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Low and high tunnels and root-zone heating systems are proven tools in horticultural production. However, impacts of their individual and combined application on crop yield, composition, and microclimates are under-reported. We set out to enhance the record of management strategy effects on abiotic environmental conditions and cropping variables in open field and high-tunnel settings. In each setting, raised bed plots were subsurface heated (underlain by electric heating cables), aerial covered (0.8-mil, clear, vented, low tunnels), subsurface heated and aerial covered, or unheated and uncovered (control). The study was repeated four times in spring and fall seasons across 3 years in Wooster, OH. Red-leaved romaine lettuce (Lactuca sativa ‘Outredgeous’ and ‘Flagship’) was direct seeded in all plots in early October and late March and harvested after ≈4 weeks. Subsurface and aerial temperatures were monitored throughout the experiments. Here, we report primarily on treatment effects on crop microclimate conditions, including temperature and light, and related cropping variables. Subsurface and aerial temperatures varied consistently with plot microenvironment management. Relative to control plots, variability in shoot- and root-zone temperatures generally increased and decreased, respectively, with the addition of low tunnels and electric heating cables, regardless of setting. Still, the relative influence of aerial and soil temperature on crop biomass appeared to differ by setting; aerial temperature correlated most strongly with yield in the high tunnel, while the combination of aerial and root-zone temperature correlated most strongly with yield in the field. Growing degree day accumulation was least in control plots. And, the highest thermal energy to plant biomass conversion efficiency was recorded in the high tunnel. Comparing study-wide and historical climatic data collected in Wooster and other locations in the region suggests that results reported here may hold over a larger area and longer time frame in Wooster, OH.

Low and high tunnels and root-zone heating systems are proven tools in horticultural production. However, impacts of their separate and combined application on crop yield, composition, and microclimates are underreported. We addressed these gaps in the literature by exposing lettuce (Lactuca sativa) to four microclimates established with low and high tunnels and root-zone heating during the spring and fall of 2 years in Wooster, OH. Red-leaved romaine lettuce cultivars Outredgeous and Flagship were direct-seeded into raised beds in both outdoor and high-tunnel settings in early October and late March and harvested multiple times over 4 weeks. Half of all plots in each setting were underlain by electric heating cables, and half were covered with 0.8-mil, clear, vented, low tunnels. A growing medium consisting of peat moss, compost, soil, and red clover (Trifolium pratense) hay was used, and all plots were overhead-irrigated. Soil and air temperatures were monitored throughout the experiments, which were repeated four times (2 seasons/year × 2 years). Here, we report primarily on treatment effects on crop yield and related variables. Root- and shoot-zone conditions and cultivar significantly affected leaf biomass in both settings (outdoor, high tunnel), while population was more often affected in the outdoor experiments. Microclimate main effects were more prevalent than cultivar effects or interactions. Leaf yield was greater in low-tunnel-covered and bottom-heated plots than in uncovered and unheated plots. We take these data as further evidence of the potential to alter lettuce yield through root- and shoot-zone microclimate modification, particularly in regions prone to dynamic seasonal and within-season temperature and light conditions. The data also suggest that the relative performance of low and high tunnels in the production of short-statured, quick-cycling crops during fall and spring be more thoroughly evaluated.

BACKGROUND: Understanding the effects of temperature and nitrogen levels on key variables, particularly under field conditions during cool seasons of temperate climates, is important. Here, we document the impact of root-zone heating and nitrogen (N) fertility on the accumulation and composition of fall- and spring-grown lettuce biomass. A novel, scalable field system was employed. RESULTS: Direct-seeded plots containing a uniform, semi-solid, and nearly stable rooting medium were established outdoors in 2009 and 2010; each contained one of eight combinations of root-zone heating (−/+) and N fertility (0, 72, 144, and 576 mg day −1 ). Root-zone heating increased but withholding N decreased biomass accumulation in both years. Low N supplies were also associated with greater anthocyanin and total antioxidant power but lower N and phosphorus levels. Tissue chlorophyll a and vitamin C levels tracked root-zone temperature and N fertility more closely in 2009 and 2010, respectively. CONCLUSIONS: Experimentally imposed root-zone temperature and N levels influenced the amount and properties of fall- and spring-grown lettuce tissue. Ambient conditions, however, dictated which of these factors exerted the greatest effect on the variablesmeasured.Collectively,theresultspointtothepotentialforgainsinsystemsustainabilityandproductivity,including with respect to supplying human nutritional units. c � 2011 Society of Chemical Industry

Inclusion of a winter legume cover crop into a crop rotation has been suggested as a method to provide a substantial portion of the N requirement of the following crop. While the benefits of winter cover crops such as reduced soil erosion, increased soil organic matter, and increased mulch cover have been well documented, the N contribution to the subsequent crop has shown to be variable. The objective of this study was to determine the N contribution from a red clover (L.) cover crop following wheat (L.) to a subsequent corn (L.) crop. The experiment was conducted at two western Ohio locations over 3 yr. At both locations, red clover was either interseeded into wheat or seeded after harvest, the red clover cover crop was eliminated with tillage or herbicide application, and corn was planted with three N rates (0, 90, and 180 kg N ha). The data revealed that for three of the four site years (when the cover crop was successfully established) there was no N contribution attributable to the presence of red clover. The one site that did show a N contribution revealed that the amount of N contributed was less than 90 kg N ha However, even when no N benefit was found, yields were improved by non-N-related rotational effects. Significant reductions in N fertilization rates following a red clover cover crop are likely to result in lost corn yield opportunities in western Ohio.

Nitrogen use efficiency (NUE) in cereal grain production is estimated to be 33% throughout the world, and can be lower when N is applied in single, pre-plant applications compared with split N applications. This study was conducted to evaluate tillage system and anhydrous ammonia (AA) application methods on yield, N uptake, and NUE in hard red winter wheat (Triticum aestivum L.), using a narrow (10 cm) nozzle spacing on a V-blade (Noble or sweep blade) applicator and wide (46 cm) nozzle spacing on a knife applicator. Over the four-year period evaluated, conventional tillage was significantly higher in grain yield in five of eight site years over no-till. However, no-till was significantly higher in grain yield at Lahoma in 2003 where the highest overall grain yield was observed. Mixed results were evaluated in NUE for tillage; four site years of no significant differences between tillage systems and the other four site years split evenly between conventional-till and no-till. The V-blade improved...

As research intensifies on developing precision agricultural practices for corn (Zea mays L.) production, an important component will be to identify the scale at which these practices should be implemented. We hypothesized that optical sensing can be used to measure individual corn plant biomass and N uptake. A 3-yr study was conducted at three locations in Oklahoma. Optical sensor readings of normalized difference vegetation index (NDVI) and plant height measurements were collected on individual corn plants at various growth stages ranging from V8 (collar of eighth leaf unfolded) to VT (last branch of the tassel is completely visible) and correlated with individual plant biomass, forage yield per unit area occupied by the plant, and N uptake of that plant. Individual plant height measurement, collected before reproductive growth, was a good predictor of plant biomass across the six site years of the study (r 2 = 0.81). The index of NDVI X plant height provided the highest correlation with by-plant forage yield on an area basis. Optical sensor and plant height measurements collected at the V8 to V10 (collar of 10th leaf unfolded) growth stage can distinguish individual plants and provide information as to their biomass accumulation and N uptake. This research demonstrates that by-plant information can be collected and used to direct high resolution N applications. The index, NDVI X plant height, may be used to refine midseason fertilizer N rates based on expected N removal and by-plant measurements at or before V10.

resulting in an estimated 1066 kg ha 1 (17 bu ac 1 ) Corn ( Zea mays L.) grain yields are known to vary from plant to yieldlossover354commercialfields.LauerandRankinplant, but the extent of this variability across a range of environments (2004) and Liu et al. (2004) had differing results, notinghas not been evaluated. This study was initiated to evaluate by-plant that PSV did not significantly alter grain yields in Wis- corn grain yield variability over a range of production environments consin and Ontario, Canada, respectively. Nafziger et and to establish the relationships among mean grain yield, standard al. (1991) noted that uneven emergence of corn can deviation, coefficient of variation, and yield range. A total of forty- occur when soils are dry at the time of planting and six 8- to 30-m corn transects were harvested by plant in Argentina, could lead to decreased grain yields. It is generally ac- Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma from 2002 cepted that when adjacent plants differ by more than

Anhydrous ammonia, the most widely used nitrogen (N) fertilizer in production agriculture, can be subject to extensive losses by volatilization if it is not carefully applied. A laboratory exercise was developed for a senior-level soil nutrient management class to help students learn the impact of rate, application depth,andsoiltextureonammonia(NH3)volatilizationfromanhydrous ammonia. Sand and loam soil textures were evaluated at 5-, 10-, and 15-cm application depths and 112 and 224 kg N ha -1 rates of NH3, simulated by reacting ammonium chloride (NH4Cl) and sodium hydroxide (NaOH). Soil-retained ammonium (NH4) was measured in a potassium chloride (KCl) extraction of the soil 1 wk after treatment. Students developed a table and graphs that showed trends in NH3 loss with respect to applicationdepth,soiltexture,andfertilizerrate.Lossesranged from 85% for the high N rate applied at 5 cm in sandy soil to 1.0% for the low rate applied at 15 cm in loam soil. The exercise helped students identify causes of NH3 loss associated with anhydrous ammonia application. ANHYDROUS AMMONIA is the most widely used nitrogen (N) fertilizerinproductionagriculturetodaywithmorethan15billionkgproducedannuallyforagriculturaluseintheUSA(The Fertilizer Inst., 2000). Its high N percentage (82%) and relatively low cost make it an important N fertilizer source. A common concern associated with the application of anhydrous ammonia is the loss of N by volatilization. Several factors such as soil pH, soil moisture, soil texture, and depth of application play a large role in the amount of N lost by

Understanding the effects of temperature and nitrogen levels on key variables, particularly under field conditions during cool seasons of temperate climates, is important. Here, we document the impact of root-zone heating and nitrogen (N) fertility on the accumulation and composition of fall- and spring-grown lettuce biomass. A novel, scalable field system was employed.Direct-seeded plots containing a uniform, semi-solid, and nearly stable rooting medium were established outdoors in 2009 and 2010; each contained one of eight combinations of root-zone heating (-/+) and N fertility (0, 72, 144, and 576 mg day(-1)). Root-zone heating increased but withholding N decreased biomass accumulation in both years. Low N supplies were also associated with greater anthocyanin and total antioxidant power but lower N and phosphorus levels. Tissue chlorophyll a and vitamin C levels tracked root-zone temperature and N fertility more closely in 2009 and 2010, respectively.Experimentally imposed root-zone temperature and N levels influenced the amount and properties of fall- and spring-grown lettuce tissue. Ambient conditions, however, dictated which of these factors exerted the greatest effect on the variables measured. Collectively, the results point to the potential for gains in system sustainability and productivity, including with respect to supplying human nutritional units.

Asparagus (Asparagus officinalis L.) spears (cv. UC 157) trimmed to 20 cm were cooled 0, 4, 8, 12, 16, and 20 hours after harvest and evaluated for resistance to shear at 5 and 10 cm above the cut end immediately after cooling and during storage at 0.5, 2.5, and 5C. Resistance to shear increased during cooling delays and with time in storage. Initial cooling delays and simulated marketing conditions (transfer to 15C for 1 day) were the principal causes of increased resistance to shear. A 4-hour cooling delay resulted in an average 40% increase in resistance to shear. Transfer to 15C for 1 day resulted in a greater increase in shear force in the rapidly cooled than in the delayed-cooled spears. Increases in resistance to shear during storage varied from 0% to 50% and depended on the storage temperature, time, and the initial cooling delay. Spears trimmed to a green base showed less increase in shear force after storage than did spears trimmed to a white base. The visual quality of asparagus stored for 14 days was similar (excellent) among spears from different storage temperatures and between green- and white-base spears. Storage quality after 24 days had decreased more in spears stored at 5C than at 2.5 or 0.5C, and more in the green-base than the white-base spears.