Manufactured fertiliser should be used to make up the difference, with applications of organic manure being made in late winter to summer (which may also be beneficial in reducing phosphorus losses).
Dylid defnyddio gwrtaith wedi'i weithgynhyrchu i wneud iawn am y gwahaniaeth, gan wasgaru tail organig ddiwedd y gaeaf hyd at yr haf (a allai fod yn fuddiol wrth leihau colledion ffosfforws hefyd).