2007 Annual Report 1a.Objectives (from AD-416) 1)Determine the effects of reduced tillage and fall-planted cover crops in irrigated potato production systems on weed dynamics and develop weed management strategies that minimize the negative impacts of weeds. 2)Understand the processes controlling soil biological activity and community structure of the:(i)soil micro-flora, (ii)plant pathogens, (iii)nematodes, and (iv)insects under reduced tillage and cover crops in irrigated potato production systems. 3)Determine and understand the mechanisms controlling carbon and nitrogen cycling and trace gas fluxes under reduced tillage in irrigated potato production systems. 4)Evaluate potato crop performance, potato tuber quality, soil fertility and nitrate leaching below the rootzone under variable rates of preplant and inseason N applications under conventional and reduced tillage. 5)Evaluate the soil and plant growth parameters of a potato growth model, and validate the model for major potato cultivars and different management practices. 1b.Approach (from AD-416) 1)A standard and reduced tillage practice will be evaluated in a 3-year crop rotation of field corn/field corn/potato. The experimental design is a randomized strip split plot design with 4 replications, and includes 4 N treatments in each tillage treatment. The treatments consist of preplant N application rates of 56, 112, and 168 kg N ha-1 with remaining N (total N at 336 kg ha-1) applied as inseason fertigation beginning 3 weeks after emergence. 2)A 4-year crop rotation of winter wheat/sweet corn/sweet corn/potato and cover crop treatments will be investigated. Cover crops include white mustard, winter wheat, and oat-hairy vetch. 3)In a parallel experiment, the effects of different rates of preplant N and rates and frequencies of inseason N application on the tuber yield and quality of Ranger Russet and Umatilla Russet cultivars will be investigated. In all the above trials, effects of various treatments on:(i)microbial diversity and activity; (ii)nitrogen transformation, uptake, and losses; (iii)weed management; (iv)pathogens and nematodes populations; (v)gas fluxes; (vi)nutrient cycling and soil quality will be evaluated. 4)The data will be used to develop decision support systems for sustainable management of irrigated potato rotation system. Formerly 5354-13610-002-00D (11/03). 3.Progress Report Thousands of acres of grasslands are converted to irrigated cropland every year. From a soils perspective, the removal of native vegetation and mixing of the soil surface influence soil structure, carbon and nitrogen losses, disrupt microbial communities, increase wind erosion. The objective of this study is to quantify the effects of installing irrigated cropfields in desert habitat on soil environments. Soil was sampled from a 19 m grid before and after excavation of a 16 acre pivot circle on a native desert steppe area located near Paterson, Washington. Soil samples were analyzed for soil pH, nematode population density, soil moisture content, Mehlich III extractable nutrients (P, K, S, Ca, Mg, Mn, Cu, Fe), C and N mineralization rates, and NH4-N and NO3-N concentrations. Before and after excavation, spatial and elevation coordinates were measured using Real Time Kinematic GPS equipment. Electrical conductivity was determined after excavation at 1 ft. and 3 ft. depths with the use of Coulter electrodes. Remote sensing images were captured throughout the process. To determine the effect of excavation on growth patterns, wheat yields (planted in fall 2006) and protein concentration were also determined at various points throughout the field. Nematode populations decreased significantly after excavation and irrigation, with the largest populations in areas of minimal soil movement. Nitrogen mineralization potential appears to be closely correlated to soil moisture content, and electrical conductivity and soil pH appears to be closely correlated to topography prior to excavation. 4.Accomplishments Root-knot nematode resistance potato lines overcome by hairy nightshade. Columbia root-knot nematode is a major pest of potato in the Pacific Northwest and is controlled by costly soil fumigation. Nematode resistant potato breeding lines developed by ARS scientists at Prosser, WA segregated in response to nematode damage on tubers when grown in the presence hairy nightshade. Some lines possessed only root resistance and lacked tuber resistance, while other lines possessed both root and tuber resistance. These findings demonstrate how weed hosts of root-knot nematodes may negate the positive impact of growing resistant potatoes that lack tuber resistance and the importance of weed control on managing plant parasitic nematode populations. Potato breeders can use this information to select for both root and tuber resistance in breeding materials. NP 207, Component 2 - Speciality Crop Production System, Objective 2A2. Develop ecological based pest mangement stategies. Irrigated Switchgrass Production. Perennial herbaceous bioenergy crops have the potential to sequester soil C, supply a portion of U.S. energy needs and reduce atmospheric CO2 enrichment when used as a fuel. Assessments of the export of essential plant nutrients (N, P, K, and S) were measured to determine reductions in soil fertility that impact fertilizer recommendations and identify C sequestration potential. Aboveground biomass yields averaged 22 metric tons/ha/year (dry weight basis), required 1kg of N to produce 83 kg of biomass and produced an estimated 7,500 L ethanol/ha. Bioenergy crop producers can use this information to adjust fertilization rates to meet their feedstock production goals. In addition, these data can be used in the development of secondary markets, such as C-trading or by ethanol producers interested in nutrient recovery for production of fertilizer or animal feed supplements. NP 207, Component 1 - Agronomic Crop Production System, Objective 1B. Identify optimal economic strategies for bio-based energy production. 5.Significant Activities that Support Special Target Populations None. 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 28 Number of newspaper articles and other presentations for non-science audiences 22 Review Publications Boydston, R.A., Seymour, M.D., Brown, C.R., Alva, A.K. 2006. Freezing behavior of potato (solanum tuberosum), cultivar 'russet burbank' tubers in soil. American Journal of Potato Research. 83: 305-315. 2006. Boydston, R.A. 2007. Potato (Solanum tuberosum) and Weed Response to Postemergence Applied Halosulfuron, Rimsulfuron, and EPTC. Weed Technology. 21:465-469. Cochran, R.L., Collins, H.P., Kennedy, A.C., Bezdicek, D.F. 2006. Soil carbon pools and fluxes following land conversion in a semi-arid shrub-steppe ecosystem. Biology and Fertility of Soils. 43:479-489. Collins, H.P., Delgado, J.A., Alva, A.K., Follett, R.F. 2007. Use of 15n isotopic techniques to estimate nitrogen cycling from a mustard cover crop to potatoes. Agronomy Journal. 99: 27-35, 2007. Smith, J.L., Collins, H.P. Managing soil microorganisms and their processes. Book Chapter pp 471-502. 2007. Williams, M., Boydston, R.A., Davis, A.S. 2006. Canopy variation among three sweet corn hybrids and implications for light competition. HortScience. 41:1449-1454. Alva, A.K. 2006. Sustainable nutrient management in sandy soils - fate and transport of nutrients from animal manure verses inorganic sources. Journal of Sustainable Agriculture. Vol 28: 139-155. 2006. Alva, A.K. Petiole and soil nitrogen concentrations during the growing season of two potato cultivars as influenced by different nitrogen management practices. Commun. Soil Sci. Plant Anal. 38, 403-421. 2007. Kumar, K.S., Sajwan, K.S., Alva, A.K., Manian, S. 2007. Effects of Surface Fire on Litter Decomposition and occurance of microfungi in a Cymbopogon polyneuros Dominated Grassland. Archives of Agronomy and Soil Science. 53: 205-219, 2007. Liu, G.D., Li, Y.C., Alva, A.K. 2007. High water regime can reduce ammonia volatilization from soils. Communications in Soil Science and Plant Analysis. 38: 1203-1220.