliar analysis at the commencement of the trial indicated that all of the test nutrients were at adequate concentrations. The effects of application of fertilizer on foliar nutrient concentrations were observed for four years in the thinned stand. There was no evidence that growth responses to nitrogen fertilizer were constrained by the availability of sulphur.