• Authors:
    • Conklin, A. E.
    • Teasdale, J. R.
    • Cavigelli, M. A.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 3
  • Year: 2008
  • Summary: Despite increasing interest in organic grain crop production, there is inadequate information regarding the performance of organically-produced grain crops in the United States, especially in Coastal Plain soils of the mid-Atlantic region. We report on corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) yields at the USDA-ARS Beltsville Farming Systems Project (FSP), a long-term cropping systems trial established in Maryland in 1996 to evaluate the sustainability of organic and conventional grain crop production. The five FSP cropping systems include a conventional no-till corn-soybean-wheat/soybean rotation (NT), a conventional chisel-till corn-soybean-wheat/soybean rotation (CT), a 2-yr organic corn-soybean rotation (Org2), a 3-yr organic corn-soybean-wheat rotation (Org3), and a 4- to 6-yr organic corn-soybean-wheat-hay rotation (Org4+). Average corn grain yield during 9 yr was similar in NT and CT (7.88 and 8.03 Mg ha-1, respectively) but yields in Org2, Org3, and Org4+ were, respectively, 41, 31, and 24% less than in CT. Low N availability explained, on average, 73% of yield losses in organic systems relative to CT while weed competition and plant population explained, on average, 23 and 4%, respectively, of these yield losses. The positive relationship between crop rotation length and corn yield among organic systems was related to increasing N availability and decreasing weed abundance with increasing rotation length. Soybean yield averaged 19% lower in the three organic systems (2.88 Mg ha-1) than in the conventional systems (3.57 Mg ha-1) and weed competition alone accounted for this difference. There were no consistent differences in wheat yield among cropping systems. Crop rotation length and complexity had little impact on soybean and wheat yields among organic systems. Results indicate that supplying adequate N for corn and controlling weeds in both corn and soybean are the biggest challenges to achieving equivalent yields between organic and conventional cropping systems.
  • Authors:
    • Mora, G.
    • Helmers, M.
    • Shepherd, G.
    • Asbjornsen, H.
  • Source: Plant and Soil
  • Volume: 308
  • Issue: 1-2
  • Year: 2008
  • Summary: In agricultural landscapes, variation and ecological plasticity in depth of water uptake by annual and perennial plants is an important means by which vegetation controls hydrological balance. However, little is known about how annual and perennial plants growing in agriculturally dominated landscapes in temperate humid regions vary in their water uptake dynamics. The primary objective of this study was to quantify the depth of water uptake by dominant plant species and functional groups growing in contrasting annual and perennial systems in an agricultural landscape in Central Iowa. We used stable oxygen isotope techniques to determine isotopic signatures of soil water and plant tissue to infer depth of water uptake at five sampling times over the course of an entire growing season. Our results suggest that herbaceous species (Zea mays L., Glycine max L. Merr., Carex sp., Andropogon gerardii Vitman.) utilized water predominantly from the upper 20 cm of the soil profile and exhibited a relatively low range of ecological plasticity for depth of water uptake. In contrast, the woody shrub (Symphoricarpos orbiculatus Moench.) and tree (Quercus alba L.) progressively increased their depth of water uptake during the growing season as water became less available, and showed a high degree of responsiveness of water uptake depth to changes in precipitation patterns. Coexisting shrubs and trees in the woodland and savanna sites extracted water from different depths in the soil profile, indicating complementarity in water uptake patterns. We suggest that deep water uptake by perennial plants growing in landscapes dominated by rowcrop agriculture can enhance hydrologic functioning. However, because the high degree of ecological plasticity allows some deep-rooted species to extract water from surface horizons when it is available, positive effects of deep water uptake may vary depending on species' growth patterns and water uptake dynamics. Knowledge about individual species' and plant communities' depth of water uptake patterns in relation to local climate conditions and landscape positions can provide valuable information for strategically incorporating perennial plants into agricultural landscapes to enhance hydrologic regulation.
  • Authors:
    • Fabian, E.
    • Pegoraro, R.
    • Bertol, I.
    • Zoldan Junior, W.
    • Zavaschi, E.
    • Vazquez, E.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 32
  • Issue: 1
  • Year: 2008
  • Summary: Surface soil roughness is affected by many factors, such as the residual effect of the soil management, tillage and rainfall erosivity and, together with the soil cover of crop residues, influences water erosion. The objective of this study was to determine the effects of a chiselling operation, together with rainfall erosivity, on soil surface roughness, from June 2005 to March 2006, in an aluminic Typical Hapludox, under the following soil management systems: bare soil under conventional tillage (BCT), cultivated soil under conventional tillage (CCT), no-tillage in a never-tilled soil with burnt plant residues (BNT), and traditional no-tillage (TNT). The crop sequence in the treatments CCT, BNT and TNT was black oat, soyabean, common vetch, maize, black oat, common bean, fodder radish, soyabean, common vetch, maize and black oat. Five simulated rain tests were applied, with a constant intensity of 64 mm h -1 and durations of 20, 30, 40, 50, and 60 min each. Natural rains during the experimental period accounted for 57 mm, between the 2nd and 3rd rainfall test; 21 mm, between the 3rd and 4th test; and, 30 mm, between the 4th and 5th test. The surface roughness was determined immediately before and immediately after the chiseling tillage, and immediately after each test of rain simulation. The original and linear soil surface roughness was not influenced by the management, unlike random roughness, at the end of a six-month fallow period. The original, linear and random roughness in different soil management systems was affected by a six-month fallow period, when the soil was subjected to chiselling. Random roughness was less influenced by soil slope than by tillage marks, which decreased with the increasing rainfall erosivity. The coefficient of decay of this kind of soil roughness was similar in the studied soil management systems under no tillage and conventional tillage.
  • Authors:
    • Diaz-Zorita, M.
    • Penon, E.
    • Coviella, C.
    • Ciocco, C.
    • Lopez, S.
  • Source: Spanish Journal of Agricultural Research
  • Volume: 6
  • Issue: 1
  • Year: 2008
  • Summary: Biological nitrogen fixation (BNF) is of key importance in the N balance of soybean ( Glycine max) crops. A number of authors have suggested that a negative balance may occur under high yield conditions. Few studies have measured the contribution of BNF to soil N in the pampas region. The aims of the present study were to compare three BNF determination methods - two isotopic methods using sorghum or a non-nodulating soybean isoline as a reference crop, and one involving the calculation of the difference in N content between the nodulating and non-nodulating soybean isolines - and to estimate the N balance in soybean crops raised under conventional tillage and no tillage practices. The study was performed in 2004-2005; a complete randomised block design was used with three replicates (plot dimensions 3*7 m). The different methodologies estimated BNF to account for 45-58% of total plant N, equivalent to 94 to 123 kg N ha -1. Depending on the methodology for estimating the BNF the soil N balance varied between -7 and 22 kg N ha -. With an average grain yield of 1,618 kg ha -1 and a BNF accounting for approximately 50% of total plant N (i.e., 115 kg N ha -1), the soil N balance was slightly positive (14 kg ha -1) and independent of the tillage practice. The tillage systems had no effect (P
  • Authors:
    • Durigan, J.
    • Correia, N.
  • Source: Bioscience Journal
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: To evaluate the effect of cover crops [sorghum ( Sorghum bicolor 'Sara'), coverage sorghum ( S. bicolor * S. sudanensis 'Cober Exp'), forage millet ( Pennisetum americanum 'BN2'), common millet ( Pennisetum americanum), finger millet ( Eleusine coracana) and St. Lucia Grass ( Brachiaria brizantha)] and treatment with spontaneous vegetation, in soil fertility after two years under no-tillage systems, experiment was conducted at the farm 'Tres Marcos', Uberlandia, MG - Brazil. The soil was collected in February 2005, after the harvest of the soybean grains (cv. M-SOY 6101), in depths of 0-5 cm, 5-10 cm and 10-20 cm. The coverage resulted in soil chemical properties alteration, with different responses at the sampling depths studied. In first 5 cm of soil, was observed higher pH, organic matter, exchangeable Ca and Mg, base saturation, bases content and effective cation exchange capacity than in deeper samples. The soil kept with spontaneous vegetation showed the highest pH, Ca and Mg levels, base saturation and effective cation exchange capacity, while the soil under cover crop showed higher P and organic matter levels.
  • Authors:
    • Hons, F.
    • Wright, A.
    • Dou, F.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 39
  • Issue: 5/6
  • Year: 2008
  • Summary: Distribution of dissolved (DOC) and soil organic carbon (SOC) with depth may indicate soil and crop-management effects on subsurface soil C sequestration. The objectives of this study were to investigate impacts of conventional tillage (CT), no tillage (NT), and cropping sequence on the depth distribution of DOC, SOC, and total nitrogen (N) for a silty clay loam soil after 20 years of continuous sorghum cropping. Conventional tillage consisted of disking, chiseling, ridging, and residue incorporation into soil, while residues remained on the soil surface for NT. Soil was sampled from six depth intervals ranging from 0 to 105 cm. Tillage effects on DOC and total N were primarily observed at 0-5 cm, whereas cropping sequence effects were observed to 55 cm. Soil organic carbon (C) was higher under NT than CT at 0-5 cm but higher under CT for subsurface soils. Dissolved organic C, SOC, and total N were 37, 36, and 66%, respectively, greater under NT than CT at 0-5 cm, and 171, 659, and 837% greater at 0-5 than 80-105 cm. The DOC decreased with each depth increment and averaged 18% higher under a sorghum-wheat-soybean rotation than a continuous sorghum monoculture. Both SOC and total N were higher for sorghum-wheat-soybean than continuous sorghum from 0-55 cm. Conventional tillage increased SOC and DOC in subsurface soils for intensive crop rotations, indicating that assessment of C in subsurface soils may be important for determining effects of tillage practices and crop rotations on soil C sequestration.
  • Authors:
    • Sweeney, D.
    • Kelley, K.
  • Source: Crop Management
  • Issue: November
  • Year: 2008
  • Summary: Field studies were conducted from 1999 through 2004 in southeastern Kansas to evaluate the influence of tillage method [conventional (CT) and no-till (NT)], row spacing-population system (7.5-, 15-, and 30-inch rows planted at 225,000, 175,000, and 125,000 seeds/acre, respectively), and glyphosate application timing on soybean [ Glycine max (L.) Merr.] yield, weed control, and net economic returns. Herbicide treatments were: (i) preplant residual (pendimethalin) followed by glyphosate at 3 weeks after planting (WAP); (ii) glyphosate at 3 WAP; (iii) sequential glyphosate at 3 and 5 WAP; and (iv) glyphosate at 8 WAP. Soybean followed grain sorghum [ Sorghum bicolor (L.) Moench] in a 2-year rotation. Tillage method influenced yield very little. Narrower row spacing (7.5- and 15-inch) increased soybean yields 2 to 4 bu/acre in high-yielding environments compared to 30-inch rows and also provided greater weed control. Glyphosate applied sequentially (3 and 5 WAP) provided the highest weed control, but a single glyphosate application 3 WAP often produced the greatest net return, regardless of tillage or row spacing system. The results suggest that the adoption of NT planting will likely increase soybean net returns to a greater extent than reducing row spacing in the eastern Great Plains.
  • Authors:
    • Roel, A.
    • Terra, J.
    • Pravia, M.
  • Source: Proceedings of the 9th International Conference on Precision Agriculture, Denver, Colorado, USA, 20-23 July, 2008
  • Year: 2008
  • Summary: Soil management practices impacts on sorghum ( Sorghum bicolor) productivity have rarely been evaluated at field-scale. Field-scale soil management practices effects on sorghum grain yield were evaluated in three no-till crop-pasture rotation systems during two years in Uruguay (Oxyaquic Argiudoll). Treatments were established in a randomized complete block design in strips traversing the landscape in a sorghum-soyabean ( Glycine max) sequence integrated in three rotation systems: (1) continuous cropping (CC) with a winter cover crop of Lolium multiflorum; (2) short rotation (SR): two years pasture of T. pratense and L. multiflorum and two years of CC and; (3) long rotation (LR) four years pasture of Dactylis glomerata, Trifolium repens and Lotus corniculatus and two years of CC. Strips treatments included a factorial arrangement of two levels of cover crop residues (generated by winter grazing) with and without paraplough subsoiling. Strips were harvested with a combine equipped with a yield monitor. Data were analysed with mixed models accounting for spatial correlation. Yield was affected by year and rotation system but was not affected by management practices; either residue or subsoiling. Although its lower soil quality, CC had greater yield than SR and LR in 2006 (8.61 vs. 8.1 and 7.75 tonnes ha -1, respectively); however, no differences existed in 2007 (4.58 tonnes ha -1). Yield variations between field topographic zones were only found in 2007 SR (35%). Weak evidence of spatial correlation was found for soil properties at the site. No correlations were found between soil chemical properties and yield. Accounting for spatial correlation of 2006-2007 yields improved the statistical analysis. Animal treading and grazing did not appear to affect yield. For undegraded soils in temperate climates, cropping systems including no-tillage and perennial pastures preserved soil C, but did not guaranteed the same levels of grain productivity than more intensive cropping systems.
  • Authors:
    • Torbert, H.
    • Rogers, H.
    • Runion, G.
    • Prior, S.
  • Source: Journal of Plant Nutrition
  • Volume: 31
  • Issue: 4
  • Year: 2008
  • Summary: Increasing atmospheric CO 2 concentration could increase crop productivity and alter crop nutrient dynamics. This study was conducted (3 yrs) with two crops ([ Glycine max (L.) Merr.] and grain sorghum [ Sorghum bicolor (L.) Moench.]) grown under two CO 2 levels (ambient and twice ambient) using open top field chambers on a Blanton loamy sand under no-tillage. Macronutrient and micronutrient concentrations and contents were determined for grain, stover, and roots. Although elevated CO 2 tended to reduce nutrient concentrations, high CO 2 consistently increased nutrient content especially in grain tissue; this response pattern was more notable with macronutrients. The CO 2 effect was observed primarily in soybean. The consistent CO 2-induced increases in grain macronutrient contents favors reliable predictions of system outputs, however, predictions of crop nutrient inputs (i.e., stover and root contents) to the soil are less robust due to observed variability. Again, this is particularly true in regards to micronutrient dynamics in CO 2-enriched cropping systems.
  • Authors:
    • Kremer, R. J.
    • Sudduth, K. A.
    • Kitchen, N. R.
    • Jung, W. K.
  • Source: Soil Science and Plant Nutrition
  • Volume: 54
  • Issue: 6
  • Year: 2008
  • Summary: Crop management has the potential to either enhance or degrade soil quality, which in turn impacts on crop production and the environment. Few studies have investigated how crop management affects soil quality over different landscape positions. The objective of the present study was to investigate how 12 years of annual cropping system (ACS) and conservation reserve program (CRP) practices impacted soil quality indicators at summit, backslope and footslope landscape positions of a claypan soil in north-central Missouri. Claypan soils are particularly poorly drained because of a restrictive high-clay subsoil layer and are vulnerable to high water erosion. Three replicates of four management systems were established in 1991 in a randomized complete block design, with landscape position as a split-block treatment. The management systems were investigated: (1) annual cropping system 1 (ACS1) was a mulch tillage (typically >= 30% of soil covered with residue after tillage operations) corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation system, (2) annual cropping system 2 (ACS2) was a no-till corn-soybean rotation system, (3) annual cropping system 3 (ACS3) was a no-till corn-soybean-wheat (Triticum aestivum L.) rotation system, with a cover crop following wheat, (4) CRP was a continuous cool-season grass and legume system. In 2002, soil cores (at depths of 0-7.5, 7.5-15 and 15-30 cm) were collected by landscape position and analyzed for physical, chemical and biological soil quality properties. No interactions were observed between landscape and crop management. Relative to management effects, soil organic carbon (SOC) significantly increased with 12 years of CRP management, but not with the other management systems. At the 0-7.5-cm soil depth in the CRP system, SOC increased over this period by 33% and soil total nitrogen storage increased by 34%. Soil aggregate stability was approximately 40% higher in the no-till management systems (ACS2 and ACS3) than in the tilled system (ACS1). Soil aggregation under CRP management was more than double that of the three grain-cropping systems. Soil bulk density at the shallow sampling depth was greater in ACS3 than in ACS1 and ACS2. In contrast to studies on other soil types, these results indicate only minor changes to claypan soil quality after 12 years of no-till management. The landscape had minor effects on the soil properties. Of note, SOC was significantly lower in the 7.5-15-cm soil depth at the footslope compared with the other landscape positions. We attribute this to wetter and more humid conditions at this position and extended periods of high microbial activity and SOC mineralization. We conclude that claypan soils degraded by historical cropping practices will benefit most from the adoption of CRP or CRP-like management.