• Authors:
    • Meijles, E. W.
    • van Essen, E. A.
    • Bouma, J.
    • Pulleman, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: A regional survey of management and crop type and soil organic matter (SOM) content was conducted in one soil series in the Netherlands (loamy, mixed, mesic, Fluventic Eutrudept). The objective was to determine the effects of land use history on SOM contents in a prime agricultural soil, using available soil survey information and statistical analyses. Soil organic matter content is a relatively stable, integrating soil characteristic that reflects long-term land use and is an important indicator of soil quality. The SOM contents and information about past land use were obtained from 45 fields. Land use history was expressed in terms of (i) tillage; (ii) crop type; and (iii) use of chemical fertilizers, (iv) manure, and (v) biocides, for six successive periods (63-31, 31-15, 15-7, 7-3, 3-1, and 1-0 yr before sampling). Only four land use types occurred: conventional-arable, conventional-grass, organic-arable, and organic-grass. The SOM contents ranged between 17 and 88 g kg-1. Regression models of the actual SOM content as a function of crop type and management in the different periods showed that SOM contents were increased under long-term grass or, to a lesser extent, by organic farming, when compared with conventional-arable use. The regression model depends on the nature of land use history in any particular region and on the length of the selected periods, but it provides an easy method to predict SOM content as a function of management in a given soil series. The method can be an alternative to simulation modeling in situations where detailed data records from long-term field experiments are not available.
  • Authors:
    • Rhoton, F. E.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: The number of growing seasons required for no-till practices to improve soil properties should be considered before changing management systems. To evaluate this time factor, an 8-yr tillage study was conducted on a Grenada silt loam (fine-silty, mixed, active, thermic Glossic Fragiudalfs) using cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench]-corn (Zea mays L.), and soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) as test crops. Soil samples were characterized for soil organic matter (SOM), pH, exchangeable Ca and Mg, extractable P, K, Fe, Mn, Cu, and Zn, aggregate stability (AS), water dispersible clay (WDC), total clay (TC), and modulus of rupture (MR) at time 0, 4, and 8 yr. Within 4 yr, no-till (NT) resulted in statistically significant (P less than or equal to 0.05) differences compared to conventional tillage (CT). The surface 2.5 cm of the NT treatments had higher levels of SOM, exchangeable Ca, and extractable P, Mn, and Zn, but lower extractable K, Fe, and Cu. Tillage had no effect on exchangeable Mg and pH. No-till also resulted in higher AS, and lower MR, WDC, and TC in the top 2.5 cm, relative to CT. The differences in soil properties between tillage treatments were essentially independent of crop. Instead, the results are controlled by relative amounts of SOM and clay, and the extent to which these properties change with time. Undoubtedly, NT practices ran improve several fertility and erodibility-related properties of this soil within 4 yr, and-enhance its sustainability.
  • Authors:
    • Harwood, R. R.
    • Paul, E. A.
    • Robertson, G. P.
  • Source: Science
  • Volume: 289
  • Issue: 5486
  • Year: 2000
  • Summary: Agriculture plays a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. From 1991 to 1999, we measured gas fluxes and other sources of global warming potential (GWP) in cropped and nearby unmanaged ecosystems. Net GWP (grams of carbon dioxide equivalents per square meter per year) ranged from 110 in our conventional tillage systems to 2211 in early successional communities. None of the annual cropping systems provided net mitigation, although soil carbon accumulation in no-till systems came closest to mitigating all other sources of GWP. In all but one ecosystem, nitrous oxide production was the single greatest source of GWP. In the late successional system, GWP was neutral because of significant methane oxidation. These results suggest additional opportunities for lessening the GWP of agronomic systems.
  • Authors:
    • Schneider, U. A.
  • Volume: Ph.D.
  • Year: 2000
  • Authors:
    • TCG
    • Teasdale,John R.
    • Rosecrance,R. C.
    • Coffman,Charles B.
    • Starr,J. L.
    • Paltineanu,I. C.
    • Lu,Y. C.
    • Watkins,B. K.
  • Source: American Journal of Alternative Agriculture
  • Volume: 15
  • Issue: 2
  • Year: 2000
  • Summary: Sustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillage-intensive operation. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recomended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillages system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, (4) manure systemd including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporatin manure and rotary hoe plus cultication for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year. both systems average 7.8 Mg ha-1 compared to 5.7 Mg ha-1 in both the croen vetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crown vetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding system, partly because of competitions from uncontrolled weeds. Several measures of the efficience of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external N input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system perfomed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.
  • Authors:
    • Dowdy, R. H.
    • Clapp, C. E.
    • Linden, D. R.
  • Source: Soil & Tillage Research
  • Volume: 56
  • Issue: 3-4
  • Year: 2000
  • Summary: Because the adoption of conservation tillage requires long-term evaluation, the effect of tillage and residue management on corn (Zea mays L.) grain and stover yields was studied for 13 seasons in east central Minnesota. Three primary tillage methods (no-till (NT), fall chisel plow (CH), fall moldboard plow (MB)) and two residue management schemes (residue removal versus residue returned) were combined in a factorial design experiment on a Haplic Chernozem silt loam soil in Minnesota. No significant effects on grain yield were seen due to tillage treatments in 9 out of 13 years. The NT treatment resulted in lower yields than CH and MB treatments in years 6 and 7, and lower than the MB in year 8, indicating a gradual decrease in yield over time with continuous use of NT. There were differences due to residue management in 8 out of 13 years. The residue-returned treatments contributed about 1 Mg ha-1 greater yields in intermediate level dry years such as years 3 and 6, which had cumulative growing season precipitation 20 and 30% below the 9-year average, respectively. In excessively dry or long-term-average years, residues resulted in little yield difference between treatments. The most pronounced effects of residues were with the CH treatment for which yields were greater in 8 out of 13 years. The ratio of grain to total dry matter yield averaged 0.56 and did not vary with time or between treatments. These results apply primarily to soils wherein the total water storage capacity and accumulated rainfall are insufficient to supply optimum available water to the crop throughout the growing season. Under conditions with deeper soils or in either wetter or drier climates, the results may differ considerably.
  • Authors:
    • Rossoni-Longnecker, L.
    • Janke, R. R.
    • Drinkwater, L. E.
  • Source: Plant and Soil
  • Volume: 227
  • Issue: 1
  • Year: 2000
  • Summary: Abstract In 1988 an experiment was established at the Rodale Institute Experimental Farm to study weed control and nitrogen (N) management in rotations with grain crops and N-fixing green manures under reduced tillage without the use of herbicides. Tillage intensities ranging from moldboard plow (MP) to continuous no-till (NT) were compared. We present results for maize production in 1994, the seventh year of the experiment. Our goal was to further investigate reduced tillage regimes that alternated no-till with different forms of primary tillage in legume-based systems. In the chisel-disc (CD) and MP treatments comparable yields were achieved under so-called organic (weeds controlled with cultivation and green manure N source) and conventional management (weeds controlled with herbicides and mineral N fertilizer applied). Weed competition in these treatments was minimal and the N status of maize plants was essentially the same regardless of the N source (fertilizer or green manure). Of the four organic no-till maize treatments, only the mixed-tillage system with cultivation for weed control (CD-NTc) produced yields comparable to conventional NT maize. The fate of vetch N as well as temporal N dynamics were largely determined by tillage intensity and the handling of the vetch residues at maize planting. Treatments with primary tillage (CD and MP) had extremely high levels of mineral N early in the season and had greater average net N-mineralization, even though N content of hairy vetch in these treatments was equal to or lower than that in treatments with mow-killed vetch. In terms of soil mineral N concentrations, the CD-NTc treatment was similar to the other mow-killed vetch/no-till maize treatments. However, N availability in this treatment was greater, probably due to more complete decomposition of green manure residues. Cultivation for weeds not only helped control weeds but also increased mineralization of the vetch residues, which in turn increased the N supply during the period of maximum N demand by the maize. Carefully designed rotations combining tillage reductions with the use of leguminous N sources can have multiple benefits, including improved timing of N availability, reduced herbicide applications, and improved soil quality in the long term.
  • Authors:
    • Dowdy, R. H.
    • Linden, D. R.
    • Layese, M. F.
    • Allmaras, R. R.
    • Clapp, C. E.
  • Source: Soil & Tillage Research
  • Volume: 55
  • Issue: 3-4
  • Year: 2000
  • Summary: Long-term field experiments are among the best means to predict soil management impacts on soil carbon storage. Soil organic carbon (SOC) and natural abundance 13C ([delta]13C) were sensitive to tillage, stover harvest, and nitrogen (N) management during 13 years of continuous corn (Zea mays L.), grown on a Haplic Chernozem soil in Minnesota. Contents of SOC in the 0-15 cm layer in the annually-tilled [moldboard (MB) and chisel (CH)] plots decreased slightly with years of corn after a low input mixture of alfalfa (Medicago sativum L.) and oat (Avena sativa L.) for pasture; stover harvest had no effect. Storage of SOC in no-till (NT) plots with stover harvested remained nearly unchanged at 55 Mg ha-1 with time, while that with stover returned increased about 14%. The measured [delta]13C increased steadily with years of corn cropping in all treatments; the NT with stover return had the highest increase. The N fertilization effects on SOC and [delta]13C were most evident when stover was returned to NT plots. In the 15-30 cm depth, SOC storage decreased and [delta]13C values increased with years of corn cropping under NT, especially when stover was harvested. There was no consistent temporal trend in SOC storage and [delta]13C values in the 15-30 cm depth when plots received annual MB or CH tillage. The amount of available corn residue that was retained in SOC storage was influenced by all three management factors. Corn-derived SOC in the 0-15 cm and the 15-30 cm layers of the NT system combined was largest with 200 kg N ha-1 and no stover harvest. The MB and CH tillage systems did not influence soil storage of corn-derived SOC in either the 0-15 or 15-30 cm layers. The corn-derived SOC as a fraction of SOC after 13 years fell into three ranges: 0.05 for the NT with stover harvested, 0.15 for the NT with no stover harvest, and 0.09-0.10 for treatments with annual tillage; N rate had no effect on this fraction. Corn-derived SOC expressed as a fraction of C returned was positively biased when C returned in the roots was estimated from recovery of root biomass. The half-life for decomposition of the original or relic SOC was longer when stover was returned, shortened when stover was harvested and N applied, and sharply lengthened when stover was not harvested and N was partially mixed with the stover. Separating SOC storage into relic and current crop sources has significantly improved our understanding of the main and interacting effects of tillage, crop residue, and N fertilization for managing SOC accumulation in soil.
  • Authors:
    • Dao, T. H.
    • Douglas, C. L.,Jr.
    • Schomberg, H. H.
    • Allmaras, R. R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 55
  • Issue: 3
  • Year: 2000
  • Summary: Soil organic carbon (SOC) makes up about two-thirds of the C pool in the terrestrial biosphere; annual C deposition and decomposition to release carbon dioxide (CO2) into the atmospheric constitutes about 4% of this SOC pool. Cropland is an important, highly managed component of the biosphere. Among the many managed components of cropland are the production of crop residue, use of tillage systems to control crop residue placement/disturbance, and residue decomposition. An accumulation of SOC is a C sink (a net gain from atmospheric CO2) whereas a net loss of SOC is a C source to atmospheric CO2. A simple three components model was developed to determine whether or not conservation tillage systems were changing cropland from a C source to a C sink. Grain/oil seed yields and harvest indices have indicated a steadily increasing supply of crop residue since 1940, and long term field experiments indicate SOC storage in no-tillage > non moldboard tillage > moldboard tillage systems. According to adoption surveys, moldboard tillage dominated until about 1970, but non moldboard systems are now used nationally on at least 92% of planted wheat, corn, soybean, and sorghum. Consequently, since about 1980, cropland agriculture has become a C sink. Moldboard plow systems had prevented a C sink response to increases in crop residue production that had occurred between 1940 and 1970. The model has not only facilitated a qualitative conclusion about SOC but it has also been used to project production, as well as soil and water conservation benefits, when a C credit or payment to farmers is associated with the C sink in cropland agriculture.
  • Authors:
    • Mielniczuk, J.
    • Martin-Neto, L.
    • Bayer, C.
    • Ceretta, C. A.
  • Source: Soil & Tillage Research
  • Volume: 53
  • Issue: 2
  • Year: 2000
  • Summary: In weathered tropical and subtropical soils organic matter is crucial for soil productivity and its quantity depends heavily on soil management systems. This study evaluated the effect of no-till cropping systems on organic matter content and quality in a sandy clay loam Acrisol soil (Paleudult in US taxonomy) from Southern Brazil. Ten cropping systems with varying additions of C and N were conducted for 12 years (from 1983 to 1994), The addition of crop residues increased total organic carbon (TOC) and total nitrogen (TN) in the soil at 0-17.5 cm depth, and this increase was directly related with C and N added or recycled by the systems. The crop residues added to the soil were associated with reduced semiquinone free radical concentration, detected by electron spin resonance (ESR), in the organo-mineral aggregates <53 mu m and humic acid (HA) samples, in the soil at 0-2.5 cm depth. This showed that stable organic matter originating from crop residues was less humidified than the original soil organic matter. Results obtained from organo-mineral aggregates showed a higher amplitude (highest and lowest values were 5.47 and 2.09 x 10(17) spins g(-1) of TOC, respectively) of semiquinone free radical concentration than HA samples (highest and lowest values were 2.68 and 1.77 x 10(17) spins g(-1) of HA, respectively). These data showed that alterations due to tillage in soil organic matter characteristics, e.g,, humification degree can be better identified through a combination of soil physical fractionation and spectroscopic analysis. Semiquinone content in the HA samples, detected by ESR, related significantly to aromaticity, as measured by nuclear magnetic resonance (NMR) of C-13. Management systems including no-till and cropping systems with high C and N additions to the soil improved its quality in Southern Brazil. (C) 2000 Elsevier Science B,V. All rights reserved.