• Authors:
    • Lewis, D. B.
    • Kaye, J. P.
    • Jabbour, R.
    • Barbercheck, M. E.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 26
  • Issue: 4
  • Year: 2011
  • Summary: Weed management is one of the primary challenges for producers transitioning from conventional to organic agriculture. Tillage and the use of cover crops are two weed control tactics available to farmers transitioning to organic management, but little is known about their interactive effects on soil quality during the transition period. We investigated the response of soils to tillage and initial cover crop during the 3-year transition to organic in a cover crop-soybean ( Glycine max)-maize ( Zea mays) rotation in the Mid-Atlantic region of the USA. The tillage treatment contrasted full, inversion tillage with moldboard plowing (FT) versus reduced tillage with chisel plowing (RT). The cover crop treatment contrasted annual versus mostly perennial species during the first year of the rotation. The experiment was initiated twice (Start 1 and Start 2), in consecutive years in adjacent fields. By the end of the experiment, labile carbon, electrical conductivity, pH and soil moisture were all greater under RT than under FT in both starts. Soil organic matter and several other soil attributes were greater under RT than under FT in Start 1, but not in Start 2, perhaps owing to differences between starts in initial field conditions and realized weather. Soil attributes did not differ between the two cover crop treatments. Combining our soils results with agronomic and economic analyses on these plots suggests that using RT during the organic transition can increase soil quality without compromising yield and profitability.
  • Authors:
    • Ziadi, N.
    • Angers, D. A.
    • Morel, C.
    • Parent, L. E.
    • Messiga, A. J.
  • Source: Geoderma
  • Volume: 164
  • Issue: 3-4
  • Year: 2011
  • Summary: Under long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0-5 cm layer from plots under NT and MP receiving 35 kg P ha -1 and 160 kg N ha -1. Samples were separated into three water-stable aggregate-sized classes (macro, 2000-250 m; meso, 250-180 m; micro, 180-53 m) and (silt+clay)-sized particles (<53 m) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt+clay)-sized particles < micro- < meso- < macro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt+clay)-sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes under NT in relation to Pw concentration was also observed for carbon content, indicating that Pw is influenced by soil aggregation as driven by SOM accumulation. The lower Pw concentration in (silt+clay)-sized particles could be explained by a greater retention of P by reactive oxides and highly disordered alumino-silicates present on (silt+clay)-sized particles, thereby reducing the soluble P released from these particles. One important aspect of this study is the contrasting P sorption characteristics of solid particles under NT and MP. The P sorption maxima (S max value) of the (silt+clay)-sized particles was twice that of the water-stable aggregates. Sorption characteristics reflect the hierarchy observed under NT for organic C and Pw, indicating a closer link between SOM and P dynamics within soil aggregates in contrast with MP.
  • Authors:
    • Wood,C. W.
    • Price,A. J.
    • Mulvaney,M. J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Limited input producers may adopt no-till production if sufficient weed suppression can be achieved. High-biomass producing cover crops used in conjunction with organic mulches may provide sufficient weed control in no-till vegetable production. Our objective was to quantify weed suppression from a forage soybean summer cover crop and three types of organic mulches applied after collard ( Brassica oleracea L.) planting. Forage soybean residue did not suppress weeds, but mulches were generally effective. Broadleaf and sedge weeds decreased in population size over the three-year period, but grass weed management remained problematic until three years after conversion to no-till. Grass suppression was greater when mulches were applied after the first year. Collard yield, averaging 17,863 kg ha -1, was not affected by any cover crop or mulch treatment.
  • Authors:
    • Nenova, L.
    • Ivanova, I.
    • Stoyanova, S.
  • Source: Banat's Journal of Biotechnology
  • Volume: 2
  • Issue: 4
  • Year: 2011
  • Summary: A study was conducted from 2008 to 2010 in Bulgaria to evaluate the weed infestation in field crops, grown in crop rotation by organic farming. Beans cv. Obraztsov chiflik, wheat cv. Yantur, soyabeans cv. Zarya, and winter oats line RS-2 were studied. Two variants were used and foliar fertilization using Humustim in four replications, the size of harvesting plot was 52. 5 m 2. Crop rotation technological schemes were applied according to the requirements of the organic farming without using chemicals. During crop rotation, the density of perennial weeds remained relatively constant. In variants with fertilization by Humustim, the total number of weeds decreased compare to those without fertilization. The lowest density of weed infestation was observed in wintering oats, grown after soybeans-100 pcs. /m 2 and in wheat, grown after field beans-122 pcs. /m 2.
  • Authors:
    • Nord, E. A.
    • Curran, W. S.
    • Mortensen, D. A.
    • Mirsky, S. B.
    • Jones, B. P.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Rolled cover crop mulches can suppress weeds in subsequent cash crops, reduce the need for herbicides, and allow organic no-till cash crop establishment. This study investigated the weed suppressiveness of a cereal rye ( Secale cereale L.) cover crop mulch across varying weed seedbank density. Cereal rye was seeded at two dates in the fall and terminated at five dates in the spring to create biomass ranging from 100 to 1600 g m -2. The first three termination dates included both herbicide (glyphosate) and rolling of the rye, while later three dates were only rolled. Soybean [ Glycine max (L.) Merr.] was no-till planted after rye termination, and weed biomass and soybean yield were assessed. Spring termination date more strongly affected cereal rye biomass than fall planting date; a termination delay of 5 to 15 d compensated for a planting delay of 30 d. Weed biomass generally declined with increasing cereal rye biomass, and this relationship was stronger at higher weed seedbank densities. Supplemental weed control reduced weed biomass compared to no supplemental control and postherbicide was more effective than cultivation. While increasing cereal rye biomass was associated with a decline in soybean yield in 2009, it did not consistently impact soybean stand. Instead soybean stand establishment appeared to be impacted by high cover crop biomass and changing edaphic conditions at planting. Future research should focus on improved technology for direct seeding in high residue environments and developing longer term cropping systems less reliant on tillage and herbicides.
  • Authors:
    • Mendes, I.
    • de Castro Lopes, A.
    • Nunes, R.
    • Gomes de Sousa, D.
  • Source: Revista Brasileira de Ciencia do Solo
  • Volume: 35
  • Issue: 4
  • Year: 2011
  • Summary: MANAGEMENT SYSTEMS AND THE CARBON AND NITROGEN STOCKS OF CERRADO OXISOL UNDER SOYBEAN-MAIZE SUCCESSION Carbon and N stocks in soils are determined by the balance between addition and losses, and tillage and cropping systems are decisive in this process. This study aimed to evaluate the effect of soil management systems based on tillage, cover crops and P fertilization on C and N stocks in physical fractions of the soil organic matter and on microbial biomass and respiration in a soil after 11 years under soybean-maize rotation. The experiment was initiated in 1999 in an Oxisol with adequate level of available P to obtain form 80 to 90 % of potential yields of annual crops. The experiment was arranged in a split-plot design in randomized blocks, with three management systems based on soil tillage and cover crop (conventional tillage with pearl millet, no-tillage with pearl millet and no-tillage with velvet bean) assigned to the main plots and two P levels (0 and 100 kg ha(-1) yr(-1) of P2O5 as triple superphosphate applied at sowing) in subplots. Soil samples were collected at the grain filling stage of soybean (March 2010), from the soil layers 0-5, 5-10 and 10-20 cm, and subjected to physical fractionation of organic matter and microbial analysis. The no-tillage system resulted in stratification of organic C and N while conventional tillage resulted in a more homogeneous distribution in the 0-20 cm layer. Phosphorus fertilization for 11 years led to an accumulation of organic C and N in the soil, regardless of tillage and cover crop systems. Higher stocks of organic C and total N, higher microbial biomass C and lower microbial respiration were found under no-tillage than conventional tillage, both with pearl millet as cover crop. In the no-tillage systems, greater stocks of organic C and total N, similar microbial biomass C and higher microbial respiration were found with pearl millet as cover crop compared to velvet bean. The conversion rate of C added by crops to soil organic C was 4.0, 8.2 and 14.3 % for conventional tillage with pearl millet and no-tillage with pearl millet and with velvet bean, respectively.
  • Authors:
    • Wakatsuki, T.
    • Obi, M.
    • Okpara, I.
    • Obalum, S.
  • Source: Tropical and Subtropical Agroecosystems
  • Volume: 14
  • Issue: 2
  • Year: 2011
  • Summary: A key indicator of soil quality as organic carbon needs to be enhanced in the highly weathered soils predominant in southeastern Nigeria through appropriate tillage-mulch practices and cropping systems. We subjected a degraded Typic Paleustult (sandy loam) at Nsukka to no-till (NT) and conventional tillage (CT) and bare fallow (B) and mulch cover (M). This was duplicated with one sole-cropped to sorghum and the other to soybean as separate crop treatments during 2006 and 2007 growing seasons. The CT resulted in higher available P (P av) (under soybean) and cation exchange capacity (CEC) (under both crops) than the NT. Mulch gave lower P av under sorghum and vice versa under soybean. Exchangeable Ca was lowered while exchangeable acidity was enhanced with mulch under soybean. Overall, soil organic carbon and exchangeable Mg, Na and acidity were enhanced under soybean relative to sorghum; the reverse was the case for P av. However, the soil's CEC indicated comparable values in both cropping systems. Our results suggest that cropping 'CT with M' soil to soybean could be a promising agronomic combination for enhancing the SOC and fertility status of the soil.
  • Authors:
    • de Assis, R. L.
    • Madari, B. E.
    • Petter, F. A.
    • Pacheco, L. P.
    • Leandro, W. M.
    • Barbosa, J. M.
    • Oliveira de Almeida Machado, P. L.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 5
  • Year: 2011
  • Summary: The cover crops in no-till system can contribute to the formation of mulch and nutrient cycling to annual crops in succession. The objective of this study was to evaluate biomass production and nutrient cycling of cover crops sown in the second growing season, in crop rotation after upland rice and soybean, in no-tillage and conventional tillage systems, on a Red Latassol of Rio Verde, state of Goias, from April 2008 to April 2010. The experiment was evaluated in randomized strips, in a 5 x 6 factorial design, with four replications. In the horizontal strips two soil management systems (after three years of no-tillage and conventional systems) were evaluated and the cover crops in the vertical strips. Biomass and ground cover and nutrient cycling rates were only evaluated in the no-till treatments, in a 5 x 6 factorial arrangement, where the plots were subdivided, corresponding to six harvest dates of dried biomass 0, 15, 30, 60, 90 and 120 days after cutting of the cover crops. The following cover crops were sown in the second growing season: Brachiaria ruziziensis, Pennisetum glaucum and B. ruziziensis + Cajanus cajan and a fallow treatment as reference. Biomass production and the rates of soil cover and nutrient accumulation and release by cover crops as well as rice and soybean yield were evaluated. B. ruziziensis and B. ruziziensis + C. cajan performed best in biomass production, ground cover and nutrient accumulation at the end of the cover crops. The nutrients N and K had the highest concentration in the biomass, and the highest nutrient release to the soil was observed for K and P. The highest rice yield was observed when grown in no-tillage on crop residues of P. glaucum and B. ruziziensis, while soybean yields did not differ in the treatments.
  • Authors:
    • Santos, H.
    • Fontaneli, R.
    • Spera, S.
    • Dreon, G.
  • Source: Revista Brasileira de Ciencias Agrarias
  • Volume: 6
  • Issue: 3
  • Year: 2011
  • Summary: Soil fertility attributes were evaluated on a typical dystrophic Red Latosol (typic Haplorthox) located in Passo Fundo, State of Rio Grande do Sul, Brazil, twelve years after the establishment (1993, 2000, 2002 and 2005) of five integrated crop/livestock farming production systems: system I - wheat/soybean, white oat/soybean, and common vetch/corn; system II - wheat/soybean, white oat/soybean, and grazed black oat+grazed common vetch/corn; system III - perennial cool season pastures (fescue+white clover+red clover+birds foot trefoil); system IV - perennial warm season pastures (bahiagrass+black oat+rye grass+white clover+red clover+birds foot trefoil); and system V - alfalfa as hay crop. The plots under systems III, IV, and V returned to system I after the summer of 1996. However, in the summer of 2002, in the systems III, IV and V, what used to be crop returned to pasture and what used to be pasture returned to crop. An acidification process occurred in all layers by the lowest pH values and higher concentration and saturation by Al, in comparison to the soil in 1998. The organic matter level and the P, K and Al levels increased between 1998 to 2002, in all sampled layers, while the opposite occurred with pH, Ca and Mg contents.
  • 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.