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Experiments were conducted to determine the influence of cultural management practices on weed growth in nursery containers. Experiments 1 and 2 evaluated the effects of dolomitic lime rate and application method on substrate pH, creeping woodsorrel (Oxalis corniculata L.) establishment in containers, and growth of azalea (Rhododendron ‘Rosebud’) and pieris (Pieris japonica ‘Claventine’). Creeping woodsorrel shoot fresh weight was negatively correlated to substrate pH (r = -0.67, p = 0.0001). Creeping woodsorrel germinated and established poorly in substrates with pH greater than 6.7. In Experiment 3 and 4 containers were topdressed with a uniform layer of pulverized or pelletized dolomitic limestone at several rates. The most significant pH effect occurred on the surface layer. Topdressing containers with 40 g of lime provided creeping woodsorrel control. In Expeiment 5 incorporating the same lime rates used in Experiment 3 and 4 caused chlorosis in azalea and pieris while topdressed lime ultimately caused no change in growth or foliar color regardless of rate applied.
The effect of nitrogen (N) form on establishment and growth of bittercress (Cardamine oligosperma Nutt.), prostrate spurge (Chamaesyce maculata L.), pearlwort (Sagina procumbens L.), common groundsel (Senecio vulgaris L.), northern willowherb (Epilobium ciliatum Rafin.), or creeping woodsorrel. Injectors delivered 150 ppm N using either ammonium sulfate ((NH4)2SO4) (AS), ammonium nitrate (NH4NO３) (AN), calcium nitrate plus magnesium nitrate (Ca(NO３)２+ Mg(NO３)２) (CMN), or urea (CO(NH2)2) (UR). Weeds in containers receiving no N (non-treated controls) germinated in lower numbers and produced less biomass. Nitrogen form affected container weed establishment and growth especially in creeping woodsorrel and prostrate spurge. Across all species, CMN tended to reduce growth and flower number compared to other N forms. Weeds fertilized with AN were always among the largest with the most inflorescences.
The effects of substrate particle size and herbicide rate on weed establishment and growth in containers were evaluated in three experiments. Across the three experiments, pearlwort established with higher numbers in containers with the finest substrate. Subsequent pearlwort growth was reduced in two of the three experiments with coarser substrates. As rate of Rout increased pearlwort growth decreased. Northern willowherb (Epilobium ciliatum Rafin) responded more to herbicide rate than substrate particle size in one experiment 2, however, in Experiment 3 it germinated and grew larger in fine bark compared to medium bark. Common groundsel (Senecio vulgaris L.) established and grew larger with decreasing particle size and herbicide rate. |
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