Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
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annual <strong>crop</strong>s while increasing organic matter and carbon sequestration in the soil (Sebillotte,<br />
1980; Viaux et al., 1999; Eltun et al., 2002; Entz et al., 2002). Moreover, nitrogen fixing<br />
legume species inclu<strong>de</strong>d in the PFC mixtures may reduce the need nitrogen fertilisation in the<br />
grassland and in the following annual <strong>crop</strong>s improving the energy efficiency of the system<br />
(Entz et al., 2002). However, the organic matter and nutrients accumulated during the period<br />
of the perennial <strong>crop</strong> may only partly be used by the following annual <strong>crop</strong>s, while other parts<br />
may be lost through leaching, especially if the <strong>temporary</strong> grassland is terminated by <strong>de</strong>ep<br />
ploughing (Viaux et al., 1999).<br />
A.V.4 Expected impacts on <strong>crop</strong> production<br />
Introducing perennial <strong>crop</strong>s into <strong>crop</strong> <strong>rotations</strong> may have various (positive and negative)<br />
impacts on <strong>crop</strong> yields and farm profitability. The economic profitability of perennial <strong>crop</strong>s<br />
may be lower than for annual (cash) <strong>crop</strong>s due to lower marked prices. The low economical<br />
value of forage biomass might however be partly compensated for by rather low production<br />
costs (Bulson et al., 1996; Entz et al., 2002). Moreover, perennial <strong>crop</strong>s create other long-term<br />
amenities, including improvements of soil structure and fertility and reductions in pest<br />
pressures (Entz et al., 2002; Katsvairo et al., 2006a). Therefore, perennial <strong>crop</strong>s may also lead<br />
to significant yield increases and savings of fertilizer and pestici<strong>de</strong> inputs in the subsequent<br />
annual <strong>crop</strong>s. In addition to these variations, public subsidies may favour or penalize perennial<br />
<strong>crop</strong>s. In Iowa, USA, perennial alfalfa get lower subsidies than annual <strong>crop</strong>s such as corn and<br />
soy bean (Liebman et al., 2008). In the European Union, all <strong>crop</strong> types should get the same<br />
amount of subsidies (‘<strong>de</strong>coupling’) since the application of the 2003 CAP reform (which may<br />
differ in the member states). In some European countries or regions, mixed farming systems<br />
may even profit from specific subsidies in the framework of the ‘second pillar’ of the CAP.<br />
The importance of the different impacts on <strong>crop</strong> yields and farm profitability will <strong>de</strong>pend on<br />
climatic, agronomic, economic and politic factors and may thus strongly differ between<br />
regions and farming systems. The three studies cited in the following have thus only an<br />
exemplary character.<br />
• A Canadian study suggests that production cost of forage-based systems was lower than<br />
for continuous grain production systems but higher than a wheat-fallow system.<br />
Interestingly, including a 2- or 3-year forage <strong>crop</strong> in a 6-year rotation was found to<br />
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