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Algorithms for variable-rate application of manure

An undesired surplus of nutrients in agricultural soils can be attributed among others to a uniform application of fertilisers as it does not address the small-scale variation of nutrients in soils. Site-specific fertilisation can reduce nutrient surpluses. Algorithms for a site-specific input of manure are missing so far, but are crucial for a purely demand-driven input of nutrients. This report describes conditions and algorithms for the variable-rate application of slurry.

Slurry application should follow the P demand of crops as otherwise an overfertilisation with P is common. Consequently, soils with excessively high P contents receive no P fertiliser, soils with sufficiently high P content application rates equal the P offtake by harvest products and on soils with an insufficiently high P-content for maximum yields application rates need to be higher than the offtake. Nitrogen will be applied in organic and mineral form so that for both nutrients, N and P, the demand will correspond with the actual fertiliser rate. Thus a balanced application of nitrogen and phosphorus is achieved.

This report on the “Algorithms for variable-rate application of manure” was prepared as part of work package 4 on manure standards of the project Baltic Manure.


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