Fitomassa e relação C/N em consórcios de sorgo e milho com espécies de cobertura

The objective of this work was to quantify the biomass production, the content and accumulation of nitrogen (N) and the carbon/nitrogen (C/N) relation in monocultures of sorghum (Sorghum bicolor) and corn (Zea mays), and intercrops with pigeon pea (Cajanus cajan), sun hemp (Crotalaria juncea), white lupine (Lupinus albus), sunflower (Helianthus annuus) and turnip forage (Raphanus sativus), managed in different stages. The experiment was carried out from March to July 2008, in a Haplic Acrisol, medium texture, under no-tillage. A randomized complete block design, with four replicates and split plots with the following treatments: monocultures of sorghum and maize and their intercrops with pigeon pea, sunn hemp, sunflower, turnip forage, white lupine, in the plots; and cut management times, at 60, 90 and 120 days after sowing, in the subplots. Intercrops of sorghum and maize with other species significantly outweighed the biomass productivity of their monocultures, which accumulated less N and had higher C/N ratio of biomass. The best cut management time is at 120 days after sowing of the cover crops, for dry biomass yield. Cutting at 90 days after sowing promoted the greater N accumulation and the lower C/N ratios.