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Several recent studies have reported that mefluidide {N‐[2,4‐di‐methyl‐5‐[[(trifluoromethyl)sulfonyl]sulfonyl]amino]phenyl]acetamid} can improve the forage quality of perennial cool‐season grasses; however, there is no published information concerning the response of summer annual grasses to this growth regulator. The purpose of this study was to examine the influence of different rates of mefluidide application on growth, total‐N, and NO3N concentration in pearl millet [Pennisetum americanum(L.) Leeke]. In controlled environment experiments, mefluidide inhibited the growth of pearl millet when applied at the vegetative stage. On a whole plant basis, total N increased linearly with mefluidide rate from 1.3 mol kg‒1in control plants to 2.4 mol kg‒1in 1.12 kg ha‒1mefluidide‐treated plants. Nitrate‐N concentration increased linearly from 14.3 mmol kg‒1in control plants to 278.6 mmol kg‒1in 1.12 kg ha‒1mefluidide‐treated plants. Similar results were obtained for leaf tissue, the largest differences occurring as mefluidide rate was increased to 1.12 kg ha‒1. Total N increased from 1.7 mol kg‒1in control leaves to 2.7 mol kg‒1in 1.12 kg ha‒1mefluidide leaves, and to 2.8 mol kg‒1in 2.24 kg ha‒1mefluidide‐treated leaves. Nitrate‐N increased from 42.8 mmol kg‒1in control leaves to 314.3 mmol kg‒1in 1.12 kg ha‒1mefluidide‐treated leaves and declined to 250 mmol kg‒1in 2.24 kg ha‒1mefluidide‐treated leaves. Concentrations of total N and NO3‐N were inversely related to dry matter yield, implying that accumulations were a result of sustained nitrate uptake in the absence of growth. Levels of NO3‐N were reached that could be potentially hazardous to livestock, indicating that mefluidide should be used with caution on pearl millet.

Sample moisture may impair accuracy in predicting forage quality based on near infrared‐reflectance (NIR), but the literature contains little specific information on the topic. The purpose of this study was to determine the extent to which moisture interferes with the ability of NIR to predict acid detergent fiber (ADF) in silage‐type sorghums [Sorghum bicolor(L.) Moench.]. Comparisons were made between laboratory and predicted ADF on samples that were oven‐dry or had been stored at 43% (low), 63% (medium), and 100% (high) relative humidities. Results showed no significant differences between laboratory and predicted ADF for samples that were dry or had been stored under conditions of low humidity. However, when samples were stored under medium or high relative humidities, a significant (P ≤ 0.05) over‐estimation of ADF resulted. Increased sample moisture lowered predictability, since the standard error of estimate increased from 1.27 and 1.18 for dry and low moisture samples, to 2.28 and 4.15 for medium, and high moisture samples, respectively. Consistently repeatable ADF values were obtained when calibrations and NIR analyses were conducted on oven‐dry material, which emphasizes that NIR analyses should be conducted only on recently oven‐dried material that has been stored in a desiccator.

Near infrared reflectance spectroscopy (NIRS) has become widely accepted for the analysis of forage quality parameters. However, this technology has not been tested adequately for its capacity to analyze forages for antiquality parameters. Our objectives were to evaluate the utility of NIRS to determine the tannin concentration of sericea lespedeza [Lespedeza cuneata(Dum.‐Cours.) G. Don.] and to quantify the seasonal tannin fluctuations of various high‐ and low‐tannin entries. We assayed tannin concentration of nine sericea entries grown on a Cecil coarse sandy loam (clayey, kaolinitic, thermic Typic Hapludult) near Athens, GA, and harvested in June, August, and October in each of 3 yr. Calibration equations were obtained by regression of the vanillin‐HCl tannin values on NIR spectra from 100 randomly selected samples using a scanning NIR monochromator spectro‐computer system. Five wavelengths were required to derive the best equation with a standard error of calibration of 14.0 g kg−1dry matter (DM). Analysis of the remaining samples gave a standard error of analysis of 15.0 g kg−1DM, which was similar to the standard of the reference method in our laboratory (SE = 12.1 kg−1DM). Differences in tannin concentration of sericea lespedesa were due to an entry ✕ season ✕ year interaction (P< 0.0001). Tannin concentrations increased in summer but returned to lower levels in autumn. These fluctuations were greater in the high‐ than low‐tannin entries (P< 0.05). We conclude that NIRS can analyze the tannin concentration of high‐ and low‐tannin sericea lespedeza with an accuracy similar to the reference method. Use of NIPS should allow breeders to screen larger numbers of sericea lespedeza lines than would otherwise be possible.

Because of simplicity and minimum cost, one of the most promising approaches to carbohydrate analysis uses high performance liquid chromatography (HPLC) to separate neutral sugars on cation exchange resins, with only water as the mobile phase. The purpose of this research was to evaluate this technique for the analysis of carbohydrates in forage grasses. Stem bases from field‐grown tall fescue (Festuca arundinaceaSchreb.) were sequentially extracted with 95% ethanol and de‐ionized water to remove free sugars and fructosans, respectively. The fructosan extract was hydrolized with 1.0 NH2SO4. Tall fescue leaf tissue was treated with neutral detergent and the resulting neutral detergent fiber (NDF) was treated with 1.0 NH2SO4to remove and hydrolize hemicellulose. The neutralized extracts were chromatographed on a column containing Aminex Ql5‐S, Ca++, with water as mobile phase. Neutral sugars identified in 95% ethanol extracts were glucose, sucrose, and fructose. Fructosan hydrolizates contained glucose and fructose, and hemicellulose hydrolizates of leaf tissue contained xylose, arabinose, and a small amount of glucose. Baseline separation of all sugars was achieved within 39 min and injections could be made every 20 min. Although retention times were longer than those obtained using other methods, ease of operation, minimum cost, and column stability over time make this technique suitable for use with automatic sampling devices and data acquisition systems.

There is little information concerning critical Mn deficiency and toxicity levels in forage plants, or how plant Mn concentration affects other plant constituents associated with forage quality. This study was undertaken to investigate possible interactions between plant Mn concentration and the growth and forage quality of wheat (Triticum aestivumL. cv. Stacy). Wheat plants were grown in nutrient solution containing 0.005, 0.02, 0.05, 0.25, 1, 5, 25, 100, 200, and 500 µg/g Mn. Plants were grown for 30 days after transplanting into nutrient solution and were harvested at the three‐leaf stage, lyophilized, and weighed. Manganese concentration, in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), in vitro cell wall disappearance (IVCWD), total nonstructural carbohydrates (TNC), and Ca and Mg concentrations were determined on wheat shoot. Critical Mn deficiency and toxicity levels affecting normal growth of wheat shoot were determined to be 35 and 475 µg/g dry wt, respectively. These values are useful in determining deficiency and toxicity in wheat production. Percentage NDF, IVDMD, TNC, and IVCWD were reduced in tissue from plants that were critically Mn‐deficient. In vitro dry matter disappearance and TNC were increased in tissue from critically Mn‐toxic plants. In vitro dry matter disappearance ranged from 71 to 89%, with the lowest values observed for Mn‐deficient and the highest for Mn‐toxic plants. The high IVDMD of the Mn‐toxic plants appeared to be related to an accumulation of TNC, while the relatively lower IVDMD of the Mn‐deficient plants was related to reduced cell wall digestibility. Both Ca and Mg concentrations decreased as Mn concentration in the plants increased above 475 µg/g. Results of this study indicate that Mn deficiency and toxicity in wheat have a significant effect on amount of growth and the concentration of plant constituents associated with forage quality. These constituents remain relatively constant over the adequate range of Mn nutrition and plant Mn concentration should be kept within the 35 and 475 µg/g range.

Suppression of woody plants by grasses has been widely reported; but few studies have investigated the factors responsible for the reduced growth and poor appearance often shown by ornamental trees and shrubs planted in association with turfgrass. This research was undertaken to determine the major factors responsible for this phenomenon. A field study, conducted over two growing seasons, evaluated the growth of flowering dogwood (Cornus floridaL.) and forsythia (Forsythia intermediaSpaeth.) planted in established sod (Enfield silt loam soil, Typic Dystrochrept). Treatments included different sized areas of turf‐free space (0.3m2, 0.7m2, and 23.7m2), surface and subsurface placement of fertilizer and irrigation, and two mowing heights (10 cm and 4 cm). Turfgrass significantly reduced the growth of both woody species. Although supplementary fertilizer, applied as a topdressing, failed to benefit the ornamentals, subsurface treatments resulted in considerable increases in growth. Competition for moisture did not appear to be responsible for the observed differences in growth, since maintaining a high level of soil moisture failed to overcome the inhibitory effects of the turfgrass. Competition for N, however, was indicated by results of leaf tissue analysis. A bioassay experiment tested the hypothesis that the competitive nature of turfgrasses involves an allelopathic mechanism. Aqueous leachates of the roots of perennial ryegrass (Lolium perenneL.), red fescue (Festuca rubraL.), and Kentucky bluegrass (Poa pratensisL.) were applied to rooted cuttings of forsythia. Top growth of the forsythia was inhibited by leachates from all three turfgrass species. Root growth was suppressed by ryegrass and red fescue leachates. Results of these experiments indicate that the suppression of woody plants by turfgrasses may involve chemical inhibition as well as direct competition for available N.

High temperatures during the growth of forage grasses adversely affect forage quality, but there is little information concerning possible temperature effects on the digestion characteristics of the cell wall. The purpose of this study was to examine the influence of different temperature regimes on the amount, the rate, and the extent of in vitro cell wall digestion in tall fescue (Festuca arundinaceaSchreb.). Vegetatively propagated tall fescue plants were grown in a controlled environment over a period of 315 days, during which time the temperature was changed sequentially from 13/10 (T1), to 20/18 (T2), 30/27 (T3), and back to 13/10 (T4)°C, day/night, for a 14‐h photoperiod. Plants were harvested three times at 28‐day intervals at each temperature, after which the temperature was changed. Leaf material from the second and third harvests at each temperature was oven‐dried and ground for analysis. The first harvest at each temperature was discarded in order to reduce the confounding of treatments. Concentrations of neutral detergent fiber (NDF), cellulose, and hemicellulose increased with temperature up to T3 and decreased at T4, while lignin concentration remained about the same. Digestible NDF represented a greater proportion of dry matter in all temperature treatments but showed less variation with treatments than did indigestible NDF. Concentrations of indigestible NDF increased each time temperature was raised and decreased when temperature was lowered. Indigestible NDF concentrations were equivalent to T1 and T4. Rates of digestion of potentially digestible NDF followed first order reaction kinetics, and there were no temperature‐related differences in digestion rate constants. No direct relationship was shown between lignin concentration and digestion. The results indicate that high temperature causes reduced cell wall digestibility by increasing the amount of indigestible cell wall without affecting the rate of digestion of the more labile fraction.

Increasing growth temperature lowers digestibility of tall fescue (Festuca arundinaceaSchreb.) cell walls, but specific tissue responses have not been fully elucidated. The objectives of our research were to determine the effect of increasing growth temperature on leaf anatomy, histological reactions for lignin, alkali‐extractable phenolic acids, and the digestion of different tissue types by rumen microorganisms after 4, 10, 24, or 48 h. Plant material was grown in a controlled environment in which temperature was changed sequentially from 13/10°C (T1), to 20/18°C (T2), to 30/27°C (T3), and back to 13/10°C (T4). Two consecutive harvests of uppermost leaf blades following 28 days growth were made at each temperature, and analyses were performed on leaf blades. Histological reactions for lignin and leaf anatomy were similar for all treatments but with higher amounts of lignified vascular tissue in T3. At incubation times less than 48 h, leaf tissues from plants grown at T1 or T4 were degraded, as determined by scanning electron microscopy, to a greater extent than those at T2 or T3. However, after 48 h, tissues from plants grown at T2 were clearly the most degraded, and the order for all digestible tissues was as follows: T2 > T4 > T1 > T3. From 786 to 854 g kg−1of the phenolic acids extracted from forage with 1 MNaOH were trans‐p‐coumaric and trans‐ferulic acids. Increases in growth temperature tended to increase levels of these and other phenolic acids, with T3 resulting in the highest level; amounts at T1 were lower (P≤10.05) than those at T2 through T4. Increased temperature resulted in a lower digestibility of easily degraded tissues without causing a marked change in leaf anatomy or histological reaction for lignin. Increased levels of p‐coumaric and ferulic acids up to T3 suggest that these compounds may contribute to limiting the digestibility of leaf blade tissues at higher temperatures.