• Authors:
    • Power, J. F.
    • Wiese, R.
    • Flowerday, D.
  • Source: Journal of Environmental Quality
  • Volume: 30
  • Issue: 6
  • Year: 2001
  • Summary: The U.S. Department of Agriculture funded the Management Systems Evaluation Area (MSEA) research project in 1990 to evaluate effectiveness of present fanning systems in controlling nitrate N in water resources and to develop improved technologies for farming systems. This paper summarizes published research results of a five-year effort. Most research is focused on evaluating the effectiveness of farming system components (fertilizer, tillage, water control, cropping systems, and soil and weather variability). The research results show that current soil nitrate tests reliably predict fertilizer N needed to control environmental and economic risks for crop production. A corn (Zea mays L.)-soybean [Glycine mar (L.) Merr.] rotation usually controls risk better than continuous corn, but both may result in unacceptable nitrate leaching. Reduced tillage, especially ridge-till, is better than clean tillage in reducing risk. The drainage controls nitrate in ground water, but discharge may increase nitrate in surface waters. Sprinkler irrigation systems provide better water control than furrow irrigation because quantity and spatial variability of applied water is reduced. Present farming systems have two major deficiencies: (i) entire fields are managed uniformly, ignoring inherent soil variability within a field; and (ii) N fertilizer rates and many field practices are selected assuming normal weather for the coming season. Both deficiencies can contribute to nitrate leaching in parts of most fields.
  • Authors:
    • Ottow, J. C. G.
    • Benckiser, G.
    • Weiske, A.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 60
  • Issue: 1-3
  • Year: 2001
  • Summary: In a 3-year field experiment the effect of the new nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate, trade name ENTEC) on the release of N2O and on methane oxidation was examined in comparison to dicyandiamide (DCD). Soil samples were analysed for the concentrations of ammonium, nitrite, nitrate and for the degradation kinetics of DMPP as well as DCD. DMPP decreased the release of N2O by 41% (1997), 47% (1998) and 53%(1999) (with an average of 49%) while DCD reducedN2O emissions by 30%(1997), 22%(1998) and 29% (1999) (with an average of 26%), respectively. Both nitrification inhibitors (NI) failed to affect methane oxidation negatively. The plots that received DCD or DMPP, respectively, even seem to function as enhanced sinks for atmospheric methane. DMPP apparently stimulated methane oxidation by ca. 28% in comparison to the control. The concentrations of ammonium remained unaffected by nitrification inhibitors whereas the amounts of nitrite diminished in the plots treated with DCD by 25% and with DMPP by 20%, respectively. Nitrate concentrations in soil were in both NI treatments 23% lower than in the control. DMPP and DCD did not affect the yields of summer barley, maize and winter wheat significantly. Dicyandiamide was mineralized more rapidly than DMPP (data for the cropping season in 1997 as an example).
  • Authors:
    • Samson, R. A.
    • Girouard, P.
    • Fyles, J. W.
    • Zan, C. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 86
  • Issue: 2
  • Year: 2001
  • Summary: The conversion of relatively undisturbed ecosystems such as forests and grasslands to intensively managed agroecosystems has had major impacts on global carbon (C) cycling largely as a result of land clearing, cultivation, and replacement of perennial vegetation by annual crops. Numerous studies have demonstrated the ability of fast-growing perennial plant species dedicated to bioenergy production to sequester substantial amounts of C. Thus, the conversion of conventionally managed agricultural land to perennial bioenergy crops can be expected to increase C stored in above- and belowground biomass and in soil organic matter because of their perennial nature and greater root biomass. In this study, C storage was compared among five ecosystems in southwestern Quebec including two perennial crops, switchgrass (Panicum virgatum L.), and willow (Salixalbaxglatfelteri L.), and an annual corn (Zea mays L.) crop at two sites of differing soil fertility, a 20-year-old abandoned field, and a mature hardwood forest. After 4 years of production, corn had significantly higher levels of aboveground C than willow at the less fertile site, but no significant differences were detected at the more fertile site. Both perennial systems had significantly higher root C than the corn system but switchgrass had significantly higher root C levels below 30 cm compared with willow and corn. Soil organic C under willow at the more fertile site was higher than under the other managed or unmanaged systems, including willow at the less fertile site. The results of this study suggest that perennial energy crops grown on relatively fertile soils, have the potential to increase substantially soil C levels compared with conventional agricultural systems or unmanaged systems.
  • Authors:
    • Ball, A.
    • Pretty, J.
  • Year: 2001
  • Authors:
    • Wagoner, P.
    • Drinkwater, L. E.
    • Douds, D. D.
    • Galvez, L.
  • Source: Plant and Soil
  • Volume: 228
  • Issue: 2
  • Year: 2001
  • Summary: Low-input agricultural systems that do not rely on fertilizers may be more dependent on vesicular-arbuscular mycorrhizal [VAM] fungi than conventionally managed systems. We studied populations of spores of VAM fungi, mycorrhiza formation and nutrient utilization of maize (Zea mays L.) grown in moldboard plowed, chisel-disked or no-tilled soil under conventional and low-input agricultural systems. Maize shoots and roots were collected at four growth stages. Soils under low-input management had higher VAM fungus spore populations than soils under conventional management. Spore populations and colonization of maize roots by VAM fungi were higher in no-tilled than in moldboard plowed or chisel-disked soil. The inoculum potential of soil collected in the autumn was greater for no-till and chisel-disked soils than for moldboard plowed soils and greater for low-input than conventionally farmed soil. The effects of tillage and farming system on N uptake and utilization varied with growth stage of the maize plants. The effect of farming system on P use efficiency was significant at the vegetative stages only, with higher efficiencies in plants under low-input management. The effect of tillage was consistent through all growth stages, with higher P use efficiencies in plants under moldboard plow and chisel-disk than under no-till. Plants grown in no-tilled soils had the highest shoot P concentrations throughout the experiment. This benefit of enhanced VAM fungus colonization, particularly in the low-input system in the absence of effective weed control and with likely lower soil temperatures, did not translate into enhanced growth and yield.
  • Authors:
    • Baldock, J. A.
    • Drury, C. F.
    • Gregorich, E. G.
    • Greaves, Travis
  • Source: Canadian Journal of Soil Science
  • Volume: 81
  • Issue: 1
  • Year: 2001
  • Summary: Legume-based cropping systems could help to increase crop productivity and soil organic matter levels, thereby enhancing soil quality, as well as having the additional benefit of sequestering atmospheric C. To evaluate the effects of 35 yr of maize monoculture and legume-based cropping on soil C levels and residue retention, we measured organic C and 13C natural abundance in soils under: fertilized and unfertilized maize (Zea mays L.), both in monoculture and legume-based [maize-oat (Avena sativa L.)-alfalfa (Medicago sativa L.)-alfalfa] rotations; fertilized and unfertilized systems of continuous grass (Poa pratensis L.); and under forest. Solid state 13C nuclear magnetic resonance (NMR) was used to chemically characterize the organic matter in plant residues and soils. Soils (70-cm depth) under maize cropping had about 30-40% less C, and those under continuous grass had about 16% less C, than those under adjacent forest. Qualitative differences in crop residues were important in these systems, because quantitative differences in net primary productivity and C inputs in the different agroecosystems did not account for observed differences in total soil C. Cropping sequence (i.e., rotation or monoculture) had a greater effect on soil C levels than application of fertilizer. The difference in soil C levels between rotation and monoculture maize systems was about 20 Mg C ha-1. The effects of fertilization on soil C were small (~6 Mg C ha-1), and differences were observed only in the monoculture system. The NMR results suggest that the chemical composition of organic matter was little affected by the nature of crop residues returned to the soil. The total quantity of maize-derived soil C was different in each system, because the quantity of maize residue returned to the soil was different; hence the maize-derived soil C ranged from 23 Mg ha-1 in the fertilized and 14 Mg ha-1 in the unfertilized monoculture soils (i.e., after 35 maize crops) to 6-7 Mg ha-1 in both the fertilized and unfertilized legume-based rotation soils (i.e., after eight maize crops). The proportion of maize residue C returned to the soil and retained as soil organic C (i.e., Mg maize-derived soil C/Mg maize residue) was about 14% for all maize cropping systems. The quantity of C3-C below the plow layer in legume-based rotation was 40% greater than that in monoculture and about the same as that under either continuous grass or forest. The soil organic matter below the plow layer in soil under the legume-based rotation appeared to be in a more biologically resistant form (i.e., higher aromatic C content) compared with that under monoculture. The retention of maize residue C as soil organic matter was four to five times greater below the plow layer than that within the plow layer. We conclude that residue quality plays a key role in increasing the retention of soil C in agroecosystems and that soils under legume-based rotation tend to be more "preservative" of residue C inputs, particularly from root inputs, than soils under monoculture.
  • Authors:
    • Williams, S.
    • Schuler, J.
    • Killian, K.
    • Kautza, T.
    • Elliott, T.
    • Easter, M.
    • Cipra, J.
    • Bluhm, G.
    • Paustian, K.
    • Brenner, J.
  • Year: 2001
  • 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:
    • Ahmed, A. S.
    • Abd El-Aal, R. S.
    • Soltan, S. A.
    • Ismail, M. A.
  • Source: Annals of Agricultural Science, Moshtohor
  • Volume: 39
  • Issue: 4
  • Year: 2001
  • Summary: To investigate the capability of plants to utilize the different soil nutrients and hence their crop productivity and water use efficiency (WUE), a field experiment was undertaken in Ismalia, Egypt, during 1999 summer season. Maize, as an indicator plant, was grown under both surface drip irrigation (SDI) and subsurface drip irrigation (SSDI). Under both irrigation systems, 3 regimes of irrigation water were applied, i.e. 60, 80 and 100% of water consumptive use of maize in the area. Soil samples were taken every other day one time just before irrigation and another at ~7 h after irrigation to follow up the movement and distribution of soluble salts and moisture in the soil profile. The soluble salt accumulation phenomenon was followed up through the uppermost 10 cm of soil surface while the soil moisture was estimated every 10 cm of soil downward till a 60 cm soil depth. Soil salinity tended to increased in the soil surface with decreasing the irrigation regime under both irrigation systems. The soil moisture content retained was higher under SSDI than under SDI. Soil available N, P and K tended to increased as the irrigation regime decreased, while available Fe, Mn and Zn in the soil decreased with decreasing the irrigation regime. The SDI significantly increased the maize grain contents of N and P compared to SSDI. Grain and straw yields increased significantly under SSDI compared with SDI. The highest grain or straw yield was recorded with the highest rate of irrigation regime. The total contents (uptake) of N, P and K as well as Fe, Mn and Zn in maize grain increased significantly under SSDI compared with SDI. The medium level of irrigation regime (80%) recorded higher values of both maize grain and straw yields under SSDI than under SDI. The WUE was significantly higher under SSDI compared to SDI. It decreased with decreasing irrigation regime.
  • Authors:
    • Zybalov, V.
  • Source: Mezhdunarodnyi Sel'skokhozyaistvennyi Zhurnal
  • Issue: 5
  • Year: 2001
  • Summary: Field trials were carried out at 2 sites in Russia to assess the effectiveness of rape as a weed-removing crop in different rotations. Rotations were fallow-wheat-barley-maize-wheat, and vetch-oat mixture and rape-wheat-barley-maize-wheat, with a control involving pure fallow. The degree of weediness (number of weeds/m 2) and species composition of weeds in young crops of wheat and barley was assessed twice (at tillering stage and before harvest). Before harvesting, weed mass was also assessed and the numbers of weed seeds in soil samples were determined. The substitution of rape crops for fallow in rotations resulted in significant reductions in weed numbers and weed seeds in soil. It is concluded that rape is effective in reducing levels of weeds in young crops and soils, even when minimal or no soil preparation is carried out.
  • Authors:
    • Christoffoleti, P. J.
    • Shiratsuchi, L. S.
  • Source: The BCPC Conference: Weeds, 2001, Volume 1 and Volume 2. Proceedings of an international conference held at the Brighton Hilton Metropole Hotel, Brighton, UK, 12-15 November 2001
  • Year: 2001
  • Summary: Weed control represents a high percentage of the production costs in no-till systems in Brazil, and chemical control using herbicides is by far the most important method used. However, the weeds are not uniformly or randomly distributed but have a patchy distribution such that the broadcast application of herbicides can spray post-emergence herbicides in areas where there are no weeds. Therefore, this work had the objective of demonstrating the potential of saving of herbicides in the no-till production system of the Brazilian agriculture, based on weed seed bank and weed seedling maps. The density of several weeds was mapped using a backpack DGPS and laptop computer. Experiments were conducted in Sao Paulo [date not given] in a 17.7-ha field of no-till maize under centre pivot irrigation. Seed bank data was determined from soil cores collected from a depth of 0.05 m in the centre of a 20*20 m grid and emergence assessments in a greenhouse. On the same grid size, weed seedlings were counted in 0.25 m 2 quadrats. Resultant maps showed a high weed density in the seed bank over just 4.67 ha, which was only 26% of the field area. The seedling maps demonstrated that grasses and broadleaf weeds had different distributions with broadleaf weeds occupying 12.6% of the field and grasses 87.4%. The targeting of herbicide to weed patches using pre- and postemergent herbicides has the potential to reduce herbicide use compared to broadcast application giving both environmental and economic advantages.