• Authors:
    • MacLeod, J. A.
    • Gillam, K. M.
    • Zebarth, B. J.
    • Burton, D. L.
  • Source: Canadian Journal of Soil Science
  • Volume: 88
  • Issue: 2
  • Year: 2008
  • Summary: The timing of fertilizer nitrogen (N) application influences the availability of NOT as a substrate for denitrification. This study examined the effect of split application of fertilizer N on N2O emissions and denitrification rate in potato (Solanum tuberosum L.) production over 2 yr. Three treatments were used: 0 or 200 kg N ha(-1) at planting, and 120 kg N ha(-1) at planting plus 80 kg N ha(-1) at final hilling. Fertilizer N application increased cumulative N2O emissions. Split fertilizer N application decreased cumulative N2O emissions in 2003, but not in 2002, compared with all fertilizer N applied at planting. A greater proportion of N2O emissions occurred between planting and hilling in 2003 (67%) compared with 2002 (17%). In 2003, the higher emissions during this period resulted from the coincidence of high soil NOT availability and increased rainfall resulting in reduced aeration. Split N application was effective in reducing N2O emissions by minimizing the supply of NOT when demand for terminal electron acceptors was high. v emissions were higher in the potato hill relative to the furrow; however, denitrification rate was higher in the furrow. Nitrate intensity (NI) expresses the exposure of the soil microbial population to NO3- and was calculated as the summation of daily soil nitrate concentration over the monitoring period. Cumulative N2O emissions were positively related to NI across year, N fertility treatment and row location. Denitrification was not related to NI, reflecting the primary role of NOT in influencing the N2O:N-2 ratio of denitrification rather than the magnitude of the overall process. Split N application was an effective strategy for reducing N2O emissions in years where there was significant rainfall during the period between planting and hilling.
  • Authors:
    • Raper, R. L.
    • Wood, C. W.
    • Reeves, D. W.
    • Shaw, J. N.
    • Franzluebbers, A. J.
    • Causarano, H. J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 1
  • Year: 2008
  • Summary: Quantification of the impact of long-term agricultural land use on soil organic C (SOC) is important to farmers and policyrnakers, but few studies have characterized land use and management effects on SOC across physiographic regions. We measured the distribution and total stock of SOC to a depth of 20 cm under conventional tillage (CvT), conservation tillage (CsT), and pasture in 87 production fields from the Southern Piedmont and Coastal Plain Major Land Resource Areas. Across locations, SOC at a depth of 0 to 20 cm was: pasture (38.9 Mg ha(-1)) > CsT (27.9 Mg ha(-1)) > CvT (22.2 Mg ha(-1)) (P <= 0.02). Variation in SOC was explained by management (41.6%), surface horizon clay content (5.2%), and mean annual temperature (1.0%). Higher clay content and cooler temperature contributed to higher SOC. Management affected SOC primarily at the soil surface (0-5 cm). All SOC fractions (i.e., total SOC, particulate organic C, soil microbial biomass C, and potential C mineralization) were strongly correlated across a diversity of soils and management systems (r = 0.85-0.96). The stratification ratio (concentration at the soil surface/concentration at a lower depth) of SOC fractions differed among management systems (P <= 0.0001), and was 4.2 to 6.1 under pastures, 2.6 to 4.7 under CsT and 1.4 to 2.4 under CvT; these results agree with a threshold value of 2 to distinguish historically degraded soils with improved soil conditions from degraded soils. This on-farm survey of SOC complements experimental data and shows that pastures and conservation tillage will lead to significant SOC sequestration throughout the region, resulting in improved soil quality and potential to mitigate CO2 emissions.
  • 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:
    • Leser, J. F.
    • Wheeler, T. A.
    • Keeling, J. W.
    • Mullinix, B.
  • Source: JOURNAL OF NEMATOLOGY
  • Volume: 40
  • Issue: 2
  • Year: 2008
  • Summary: Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log 10 (J2+1)/500 cm 3 soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log 10(J2+1)/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18°C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10°C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.
  • Authors:
    • Zieminska-Smyk,M.
  • Source: Annales Universitatis Mariae Curie-Skodowska. Sectio E, Agricultura
  • Volume: 63
  • Issue: 3
  • Year: 2008
  • Summary: The characteristics of weeding in cereals were based on 68 phytosociological releves taken from ploughlands of traditional management. The main crops there were: rye, winter wheat, spring wheat, mixture of oat and barley, oat and triticale. Most of the records were taken from winter wheat (30). Cereal was the main crop of the area in Skierbieszowki Landscape Park. 26 samples were taken from spring cereals and 42 samples from winter cereal. Segetal weeds communities of the winter cereals were richer than spring cereals when the number of species is considered, which is shown with an average number of weed species in one single sample: 20.3 species in winter cereals and 17.7 species in spring cereals. Weed coverage varied from 20% to 70% but only occasionally reached 70%. Cereals fields were not very weeded because of good fertilization and crop protection chemicals. Most of the weeds in spring and winter cereals were short-lived rather than perennial, which can be a result of progress rhythm in arable crops. Spring cereals were less weeded than winter cereals. It can be noticed by covering coefficient which were 7.500 in spring cereals and 9.600 in winter cereals.
  • Authors:
    • Rossi, R.
    • Harsh, J.
    • Huggins, D.
    • Koenig, R.
    • Brown, T.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 3
  • Year: 2008
  • Summary: Soil acidification threatens dryland crop production in the inland Pacific Northwest. Our objective was to assess the efficacy of lime to lower soil acidity, alter Al chemistry, and increase crop yield in a direct-sown system in Washington, USA. Treatments of subsurface banded fertilizer (120-168 kg N ha -1 year -1) alone or with subsurface banded lime (224 kg ha -1 year -1), or a one-time broadcast application of lime (7000 kg ha -1) or elemental S (1000 kg ha -1) were initiated in spring 2002. Grain yield was measured annually from 2002 to 2005 in a spring barley ( Hordeum vulgare)-spring wheat ( Triticum aestivum)-winter wheat rotation. Soil was sampled in spring 2004 to assess pH and model Al speciation. Low pH was evident at the depth of fertilizer placement (5-10 cm). Broadcast lime increased pH in the surface 15 cm, although reductions in Al 3+ activity ((Al 3+)) occurred only in the 0- to 5-cm layer. Relative to banded N, there was no increase in pH at the 5- to 10-cm depth where banded lime was placed. At the 0- to 5-cm depth, lower pHs were observed with broadcast S (4.6) compared with the banded N control (5.1) or banded lime (5.0). There was no effect of treatment on yield. Modelling suggests that soluble Al is dominated by organic matter-Al complexes (fulvic acid, FA; FA 2Al + and FA 2AlOH 0). Solid- and solution-phase organic complexes may control (Al 3+) at pH
  • 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:
    • Pala, M.
    • Rashid, A.
    • Masri, S.
    • Matar, A.
    • Singh, M.
    • Ibrikci, H.
    • Ryan, J.
  • Source: European Journal of Agronomy
  • Volume: 28
  • Issue: 2
  • Year: 2008
  • Summary: Given the complex nature of rainfed cropping systems in Mediterranean agriculture and the dynamic nature of phosphorus (P) in soils, agronomic assessment of P fertilization must be long term in order to consider residual effects. Thus, a 9-year study involved initial relatively large applications of P (0, 50, 100, 150, 200 kg P 2O 5 ha -1) and yearly smaller dressings (0, 15, 30, 45, 60 kg P 2O 5 ha -1) in a trial involving dryland cereals (wheat/barley) in rotation with legumes (chickpea, lentil, or vetch) at three locations with varying mean annual rainfall in northern Syria; Breda (270 mm), Tel Hadya (342 mm) and Jindiress (470 mm). Assessment was made of grain, straw and total biomass yield and crop P uptake and available P (Olsen). While crop responses varied due to seasonal rainfall fluctuations, they tended to decrease with increasing initial available soil P levels (2.7, 6.2, and 4.4 mg kg -1 for Breda, Tel Hadya and Jindiress, respectively). Residual P was not significant for cereals or legumes at any site, but direct P was significant for both crops at Breda and Jindiress, as well as for legumes at Tel Hadya. In contrast, residual and direct P significantly influenced Olsen-P and seasonal and total P uptake. With no P fertilizer, or where minimal amounts (15 kg P 2O 5 ha -1) were applied annually, the balance between applied P and crop P offtake became increasingly negative; after 8 years without applied P, the P balance was -54, -38, -27, -17, and +7 kg ha -1 for the initial (residual) P application of 0, 50, 100, 150, and 200 kg P 20 5, respectively. This was counterbalanced by the higher annual application rates and to a lesser extent the amounts of P applied initially. The study demonstrated the highly variable nature of crop responses to fertilizer P under semi-arid field conditions over several years, with soil moisture from seasonal rainfall being the dominant influence on overall yields. While crop responses may not occur in any given year, especially if available P is near or above critical threshold levels, dryland cropping without P fertilizer is unsustainable in the long run.
  • Authors:
    • Lawrence, R.
    • Jones, C.
    • Weist, D.
    • Schulthess, U.
    • Christensen, N.
  • Source: Proceedings of the 9th International Conference on Precision Agriculture, Denver, Colorado, USA, 20-23 July, 2008
  • Year: 2008
  • Summary: RapidEye's five satellites to be launched in the summer of 2008 will make it possible to regularly monitor the N-status of crops from space. The sensors on board of each satellite are equipped with five broad bands: blue, green, red, rededge, and NIR. This opens new avenues for red-edge based algorithms to predict the N-status of cereals. In a study conducted in Montana in 2007, we obtained the best results to predict tissue N content (TNC) of irrigated spring wheat and barley, as well as dryland barley from the following algorithm, based on light reflectance (R) of the canopy in the red, red-edge, and NIR bands: ( TNC= RNIR - Rred-edge )/( RNIR -s* Rred ) where s stands for slope of the soil line, i.e. the separately measured bare soil reflectance of the NIR band divided by the red band. Red-edge band based algorithms will open new avenues to optimize in-season N management of cereals, and for monitoring and verifying the efficacy of N fertilization.
  • Authors:
    • Easley, S.
    • Sheedy, J.
    • Smiley, R.
  • Source: Plant Disease
  • Volume: 92
  • Issue: 12
  • Year: 2008
  • Summary: Dryland field crops in the Pacific Northwest United States are commonly produced in silt loams infested by the root-lesion nematodes Pratylenchus neglectus and P. thornei. Soils at 30 sites in Oregon were sampled from 0 to 120 cm depth to examine the vertical distribution of these Pratylenchus spp. Both species were distributed through entire soil profiles of all cropping systems. Populations were generally greatest in the surface 30 cm, but sometimes high populations were detected at depths greater than 45 cm. Sampling to 30 cm depth allowed detection of more than 50% of the population in most sites, while sampling to 45 cm depth yielded more than 75% of the population in over 75% of the sites evaluated. Therefore, soil samples should be collected to 30 to 45 cm depth to accurately estimate populations of Pratylenchus spp. in dryland crops produced on silt loams in the Pacific Northwest. Populations of Pratylenchus spp. were found to be related to the most recently planted crop, with populations after barley, after wheat, and during summer fallow being detected in ascending order.