Harry Percival, a former colleague and staff member at Manaaki Whenua-Landcare Research and NZ Soil Bureau, DSIR, died of a heart attack at his home in Palmerston North, on 23 March 2024. 

Harry was born in Wellington on 31 August 1943. He attended primary school at Te Aro Valley and Silverstream (Upper Hutt), and secondary school at New Mana College where he was head prefect. He then enrolled at Victoria University of Wellington (VUW), gaining a BSc degree in 1965, an MSc (Hons) in 1966, and a PhD degree in Chemistry in 1970 under Professor J.F. Duncan. 

Harry’s PhD study, like that of his long-time scientific colleague, G. Jock Churchman, was funded by a government grant, in the form of four PhD scholarships, to the NZ Pottery and Ceramic Research Association (PACRA). The first of these scholarships was awarded to Harry at VUW to investigate the chemical and structural changes that occur when the clay mineral, halloysite, was fired. The second award went to Jock to study the low-temperature dehydration of halloysite at Otago University. 

After completing his PhD degree, Harry spent an obligatory year (1971) at PACRA headquarters in Gracefield, Lower Hutt. Because of a hefty cut in operational funding, Harry (and Jock) had to find alternative employment. In Harry’s case it was a postdoctoral fellowship from the Institut de Chimie Industrielle, Université Libre de Bruxelles in Belgium under Professor W.L. Keyser, while Jock took up a fellowship in Wisconsin, USA. 

In late 1973 Harry returned to New Zealand to work for the New Zealand Fertilizer Manufacturer’s Research Association (NZFMRA) in Otara, Auckland as a research chemist. The following year Harry was appointed director of PACRA allowing him to do a business trip to several European countries in 1978. This appointment, however, proved to be a poisoned chalice. When funds were cut, Harry had to dismiss some staff members, a task that must have taken a toll on his generous and friendly nature if not his constitution. PACRA itself went to the wall in 1981 when Harry, together with Carin Burke, joined the NZ Soil Bureau, DSIR at Taita, Lower Hutt. 

There Harry worked on the equilibrium and kinetic relationships between soil minerals and solutions. He also did research into the behaviour and fate of heavy metals in soil that had been amended with sewage sludge. In 1988 he was appointed science manager (marketing) of NZ Soil Bureau as well as being responsible for the purchase and installation of a modern X-ray diffractometer. 

The DSIR Taita campus closed down in December 1993. In 1994 Harry and wife, Keitha Giddens, moved to Palmerston North to join Manaaki Whenua-Landcare Research where he was team leader in the Environmental Processes group, while Keitha was a senior technician in the environmental chemistry laboratory. When Keitha retired in 2003, Harry decided to take early retirement allowing him to do some tramping in New Zealand, read books, attend cinema but most of all to play golf. Indeed, Harry kept playing his favourite sport until two days before his passing. 

Harry had been a member of the New Zealand Institute of Chemistry (NZIC) since 1970, becoming a Fellow in 1981. He also held membership in the Wellington and Manawatu branches of the Royal Society of New Zealand, the NZ Society of Soil Science, and the NZ Association of Scientists. Harry was national president of NZIC in 1990/91. 

Bibliography

Harry was the principal author or co-author of several laboratory and scientific reports for PACRA, NZFMRA, NZ Soil Bureau, DSIR Land Resources and Landcare Research. He was also the author/co-author and presenter of oral and poster papers at NZIC annual meetings and at international conferences in Canada, Austria and Sweden.

Below is a selection of Harry’s scientific publications listed in chronological order:

• Duncan, J.F. and H.J. Percival. 1968. Modification of chemical properties of iron cyanides in soil solutions. Australian Journal of Chemistry 21: 2175−2188.
• Foster, P.K. and H.J. Percival, 1974. Kiln atmosphere as a variable in ceramic firing. New Zealand Journal of Science 17: 49−58.
• Percival, H.J., J.F. Duncan, and P.K. Foster. 1974. Interpretation of the kaolinite-mullite reaction sequence from infrared absorption spectra. Journal of the American Ceramic Society 57: 57−61.
• Claridge, G.G.C. and H.J. Percival. 1980. Clay for brick-making: A study of the suitability of the soils of the Pacific Islands. New Zealand Journal of Science 23: 335−342.
• Wells, N., H.J. Percival, and G.J. Churchman. 1985. Potential of five New Zealand clays for coating paper. New Zealand Journal of Technology 1: 109−114.
• Cowling, J.C., T.W. Speir, and H.J. Percival. 1987. Potential problems with the determination of Olsen and microbial P of soils due to the instability of 0.5M sodium bicarbonate. Communications in Soil Science and Plant Analysis 18: 637−652.
• Singleton, P.R., M. McLeod, and H.J. Percival. 1989. Allophane and halloysite content and soil solution silicon in soils from rhyolitic volcanic material, New Zealand. Australian Journal of Soil Research 27: 67−77.
• Lowe, D.J. and H.J. Percival, 1993. Clay mineralogy of tephras and associated paleosols and soils, and hydrothermal deposits, North Island. Guide Book for New Zealand Pre-conference Field Trip F.1, 10^th International Clay Conference, Adelaide, Australia, 110 pp.
• Percival, H.J. 1995. Relative stabilities of selected clay minerals in soils based on a critical selection of solubility constants. In Clays: Controlling the Environment. Proceedings of the 10th International Clay Conference, 1993, Adelaide (Eds.), G.J. Churchman, R.W. Fitzpatrick, and R.A. Eggleton, pp. 462–468. Melbourne, Australia: CSIRO Publishing.
• Percival, H.J., K.M. Giddens, R. Lee, and J.S. Whitton. 1996. Relationships between soil solution aluminium and extractable aluminium in some moderately acid New Zealand soils. Australian Journal of Soil Research 34: 769−779.
• Dahlgren, R.A., H.J. Percival, and R.L. Parfitt. 1997.Carbon dioxide degassing effects on soil solutions collected by centrifugation. Soil Science 162: 648−655.
• Giddens, K.M., R.L. Parfitt, and H.J. Percival. 1997. Comparison of some soil properties under Pinus radiata and improved pasture in New Zealand. New Zealand Journal of Agricultural Research 40: 409−416.
• Parfitt, R.L., H.J. Percival, R.A. Dahlgren, and L.F. Hill. 1997. Soil and solution chemistry under pasture and radiata pine in New Zealand. Plant and Soil 191: 279−290.
• Percival, H.J., T.W. Speir, and A. Parshotam. 1999. Soil solution chemistry of contrasting soils amended with heavy metals. Australian Journal of Soil Research 37: 993−1004.
• Speir, T.W., H.A. Kettles, H.J. Percival, and A. Parshotam. 1999. Is soil acidification the cause of biochemical responses when soils are amended with heavy metal salts? Soil Biology & Biochemistry 31: 1953−1961.
• Theng, B.K.G., G.G. Ristori, C.A. Santi, and H.J. Percival. 1999. An improved method for determining the specific surface areas of topsoils with varied organic matter content, texture and clay mineral composition. European Journal of Soil Science 50: 309−316.
• Percival, H.J., R.L. Parfitt, and N.A. Scott. 2000. Factors controlling soil carbon levels in New Zealand grasslands: Is clay content important? Soil Science Society of America Journal 64: 1623−1630.
• Yuan, G., B.K.G. Theng, R.L. Parfitt, and H.J. Percival. 2000. Interactions of allophane with humic acid and cations. European Journal of Soil Science 51: 35−41.
• Taylor, M.D. and H.J. Percival. 2001. Cadmium in soil solutions from a transect of soils away from a fertiliser bin. Environmental Pollution 113: 35−40.
• Yuan, G., H.J. Percival, B.K.G. Theng, and R.L. Parfitt. 2002. Sorption of copper and cadmium by allophane-humic complexes. In: A. Violante, P.M. Huang, J.-M. Bollag and L. Gianfreda (Editors), Developments in Soil Science 28A: 37–47.
• Percival, H.J., 2003. Soil and soil solution chemistry of a New Zealand pasture soil amended with heavy metal-containing sewage sludge. Australian Journal of Soil Research 41: 1−17.
• Speir, T.W., A.P. van Schaik, H.J. Percival, M.E. Close, and L. Pang. 2003. Heavy metals in soil, plants and groundwater following high-rate sewage sludge application to land. Water, Air, and Soil Pollution 150: 319−358.
• Thayalakumaran, T., I. Vogeler, D.R. Scotter, H.J. Percival, B.H. Robinson, and B.E. Clothier. 2003. Leaching of copper from contaminated soil following the application of EDTA. I. Repacked soil experiments and a model. Australian Journal of Soil Research 41: 323−333.
• Thayalakumaran, T., I. Vogeler, D.R. Scotter, H.J. Percival, B.H. Robinson, and B.E. Clothier. 2003. Leaching of copper from contaminated soil following the application of EDTA. II. Intact core experiments and model testing. Australian Journal of Soil Research 41: 335−350.
• Thayalakumaran, T., B.H. Robinson, I. Vogeler, D.R. Scotter, B.E. Clothier, and H.J. Percival. 2003. Plant uptake and leaching of copper during EDTA-enhanced phytoremediation of repacked and undisturbed soil. Plant and Soil 254: 415−423.
• Yeates, G.W., H.J. Percival, and A. Parshotam. 2003. Soil nematode responses to year-to-year variation of low levels of heavy metals. Australian Journal of Soil Research 41: 613−625.
• Schipper, L.A., H.J. Percival, and G.P. Sparling. 2004. An approach for estimating when soils will reach maximum nitrogen storage. Soil Use and Management 20: 281−286.
• Horswell, J., H.J. Weitz, H.J. Percival, and T.W. Speir. 2006. Impact of heavy metal amended sewage sludge on forest soils as assessed by bacterial and fungal biosensors. Biology and Fertility of Soils 42: 569−576.
• Speir, T.W., A.P. van Schaik, L.C. Hunter, J.L. Ryburn, and H.J. Percival. 2007. Attempts to derive EC₅₀ values for heavy metals from land-applied Cu-, Ni-, and Zn-spiked sewage sludge. Soil Biology & Biochemistry 39: 539−549.