David L. Hensley

Pre-plant incorporation of nitrogen fertilizer to spring- and fall-planted bareroot Scotch pine☆

Abstract Nitrogen (56, 112 or 224 kg N ha −1 ) was applied as ammonium nitrate or urea formaldehyde before planting Pinus sylvestris seedlings in the fall and spring. Controls received no fertilization. Survival and growth were measured. There were significant effects of N fertilization on survival. Higher levels of N resulted in lower survival without increased growth. Slow-release N allowed increased rates to be utilized without reducing survival, but there was no benefit in the higher N rates in terms of growth.

Mode of Action of Bentazon in Depressing Nitrogen Fixation by Dry Bean (Phaseolus vulgaris)

Bentazon has been shown to produce short-term reduction in nitrogen fixation capacity by Phaseolus vulgaris. The following studies were initiated to ascertain the mode of action of the chemical. Bentazon was directly applied to nodules of P. vulgaris at 0.0, 12.5, 37.5 and 62.5 ml/liter (0, 1, 3 and 5 x rates) by vacuum infiltration for intervals of one to three hours. There was no depression of nitrogen fixation, except with bentazon applied at 5 x rate (62.5 ml/liter). Leghemoglobin concentrations in excised nodules were examined from bentazon (3 x rate) treated, four-week-old P. vulgaris. No significant degradation of the hemoprotein could be detected by spectrophotometry. Four-week-old P. vulgaris were treated with bentazon (3 x rate) and darkened for 6 days to deplete carbohydrate levels in nodules. Nodules were then assayed for nitrogenase activity with and without the addition of vacuum infiltrated sucrose at 0.0, 0.5, 1.0 and 2.0 M concentrations for a one hour period. 2.0 M sucrose concentration proved significantly advantageous in providing greatest recovery in nitrogenase activity assayed by acetylene reduction. Plants were also grown without darkness and again exposed to sucrose levels listed above. No statistically significant differences were found in nitrogenase activity among any of the treatments.