• Authors:
    • Hubbard, K. G.
    • Mahmood, R.
  • Source: Journal of Hydrology
  • Volume: 280
  • Issue: 1/4
  • Year: 2003
  • Summary: Soil moisture (SM) plays an important role in land surface and atmospheric interactions. It modifies energy balance at the surface and the rate of water cycling between the land and atmosphere. In this paper we provide a sensitivity assessment of SM and ET for heterogeneous soil physical properties and for three land uses including irrigated maize, rainfed maize, and grass at a climatological time-scale by using a water balance model. Not surprisingly, the study finds increased soil water content in the root zone throughout the year under irrigated farming. Soil water depletes to its lowest level under rainfed maize cultivation. We find a 'land use' effect as high as 36 percent of annual total evapotranspiration, under irrigated maize compared to rainfed maize and grass, respectively. Sensitivity analyses consisting of comparative simulations using the model show that soil characteristics, like water holding capacity, influence SM in the root zone and affect seasonal total ET estimates at the climatological time-scale. This 'soils' effect is smaller than the 'land use' effect associated with irrigation but, it is a source of consistent bias for both SM and ET estimates. The 'climate' effect basically masks the 'soils' effect under wet conditions. These results lead us to conclude that appropriate representation of land use, soils, and climate are necessary to accurately represent the water and energy balance in real landscapes.
  • Authors:
    • Galatowitsch, S. M.
    • Mulhouse, J. M.
  • Source: Plant Ecology
  • Volume: 169
  • Issue: 1
  • Year: 2003
  • Summary: In the mid-1980's, thousands of wetlands in the mid-continental Unites States were restored by interrupting drainage lines; revegetation of these systems, often cropped for decades and positioned in a predominantly agricultural landscape, relied solely on natural recolonization. A study of 64 of these wetlands determined that by 1991, three years after initial reflooding, aquatic species had efficiently recolonized whereas sedge meadow and wet prairie species had not. In 2000, 41 of these restorations that had not been significantly altered or returned to cultivation were revisited and their floras characterized by cover within distinct zones. While species richness increased on every site, the rate of accumulation varied widely. Furthermore, species that had colonized since 1991, including a variety of native wet prairie and sedge meadow species, were detected only at very low abundance. In contrast, Phalaris arundinacea L., an invasive perennial, was now present on every site, often at covers approaching 75-100% in the zones in which it occurred. Other invasive perennials, including Cirsium arvense (L.) Scop. and Typha angustifolia L./glauca Godr., had expanded significantly on many sites. The overall dominance of invasive perennials has resulted in basins that are becoming more similar over time. However, present variations in species richness and composition can be attributed to flooding frequency, and, potentially, basin size and isolation from nearby natural wetlands, as shown by TWINSPAN and graphical analysis. Basins that have not been flooded at midsummer for at least seven of 12 years are among the most depauperate in the study. Yet even frequently flooded basins lack diversity if they are small (
  • Authors:
    • Jones, R. H.
    • Leonard, B. R.
    • Gore, J.
  • Source: Environmental Entomology
  • Volume: 32
  • Issue: 1
  • Year: 2003
  • Summary: Field and laboratory studies evaluated the influence of selected crop hosts on Helicoverpa zea population dynamics in relation to genetically engineered Bt (Bollgard) and non-Bt cottons. Host specific H. zea colonies were initiated with a colony originally collected from sweetcorn. The colony was allowed to complete one generation on meridic diet then split into cohorts and allowed to complete one generation on field maize, grain sorghum, soyabean, cotton, or meridic diet in individual 29.5 ml plastic cups. During the first part of the study, larval developmental times, pupal weights, and survival were measured. H. zea survival was higher on meridic diet and grain sorghum than on soyabean and cotton. The development of H. zea larvae was faster on field maize than the other larval diets. Also, H. zea required a longer period of time to complete development on cotton than on the other hosts. Pupal weights were higher on meridic diet than the plant hosts. Pupal weights of H. zea that completed larval stadia on cotton were lower than on the other larval diets. Neonates (F 1) from each of the host specific colonies (200 per colony) were exposed to Bt and non-Bt cottons. Mortality of second generation H. zea on non-Bt and Bt cottons was measured at 96 h. H. zea larvae from the cotton colony had higher mortality on non-Bt cotton than the other host specific colonies except the grain sorghum colony. On Bt cotton, larvae from the maize colony had a higher level of mortality than larvae from the soyabean and grain sorghum colonies. These data provide valuable information for evaluating the contribution of cultivated hosts as additional, alternative refugia in Bt-cotton resistance management plans.
  • Authors:
    • Lokaj, G. R. W.
    • Majek, B. A.
    • Belding, R. D.
    • Hammerstedt, J.
    • Ayeni, A. O.
  • Source: HortTechnology
  • Volume: 13
  • Issue: 2
  • Year: 2003
  • Summary: Peach ( Prunus persica cv. Candor) trees were established and grown from 1996 to 1999 at the Rutgers Agricultural Research and Extension Center, Bridgeton, New Jersey, USA, to compare their performance under four methods of orchard floor preparation: flat no-till, flat cultivated, mound unmulched, and mound mulched orchard floors. The experimental site was flat and the soil was a well-drained Aura gravelly sandy loam (61% sand, 31% silt and 8% clay) with a pH of 6.5, cation exchange capacity of 5.7, and organic matter content of 2.0%. Soil moisture holding capacity and gas exchange capacity determine the efficacy of mounding in peach orchards. Under these conditions, the method of orchard floor preparation had no effect on peach tree trunk cross-sectional area, fruit number per tree, fruit size and yield. Thus, without irrigation, there was no advantage to the early performance of peach trees associated with orchard floor mounding on Aura gravelly sandy loam when situated on a flat terrain.
  • Authors:
    • Post, W. M.
    • West, T. O.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 6
  • Year: 2002
  • Summary: Changes agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 +/- 14 g C m(-2) yr(-1), excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 +/- 12 g C m(-2) yr(-1), excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine mar L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.
  • Authors:
    • Nelson, R. G.
  • Source: Biomass and Bioenergy
  • Volume: 22
  • Issue: 5
  • Year: 2002
  • Summary: The focus of this study was to develop a methodology to estimate "hectare-weighted", county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995-1997 in 37 states (north-south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.
  • Authors:
    • Rozelle, S.
    • Hu, R.
    • Huang, J.
    • Pray, C. E.
  • Source: The Plant Journal
  • Volume: 31
  • Issue: 4
  • Year: 2002
  • Summary: Bt cotton is spreading very rapidly in China, in response to demand from farmers for technology that will reduce both the cost of pesticide applications and exposure to pesticides, and will free up time for other tasks. Based on surveys of hundreds of farmers in the Yellow River cotton-growing region in northern China in 1999, 2000 and 2001, over 4 million smallholders have been able to increase yield per hectare, and reduce pesticide costs, time spent spraying dangerous pesticides, and illnesses due to pesticide poisoning. The expansion of this cost-saving technology is increasing the supply of cotton and pushing down the price, but prices are still sufficiently high for adopters of Bt cotton to make substantial gains in net income.
  • Authors:
    • Williams, S.
    • Schuler, J.
    • Lamm, D.
    • Killian, K.
    • Elliott, T.
    • Easter, M.
    • Cipra, J.
    • Bluhm, G.
    • Paustian, K.
    • Brenner, J.
    • Smith, P.
  • Year: 2002
  • Summary: Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric carbon-dioxide by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. Practices that increase the amount of CO2 taken up by plants (through photosynthesis), which then enter the soil as plant residues, tend to increase soil C stocks. Likewise, management practices that reduce the rate of decay or turnover of organic matter in soils will also tend to increase carbon stocks.
  • Authors:
    • Kimble, J. M.
    • Lal, R.
    • Jacinthe, P. A.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Year: 2002
  • Summary: Enhancement of soil organic carbon (SOC) stocks through mulching has been proposed, and although this practice can alter several soil properties, its impact on the temporal variability of carbon dioxide (CO2) emission from soils has not been widely investigated. To that end, we monitored CO2 fluxes from a central Ohio Luvisol (fine, mixed, mesic Aeric Ochraqualf) amended with wheat (Triticum aestivum L.) straw applied at rates of 0 (M0), 8 (M8) and 16 (M16)Mgdry matter ha1 per year and supplemented with fertilizer (244 kg per year) or without. The experimental design was a randomized complete block design with three replications. The intensity of CO2 emission was higher in the late winter (mean: 2.79 g 2 per day) and summer seasons (2.45 gCO2- 2 per day) and lowest in the autumn (1.34 gCO2- 2 per day). While no significant effect of N fertilization on CO2 emission was detected, soil mulching had a significant effect on the seasonal variation of CO2 fluxes. The percentage of annual CO2 emitted during the winter and spring was similar across treatments (17-22%); however, 43% of the annual CO2 loss in the M0 plots occurred during the summer as opposed to 26% in the mulch treatments. A close relationship (F = 0.47X +4.45, R2 = 0.97,P <0.001) was found between annual CO2 flux (F, MgCO2-C ha 1) and residue-C input (X,MgCh 1). Litter and undecomposed residue amounted to 0.32 and 0.67MgC ha 1 per year in the M8 and M16 plots, respectively. After 4 years of straw application, SOC stocks (0-10 cm) were 19.6, 25.6 and 26.5MgCh1 in the M0, M8 and M16 treatments, respectively. The results show that soil mulching has beneficial effect on SOC sequestration and strongly influence the temporal pattern of CO2 emission from soils.
  • Authors:
    • Kimble, J.
    • Follett, R. F.
    • Reeves, V. B.
    • Reeves, J. B.
    • McCarty, G. W.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: The ability to inventory soil C on landscapes is limited by the ability to rapidly measure soil C. Diffuse reflectance spectroscopic analysis in the near-infrared (NIR, 400-2500 nm) and mid-infrared (MIR, 2500-25 000 nm) regions provides means for measurement of soil C. To assess the utility of spectroscopy for soil C analysis, we compared the ability to obtain information from these spectral regions to quantify total, organic, and inorganic C in samples representing 14 soil series collected over a large region in the west central United States. The soils temperature regimes ranged from thermic to frigid and the soil moisture regimes from udic to aridic. The soils ranged considerably in organic (0.23-98 g C kg-1) and inorganic C content (0.0-65.4 g CO3-C kg-1). These soil samples were analyzed with and without an acid treatment for removal of CO3. Both spectral regions contained substantial information on organic and inorganic C in soils studied and MIR analysis substantially outperformed NIR. The superior performance of the MIR region likely reflects higher quality of information for soil C in this region. The spectral signature of inorganic C was very strong relative to soil organic C. The presence of CO3- reduced ability to quantify organic C using MIR as indicated by improved ability to measure organic C in acidified soil samples. The ability of MIR spectroscopy to quantify C in diverse soils collected over a large geographic region indicated that regional calibrations are feasible.