Towards the strategy for phosphorus and potassium rate calculation
2002
Bujnovsky, R. | Miklovic, D. (Soil Science and Conservation Research Institute, Bratislava (Slovak Republic)) | Fotyma, M. | Jadczyszyn, T. | Karklins, A. | Klir, J. | Shepherd, M.
Current recommendation systems in four Central European countries and in the United Kingdom were compared. This comparison included attention to the basic features of recommendation systems with respect to phosphorus and potassium as well as on practical testing of the P and K-rate calculation on a common set of 111 soils and a defined crop rotation. The balance principle represents the main starting point for nutrient rate calculation. In several countries this approach is transformed into index methods. Nearly all recommendation systems are field models rather than whole farm models. At "optimum" soil PK-status, recommended rates match crop off-takes. Below and above these levels PK-rates are increased or decreased, respectively. At very high levels of available soil nutrient supply, fertilisation is usually but not always omitted. Nearly all systems tend to calculate the recommendation without manure and subtract the manure or crop residue phosphorus and potassium supply from this to determine the fertilizer amount. Differences between recommendation systems and PK-rate calculation are explained through different approaches to nutrient removal by the crops, different calibration schemes for available soil nutrient content as well as consideration of utilisable nutrients from animal manure. There is opportunity to progress recommendation system development at the country level as well as the creation of a common recommendation system. To reach this goal it is necessary to unify the principles of nutrient rate calculation
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