Some effects of nitrate‐treated soil upon the sensitivity of buried redroot pigweed (Amaranthus retroflexusL.) seeds to ethylene, temperature, light and carbon dioxide

AbstractFresh dormant redroot pigweed (Amaranthus retroflexusL.) seeds were buried 5 cm deep in the field at Stoneville, MS in November 1981. Potassium nitrate (200 kg ha1) or nothing was applied to the soil in the fall of 1981 and the late winter of 1982. Seeds were recovered at intervals under darkness during the following 2 years and tested for responses to ethylene, temperature, light and carbon dioxide. During the first overwintering, nitrate enhanced loss of primary dormancy and increases seed sensitivity to temperature, light and ethylene. The loss of dormancy reached a maximum at 25 to 30 weeks (early summer) after burial. Examination of the recovered seeds indicated that about 80% of the non‐treated seeds and 98% of the nitrate‐treated seeds germinatedin situduring the period of maximum loss of dormancy. Thus, after one overwintering period, about 20% of the original buried seed population remained dormant in nontreted soil and 2% remained dormant in the nitratetreated soil. After the second overwintering, the percentages of dormant seeds remaining in nontreated or treated soil were both only 1–2%. Nitrate reduced dormancy and enhanced germination in early summer following the first overwintering. Regardless of treatment, the remaining 1 2% of seeds in soil after the second year were of low sensitivity to the germination stimuli (ethylene, temperature, light) and constituted the long‐lived portion of the original seed population.