• Authors:
    • Merrill, S.
    • Tanaka, D.
    • Anderson, R.
  • Source: Agricultural Water Management
  • Volume: 58
  • Issue: 3
  • Year: 2003
  • Summary: The predominate crops grown in the northern Great Plains of the United States are cereal grains, which are well adapted to the region's semiarid climate and short growing season. However, rotations are changing because minimum- and no-till production systems improve precipitation-use-efficiency. Therefore, producers are seeking diversity in crop choices to improve the design of their rotations. Our objective with this study was to examine water relations and agronomic performance of seven broadleaf crops that may be suitable for a semiarid climate. Dry pea ( Pisum sativum L.), dry bean ( Phaseolus vulgaris L.), and sunflower ( Helianthus annuus L.) were the most favorable for this region considering crop yield and water-use-efficiency (WUE). Soybean ( Glycine max L.), crambe ( Crambe abyssinica Hochst), canola ( Brassica rapa L.), and safflower ( Carthamus tinctorius L.) were less successful. Water use for grain production ranged from 23 to 37 cm among crops whereas water-use-efficiency varied three-fold. Soil water extraction patterns differed between sunflower and dry pea, with sunflower extracting more water as well as accessing water deeper in the soil profile. Integrating oilseed and legume crops with cereal grains in a cycle-of-four rotation will aid producers in managing diseases and weeds, as well as improve grain yield due to the rotation effect.
  • Authors:
    • Gracia, R.
    • Moret, D.
    • Arrúe, J. L.
    • López, M. V.
  • Source: Soil & Tillage Research
  • Volume: 72
  • Issue: 1
  • Year: 2003
  • Summary: Maintenance of crop residues on the soil surface is considered the most effective method to control wind erosion. In semiarid Aragon (NE Spain), where the risk of wind erosion can be high, the adoption of conservation tillage systems has been encouraged as a fallow management alternative. However, little information concerning the dynamics of residue cover during fallow is available for this area. We report here results on the evolution of barley residues during two fallow periods under conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). The three tillage treatments were compared under both continuous cropping (CC) and cereal-fallow (CF) rotation. The CC system involves a summer fallow period of 5-6 months and the CF rotation a long-fallow of 17-18 months. Effects of specific tillage operations on soil cover are also presented and discussed in relation to wind erosion control during the long-fallow period. Average dry mass of barley residues at harvest was 1395 and 729 kg ha(-1) in the first and second year of the study, respectively. In general, crop residues at harvest were not significantly affected by tillage or cropping system. Primary tillage operations had the major influence on residue incorporation with reduction percentages of residue cover of 90-100% in CT (mouldboard ploughing) and 50-70% in RT (chiselling). During the two long-fallow periods, large clods (4-10 cm diameter) produced by mouldboard ploughing did not fully compensate for the complete burial of residues and the soil surface was insufficiently protected against wind erosion (soil covers
  • Authors:
    • Sadras, V. O.
    • Andrade, F. H.
    • Calvino, P. A.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 2
  • Year: 2003
  • Summary: The aim of this study was to investigate the influence of rainfall, soil depth, and crop management practices on the yield of dryland maize ( Zea mays L.) crops of the Argentine Pampas. We were concerned with the relevance of known physiological mechanisms in commercial crops and with developing a framework to quantify the impact of improved management practices on crop yield. Our approach included three steps. First, baseline functions were developed to quantify the relationship between yield and water availability (W) during the critical period for kernel set. Second, baseline functions were tested using an independent data set. Third, using the baseline functions as benchmarks, the effects on yield of soil depth and crop management practices were evaluated. Yield varied between 4.2 and 10 t ha -1, and most of this variation (>84%) was accounted for by W during the period bracketing flowering. Shallow soils presented lower yield than deep soils at a given rainfall. Using yield vs. W functions to account for the effect of variation in W, we quantified the impact of crop management on productivity. Technology-related yield increases were (a) 2.3 t ha -1 from the late 1980s to the mid-1990s, mainly explained by P fertilization, better and earlier weed control, and improved hybrids; (b) 0.9 t ha -1 from the mid-1990s to 1996-1998, related to no-till and higher plant density; and (c) 0.8 t ha -1 from 1996-1998 to 1999-2000, mainly explained by enhanced rates of N fertilization.
  • Authors:
    • Marland, G.
    • West, T. O.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: 3
  • Year: 2002
  • Summary: Agricultural ecosystems have the potential to sequester carbon in soils by altering agricultural management practices (i.e. tillage practice, cover crops, and crop rotation) and using agricultural inputs (i.e. fertilizers and irrigation) more efficiently. Changes in agricultural practices can also cause changes in CO2 emissions associated with these practices. In order to account for changes in net CO2 emissions, and thereby estimate the overall impact of carbon sequestration initiatives on the atmospheric CO2 pool, we use a methodology for full carbon cycle analysis of agricultural ecosystems. The analysis accounts for changes in carbon sequestration and emission rates with time, and results in values representing a change in net carbon flux. Comparison among values of net carbon flux for two or more systems, using the initial system as a baseline value, results in a value for relative net carbon flux. Some results from using the full carbon cycle methodology, along with US national average values for agricultural inputs, indicate that the net carbon flux averaged over all crops following conversion from conventional tillage to no-till is -189 kg C ha(-1) year(-1) (a negative value indicates net transfer of carbon from the atmosphere). The relative net carbon flux, using conventional tillage as the baseline, is -371 kg C ha(-1) year(-1), which represents the total atmospheric CO2 reduction caused by changing tillage practices. The methodology used here illustrates the importance of (1) delineating system boundaries, (2) including CO2 emissions associated with sequestration initiatives in the accounting process, and (3) comparing the new management practices associated with sequestration initiatives with the original management practices to obtain the true impact of sequestration projects on the atmospheric CO2 pool.
  • Authors:
    • Marland, G.
    • West, T. O.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 91
  • Issue: 1-3
  • Year: 2002
  • Summary: The atmospheric CO2 concentration is increasing, due primarily to fossil-fuel combustion and deforestation. Sequestering atmospheric C in agricultural soils is being advocated as a possibility to partially offset fossil-fuel emissions. Sequestering C in agriculture requires a change in management practices, i.e. efficient use of pesticides, irrigation, and farm machinery. The C emissions associated with a change in practices have not traditionally been incorporated comprehensively into C sequestration analyses. A full C cycle analysis has been completed for agricultural inputs, resulting in estimates of net C flux for three crop types across three tillage intensities. The full C cycle analysis includes estimates of energy use and C emissions for primary fuels, electricity, fertilizers, lime, pesticides, irrigation, seed production, and farm machinery. Total C emissions values were used in conjunction with C sequestration estimates to model net C flux to the atmosphere over time. Based on US average crop inputs, no-till emitted less CO2 from agricultural operations than did conventional tillage, with 137 and 168 kg C ha(-1) per year, respectively. Changing from conventional tillage to no-till is therefore estimated to both enhance C sequestration and decrease CO2 emissions. While the enhanced C sequestration will continue for a finite time, the reduction in net CO2 flux to the atmosphere, caused by the reduced fossil-fuel use, can continue indefinitely, as long as the alternative practice is continued. Estimates of net C flux, which are based on US average inputs, will vary across crop type and different climate regimes. The C coefficients calculated for agricultural inputs can be used to estimate C emissions and net C flux on a site-specific basis. Published by Elsevier Science B.V.
  • Authors:
    • Peters, M.
    • Paustian, K.
    • House, R. M.
    • Sperow, M.
  • Source: Agricultural Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Authors:
    • Steiner, J. L.
    • Franzluebbers, A. J.
  • Source: Agricultural Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Summary: No-tillage crop production has become an accepted practice throughout the U.S. The Kyoto Protocol on climate change has prompted great interest in conservation tillage as a management strategy to help sequester CO2 from the atmosphere into soil organic matter. Numerous reports published in recent years indicate a large variation in the amount of potential soil organic carbon (SOC) storage with no tillage (NT) compared with conventional tillage (CT). Environmental controls (i.e., macroclimatic variables of temperature and precipitation) may limit the potential of NT to store SOC. We synthesized available data on SOC storage with NT compared with CT from published reports representing 111 comparisons from 39 locations in 19 states and provinces across the U.S. and Canada. These sites provided a climatic continuum of mean annual temperature and precipitation, which was used to identify potential SOC storage limitations with NT. Soil organic C storage potential under NT was greatest (~0.050 kg · m -2· yr-1) in subhumid regions of North America with mean annual precipitation-to-potential evapotranspiration ratios of 1.1 to 1.4 mm · mm-1. Although NT is important for water conservation, aggregation, and protection of the soil surface from wind and water erosion in all climates, potential SOC storage with NT compared with CT was lowest in cold and dry climates, perhaps due to prevailing cropping systems that relied on low-intensity cropping, which limited C fixation. Published data indicate that increasing cropping intensity to utilize a greater fraction of available water in cold and dry climates can increase potential SOC storage with NT. These analyses indicate greatest potential SOC storage with NT would be most likely in the relatively mild climatic regions rather than extreme environments.
  • Authors:
    • Grove, J. H.
    • Dí­az-Zorita, M.
  • Source: Soil & Tillage Research
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: Surface accumulation of soil organic carbon (SOC) under conservation tillage has significant effects on stratification of other nutrients, on crop productivity and in ameliorating the greenhouse effect via atmospheric CO, sequestration. A measure of SOC stratification relative to deeper soil layers has been proposed as a soil quality index. Our objective was to determine the effects of the duration of tillage practices upon the SOC and extractable P distribution with depth in Maury silt loams (Typic Paleudalfs) at similar levels of corn (Zea mays L.) productivity without P fertilization. Soil samples (0-20.0 cm in 2.5 cm increments) were collected under moldboard tillage (MT), chisel tillage (CT) and no-tillage (NT) and in surrounding tall fescue (Festuca arundinacea L.) sods selected from three tillage experiments (1-2-, 8- and 29-year durations) in Kentucky. SOC stratification was greater under conservation tillage (CT and NT) and sods than under MT. SOC and soil-test-extractable P stratification were positively related. Increasing the duration under NT caused the thickness of C stratification to increase. In NT soils, C stratification ratio (CSR) approached CSR in the nearby long-term sods with time. Conservation tillage rapidly promoted the occurrence of CSR greater than 2 while MT always resulted in values lower than 2. The rapid initial change in CSR suggests characterization of thin soil layers (i.e. 2.5 cm depth increments) is desirable under conservation tillage. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Kennedy, G. G.
    • Barbercheck, M. E.
    • Walgenbach, J. F.
    • Hummel, R. L.
    • Hoyt, G. D.
    • Arellano, C.
  • Source: Environmental Entomology
  • Volume: 31
  • Issue: 1
  • Year: 2002
  • Summary: Populations of endemic soil entomopathogens (nematodes and fungi) were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC. Two tillage types (conventional plow and disk versus conservation tillage), two input approaches (chemically versus biologically based), and two cropping schedules (continuous tomato versus 3-yr rotation of corn, cucumber, cabbage, and tomato) were employed in large plots from 1995 to 1998. A Galleria mellonella (L.) trap bioassay was used to identify and monitor activity of Steinernema carpocapsae, Heterorhabditis bacteriophora, Beauveria bassiana, and Metarhizium anisopliae populations during the vegetable growing season (April-September). Seasonal detection of entomopathogens was significantly higher in conservation compared with conventional tillage systems. The strip-till operation did not affect levels of detection of S. carpocapsae. Pesticide use significantly reduced detection of entomopathogenic fungi. Type of ground cover significantly affected temperature in the upper 12 cm of soil; highest soil temperatures were observed under black plastic mulch and bare ground, whereas lowest temperatures were observed under rye mulch and clover intercrop. The high soil temperatures associated with certain ground covers may have reduced entomopathogen detection or survival. Although type of tillage appeared to be the primary factor affecting survival of endemic soil entomopathogens in our system, other factors, such as pesticide use and type of ground cover, can negate the positive effects of strip-tillage.
  • Authors:
    • Hoyt, G. D.
    • Walgenbach, J. F.
    • Hummel, R. L.
    • Kennedy, G. G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 93
  • Issue: 1-3
  • Year: 2002
  • Summary: Populations of foliar insect pests and natural enemies were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC, USA. Two types of tillage (conventional plow and disk, strip-tillage), two input approaches (chemically-based, biologically-based) and two cropping schedules (continuous tomato (Lycopersicon esculentum Mill.), 3-year rotation of corn (Zea mays L.), cucumber (Cucumis sativus L.) and tomato) were employed from 1995 to 1998. Tomato pest pressure was relatively low in all years, resulting in a limited impact of production systems on potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), and its associated parasitoids and predators. Thrips (Frankliniella spp. (Thysanoptera)) populations were significantly higher in the biological input treatments in 3 of 4 years. Lepidopterous (primarily Helicoverpa zea Boddie (Lepidoptera: Noctuidae)) damage on tomato was significantly higher in biological treatments in all years, damage by thrips and pentatomids (Hemiptera: Pentatomidae) increasing each year in the continuous tomato crop schedule. Most insect populations were significantly influenced by type of insecticide input or ground cover. Few population measurements were affected by tillage type. Foliar insect problems in commercial vegetable production may be associated predominantly with insecticide input (i.e. more damage with biologically based insecticides) and use of intercropping (i.e. more damage in systems with living mulch); however, the long term effects of tillage and crop rotation remain to be seen. (C) 2002 Elsevier Science B.V. All rights reserved.