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Sustainable phosphorous fertilisation of potatoes (Potato CHIPS) - HH3504SPO

This project has two independent aims: (1) to investigate the use of struvite as an alternative to chemical P fertilisers and (2) to develop an oligonucleotide microarray to monitor the P status of the potato crop.

The UK horticultural and agricultural industries rely on large inputs of phosphate (P) fertilisers to maintain crop yields and quality. However, the use of non-renewable, chemical P fertilisers is unsustainable, and the alternatives to chemical P-fertilisers must be identified as an immediate priority. Preliminary observations indicate that a natural waste-product, struvite [(NH4)Mg(PO4)·6(H2O)], could provide an alternative to chemical P fertilisers for crop production. Struvite precipitates out of sewerage sludge and can be reclaimed from animal wastes. Its disposal to landfill is expensive, and raises the risk of local pollution. Thus, the use of struvite as a fertiliser is an attractive proposition. The first aim of this project is to assess the potential of struvite as a P fertiliser for potatoes and to compare the effectiveness of struvite with a chemical P fertiliser, triple super phosphate (TSP), in field trials on P gradients (Defra soil P indices between 2 and 9) established at HRI-Wellesbourne. If struvite generates a consistent P response, comparable to that of TSP, technology transfer initiatives will be implemented. These will include articles in the trade and scientific press. This aspect of the work has Industrial support, and is partly sponsored through an ENTRUST-registered project from the Cherub Environmental Trust.

Excessive P fertiliser applications are also costly, and can lead to unnecessary pollution. Inefficient P fertilisation is a particular problem for the potato crop, which utilises little of the P fertiliser applied (RB209: Defra Fertiliser Recommendations). Often more P is applied than is required because chemical assays of soil and plant P are unreliable. Novel biosensor technologies, exploiting knowledge of the changes in plant gene expression that occur under P starvation, could better inform P fertiliser applications. These technologies provide an insight into the immediate physiological P requirement of the crop. The second aim of this project is to develop an oligonucleotide microarray (`potato chip`) to monitor the relative expression of diagnostic genes in the youngest fully expanded leaves of potatoes and, thereby, deduce the P status of the potato crop. This technique is called `transcript profiling`. First, the genes expressed in youngest fully expanded leaves of potatoes that respond rapidly and specifically to low P bioavailability will be identified. Then the mRNA (transcript) sequences of these genes will be used to design potato chips that will allow the transcript profiling of potato leaves. These potato chips will be tested using mRNA extracted from leaf tissue of potatoes with contrasting P status grown both hydroponically following the removal of P from the nutrient solution or in soils with different P indices. The final `alpha-design` potato chip will undergo rigorous biological and statistical testing to determine the confidence with which the occurrence of an incipient P deficiency in the potato crop can be predicted. In practice, these potato chips will become a management tool for precision agriculture. They will allow farmers to monitor the immediate physiological P status of their crops in order to optimise the application of P fertilisers.

In addition to their practical use in fertiliser-management programs, potato chips can be used to assay plant P status in both laboratory and field experiments. For example, potato chips could be used to ratify computer predictions for the effects of different fertilisers on plant P status, to determine the roles of root or soil structure in the acquisition of P, or to investigate the effects of mycorrhizal associations on plant P status. Knowledge of the genes that respond to P starvation will improve our basic understanding of the physiology of P nutrition in potato. Furthermore, identifying and manipulating the regulatory elements that co-ordinate physiological, biochemical and genetic responses to P starvation could be used to optimise root exploitation of the soil volume, maximise the uptake of phosphate from the soil solution or improve P use efficiency. Thus, there is great potential for the use of potato chips in both basic and applied research to reduce the phosphate fertiliser requirement of crops.

This project will contribute to Defra`s policy objective to develop strategies that lead to reduction in the use of chemical fertilisers on horticultural crops. It will deliver to specific scientific targets in HH35 `Sustainable Crop Nutrition` by (1) investigating the utility of struvite as a viable alternative to chemical P-fertilisers, (2) developing new strategies (potato chips) to maximise the efficient use of fertilisers for plant growth while minimising impact on the environment and (3) providing information on the physiological, biochemical and genetic responses to P starvation.


01. To perform three field trials to assess the potential of struvite as an alternative to chemical P fertilisers (within 40 months)
02. To shortlist P-responsive genes in leaves of Arabidopsis thaliana (within 8 months)
03. To shortlist sequenced transcripts of between 20 and 50 P-responsive genes expressed in potato leaves (within 23 months)
04. To design, manufacture and test a prototype potato chip (within 30 months)
05. To produce and test an alpha-design potato chip (within 48 months)

Project Documents
• Final Report : Sustainable Phosphorus Fertilisation of Potatoes   (3806k)
• Annual Report : Sustainable phosphorus fertilisation of potatoes   (744k)
• Final Report - Annex : Sustainable Phosphorus Fertilisation of Potatoes Annex 1   (5702k)
• Final Report - Annex : Sustainable Phosphorus Fertilisation of Potatoes Annex 2   (1027k)
Time-Scale and Cost
From: 2004

To: 2008

Cost: £569,007
Contractor / Funded Organisations
Horticulture Research International, Warwick - HRI
Allocated - WHRI              
Natural Resource Use              
Sustainable Farming and Food              
Fields of Study