• Authors:
    • Bradshaw, B.
    • Knowler, D.
  • Source: Food Policy
  • Volume: 32
  • Issue: 1
  • Year: 2006
  • Summary: In light of growing concerns over the implications of many conventional agricultural practices, and especially the deep tilling of soils, the Food and Agriculture Organization of the United Nations (FAO), among others, has begun to promote a package of soil conserving practices under the banner of 'conservation agriculture'. While the title might be novel, its associated practices have long been employed by farmers, and studied by social scientists seeking to understand the reasons for their adoption and non-adoption. This paper reviews and synthesizes this past research in order to identify those independent variables that regularly explain adoption, and thereby facilitate policy prescriptions to augment adoption around the world. While a disaggregated analysis of a subset of commonly used variables reveals some underlying patterns of influence, once various contextual factors (e.g. study locale or method) are controlled, the primary finding of the synthesis is that there are few if any universal variables that regularly explain the adoption of conservation agriculture across past analyses. Given the limited prospect of identifying such variables through further research, we conclude that efforts to promote conservation agriculture will have to be tailored to reflect the particular conditions of individual locales.
  • Authors:
    • Zhang, F. S.
    • Halvorson, A. D.
    • Mosier, A. R.
    • Liu, X. J.
  • Source: Plant and Soil
  • Volume: 280
  • Issue: 1-2
  • Year: 2006
  • Summary: To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N2O, CH4 and CO2 from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004. Trace gas flux measurements were made 2-3 times per week, in zero-N fertilizer plots that were cropped continuously to corn (Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0, 5 and 10 cm in Exp. 2, respectively) were used. Liquid urea-ammonium nitrate (UAN, 224 kg N ha)1) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N2O, CH4 and CO2 ranged from 3.9 to 5.2 lg N m)2 h)1, 60.5 to 92.4 lg N m)2 h)1, )0.8 to 0.5 lg C m)2 h)1, and 42.1 to 81.7 mg C m)2 h)1 in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N2O emissions compared with shallow N placement (0 and 5 cm) while CH4 and CO2 emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged N2O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission and CH4 oxidation but increased N2O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N2O, CH4 and CO2 was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT- and NT-soils.
  • Authors:
    • Vitousek, P. M.
    • Matson, P. A.
  • Source: Conservation Biology
  • Volume: 20
  • Issue: 3
  • Year: 2006
  • Summary: How can intensive agricultural systems be designed so that they have fewer and smaller impacts on surrounding ecosystems? This is not a new challenge, but its importance to conservation—particularly in developing regions—has become apparent in recent years. This challenge is a major part of the ongoing effort to provide for the needs of a growing human population and at the same time sustain the life-support systems of the planet.
  • Authors:
    • Baker, J. M.
    • Molina, J. A. E.
    • Allmaras, R. R.
    • Clapp, C. E.
    • Dolan, M. S.
  • Source: Soil & Tillage Research
  • Volume: 89
  • Issue: 2
  • Year: 2006
  • Summary: Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0-20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20-25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha-1, respectively) than with NT (13 and 1.2 Mg SOC and N ha-1, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.
  • Authors:
    • Sweeney, D.
    • Kilgore, G.
    • Whitney, D.
    • Schwab, G.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 3
  • Year: 2006
  • Summary: Reduced- and no-tillage seedbed preparation methods coupled with broadcast P applications lead to an accumulation of available P in the surface 0- to 5-cm soil layer and a depletion of available P deeper in the profile. A 3-yr study determined the effects of tillage and fertilizer P management on P uptake and grain yield for P-stratified soils. Tillage practices were moldboard plow (once at the start of the study followed by reduced tillage), reduced tillage (disk followed by field cultivation), and no-tillage. Four P management methods were imposed: (i) no P; (ii) 20 kg P ha -1 applied as a surface broadcast; (iii) 20 kg ha -1 applied as a banded starter, 5 cm to the side and 5 cm below the seed; or (iv) 20 kg ha -1 applied in a deep placed band, 13 to 15 cm on 0.7-m centers. The one-time moldboard plowing produced higher early season dry matter yields for corn ( Zea mays L.), wheat ( Triticum aestivum L.), and soybean [ Glycine max (L.) Merr.] compared with the no-tillage system, but tillage effects on final grain yield were inconsistent. Subsurface placement of P generally increased P uptake and grain yield of corn and sorghum [ Sorghum bicolor (L.) Moench], but had little effect on grain yield of soybean. Results indicate that subsurface applications of P fertilizers should be considered if soil test P is highly stratified within the surface 0- to 15-cm layer and the 15-cm composite is medium or below for available P.
  • Authors:
    • Lampurlanés, J.
    • Cantero-Martínez, C.
  • Source: Soil & Tillage Research
  • Volume: 85
  • Issue: 1-2
  • Year: 2006
  • Summary: The objective of this study was to investigate the effect of tillage and cropping system on near-saturated hydraulic conductivity, residue cover and surface roughness to improve soil management for moisture conservation under semiarid Mediterranean conditions. Three tillage systems were compared (subsoil tillage, minimum tillage and no-tillage) under three field situations (continuous crop, fallow and crop after fallow) on two soils (Fluventic Xerochrept and Lithic Xeric Torriorthent). Soil under no-tillage had lower hydraulic conductivity (5.0 cm day(-1)) than under subsoil tillage (15.5 cm day(-1)) or minimum tillage (14.3 cm day(-1)) during 1 of 2 years in continuous crop due to a reduction of soil porosity. Residue cover at sowing was greater under no-tillage (60%) than under subsoil or minimum tillage (
  • Authors:
    • Garbuio, F. J.
    • Barth, G.
    • Caires, E. F.
  • Source: Soil & Tillage Research
  • Volume: 89
  • Issue: 1
  • Year: 2006
  • Summary: Brazil has extensive pasturelands that could be used, in part, for grain production. A no-till system was established on pastureland to obtain a suitable method for liming upon conversion from pasture to a no-till cropping system. The study was conducted during the period from 1998 to 2003, in Parana State (Brazil), on a clayey, kaolinitic, thermic Rhodic Hapludox. Soil chemical properties and grain production were evaluated after application of dolomitic lime. The experimental treatments were: control (no lime), split application of lime on the surface (three yearly applications of 1.5 t ha -1), surface lime (4.5 t ha -1), and incorporated lime (4.5 t ha -1). The lime rate was calculated to raise the base saturation in the topsoil (0-0.20 m) to 70%. The cropping sequence was: soyabean ( Glycine max L. Merril), barley ( Hordeum distichum L.), soyabean, wheat ( Triticum aestivum L.), soyabean, corn ( Zea mays L.), and soyabean. When surface-applied, liming neutralized acidity and increased exchangeable Ca 2++Mg 2+ to a depth of 0.10 m, and to a depth of 0.20 m, when incorporated. Split application of lime on the surface resulted in a slower neutralization reaction only in the first year after liming. Soil pH increased with liming and resulted in a decline of exchangeable Al 3+ and an increase in base saturation. At 0-0.05 m depth, lime incorporation resulted in lower levels of soil organic matter than surface application. It took 4-5 years after lime incorporation for soil organic matter to return to its baseline value. Liming increased grain yield in only one crop of soyabean, and only when lime was surface-applied at the full rate. However, cumulative grain yield was higher with liming than in the control treatment (no lime), regardless of the application method. Surface application of lime, at either full or split rates, was the best alternative to neutralize soil acidity when establishing a no-till system on pastureland because, in addition to conserving soil structure, it provided a greater economic return.
  • Authors:
    • Volk, L. B. D.
    • Cogo, N. P.
    • Castro, L. G.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 30
  • Issue: 2
  • Year: 2006
  • Summary: Although being temporary, the presence of tillage-induced surface roughness in the soil is an important requirement in conservation tillage systems. The reason is that surface roughness increases both surface retention and surface infiltration of water in the soil, reduces runoff velocity and volume, and traps eroded sediments, thus reducing water erosion damages. With this in mind, this study was developed with the objective of evaluating modifications in soil surface roughness by tillage and rainfall actions related to water erosion, in the absence and presence of mulch cover. The experiment was carried out in the field, at the Agriculture Experimental Station of the Federal University of Rio Grande do Sul (EEA/UFRGS), in Eldorado do Sul County, Rio Grande do Sul State, Brazil, in 1996 and 1997, using simulated rainfalls on a sand), clay loam Paleudult with 0.07 m m(-1) slope steepness. The tillage types evaluated in the study included plowing, plowing plus double-disking and no-till, all them in the absence and presence of 60% soil cover (oat residue), submitted to four simulated rainfall tests. The first test consisted of a rainfall segmented in four portions, lasting for 20, 20, 30, and 30 min, separated 30 to 40 min front each other, applied immediately after tillage. The remaining tests consisted of uninterrupted rains of 90-min duration, applied 1, 20, and 35 days after the first rain. These rainfalls were applied with the rotating-boom rainfall simulator at a constant intensity of 64.0 mm h(-1). Tillage caused greater changes in the soil surface roughness titan rainfall. Soil surface roughness was most reduced by rain action in the very first event in recently-tilled soil, in the pre-runoff period. Soil surface roughness impeded or delayed runoff ill treatments with soil Mobilization in the rainfall segments with short duration applied soon after tillage, impeding or reducing water and soil losses in that period, regardless of soil cover. In the continuous, subsequent long rains, surface roughness did not influence water loss in the studied treatments without cover, where it was high throughout the experimental period, but it did reduced water loss in the presence of cover. Water loss in no-till was high for such rains throughout the experiment. Under the same rain type, soil loss reduction as influenced by roughness was more evident in the absence of cover, whereas it was substantially obscured in its presence. Mulch of crop residue added to the soil surface did not preserve the initially high surface roughness created by tillage in the degraded soil used in the study. Nevertheless, by the end of the experiment more than half of the theoretical initial water and sediment retention capacity still remained in the microdepressions formed by roughness. The obtained data were consistent with theories and concepts used in soil erosion mechanics studies.
  • Authors:
    • Franzluebbers, A. J.
    • Causarano, H. J.
    • Reeves, D. W.
    • Shaw, J. N.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: Past agricultural management practices have contributed to the loss of soil organic carbon (SOC) and emission of greenhouse gases (e.g., carbon dioxide and nitrous oxide). Fortunately, however, conservation-oriented agricultural management systems can be, and have been, developed to sequester SOC, improve soil quality, and increase crop productivity. Our objectives were to (i) review literature related to SOC sequestration in cotton (Gossypium hirsutum L.) production systems, (ii) recommend best management practices to sequester SOC, and (iii) outline the current political scenario and future probabilities for cotton producers to benefit from SOC sequestration. From a review of 20 studies in the region, SOC increased with no tillage compared with conventional tillage by 0.48 +/- 0.56 Mg C ha(-1) yr(-1) (H(0): no change,p
  • Authors:
    • Chan, K. Y.
    • Heenan, D. P.
  • Source: Soil Use and Management
  • Volume: 21
  • Issue: 4
  • Year: 2005