Anaerobically digested sewage sludge, and wood and bark residues were added to a Nunn clay loam at several mixtures and rates up to 224 dry metric tons/ha in laboratory and greenhouse studies to determine the effect on wheat (Triticum aestivum L. em. Thell) growth and on nitrate accumulation in the soil.With increasing proportions of sludge and decreasing wood‐bark residues, there was an increase in wheat growth at all application rates except 224 metric tons/ha, wherein the yield dropped with the 100% sludge treatment. Results were similar with the wood‐sludge and bark‐sludge mixtures with only slight variations.Nitrate accumulation was low whenever the wood residue‐sludge mixtures had more than 50% wood residue. Relative NO3−‐N accumulation indices were determined for each application rate and each wood‐bark‐sludge combination, showing the N immobilization tendency of the wood‐bark‐sludge mixtures.The relationship between wheat growth in the greenhouse and nitrate accumulation in the laboratory soils has a correlation coefficient of 0.82 (significant at 0.99 probability level). Therefore, the wheat growth may have been limited by lack of nitrate resulting from immobilization of N when high proportions of wood residues were added in the organic waste. Maximum wheat growth occurred with the same treatments in the greenhouse that caused the soil in the laboratory to accumulate about 300 ppm of NO3−‐N in a 2 month period. For this study, near maximum wheat growth resulted from several different mixtures and rates of wood (W), bark (B), and sludge (S), including 224 metric tons/ha of WB‐25%S‐75%, 224 metric tons/ha of B‐25%S‐75%, 224 metric tons/ha of W‐50%S‐50%, and 112 metric tons/ha of W‐25%S‐75%.

Carbon dioxide production during a 367‐day period was used in assessing the rate of carbon oxidation when wood (W), bark (B), and wood‐bark (WB) mixture from Engelmann spruce (Picea Engelmannii Parry) were each mixed in different proportions with anaerobically digested sewage sludge and each mixture applied to a Nunn clay loam at rates of 22.4 to 224 metric tons/ha.Generally, as the application rate of organic material increased the CO2 production increased, but nonadditively for most time intervals. At the 22.4‐metric tons/ha rate, there were no consistent differences in CO2 production with variations in the proportion of wood materials to sludge. At the higher application rates, as the percentage of wood materials increased and sludge decreased, the CO2 accumulation increased up to 75% wood material — 25% sludge, then dropped with 100% wood material. The 22.4‐metric tons/ha application of 100% sludge also resulted in lower CO2 production rates than the mixtures of wood materials and sludge. The percentage decomposition of the added residues increased with decrease in application rate of the treatments, with values ranging from 11 to 55%.In concurrent studies, attempts were made to correlate CO2 production with N mineralized in laboratory incubation studies and with wheat growth in a greenhouse pot experiment. The appropriate regression equations were derived to describe the relationships obtained. It was concluded that microbial respiration was a good index of plant‐available N in soil, except where plant nutrients were deficient due to microbial immobilization, or where toxic factors were limiting to microbial activity.

Young-growth ponderosa pine on two different sites in northern New Mexico were evaluated for differences in fibril angle. Measurements were made radially at the butt end, mid-length, and top end of the merchantable stem divided into multiple 8-foot log lengths. Results indicated that the butt ends have larger fibril angles than the other two locations. Fibril angle did not vary significantly with either site index from 55 to 100 or d.b.h. from 9 to 14 inches. Keywords: Ponderosa pine, fibril angle, young growth, site index Management Implications Loss of lumber grade from excessive warp usually results from abnormal and/or asymmetrical shrinkage when lumber dries. In conifers, fibril angle, juvenile wood, compression wood, grain orientation, and knots have been associated with excessive lumber warpage. Longitudinal shrinkage typically ranges from 0.1% to 0.3% when wood is dried from green to ovendry conditions. Longitudinal shrinkage greater than 0.3% from green to overdry conditions for straight grain material is considered abnormal and is related to deviation of the microfibrils (fibril angle) from the longitudinal axis of the tracheid. Study results indicated that the fibril angle of young-growth ponderosa pine did not significantly vary with site index from 55 to 100 or d.b.h. from 9 to

Growing site index did not affect either the grade or the amount of warp. 2. Smaller trees and logs had lower grade recovery and more warp than larger trees and logs. 3. Log position in tree had little effect on grade recovery and warp when log diameter was accounted for. 4. Logs 8 inches or less in diameter, regardless of location in tree, had similar grade and warpage, and were affected only by moisture content. These research results should help the buyers and sellers to determine the stumpage value of timber. Height to 4-inch top d.i.b. (feet) 36.2 ±6.8 47.4 ± 10.9 Height to 6-inch top d.i.b. (feet) 30.5 ± 7.3 39.5 ±10.8 Volume, gross scale of logs (cubic feet) 10.8 ±5.5 13.6± 7.0 No. of 8-foot logs per tree 3.1 ±0.9 4.0 ± 1.2 Age at stump (years) 76 ±19 78 ±24 Lean (degrees) 2.2 ±1.9 2.2 ± 1.9 ''Each mean and standard deviation is based on a sample of 41 trees. U.S. Department of Agriculture Forest Service Rocky Mountain Forest and Range Experiment Station The Rocky Mountain Station is one of eight regional experiment stations, plus the Forest Products Laboratory and the Washington Office Staff, that make up the Forest Service research organization RESEARCH FOCUS Research programs at the Rocky Mountain Station are coordinated with area universities and with other institutions. Many studies are conducted on a cooperative basis to accelerate solutions to problems involving range, water, wildlife and fish habitat, human and community development, timber, recreation, protection, and multiresource evaluation.