YIELD AND QUALITY COMPONENTS OF SILAGE MAIZE IN KILLED AND LIVE COVERCROP SODS

In sloping areas with high precipitation, planting maize into live win ter cover crop sods may help to alleviate the environmental problems a ssociated with clean-tillage production systems of maize. The present study evaluates the performance of silage maize (Zea mays L.) under se veral cultivation methods: CC (conventional cropping system, i.e., mai ze was sown into the bare, autumn-ploughed soil); LGS/CK (maize was pl anted into a living Italian ryegrass (Lolium multiflorum Lam.) sod whi ch was subsequently herbicidally killed); and LGS/MR (similar to LGS/C K, but the ryegrass was mechanically regulated). The research was cond ucted in the midlands of Switzerland on a fertile sandy loam under hum id conditions during three cropping seasons. With 110 kg N ha(-1) (fer tilizer nitrogen plus mineral nitrogen of the soil at maize planting), the CC system was much more productive than were the LGS/CK and LGS/M R systems in terms of dry matter and nitrogen yields of maize. Increas ing the nitrogen supply to 250 kg N ha(-1) considerably reduced the yi eld advantage of CC over the LGS/CK and LGS/MR systems, indicating tha t nitrogen was the most limiting factor for maize yield in the mulch s eeding systems. With 250 kg N ha(-1), the LGS/CK and LGS/MR systems pr oduced greater total yields of digestible organic matter (maize plus r yegrass) than did the CC system, whereas the total nitrogen yield was similar for all cropping systems. The whole-shoot concentrations of ni trogen were highest under CC, irrespective of the level of nitrogen su pply. With 110 kg N ha(-1), concentrations of phosphorus and magnesium were clearly higher for the mulch seeding systems. There were only mi nor differences among the cropping methods in the concentrations of po tassium and calcium in the whole shoot. When 250 kg N ha(-1) were appl ied, there were no significant variations among the cropping systems i n the concentrations of minerals. Changes in the botanical composition of the cover crop sod and in the time and method of cover crop contro l may help to reduce the competition for nitrogen between maize and th e living mulch. (C) 1997 Elsevier Science B.V.