Productividad de la rotación anual raigrás-maíz en GaliciaEvaluación durante cinco años en regadío y secano y bajo dos sistemas de siembra

Abstract

Biomass production of a ryegrass-forage maize rotation was studied in Lugo (northwest Spain), between 1997 and 2002, under irrigated and rainfed conditions and two sowing systems, conventional sowing and direct drilling. The experiment included a short-duration biannual ryegrass to compare with the intensive forage rotation. Average fve-year dry matter (MS) forage yields of the intensive rotation (two crops per year) were 28.00, 21.67, 27.93 and 20.90 t ha-1 for irrigated conventional sown, rainfed conventional sown, irrigated direct drilled, and rainfed direct drilled plots, respectively. Average MS forage yields of the biannual ryegrass were 15.69 and 8.27 t ha-1 for irrigated and rainfed treatments. Forage yields of the more intensive rotation were much higher than those of the biannual ryegrass. Even the biomass production of the intensive rotation (fve year average) under rainfed conditions, was 36% higher than biomass of the irrigated biannual ryegrass. Biomass yield of the ryegrass-forage maize rotation was not affected by the sowing system in most of the experimental years. The forage yields of irrigated treatments were much higher than those of rainfed treatments. For the ryegrass-forage maize rotation, this was due to the large production of irrigated maize. In four out of fve years, ryegrass production after rainfed maize was higher than after irrigated maize. For the biannual ryegrass, forage yields of irrigated treatments were also higher than yields of rainfed treatments. The rainfed biannual ryegrass did not recover from the frst year summer drought in 1998 and there was no fall re-growth, thus the second year forage production was zero