• Authors:
    • Sojka, R. E.
    • Bjorneberg, D. L.
    • Aase, J. K.
  • Source: Transactions of the ASAE
  • Volume: 44
  • Issue: 3
  • Year: 2001
  • Summary: Zone subsoiling on irrigated land has been successfully used to improve potato ( Solanum tuberosum) yield and quality. Zone subsoiling under furrow irrigation may disrupt water flow and influence infiltration and soil erosion. We hypothesized that zone subsoiling, done appropriately, will maintain integrity of irrigation furrows, improve small grain (barley) and dry bean ( Phaseolus vulgaris) growth and yield, and not adversely affect water flow, infiltration, or erosion on furrow-irrigated soils. The experiment, which started in 1995, was conducted at the USDA-ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho, USA. The soil is a Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids). Tillage treatments were disc, disc+paratill, paratill, and no-till. There were no differences in water infiltration, runoff, or soil erosion among treatments. Bulk density differences among treatments were largest at the 0.15 to 0.20-m depth, and bulk density was ~16 to 18% greater on disc and no-till treatments than on paratill treatments. The highest frequency of low cone index (CI) values belonged to paratill treatments (65 to 80% frequency of CI values less than 2 MPa); the lowest frequency of low CI values belonged to no-till treatment (20% frequency less than 2 MPa). Cone index versus bulk density relationships depended on soil water content with a slope of 5.81 (r 2=0.70) in the wetter year of 1997, and 2.90 in the drier year of 1995 (r 2=0.60). Subsoiling can be accomplished on furrow-irrigated lands with no adverse effects on runoff, infiltration, and erosion, but under our conditions did not improve crop growth and yield.
  • Authors:
    • Power, J. F.
    • Wiese, R.
    • Flowerday, D.
  • Source: Journal of Environmental Quality
  • Volume: 29
  • Issue: 2
  • Year: 2000
  • Summary: The Management Systems Evaluation Area (MSEA) project was initiated in 1990 to evaluate existing and develop new N management technologies to reduce the potential adverse impacts of agricultural practices on surface and ground water quality, Field research sites were established in nine Midwestern states. Results from MSEA research showed that nitrate leaching was greatly reduced by changing from furrow to sprinkler irrigation. At least 95% of the nitrate N percolating through tiled soils was intercepted and discharged into surface waters. Computer models indicated that routing tile discharge through wetlands would greatly reduce the nitrate load. Nitrate losses also were reduced by establishing controlled water tables using drainage lines for subirrigation. Preplant and presidedress soil nitrate tests were effective in determining proper N fertilizer rates and reducing nitrate losses. Banding ammoniated fertilizers slowed nitrification rates and nitrate leaching, especially if soil over the bands was packed, A major new technology was proof that crop greenness can be used to monitor crop N sufficiency, and that N deficiencies after the V8 stage can be corrected by sidedressing or fertigation (reactive N management). Inexpensive sensors or aerial photographs can be used to assess crop greenness. Using Global Positioning Systems (GPS), N-deficient areas of the field ran he managed differently from the remainder of the field. These results point to the need to develop site-specific or precision farming systems to control nitrate losses to water resources and reduce the impart of natural variability in both soils and weather.
  • Authors:
    • Schneider, U. A.
  • Volume: Ph.D.
  • Year: 2000
  • Authors:
    • Ulbrich, A. V.
    • Yada, I. F. U.
    • Lima, J. de
    • Rodrigues, B. N.
    • Fornarolli, D. A.
  • Source: Planta Daninha
  • Volume: 18
  • Issue: 2
  • Year: 2000
  • Summary: Field experiments, conducted during 1997/98 in Londrina, Parana, Brazil, bioassays and chromatographic analyses were conducted to investigate the effect of mulch (oat residues) on crop-weed competition and retention of imazaquin in no-till soyabean crop. Imazaquin was applied at 0, 75, 150 and 300 g/ha on 7000 and 14 000 kg/ha of oat residues and on soil without mulch. Twenty-four hours after imazaquin application, the field was irrigated and more samples were collected for bioassays and chromatographic analyses. The weed population consisted of Brachiaria plantaginea, Euphorbia heterophylla and Bidens pilosa. Oat residues intercepted 90% of the imazaquin before irrigation, indicating the potential of this herbicide in no-till system.
  • Authors:
    • Olsson, K. A.
    • Cockroft, B.
  • Source: Australian Journal of Soil Research
  • Volume: 38
  • Issue: 1
  • Year: 2000
  • Summary: A study on irrigated orchards in northern Victoria, Australia, on a fine sandy loam over clayey red-brown earth showed soil hardening within 2-3 months after the initial cultivation. This common yet distinct form of soil hardening is termed coalescence. Coalescence is the slow increase in soil hardness which develops during cycles of wetting and drying. The structure of a well-prepared bed of soil that is water-stable and not trafficked changes to one that is hard, although perforated with biopores. These pores facilitate the infiltration of water, drainage, and some growth of roots, but the hard matrix causes root growth and activity to be substantially reduced compared with roots in loose soil and this reduces the productivity of the crop. Coalescence is an important cause of poor responses in productivity to zero and minimum tillage systems of soil management. Isolated examples of soils in the field that remain soft, loose, and porous, after more than 2 years since cultivation were found. This suggests that it might be possible to prevent coalescence. These coalescence-stable soils, in common with virgin soils, have properties that enable them to resist coalescing. High organic matter (>4% w/w total C content) is closely related to zero coalescence.
  • Authors:
    • Nicholaichuk, W.
    • Cessna, A. J.
    • Elliott, J. A.
    • Tollefson, L. C.
  • Source: Journal of Environmental Quality
  • Volume: 29
  • Issue: 5
  • Year: 2000
  • Summary: Pesticides can be transported to groundwater more rapidly through preferential flow paths than would be predicted from their physicochemical properties. The leaching rates of the herbicides 2,4-D, bromoxynil, clopyralid, dicamba, diclofop, MCPA, and mecoprop were compared on plots at a site in Saskatchewan, Canada, tilled after harvest (conventional till, CT) and those that were not (autumn tillage operation omitted, NT). The soil-incorporated herbicides tri-allate and trifluralin were applied to the CT plot only. Herbicide was applied immediately prior to a leaching irrigation for salt removal, which represents a 'worst-case' scenario for pesticide leaching. Direct evidence of preferential flow was obtained when the herbicides, with the exception of tri-allate and trifluralin, were detected in the first water reaching the tile drains. Although the non-incorporated herbicides were transported preferentially at the same rate, the amounts transported depended on the solubility and adsorption coefficient ( Koc) of the herbicide. Only 0.01% of the application of the least soluble herbicide, diclofop, was transported, compared with 0.46% of the most soluble herbicide, dicamba. Preferential flow was only slightly reduced by the tillage pass. The amounts of herbicide transported to the tile drain, however, were substantially reduced on the CT plot. The tillage effect was greatest for the more soluble and less strongly absorbed herbicides. There was no clear relationship between amounts transported in the year after application and reported persistence but herbicides with the longer half-lives persisted in relatively greater amounts than the other herbicides.
  • Authors:
    • Schlesinger, W. H.
  • Source: Science
  • Volume: 284
  • Issue: 5423
  • Year: 1999
  • Summary: first paragraph, "Maintaining and increasing soil organic matter (SOM) adds to soil fertility, water retention, and crop production. Recently, many soil scientists have suggested that the sequestration of atmospheric carbon dioxide in SOM could also contribute significantly to attempts to adhere to the Kyoto Protocol. Conversion of large areas of cropland to conservation tillage, including no-till practices, during the next 30 years could sequester all the CO2 emitted from agricultural activities and up to 1% of today's fossil fuel emissions in the United States (1). Similarly, alternative management of agricultural soils in Europe could potentially provide a sink for about 0.8% of the world's current CO2 release from fossil fuel combustion (2). Beyond conservation tillage, however, many of the techniques recommended to increase carbon sequestration in soils contain hidden carbon "costs" in terms of greater emissions of CO2 into the atmosphere."
  • Authors:
    • Schlesinger, W. H.
  • Source: Science
  • Volume: 284
  • Issue: 5423
  • Year: 1999
  • Summary: Maintaining and increasing soil organic matter (SOM) adds to soil fertility, water retention, and crop production. Recently, many soil scientists have suggested that the sequestration of atmospheric carbon dioxide in SOM could also contribute significantly to attempts to adhere to the Kyoto Protocol. Conversion of large areas of cropland to conservation tillage, including no-till practices, during the next 30 years could sequester all the CO2 emitted from agricultural activities and up to 1% of today's fossil fuel emissions in the United States. Similarly, alternative management of agricultural soils in Europe could potentially provide a sink for about 0.8% of the world's current CO2 release from fossil fuel combustion. Beyond conservation tillage, however, many of the techniques recommended to increase carbon sequestration in soils contain hidden carbon “costs” in terms of greater emissions of CO2 into the atmosphere.
  • Authors:
    • Gerard, C. J.
    • Choudhary, M.
    • Bordovsky, D. G.
  • Source: Soil Science
  • Volume: 164
  • Issue: 5
  • Year: 1999
  • Summary: In the Texas Rolling Plains, low rainfall results in low crop residue production and low soil organic matter. Low soil organic matter, coupled with low levels of silt and clay, give soils poor structure. An 11-year (1979-1989) field experiment was conducted to determine the effects of tillage (reduced vs. conventional), cropping, and residue management (with residue vs. without residue) on soil properties under dryland and irrigated systems. Cropping included a grain sorghum (Sorghum bicolor (L.) Moench.) and wheat (Triticum aestivum L.) monoculture and doublecropped, reduced tillage wheat-grain sorghum under irrigation only. Surface soil organic matter in plots with irrigated grain sorghum and wheat increased with time. Reduced-tillage irrigated grain sorghum and wheat, and especially reduced-tillage, double-cropped grain sorghum and wheat plots, had significantly higher organic matter content than conventional-tillage grain sorghum and wheat plots. Bulk density under the reduced tillage system was higher than with the conventional tillage system. However, saturated hydraulic conductivity (Ks) of the surface soil was increased by reduced tillage practices compared with conventional tillage. This may have been attributable to higher amounts of microaggregates and larger macropores under the reduced tillage system. Residue removal decreased the Ks of surface soil, especially in reduced-tillage grain sorghum and wheat plots. Microaggregation values were higher with residue retained than with residue removed (27.1 vs. 23.5 g kg-1 in dryland and 32.3 vs. 27.1 g kg-1 in irrigation). Results indicate that residue removal from Rolling Plains soils should be discouraged. Because of higher bulk density, use of a reduced tillage system may result in the need for occasional deep chiseling to reduce the effects of compaction.
  • Authors:
    • Walters, D. T.
    • Kessavalou, A.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Use of a winter rye (Secale cereale L.) cover crop following soybean [Glyceine max (L.) Merr.] has been shown to reduce the soil erosion potential in a corn (Zea mays L.)-soybean rotation system, but little is known about the effect of rye on residual soil NO(3)-N (RSN). An irrigated field study was conducted for 4 yr on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudoll) to compare crop rotation and winter rye cover crop following soybean effects on RSN under several tillage practices and N fertilization rates. Treatments each gear were (i) tillage: no-till or disk; (ii) rotation: corn following soybean/rye (Cbr) or soybean/rye following corn (BRc), corn following soybean (Cb) or soybean following corn (Bc), and corn following corn (Cc); and (iii) N rate: 0, 100, and 300 kg N ha(-1) (applied to corn). Rye in the Cbr/BRc rotation was planted in the fall following soybean harvest and chemically killed in the spring of the following year prior to corn planting. Each spring, before tillage and N application, RSN was determined to a depth of 1.5 m, at 30-cm intervals. The net spring-to-spring change in RSN between subsequent spring seasons was computed for each plot, and annual aboveground N uptake for rye, corn, and soybean were determined. Rye, rotation, N rate, and tillage significantly influenced RSN in the top 1.5 m of soil. The presence of rye (BRc) reduced total spring RSN between 18 and 33% prior to corn planting in 2 of the 3 yr, compared with the no-rye system (Bc), as rye immobilized from 42 to 48 kg N ha(-1) in aboveground dry matter. Recycling of N in high-yielding rye cover crop residues led to an increase in RSN accumulation after corn in the succeeding spring. Up to 277 kg RSN ha(-1) accumulated at high rates of N following corn in the Cbr rotation, compared with 67 kg RSN ha(-1) in the no-rye system (Cb) in 1992. Regardless of the presence of rye, significant accumulation of RSN occurred following corn in the rotation sequence, while RSN declined following soybean. Less RSN was found in the top 1.5 m of soil under continuous than rotation corn, and disking tended to increase NO(3)(-) accumulation in rotation systems at high rates of N application. Although RSN declines following a rye cover crop, the ready release of this immobilized N suggests that some N credit should be given, reducing N recommendation for corn following winter rye cover, to minimize potential NO(3)(-) leaching under corn-soybean/rye rotations.