<p> Increased nitrogen (N) fertilizer additions to modern agricultural cropping systems will be necessary to feed a growing world population. However, greater nitrogen use efficiency (NUE) is required if agroecosystems are to continue to provide certain ecosystem services (e.g., greenhouse gas emission reductions and water quality goals). The aim of this research was to investigate the role of variable rate N and seeding of winter wheat (<i>Triticum aestivum</i>) for optimizing yield-water-NUE relationships across heterogeneous landscapes. Field plot studies were conducted at the Cook Agronomy Farm (CAF) near Pullman, WA during the 2010, 2011 and 2012 winter wheat harvest years. A randomized complete block split plot N rate x seeding rate experiment with N fertilizer rate as main plot and seeding rate as subplot was employed across three landscape positions. Assessed were evidence of &ldquo;haying-off&rdquo;, depletion of available water resources, and the link between yield, protein, and NUE response to landscape by N fertilization rate by seeding rate treatment combinations. A performance classification was developed to evaluate wheat performance with regard to N utilization efficiency (Gw/Nt) and N uptake efficiency (Nt/Ns) components of the NUE. </p><p> Evidence of haying-off in winter wheat was medium to high for drier landscape positions, particularly during low precipitation years and likely occurs in these landscapes most years. Treatment impacts on NUE varied by year and landscape but overall NUE decreased by 14 to 22 kg grain yield per kg N supply as N rate increased from 0 to 160 kg N ha^-1 across three landscape positions and two site years (2011 and 2012). Target NUE and maximum anthesis biomass could be achieved with a 34 to 68% reduction in typical seeding rates. The NUE-based performance classification was helpful in identifying environmental or management conditions contributing to low or high NUE indicating potential to be used as an evaluation tool. This research also included a policy fellowship focused on N₂O emission reductions and greenhouse gas offset credits that could be generated from adoption of variable rate N for wheat and concluded that offset credits alone would not provide enough incentive for adoption of variable rate N.</p>

Two groups of container experiments were conducted to study heavy metal absorption by plants. The objectives of the first group of experiments were: (1) to evaluate the effect of Cd, Pb, and Cu, on productivity, essential oil content and quality of peppermint, basil, dill, and sage, and (2) to estimate metal transfer and accumulation in plant parts and in the essential oils. In the first experiment, elevated concentrations of Cd (2, 6, and 10 mg/L), Cu (20, 60, and 150 mg/L), and Pb (50, 100, and 500 mg/L) on basil, peppermint, and sage were evaluated. Cadmium and Pb did not decrease peppermint yields. The application of Cu. at 60 and 150 mg/L reduced yields compared to the control. Basil yields were reduced by application of Cd at 6 and 10 mg/L, Ph at 500 mg/L, and Cu at 20, 60, and 150 mg/L. Sage yields were reduced by Cd at 6 and 10 mg/L, Pb at 50, 100, and 500 mg/L, and by Cu. at 60, and 150 mg/L. All three plants developed phytotoxicity symptoms in the 150 mg/L Cu treatment. In the next experiment, the following concentrations were applied to peppermint and basil growth medium (in mg/L): Cd 10; Pb 100; Cu 100; Cd 10 + Ph 100; Cd 10 + Cu 100; Ph 100 + Cu 100; Cd 10 + Ph 100 + Cu 100; and control (without metal addition). The following metal concentrations were applied to the growth medium of dill (in mg/L): Cd at 2, 6, and 10; Pb at 50, 100, and 500; Cu at 20, 60, and 150, and a control (without metal addition). Neither of the compost treatments resulted in toxic tissue concentration of heavy metals. Both compost and heavy metal applications induced alterations in the essential oil constituents of peppermint, dill, basil, and sage, without a clear trend. However, the essential oils from the four plants from all treatments were not polluted with Cd, Cu, and Pb. In conclusion, peppermint, dill, basil, and sage could be grown in metal polluted soils as cash crops or for phytoremediation, without risk of contamination of the end product, the essential oils. (Abstract shortened by UMI.)

Time of planting plays a critical role in nitrogen (N) uptake by rye cover crop (CC). Even a few days of delay in planting can severely decrease CC performance. Evaluating the amount of N accumulation related to time of planting is critical to the farmer who has to optimize the winter rye planting date based on completion of corn harvest, suitable weather conditions and time availability for fall manure application. Winter rye cover crop was planted at 6 planting dates in fall from mid August to early October at weekly intervals from 2004 to 2009. The results suggest that delay from critical planting date (CPD) will decrease rye N uptake dramatically. Suggested CPDs for northwest parts of Massachusetts are not applicable because they are too early (third to fourth week of August). CPDs for central parts of the State are from first to second week of September. Farmers in these zones can take advantage of cover crop by a better time management and planting no later than CPD. In Eastern areas of Massachusetts CPD is the third week of September. By evaluating the effect of planting date on rye growth and N accumulation throughout the State, this model provides a powerful decision making tool for increasing N recovery and reducing nutrient leaching. Sixteen units of cost effective and accurate automated lysimeters were designed and installed to measure post-harvest nitrate leaching from a rye cover crop field during the falls and winters of 2007 to 2009. The electronic system was designed to monitor soil tension and apply the equal amount of suction to the sampling media. Hourly data from soil tension and vacuum applied to the system were collected and stored by each unit. A safety system was designed for protecting vacuum pump against unexpected major vacuum leakage events. The controller can be easily reprogrammed for different performance strategies. Other major parts of lysimeter included the power supply systems, vacuum pump, vacuum tanks, sampling jars, suction cups and plates, and electronic valves. The electronic system showed a very reliable and accurate performance in the field condition.