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Rising concerns about greenhouse gases, increased fuel prices, and the potential for new high value agricultural products have raised interest in the use of maize stover for bioenergy production. However, residue harvest must be weighed against potential negative impacts on soil quality. This study, conducted in Chazy, NY, evaluated the long-term effects of 32 yr of maize (Zea mays L.) stover harvest vs. stover return on soil quality in the surface layer (5-66 mm) under plow till (PT) and no-till (NT) systems on a Raynham silt loam (coarse-silty, mixed, active, nonacid, mesic Aeric Epiaquept) using physical, chemical, and biological soil properties as soil quality indicators. Twenty-five soil properties were measured, including standard chemical soil tests, aggregate stability (WSA), bulk density, ([[rho].sub.b]) penetration resistance (PR), saturated hydraulic conductivity ([K.sub.s]), infiltrability (Infilt), several porosity indicators (aeration pores(PO > 1000), soil water potential = [PHI] > - 0.36 kPa; air-filled pores at field capacity (PO > 30), [PHI] > - 10kPa; available water capacity (AWC), - 1500 < [PHI] < - 10 kPa), total organic matter (OM), parasitic ([Nem.sub.Parasitic]) and beneficial nematode ([Nem.sub.Beneficial]) populations, decomposition rate (Decomp), potentially mineralizable N (PMN) and easily extractable (EEG) and total glomalin (TG). Only eight indicators were adversely affected by stover harvest, and most of these effects were signifcant only under NT. Almost all indicators affected by stover removal were affected equally or more adversely by tillage. A total of 15 indicators were adversely affected by tillage. Results of this study suggest that, on a silt loam soil in a temperate climate, long-term stover harvest had lower adverse impacts on soil quality than long-term tillage. Stover harvest appears to be sustainable when practiced under NT management. Abbreviations: [[rho].sub.b], bulk density; AWC, available water capacity; Decomp, cellulose decomposition rate; EEG, easily extractable glomalin concentration; [K.sub.s], saturated hydraulic conductivity; ln[K.sub.s], ln([K.sub.s] + 1); Infilt, infiltrability; NT, no-till; NT-H, NT stover harvested; NT-R, NT stover returned; [Nem.sub.Beneficial], number of beneficial nematodes; [Nem.sub.Parasitic] number of parasitic nematodes; OM, organic matter; PMN, potentially mineralizable nitrogen; PO > 30, pores with diam. > 30 [micro]m; PO > 1000, pores with diam. > 1000 [micro]m; PR, penetration resistance; PT, plow till; PT-H, PT stover harvested; PT-R, PT stover returned; SOC, soil organic carbon; TG, total glomalin concentration; WSA, water-stable aggregation (0.25-2.00 mm).

Climate change may both exacerbate the vulnerabilities and open up new opportunities for farming in the Northeastern USA. Among the opportunities are double-cropping and new crop options that may come with warmer temperatures and a longer frost-free period. However, prolonged periods of spring rains in recent years have delayed planting and offset the potentially beneficial longer frost-free period. Water management will be a serious challenge for Northeast farmers in the future, with projections for increased frequency of heavy rainfall events, as well as projections for more frequent summer water deficits than this historically humid region has experienced in the past. Adaptations to increase resilience to such changes include expanded irrigation capacity, modernized water monitoring and irrigation scheduling, farm drainage systems that collect excess rain into ponds for use as a water source during dry periods, and improved soil water holding capacity and drainage. Among the greatest vulnerabilities over the next several decades for the economically important perennial fruit crop industry of the region is an extended period of spring frost risk associated with warmer winter and early spring temperatures. Improved real-time frost warning systems, careful site selection for new plantings, and use of misting, wind machine, or other frost protection measures will be important adaptation strategies. Increased weed and pest pressure associated with longer growing seasons and warmer winters is another increasingly important challenge. Pro-active development of non-chemical control strategies, improved regional monitoring, and rapid-response plans for targeted control of invasive weeds and pests will be necessary. [ABSTRACT FROM AUTHOR]

Abstract Long-term exposure of plants to elevated CO2 often leads to downward photosynthetic acclimation. Nitrogen (N) deficiency could potentially exacerbate this response by reducing growth rate and the sink for photosynthates, but this has not always been observed. Experimentally, the interpretation of N effects on CO2 responses can be confounded by increasing severity of tissue N deficiency over time when N supply is not adjusted as demand increases. In this study, N supply ranged from sub- to supra-optimal (20–540 kgN ha–l equivalent), and relatively stable levels of tissue N concentration were obtained in all treatments by varying twice-weekly application rates in proportion to plant growth. The effects of N on photosynthesis and growth of beans (Phaseolus vulgaris L.) raised at ambient (35 Pa) and three elevated (70, 105, 140 Pa) CO2 partial pressures (p CO2 ) were evaluated. Averaging across N treatments, leaf total non-structural carbohydrates (TNC) were 2.5- to 3-fold higher and leaf N concentrations were 31–35% lower at elevated compared to ambient p CO2 . Light-saturated net CO2 assimilation rates measured at growth p CO2 (A satg ) were significantly higher (26–40% depending on N supply) in plants grown at elevated compared to ambient p CO2 . When measured at a common p CO2 of 35 Pa, the A sat of plants grown at elevated CO2 was 15–29% less than that of plants grown at 35 Pa, indicative of downward photosynthetic acclimation. The magnitude of downward photosynthetic acclimation to elevated CO2 was greater in plants grown at high (180 and 540 kgN ha–l ) compared to low (20 and 60 kgN ha–l ) N supply, and this was associated with a higher A sat at growth p CO2 , higher leaf area ratio (leaf area/total... [ABSTRACT FROM AUTHOR]

Abstract Primary events in photosynthetic (PS) acclimation to elevated CO2 concentration ([CO2]) occur at the molecular level in leaf mesophyll cells, but final growth response to [CO2] involves acclimation responses associated with photosynthate partitioning among plant organs in relation to resources limiting growth. Source–sink interactions, particularly with regard to carbon (C) and nitrogen (N), are key determinants of PS acclimation to elevated [CO2] at the whole-plant level. In the long term, PS and growth response to [CO2] are dependent on genotypic and environmental factors affecting the plant’s ability to develop new sinks for C, and acquire adequate N and other resources to support an enhanced growth potential. Growth at elevated [CO2] usually increases N use efficiency because PS rates can be maintained at levels comparable to those observed at ambient [CO2] with less N investment in PS enzymes. A frequent acclimation response, particularly under N-limited conditions, is for the accumulation of leaf carbohydrates at elevated [CO2] to lead to repression of genes associated with the production of PS enzymes. The hypothesis that this is an adaptive response, leading to a diversion of N to plant organs where it is of greatest benefit in terms of competitive ability and reproductive fitness, needs to be more rigorously tested. The biological control mechanisms which plants have evolved to acclimate to shifts in source–sink balance caused by elevated [CO2] are complex, and will only be fully elucidated by probing at all scales along the hierarchy from molecular to ecosystem. Use of environmental manipulations and genotypic comparisons will facilitate the testing of specific hypotheses. Improving our ability to predict PS acclimation to [CO2] will require the integration of results from laboratory studies using simple model systems with results from whole-plant studies that include measurements of processes operating at several scales. Abbreviations: CAM, crassulacean acid metabolism; FACE, Free-Air CO2 Enrichment; Pi, inorganic phosphate; LAR, leaf area ratio (m2 g-1); LWR, leaf weight ratio (g g-1); NAR, net assimilation rate (g m-2 d- 1); PS, photosynthetic; RGR, relative growth rate (g g-1 d-1); R:S, root/shoot ratio; rubisco, ribulose bisphosphate carboxylase/oxygenase; RuBP, ribulose bisphosphate; SLA, specific leaf area (m2 g-1); SPS, sucrose phosphate synthase; WUE, water use efficiency (g biomass g H2O-1). [ABSTRACT FROM AUTHOR]