Role of cover crops

2018 cover crops grew well and can de­liver large en­vi­ron­men­tal ben­e­fits

Irish Examiner - Farming - - COMMENT -

Cover crops have grown ex­cep­tion­ally well in 2018, largely due to ear­lier than nor­mal plant­ing and higher than nor­mal soil resid­ual N lev­els.

As a re­sult, cover crops in 2018 have the po­ten­tial to de­liver large en­vi­ron­men­tal ben­e­fits in re­duc­ing ni­trates loss.

Teagasc ex­per­i­ments have found that the re­sponse to ni­tro­gen from cover crops, for the suc­ceed­ing crop, is small, apart from legu­mi­nous crops. The chal­lenge now is how to man­age these crops to de­liver max­i­mum agro­nomic and en­vi­ron­men­tal ben­e­fit to the farm.

Un­der the Green Low-car­bon Agri-en­vi­ron­ment Scheme (GLAS), re­moval of cover crops is al­lowed af­ter De­cem­ber 1. Man­age­ment of cover crops de­pends on the species planted, avail­able ma­chin­ery and whether or not live­stock are avail­able.

Frost over win­ter will be enough to kill some species. The tim­ing and meth­ods used to re­move cover crops will also be in­flu­enced by the suc­ceed­ing crop.

Where a for­age species has been used in the crop mix­ture, graz­ing with live­stock is an ideal way to re­cy­cle nu­tri­ents, where the in­fra­struc­ture is in place.

Where there is a large biomass present, the crop may need to be bro­ken me­chan­i­cally with a disc be­fore plough­ing. It is best to do this as soon af­ter De­cem­ber 1 as pos­si­ble, to al­low the crop to de­grade ad­e­quately to aid plough­ing. Glyphosate will be the main method of de­struc­tion for most grow­ers. The rate re­quired de­pends on the species to be con­trolled, the level of biomass, and the weather con­di­tions.

Key points to re­mem­ber when ap­ply­ing glyphosate to cover crops are:

■ ap­ply early in the day, to max­imise up­take dur­ing short days;

■ ap­pli­ca­tion in cold con­di­tions will slow up­take and symp­toms will take four-to-five weeks to ap­pear. Do not ap­ply glyphosate in frosty con­di­tions (frost-dam­aged crops will have poor up­take);

■ en­sure ac­cu­rate ap­pli­ca­tion, with the cor­rect boom height, and use high wa­ter vol­umes (over 200 litres/ha); Where a di­rect drill is avail­able, the cover crop can be sprayed off in the days prior to plant­ing, and the suc­ceed­ing crop planted di­rectly into the cover crop.

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