Herbaceous weed control in young conifer plantations with formulations of nitrogen and simazine

Weed control and 2nd-year survival and growth of newly planted Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and noble fir (Abiesprocera Rehd.) seedlings were measured after application of herbicide and fertilizer in a replicated complete factorial experiment with four levels of simazine (0, 2.2, 4.4, 8.8 kg/ha), three levels of nitrogen (0, 110, 220 kg/ha), two types of nitrogen (urea prill; urea + trimamino-s-triazine (TST) prill), and two kinds of formulations (cogranular prill of simazine + nitrogen; nitrogen prill followed by liquid simazine). For the first growing season, total weed and grass control increased with increasing simazine rates. Total weed control was better when urea + TST, rather than urea alone, was applied in conjunction with simazine. Formulation and nitrogen rate were not significant. After plot treatment with 1.1 kg/ha of liquid hexazinone at the beginning of the second growing season, Douglas-fir survival decreased as rate of urea alone increased; survival decreased with lit...