Production of cool-season (C 3 ) herbage generally is low in summer and fall in the humid eastern USA. This study was conducted to determine the yields and pest problems of spring-sown turnip, Brassica rapa L.; swede, B. napus L.; rape, B. napus L.; interspecific crosses between chinese cabbage, B. campestris sensulato L., and turnip or rape; or kale, B. oleracea L., that were stockpiled. The crops were no-till seeded (turnip and swede at 1.4 kg ha-•, rape, the hybrids, and kale at 4.2 kg ha -•) into mature alfalfa (Medicago sativa L.)-grass stands. Prior to seeding, the sod was treated with isopropylamine salt of N-(phosphonomethyl) glycine at 1.1 kg a.i. ha-•. The study was made in central Pennsylvania on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalfs) soil in 1979 and 1980 and on Hublersburg silt loam (clayey, illitic, mesic Typic Hapludults) soil in 1981. Dry matter yield determinations were made sequentially at 30-day intervals from 60 to ISO days post-seeding. Fertilizer (P and K) was applied according to soil test results and 80 kg N ha-1 was applied at seeding and 70 kg N ha-• between the 60-and 90-day sampling dates. Three-year mean dry matter yields for 13 of 19 cultivars exceeded 7.0 Mg ha-• 90 days post-seeding. Yields plateaued from 80 to 160 days depending on plant species, cultivar, and year. Cultivar (across species) X sampling date, turnip cultivar X year, and swede, rape, and kale sampling date X year interactions were significant for yield. Incidence of plant diseases was positively related to slowing of growth at physiological maturity. Some New Zealand turnip and rape cultivars were more resistant to flea beetle [Phyllotreta cruciferae Goeze and P. striolata (Fab.)l than

Field trials were conducted on three cryic soils in southcentral Alaska to determine the local suitability of the Mehlich 3 extractant. Mehlich 3 extractable B, Cu, Fe, Mn and Zn, DTPA-TEA extractable Cu, Fe, Mn and Zn, and hot water extractable B were measured on soils from factorial experiments with variable rates of B, Cu, Mn, and Zn. Additional soil samples from two B rate and liming studies in central Alaska were included in extractable B comparisons. Forage rape, broccoli, and potato tissue samples were collected from the factorial studies to determine relationships between soil- and plant-available micronutrients. Crop yields were not affected by micronutrient applications Neither Mehlich 3 nor DTPA-TEA extractant predicted plant-available Cu or Fe. Coefficients of determination between soil and plant tissue B were comparable for extraction by Mehlich 3 or hot water and ranged from 0.11 to 0.82 Neither the Mn nor Zn tests accounted for more than 39% of the observed tissue nutrient concentration variation. The inclusion of soil PH and organic matter slightly improved estimates of available B, Mn, and Zn. Mehlich 3 extractable Fe was poorly related to DTPA-TEA extractable Fe. Copper extracted with Mehlich 3 was related to that extracted with DTPA-TEA (r2 = 0.73); the inclusion of soil pH improved the relationship (r2 = 0.84). Mehlich 3 extractable Mn and Zn were closely related to DTPA-TEA extractable levels (r2 = 0.91 and 0.94, respectively). The correlation between Mehlich 3 and hot water B (r2 = 0.57) was significantly improved by including soil organic matter content (r2 = 0.71). Key words: Micronutrients, extractant, Mehlich 3, DTPA, hot water

Six genera of warm‐season grasses were grown in Pennsylvania for 9 yr on a fine‐loamy, mixed mesic, Aquic Fragiudult, to determine their potential as forage grasses on droughty sites. Effects of applied N on yield, plant morphology, and N composition of forages were studied during Years 4 through 7, when N was applied to half of each plot area. Big bluestem, Andropogon gerardii Vitman, and switchgrass, Panicum virgatum L., showed much cultivar variation in stand development, whereas asiatic bluestem, Bothriochloa spp., and indiangrass, Sorghastrum nutans (L.) Nash, developed productive stands in one season. Mean yield of ‘NJ 50’ switchgrass was higher than that of all other grasses, yield of ‘Niagara’ big bluestem was higher than that of other big bluestems, and yield of ‘Ky 591’ indiangrass was higher than that of other indiangrasses. The percentage of grasses showing a yield response to applied N increased each year, from 32% in 1981 to 67% in 1984. Mean yield response to N varied greatly among cultivars, P < 0.001. Nitrogen concentration in forage varied among bluestems and indiangrasses, but not among switchgrasses. Mean N removed in first‐harvest forage ranged from 16 kg ha−1 yr−1 for untreated ‘Plains’ asiatic bluestem to 97 kg ha−1 yr−1 for N‐treated NJ 50 switchgrass. Flowerstem density and height were affected differently by N, depending upon plant species and cultivar. The sheath‐stem component of dry matter yield was 60 g kg−1 higher when N was applied than when no N was applied. In the ninth year, approximately one‐half of the cultivars had stand ratings exceeding 80% ground cover.

During plant maturation, degradability of alfalfa (Medicago sativa L.) stems declines due to accumulation of highly lignified xylary tissue. Xylem and nonxylem tissues dissected from lower alfalfa internodes were analyzed for cell wall constituents and degradability. Cell walls comprised 740 mg g(-1) of xylem and 533 mg g(-1) of nonxylem tissues. Xylem tissues contributed about 60% of the cell wall mass in internodes. Xylem walls contained 28% lignin, 4% pectin, 29% hemicellulose, and 39% cellulose as compared to 15% lignin, 25% pectin, 30% hemicellulose, and 30% cellulose in nonxylem walls. Fungal enzymes hydrolyzed 22 and 73% of the structural carbohydrates in xylem and nonxylem walls, respectively. In both cell wall fractions, the release of xylose was 56-90% lower than that of other sugars, indicating that lignin preferentially restricted xylan degradation in secondary walls and xyloglucan degradation in primary walls. Elucidation of lignin-xylose interactions may reveal strategies for improving fiber degradability of alfalfa.