Effect of nitrogen amount, time and 2,4-D+MCPA application on spatial distribution of lambsquarters seed bank in a corn field

Abstract

In order to evaluate the effect of nitrogen and herbicide management on distribution patterns of lambsquarters seed bank, an experiment was conducted in a grain corn field at the Agricultural Research Station, Ferdowsi University of Mashhad 2006 growing season.Treatments consisted of application of: 25 kg/ha nitrogen fertilizer at the time of corn planting with 2,4-D+MCPA herbicide(533 g. ai./ha 2.4.D+467 g. ai./ha MCPA), 25 kg/ha nitrogen fertilizer at the time of corn planting without herbicide, 25 kg/ha nitrogen fertilizer at the time of corn planting and six-leaf stage with herbicide, 25 kg/ha nitrogen fertilizer at the time of corn planting and six-leaf stage without herbicide, 120 kg/ha nitrogen fertilizer at the time of corn planting with herbicide, 120 kg/ha nitrogen fertilizer at the time of corn planting without herbicide 120 kg/ha nitrogen fertilizer at the time of corn planting and six-leaf stage with herbicide and 120 kg/ha nitrogen fertilizer at the time of corn planting and six-leaf stage without herbicide. Application of herbicide was useful in reducing the amount of lambsquaters seed bank. Semivariograms of seeds were fitted with spherical and exponential models.Semivariogram analysis in the levels of treatments indicated a range of influence of 0.88m to 45.12 m . The highest spatial correlation was 0.093% and the lowest was 28.81%. Weed seed bank patches was obvious in maps. Although the nitrogen fertilizer had no strong effect on reducing the amount of seed bank , the application of 2,4-D+MCPA was a useful practice in reducing weed seed bank.