Deliverable No. 33. 30/06/2019 (Action C5)
The EU Water Framework Directive requires measures to reduce nutrient losses from agricultural land. This report updates the current knowledge, used within the RBD authorities as a basis for Programmes of Measures against phosphorus losses. The report also compiles knowledge on new measures for nitrogen and phosphorus.
Some updates on the effects and methods of estimation of the scope for measures are proposed, but for several measures the knowledge base is still small. This applies to, for example, lime filter ditches, two-stage ditches and structural liming with products used today.
Narrowing the scope of measures, depending on conditions for effectiveness, is a way to have greater overall effect and obtain safer results. For wetlands, dams and buffer zones, methods are proposed to optimise placement, for example regarding hydraulic and phosphorus loads, to limit the scope of measures to areas where one can expect a certain effect.
In some cases, the scope of measures needs to be defined by other criteria than the purely scientific. For structural liming, for example, it should not only be limited to clay content but also consider factors like timing and supply of lime. For manure measures, there is a comprehensive regulatory framework, and for areas covered by the Nitrates Directive, it should be possible to assume that measures have already been implemented and that there is little room for further implementation.
How long it takes for a measure to show its effect, and how long the effect lasts, are factors to be considered in effect estimation. Measures that take a long time to show effect, such as the measure to reduce the soil’s phosphorus supply through reduced manure supply, should be removed from the Programme of Measures, which has a different time perspective in terms of impact estimates. However, it is still an important measure on farms with phosphorus-rich soil.
Measures that have not previously been included in the RBD authorities’ Programmes of Measures, include, for example, precision fertilization, catch crops, reduced tillage, cover ditching and trench maintenance, and adjustable drainage. These are measures with good potential, but where some can have contradictory effects on nitrogen and phosphorus losses.