NITROGEN, PHOSPHORUS AND MOISTURE EFFECTS ON ACCLIMATION OF WINTER PEAS

Abstract

Increased residual soil nitrogen and compaction-related waterlogging problems may relate to observed reductions in Austrian winter pea (Pisum sativum subsp. arvense (L.) Poir.) winter survival by influencing cold tolerance development. This study examines the influence of supplemental nitrogen and phosphorus on the cold tolerance of field acclimated Melrose Austrian winter peas. In 1981, on a poorly drained site, nitrogen rates of 34–101 kg N ha−1 increased LT50 to −6.9 from −7.4 °C for unfertilized peas through wk 7 of acclimation. Average winter pea LT50 after freezing at −4, −7 and −10 °C peaked at −7.7 °C at 7 wk of acclimation. LT50 was correlated (r = 0.85**) with declining epicotyl moisture (mg g−1). Survival declined from 51 to 8% between 7 and 9 wk of acclimation, corresponding to a threefold increase in average daily precipitation and waterlogged conditions. Tissue water levels (mg H2O epicotyl−1) between 7 and 9 wk of acclimation were correlated with LT50 (r = 0.64*). Winter peas cold tolerance peaked at −8.7 °C 9 wk after planting in 1982. High N rates reduced survival 16%, but did not influence LT50. Increased epicotyl N was correlated with survival (r = − 0.83**). Percent epicotyl moisture content correlated with LT50 (r = 0.70*) through 9 wk of acclimation. Phosphorus did not influence LT50 in either year.Key words: Pisum sativum subsp. arvense (L.) Poir., poor drainage, cold tolerance, plant water status, residual nutrient levels, pea (Austrian winter)