Green Manuring with Clover and Ryegrass Catch Crops Undersown in Small Grains: Effects on Soil Mineral Nitrogen in Field and Laboratory Experiments
Title:
Green Manuring with Clover and Ryegrass Catch Crops Undersown in Small Grains: Effects on Soil Mineral Nitrogen in Field and Laboratory Experiments
Author:
Breland, Tor Arvid
Appeared in:
Acta agriculturae Scandinavica. Section B, Soil and plant science
Paging:
Volume 46 (1996) nr. 3 pages 178-185
Year:
1996-09-01
Contents:
In three field trials in southern Norway, Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) or subterranean clover (T. subterraneuni L.) was undersown in spring grain at three N fertilizer rates and ploughed under in late October as a green manure for a succeeding spring grain crop. The content of topsoil (0-20 cm) mineral nitrogen was determined during the growth of the grain crop, after grain harvest and after ploughing. In addition, mineralization of nitrogen and carbon was measured in green-manured soil incubated at 15°C and controlled moisture conditions. During grain crop growth, ryegrass tended to reduce soil mineral N compared with the other treatments. After grain harvest, in a small-plot experiment where extra nitrate was added, ryegrass reduced soil nitrate N (0-18 cm) from 4.2 to 0.4 g m-2 within 13 days, while the clovers had negligible effect compared with bare soil. Up to 9.4 g N m-2 was present in above-plus below-ground ryegrass biomass at ploughing. In incubated ryegrass soil, there was a temporary net N immobilization of up to 0.9 g N m-2 as compared with unamended soil. In clover-amended soil, mineral N exceeded that in unamended soil by up to 5 g N m-2.
Journal description