Variation for biomass and residue production by dry pea

Pea (Pisum sativum L.) cultivars, grown for their dry edible seed, produce small and fragmentary harvest residues. The small residue pieces are ineffective in controlling soil erosion when the pea crop is followed by winter wheat in rotation. This presents a special problem for pea-wheat rotations common on the steep loess hills of the Palouse region of the U.S. Pacific Northwest. To determine the amount of residue produced by dry pea total aboveground biomass was measured in plots of advanced pea yield trials conducted by the USDA at three locations in the Palouse region. Samples were collected in 1993, 1994 and 1995 and the amounts of residue produced were measured. Individual entries produced from 2300 to 4760 kg/ha of total biomass. Mean harvest indices for the nurseries ranged from 35% in 1993, a dry year, to 47% in both 1993 and 1995. Seed and residue yields were smaller in 1994 than in 1993 and 1995. Residue production and seed yield were influenced by sowing date and the amount and distribution of precipitation. Despite large environmental effects on residue production, sufficient genetic variation to improve the residue yields of dry pea was observed. The large, positive and significant correlation between seed yield and residue production indicated that it is possible to increase seed yields simultaneously with residue production through the incorporation of germplasm with greater potential for vegetative growth. (C) 1999 Elsevier Science B.V. All rights reserved.