International Starch Institute: Fertilizing value of potato juice

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International Starch Institute
Science Park Aarhus, Denmark
Landspreading of Potato Fruitjuice and Fruitwater as a Fertilizer

Potato juice is an excellent fertiliser. Calculated on nutrients it is equivalent to an artificial fertiliser with same composition. In co-operation with the Ministry of Environment and the Danish Institute of Plant and Soil Science, Department of Soil Physics, Soil Tillage and Irrigation over a 3-year period we sampled soil water weekly from 128 test plots fertilised at various time of the year and with various quantities of potato juice. The soil water were sampled with probes below crop roots - two probes in each plot.

Use of potato juice equivalent to 100 kg nitrogen per ha in the autumn on grass as a catch crop does not give any significant leaching of nitrogen during the winter. The utilisation of nitrogen the following growing season is high.

Field set-up with four soil probes sampling soil water 80 cm below surface. Each probe has a porous ceramic stopper at the lower end. The probe is evacuated and suck up soil water into the probe. It is emptied once a week and the sampling repeated.
	Experimental harvester, harvesting each test plot separately.
70,000 m³ Fruit Juice Winter Basin under construction	The Danish solution: Huge winter basins for storage of potato juice and fruit water during the winter allow landspreading early spring with optimal utilisation of the valuable nutrients. Through pipelines the basins are connected with hydrants on farm irrigation systems or smaller farm basins. Radio controlled valves and flow metres facilitate remote switch between the local systems ensuring accurate distribution of the fruit juice ordered by the farmers. Distribution by road tanker: Some factories prefer to deliver the fruit juice by road in tank lorries. This method requires practically undiluted fruit juice in order to keep transportation cost low, but makes it practicable to distribute over longer distances than with pipelines and it is flexible. Distribution by pipeline: One Danish factory processing 300,000 t potatoes per year produces 450,000 t combined effluent and distributes it through 120 km of pipeline to farmers spreading the effluent as fertilizer on 7,500 ha. (Source: ElRo February 2001) The processing of 150,000 t potatoes per annum will typical require the investment of 5 -7 million USD in basins, pipes and landspreading equipment.

Keywords:potato,fruit,juice,starch,basin,effluent,sewage,land,spreading,fertilizer