Trafficking during harvesting significantly increased soil bulk density to depths of 3 to 6 inches in areas outside of primary skid trails and 9 to 12 inches in primary skid trails. On the Coastal Plain site, bedding was effective in offsetting soil compaction in areas outside of primary skid trails, forming a new soil surface, 7 to 8 inches in height, over the surface trafficked during harvest. Bedding may not be so effective in the skid trails, because the original soil surface under the bed was so compacted that root growth may be inhibited. On the Piedmont site, disking was effective in restoring bulk density to preharvest levels in the upper 3 to 5 inches of soil, but soil compaction in the upper 3 to 9 inches of drum-chopped areas may result in reduced root growth, because of mechanical impedance.

In a wide range of loblolly pine (Pinus taeda L.) plantations, very few of which were suffering from severe nutrient deficiencies, response to fertilization was related to stand conditions. Gross and net volume increment equations were developed using basal area, site index, and fertilizer treatment as predictor variables. Response to fertilization was calculated as the difference between growth estimates for control and fertilized stands at given levels of basal area and site index. Predicted 5-year volume response from fertilization with 100 lbs N/A + 50 lbs P/A is given for a range of basal area and site index levels for both the Coastal Plain and Piedmont regions. The information provided will enable the forest manager to choose stands with the greatest potential for response, and to determine the economic benefits of fertilization.

Mineralizable nitrogen (N) fractions extracted from surface soil by 2N KCl, anaerobic or aerobic laboratory incubation, autoclaving, and dilute acid were not significantly correlated to five‐year volume growth response to N fertilization, site index, or N levels of foliage or litterfall. Site index was significantly and directly correlated to foliar N concentrations and inversely correlated to the surface soil C/N ratio. The amounts of N extracted by anaerobic and aerobic laboratory incubations could be significantly predicted, using total soil N and soil acidity.

Biologic and economic optimum rates of nitrogen (N) fertilization were estimated 4 or 5 years after fertilization for 11 loblolly pine plantations which were responsive to ammonium nitrate fertilization. Despite the diversity of sites and stands examined, variation in the optimum N rates was not very great. The biologic optimum averaged 200 lbs. N per acre, while the economic optimum varied according to the value of the harvested product: for wood values at $0.70 and $0.20 per cu. ft. the average economic optima were 152 and 57 lbs. N per acre, respectively. These two economic rates captured, on average, 94 percent and 52 percent, respectively, of the maximum biologic response. The response magnitude showed considerably more variation between sites than the optimum N rates, with the maximum biologic volume response ranging from 193 to 502 cu. ft. per acre over a 5-year period.

Sulfur‐coated urea fertilizers were included in six experiments with seedlings of Pinus radiata D.Don. The fertilizers were applied in notches alongside seedlings about 2 months after planting, and tree growth was measured for 2 or 3 years. After slash burning on a strongly weathered clay soil, slow‐release nitrogen fertilizers, including three formulations of S‐coated urea, proved more effective than urea. On a more fertile pumice soil, on both slash burnt and unburnt sites, no response to N fertilizers was detected. However, where the topsoil of this soil type had been either completely or partially removed (a log landing and a windrowed area, respectively) a response to N occurred. In these two disturbed areas S‐coated urea showed no advantage over conventional soluble NH4‐N fertilizers. There were no differences between the effectiveness of the three formulations of S‐coated urea at any of the experimental sites.