ROOT DEVELOPMENT OF NITROGEN CATCH CROPS AND OF A SUCCEEDING CROP OF BROCCOLI

The root development of seven catch crop species, and of a broccoli crop following catch crops, was followed by a minirhizotron technique. Large differences in root growth patterns were found among the catch crops. Fodder radish already had a rooting depth of 112 cm 49 days after sowing, whereas Italian ryegrass did not reach this depth until 175 days after sowing. The catch crops with a fast establishment of deep rooting also reduced the mineral nitrogen content in the subsoil most. Broccoli showed a significantly higher root density in the subsoil when grown after narrow-leaved lupin and lower after winter rape than where no catch crop had been grown. The main reason for these differences appeared to be the distribution of mineral nitrogen in the soil.