• Authors:
    • Pauletti, V.
    • Piva, J.
    • Santos, N.
    • Dieckow, J.
    • Bayer, C.
    • Molin, R.
    • Favaretto, N.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: To improve C sequestration in no-till soils requires further development of crop rotations with high phytomass-C additions. The objectives of this study were (i) to assess long-term (17 years) contributions of cover crop- or forage-based no-till rotations and their related shoot and root additions to the accumulation of C in bulk and in physical fractions of a subtropical Ferralsol (20-cm depth); and (ii) infer if these rotations promote C sequestration and reach an eventual C saturation level in the soil. A wheat ( Triticum aestivum L., winter crop)-soybean ( Glycine max (L.) Merr, summer crop) succession was the baseline system. The soil under alfalfa ( Medicago sativa L., hay forage) intercropped every three years with maize ( Zea mays L., summer crop) had the highest C accumulation (0.44 Mg C ha -1 year -1). The bi-annual rotation of ryegrass ( Lolium multiflorum Lam., hay winter forage)-maize-ryegrass-soybean had a soil C sequestration of 0.32 Mg C ha -1 year -1. Among the two bi-annual cover crop-based rotations, the vetch ( Vicia villosa Roth, winter cover crop)-maize-wheat-soybean rotation added 7.58 Mg C ha -1 year -1 as shoot plus root and sequestered 0.28 Mg C ha -1 year -1. The counterpart grass-based rotation of oat ( Avena strigosa Schreb., winter cover crop)-maize-wheat-soybean sequestered only 0.16 Mg C ha -1 year -1, although adding 13% more C (8.56 Mg ha -1 year -1). The vetch legume-based rotation, with a relative conversion factor (RCF) of 0.147, was more efficient in converting biomass C into sequestered soil C than oat grass-based rotation (RCF=0.057). Soil C stocks showed a close relationship ( R2=0.72-0.98, P<0.10) with root C addition, a poor relationship with total C addition and no relationship with shoot C addition. This suggests a more effective role of root than shoot additions in C accumulation in this no-till soil. Most of the C accumulation took place in the mineral-associated organic matter (71-95%, in the 0-5 cm layer) compared to the particulate organic matter. The asymptotic relationship between root C addition and C stocks in bulk soil and in mineral-associated fraction supports the idea of C saturation. In conclusion, forages or legume cover crops contribute to C sequestration in no-till tropical Ferrasols, and most of this contribution is from roots and stored in the mineral-associated fraction. This combination of soil and rotations can reach an eventual soil C saturation.
  • Authors:
    • Jones, B. P.
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Biology and Biochemistry
  • Volume: 43
  • Issue: 2
  • Year: 2011
  • Summary: Particulate organic matter (POM) and light fraction (LF) organic matter are potentially labile (active) fractions of soil organic matter (SOM) that have been shown to be indicators of short-term changes in soil management practices (e.g. tillage, manure and fertilizer applications, and crop rotation). These two fractions consist mainly of partially decomposed plant residues, microbial residues, seeds, and spores forming organo-mineral complexes with soil mineral particles; however, they cannot be used as synonyms because of their different chemical composition and structure. Particulate-OM is recovered by size-based procedures while LF is generally recovered in two distinct fractions [free-LF (FLF) and occluded-LF (OLF)] using density-based solutions in conjunction with soil-aggregate disruption. Solutions used in these density-based separations have most commonly varied in density from 1.6 to 2.0 g cm -3. Sodium iodide (NaI) and sodium polytungstate (SPT) are the chemicals most often used to prepare the density solutions in LF recovery but comparisons of the effectiveness of two solutions have not been conducted. The objectives of this research were: (1) compare the efficiency of similar density solutions of NaI and SPT in recovering FLF; and (2) compare POM, FLF, and OLF as possible sensitive indices of short-term soil changes due to tillage management. Soil samples were collected at 0-15 cm depth from a cropping system experiment conducted on a silt loam Ultisol. Plots selected for sampling had received either reduced till (RT) or no-till (NT), and cropping was continuous corn silage for a period of 3 years prior to sampling. Solutions of NaI and SPT at densities of 1.6 and 1.8 g cm -3 were used to recover FLF, and OLF was recovered with SPT solution at a density of 2.0 g cm -3 from the soil pellet remaining after FLF recovery with SPT 1.6 g cm -3. The average total soil organic carbon (SOC) content of these samples was of 12.7 g kg -1, and carbon-POM (C-POM), carbon-FLF (C-FLF), and carbon-OLF (C-OLF) represented 22.4, 5.5, and 5.2% of it, respectively. In general, C-FLF and nitrogen-FLF (N-FLF) contents recovered did not differ significantly between chemical solutions (NaI or SPT) adjusted to the same density (1.6 or 1.8 g cm -3). Increasing the density within a specific solution (NaI or SPT) resulted in significantly higher C-FLF and N-FLF recovery. For instance, C-FLF recovery averaged 637 and 954 mg kg -1 at 1.6 and 1.8 g cm -3, respectively. For both chemicals increasing density from 1.6 to 1.8 g cm -3 reduced the variability in recovering C-FLF and N-FLF with coefficient of variation values decreasing from a range of 14.9-19.1% for densities of 1.6 g cm -3 to 6.7-10.4% when densities increased to 1.8 g cm -3. In the present work, POM and OLF were more sensitive than FLF to changes in tillage management, with significantly greater amounts of the sensitive fractions in RT samples. A better sensitivity of FLF would be expected if treatments dealing with residue input (e.g. crop rotation and cover crop) were evaluated.
  • Authors:
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 5
  • Year: 2011
  • Summary: Soil organic matter (SOM) is commonly used as an indicator of soil quality, with different fractions being used as indices to measure changes in SOM caused by management. The objective of this study was to compare whether selected SOM fractions exhibited sensitivity to short-term changes in management. The experiment was conducted for similar to 3 yr as a split-split-plot design with crop rotation as the whole-plot treatment factor, tillage as the subplot treatment factor, and cover crop management as the sub-subplot treatment factor. Soil samples were collected at the 0- to 15-cm depth. Soil organic C (SOC) and N, particulate organic matter (POM), free light fraction (FLF), Illinois soil N test (ISNT), and easily oxidizable C (EOC) were tested as possible sensitive indices to changes in management. The stable fraction SOC was only affected by cover crop management, while C and N contents and C/N ratio of the labile POM and FLF fractions were affected by additional management practices. Between POM and FLF, the latter was the most sensitive, with cover crop management having the greatest effect. Because FLF is chemically and structurally closer to plant residues than POM, the sensitivity rank position of these fractions would probably be at least more similar if only tillage management was considered. In addition, the lack of sensitivity of ISNT and EOC to any tested management practice is added to previous studies that have raised questions of the representation of the labile SOM pool through these fractions.
  • Authors:
    • Torbert, H. A.
    • Watts, D. B.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Reduced tillage, poultry litter applications, crop rotations, and winter cover cropping are management practices that could be used with conservation tillage systems to increase yields compared to conventional monoculture systems. This study evaluated cropping sequences of corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and corn-soybean rotations with wheat ( Triticum aestivum L.) covers in conventional, strip, and no-tillage (no-till) systems, following poultry litter additions to wheat cover. The study was conducted from 1991 to 2001 on a Hartsells fine sandy loam (fine-loamy, siliceous, subactive, thermic Typic Hapludults). Poultry litter (112 kg N ha -1) was applied to wheat each year in fall. Wheat not receiving poultry litter received equivalent inorganic N. Corn was fertilized with inorganic fertilizer in spring with 56 kg N ha -1 at planting followed by 168 kg N ha -1 3 wk after emergence; soybean received no fertilizer. Corn yields were influenced by tillage in 1991, 1992, 1993, 1994, 1996, 1997, 1998, and 2001 with conventional tillage producing greater yields, except in 1993 (strip tillage) and 2001 (no-till). Poultry litter increased corn yield in 1991, 1997, and 1998. Crop rotations increased corn yield for all years, except 2001. Soybean yields were not impacted by differences in tillage. Crop rotations significantly impacted soybean yield in 1992, 1995, and 1998, with higher yields observed in 1992, and 1995, and lower yields in 1998. Poultry litter significantly increased soybean yield 8 of the 9 yr evaluated. This study suggests that poultry litter use for these crop rotations in conservation tillage systems could increase sustainable yield production.
  • Authors:
    • Wells, M. L.
  • Source: HortScience
  • Volume: 46
  • Issue: 9
  • Year: 2011
  • Summary: Nitrogen (N) fertilizer application to plants at rates not adjusted for the N contribution from soil N availability may result in overapplication of fertilizer. Further understanding of proper timing of N applications based on soil N dynamics and plant demand can be valuable information for the efficient use of fertilizer N. The present study measures soil N dynamics in a pecan orchard under various N fertilizer regimes on a southeastern U.S. Coastal Plain soil. The following treatments were evaluated: 1) crimson clover (Trifolium incarnatum L.); 2) poultry litter; 3) crimson clover + poultry litter; 4) ammonium nitrate (NH(4)NO(3)); and 5) untreated control. Crimson clover provided from 20 to 75 kg.ha(-1) N over the course of the two growing seasons; however, most of the available N from crimson clover became available late in the growing season. As a result, supplemental N may be required in spring where crimson clover is used as an orchard cover crop. Poultry litter, with and without clover, provided available N consistently throughout the growing season with more N becoming available later in the season than earlier. This suggests that poultry litter applications for pecan should be timed before budbreak. Under optimum environmental conditions, N from NH(4)NO(3) is most available within the first 30 days of application. Thus, it appears that synthetic fertilizer applications using NH(4)NO(3) as the N source should be targeted at or 2 to 3 weeks after pecan budbreak.
  • Authors:
    • White, C. M.
    • Weil, R. R.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 1
  • Year: 2011
  • Summary: Cover crops can influence nutrient cycling in the agroecosystem. Forage radish (FR) (Raphanus sativus L. var. longipinnatus) is unique in terms of P cycling because of its high tissue P concentration, rapid growth in the fall, and rapid decomposition in winter and spring. In addition, FR produces a taproot that decays during the winter and leaves distinct holes in the surface soil. This study measured P uptake by FR and cereal rye (CR) (Secale cereale L.) cover crops; the Mehlich 3 P concentration (M3P) in bulk soil following FR, CR, and no cover crop (NC); and M3P in soil within 3 cm of FR taproot holes. Cover crop treatments of FR, CR, and NC were established at two sites each fall for three subsequent years in a cover crop-corn (Zea mays L.) silage rotation. Cover crop shoot P uptake ranged from 5.9 to 25 kg P ha(-1) for FR measured in the fall and from 3.0 to 26 kg P ha(-1) for CR measured in the spring. The greatest cover crop effect on bulk soil M3P was observed at the 0- to 2.5-cm depth aft er 3 yr of cover crops, with M3P values of 101, 82, and 79 mg P kg(-1) aft er FR, CR, and NC, respectively. Soil within 3 cm of FR taproot holes had greater M3P than FR and NC bulk soil. Further studies should be conducted to determine if FR could increase P removal rates in excessively high P soils or increase P availability in low P soils.
  • Authors:
    • Li, H.
    • Cheng, J.
    • Zhang, J.
    • Yue, T.
    • Xi, Z.
  • Source: Scientia Agricultura Sinica
  • Volume: 44
  • Issue: 11
  • Year: 2011
  • Summary: Objective: In this paper, the relationship between soil quality and soil biological characteristics such as soil microorganism quantity and soil enzymatic activity was studied in the intercropping system of vineyard, in order to illustrate the function of soil biological characteristics as bio-indicators of soil fertility. Method: Three such cover crops, two perennial legumes (white clover and alfalfa) and a perennial gramineous grass (tall fescue) were sown in vineyard. Soil microorganism quantity, soil enzymatic activities and soil nutrient content were analyzed and compared with that in soil cultivation. [Result] Most detected soil microorganism quantity and soil enzymatic activity, soil organic matter were increased under cover crop treatments, compared to clean tillage, tall fescue treatment decreased urease and sucrase activity. White clover and alfalfa treatments significantly increased the contents of hydrolyzable N, total N and available K, and tall fescue decreased them, while the activated organic P in tall fescue treatment was more effectively than that in white clover and alfalfa treatments. Correlation analysis indicated that soil organic matter, total N, hydrolyzable N, total P, available K showed significant or very significant positive correlation with 10 soil biological characteristic factors such as bacteria, fungi, actinomyces, azotobacter, cellulose-decomposing bacteria, urease, phosphatase, amylase, sucrase, and cellulose. The catalase activity was no significant correlation with all the soil nutrient contents, and the total K content was no significant correlations with all the soil biological characteristic factors. The soil pH in this experiment was negatively correlated with soil biological properties. Conclusion: Cover crops in the inter-rows of vineyard increased soil microorganism quantity, soil enzymatic activity and soil nutrient content, white clover and alfalfa treatments were better than tall fescue. There are significant correlations between soil biological characteristics and nutrients, and soil biological indexes could reflect the changes of soil quality.
  • Authors:
    • Gurjeet, G.
    • Malik, R.
    • Ashok, Y.
    • Kamboj, B.
    • Yadav, D.
  • Source: Environment and Ecology
  • Volume: 29
  • Issue: 4
  • Year: 2011
  • Summary: Two field experiments were conducted during kharif of 2009, to optimize ground cover by green manure cover crops before taking no-till direct seeded basmati rice and mechanical transplanted coarse grain rice. The treatments included three cover crops ( Sesbania, mungbean and cowpea) with two seed rates (X and 2X) along with check (without cover crop) under no-till after wheat harvest. The X seed rates for Sesbania, mungbean and cowpea were 30, 20 and 50 kg/ha, respectively. Farmers' field trails on the issue in question were also conducted at three locations. Weed infestation until cover crops were knocked down, was significantly reduced due to growing of cover crops as compared to plots where no cover crop was included. Minimum density and dry weight of weeds was recorded with Sesbania at 60 kg/ha seed rate which was superior to all other treatments. This could be due to ample ground cover and heavy biomass production by Sesbania. In general biomass production among green manure cover crops was followed the sequence of Sesbania > cowpea > mungbean. Due to lower cost of seed, Sesbania at 60 kg/ha was realized more economical than other cover crops. Infestation of Echinochloa sp. in rice was lowest in the plots where Sesbania was taken as preceding cover crop and it was superior to other two cover crops. There was no infestation of sedges in rice in the plots where cover crops were grown but there was infestation of sedges in check plots. There was no significant impact of different cover crops on the yield and yield attributed of rice; however, to attain higher returns, inclusion of green manure cover crops on long-term basis could be more meaningful.
  • Authors:
    • Meersmans, J.
    • Poesen, J.
    • Baets, S.
    • Serlet, L.
  • Source: Catena
  • Volume: 85
  • Issue: 3
  • Year: 2011
  • Summary: Cover crops are a very effective erosion control and environmental conservation technique. When cover crops freeze at the beginning of the winter period, the above-ground biomass becomes less effective in protecting the soil from water erosion, but roots can still play an important role in improving soil strength. However, information on root properties of common cover crops growing in temperate climates (e.g. Sinapis alba (white mustard), Phacelia tanacetifoli (phacelia), Lolium perenne (ryegrass), Avena sativa (oats), Secale cereale (rye), Raphanus sativus subsp. oleiferus (fodder radish)) is very scarce. Therefore, root density distribution with soil depth and the erosion-reducing effect of these cover crops during concentrated flow erosion were assessed by conducting root auger measurements and controlled concentrated flow experiments with 0.1 m topsoil samples. The results indicate that root density of the studied cover crops ranges between 1.02 for phacelia and 2.95 kg m -3 for ryegrass. Cover crops with thick roots (e.g. white mustard and fodder radish) are less effective than cover crops with fine-branched roots (e.g. ryegrass and rye) in preventing soil losses by concentrated flow erosion. Moreover, after frost, the erosion-reducing potential of phacelia and oats roots decreased. Amoeba diagrams, taking into account both below-ground and above-ground plant characteristics, identified ryegrass, rye, oats and white mustard as the most suitable species for controlling concentrated flow erosion.
  • Authors:
    • Pelissari, A.
    • Moraes, A.
    • Balbinot Junior, A.
    • Veiga, M.
    • Dieckow, J.
  • Source: Revista Brasileira de Agrociencia
  • Volume: 17
  • Issue: 1
  • Year: 2011
  • Summary: The objective of this study was to evaluate the effect of winter soil use on reminiscent straw on the soil, physical characteristic in superficial soil layer and maize performance cultivated in succession. One experiment was carried out in three places in the North Plateau of Santa Catarina State, Brazil, during 2006/07 crop season. Five alternatives of soil use in the winter were investigated: (1) multicropping with black oat+ryegrass+vetch+arrow leaf clover without grazing and nitrogen fertilization (multicropping cover); (2) the same multicropping, with grazing and nitrogen fertilization, 100 kg ha -1 of N (pasture with N); (3) the same multicropping, with grazing and without nitrogen fertilization (pasture without N); (4) oil seed radish, without grazing and nitrogen fertilization (oil seed radish); and (5) natural vegetation, without grazing and nitrogen fertilization (fallow). Higher straw dry mass was verified in multicropping cover. The winter annual pasture in crop-livestock system, cover crops and fallow did not affect the bulk density in 0,02 to 0,07 m of soil layer and maize performance in succession.