This year, the MINTOPE team are investigating slow release fertilisers to increase the success of cereals, such as Sorghum, and legumes like Lablab. Overcoming nutritional issues will be essential for agriculture activities following mining.
From Sorghum, we can make a range of products including gluten free beer and bread, ethanol, carbohydrates for chicken and fish pellets, and use its waste products as ‘green manure’ for increasing organic carbon in soil prior to cropping. Lablab is also a very useful plant – it adds nitrogen (N) to the soil, we can eat the leaves, seeds and pods, and it can be added as protein to chicken and fish pellets, or used as green manure, just like Sorghum.
In 2015 MINTOPE discovered that N is limiting cereal growth, and potassium (K) is limiting legume growth. This year, part of the MINTOPE activities involve investigating which rate of slow release K fertiliser produces the highest biomass for Lablab, and which slow release N is the best for Sorghum. Slow release fertilisers seem to deliver higher sustained plant productivity in the high rainfall environment of Christmas Island.
Dr Katinka Ruthrof assisted by Margaret Rogers, a dedicated MINTOPE volunteer, came from Perth in late April to harvest the nutrient trial crops. Firstly, 5-10 plants were cut from each plot (there were 5 plots testing each of the fertiliser treatments at two sites), and the plants placed in labelled paper bags into an oven for 24 hours. Parks Australia generously allowed the use of their super drying oven for five solid days. Secondly, the plants were dried and weighed and the different biomass responses to the fertiliser treatments
Young leaves from each plot were also harvested and dried in the oven too. The leaves were then ground to a fine power so that they can be taken back to Perth and to a laboratory for nutrient analysis. This will give a better idea about how healthy the plants are.
Results so far suggest that a combination of traditional fertiliser and slow release K fertiliser may be the ‘stand out’ treatment for Lablab, and that a slow release polymer coated N fertiliser is very beneficial for Sorghum growth.
The next step in the schedule will involve having the nutrients analysed in the laboratory in May and another harvest on island in June or July. Finally MINTOPE would like to thank Park Australia for their assistance with this phase of the research.