28 September 1992 Scholarship Support for Research on Soil Enhancing Value of Spent Mushroom Compost

Research into the effect of spent mushroom compost on soil fertility and vegetable growth will benefit from a Turners and Growers Scholarship of $2000 awarded to Lincoln University doctoral student Dean Stewart of Christchurch.

Dean, aged 29, is working on the project with Dr Keith Cameron of Lincoln's Soil Science Department and Professor Ian Cornforth, the head of department. The majority of the work is funded by Meadow Mushrooms Ltd., Prebbleton.

Spent mushroom compost is widely used by horticulturists as a soil amendment but its specific effects have never been closely defined. Dean's work aims to rectify this.

A split plot trial was established at Lincoln University in 1991 and results based on the first of four trial crops – sweetcorn – were presented recently at the joint conference of the NZ Society of Soil Science and the NZ Society for Horticultural Science.

Dean described how spent mushroom compost (SMC) increased the soil's nitrogen and phosphorous/potassium levels, plus the sulphur, magnesium, and calcium concentrations. Sweetcorn cob, seed and vegetative yields were all increased with the addition of SMC rates greater than 20 tonne/hectare in the absence of fertilizer, or with all rates above zero in conjunction with fertilizer. SMC additions increased the cob weight, both the total and marketable cob number, and plant tillering.

Over the next two years on the trial plots at Lincoln Dean will continue his assessments with cabbages, potatoes and leeks. Essentially the trial simulates a typical market garden situation and Dean will be looking at the growth of the crops under both normal fertilizer and SMC regimes to assess whether SMC has a comparable effect, an advantageous effect, or an advantage when used in conjunction with normal fertilizer.

Dean has also done field lysimeter work to compare leaching losses from compost and ordinary fertilizers. Preliminary results indicate that there is less nitrate leaching from SMC than from conventional fertilizer, resulting in a lower probability of aquifer pollution. In addition he is conducting laboratory incubation studies to determine the amount of nutrient released under controlled conditions, with the samples being taken from the trial plots.

In February this year he presented an evaluation of SMC as a soil amendment at a conference at Massey University which looked at the use of wastes and by-products as fertilizers and amendments for pastures and crops. In essence he made the point that spent mushroom compost improved the physical condition of the soil, enhancing soil structure development and stability.

Dean is a B.Agr.Sc.(Hons) graduate of Lincoln and in 1990 he spent time in Samoa at the University of the South Pacific's Alafua campus lecturing in soil science and carrying out research on soils in relation to taro production.

In addition to his academic achievements Dean has a notable background of sporting success. He is a past Canterbury Junior Gymnastics Champion, NZ Junior Ski Champion, and NZ Open Ski Champion, and he was a member of the NZ Ski Team for three years.

He was dux of his primary school, Beckenham, and a prefect at Cashmere High School, Christchurch.

The Turners and Growers Postgraduate Research Scholarships exist to encourage research aimed at raising standards of production methods and improving varieties of fruit, vegetables and flowers suitable for New Zealand's domestic and export markets. Dean is one of two recipients in 1992, the other is Guangyu Chen of Lincoln University who is researching the genetic manipulation of asparagus.

Ian Collins, Journalist, Lincoln University, Canterbury, New Zealand.