Cover crops have a range of potential environmental, agronomic and economic benefits. In many areas of the world with similar climate to Ireland, reduction of nutrient loss to water, particularly nitrate, is the principal motivation for using covers crops.

Irish work has demonstrated that overwinter covers, both of a sown species and natural regeneration, can substantially reduce leaching. While many benefits have been attributed to cover crops, the positive effects are often variable and require careful choice of the species used given the rotational position.

Cover crops can lead to a reduction in the effects of pests, disease and weeds in succeeding crops, but, particularly if choice of species or management are not correct, can lead to problems in succeeding crops also.

The use of cover crops can increase the content of organic matter in the soil and in particular the active pools of organic matter which are important for crop production, but many studies have shown that these effects often take a number of years to accrue and even then are often small.

Research at Oak Park and elsewhere has shown that the effects of non-leguminous cover crops on the fertiliser N requirement of succeeding crops are small and it would be difficult to recommend reduced inputs of fertiliser N where non-legumes are used alone.

While significant yield benefits can be achieved through the use of cover crops, effects of cover crops, compared with bare fallow or natural regeneration, on cereal yield under Irish conditions are variable, often small and sometimes negative. This concurs with findings in other European countries.

Given that sown cover crops incur seed, establishment and destruction costs, the use of sown species of cover crops is often not economically justified (in the absence of financial incentives to do so).

However, management factors, such as correct choice of species or species mixture, and good management in terms of sowing date and destruction date can improve the chances of achieving economically beneficial results.

Initial experiments with leguminous cover crops suggest that they may have considerable potential to reduce the fertiliser N requirements of crops under Irish conditions.

Range of species

A range of species or mixtures of species can be used as cover crops and a broad range of species will be presented at Crops & Spraying. The species to be seen will include brassicas (eg mustard, radish, fodder rape), cereals and some less familiar species such as phacelia and buckwheat.

Given the potential of legumes to contribute additional N to succeeding crops, a range of leguminous species will also be presented, such as peas, beans and vetches.

In addition to pure stands of each, a selection of species mixtures will also be presented, as those using cover crops to fulfil GLAS or EFA requirements will be required to use mixtures of species.

The pros and cons of various species and species mixtures will be discussed and guidelines for timely and cost-effective establishment and management will be provided.

Results of work at Oak Park over the last number of years in this area will also be presented. For growers new to cover or catch crops in particular, the display will provide the information required to successfully establish and manage cover or catch crops that suit their particular cropping system.