• Authors:
    • Mendez, M.
    • Vitti, M.
    • Costa, V.
    • Giacobbo, C.
    • Rufato, L.
    • Rossi, A.
    • Fachinello, J.
  • Source: Bragantia
  • Volume: 66
  • Issue: 3
  • Year: 2007
  • Summary: Field studies were conducted in Rio Grande do Sul, Brazil, to evaluate 5 different managements of black oat ( Avena nuda) crop cover. The treatments comprised: incorporation of black oat to soil; chemical management with herbicide; lodging; mowing at 5 cm; and control (uncovered soil). The sowing of the oat was accomplished by April of 2002 and the installation of the experiment by the end of August of the same year. The analysed variables were percentage of soil moisture at a depth of 15 cm, temperature of the soil at a depth of 5 cm, percentage of organic matter of the soil, soil resistance to the penetration and identification and degree of infestation by weeds. The data were submitted to analysis of variance through the F test and the averages compared by the Duncan Test. Maintenance of crop covering in orchards propitiated smaller temperature and larger soil moisture. The soil turn-over increased the diversity of weeds and the incorporation of black oat, after 60 days, had the same behaviour as the uncovered soil.
  • Authors:
    • Silva, P.
    • Ernani, P.
    • Sangoi, L.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 31
  • Issue: 3
  • Year: 2007
  • Summary: No-tillage systems, associated with black oat as preceding cover crop, have been increasingly adopted. This has motivated anticipated maize nitrogen fertilizer application, transferring it from the side-dress system at the stage when plants have 5-6 expanded leaves to when the preceding cover crop is eliminated or to maize sowing. This study was conducted to evaluate the effects of soil tillage system and timing of N fertilizer application on maize grain yield and agronomic efficiency of N applied to a soil with high organic matter content. A three-year field experiment was conducted in Lages, state of Santa Catarina, Brazil, from 1999 onwards. Two soil tillage systems were tested in the main plots: conventional tillage (CT) and no-tillage (NT). Six N management systems were assessed in the split-plots: S1, control (without N application); S2, all N (100 kg ha -1) applied at oat desiccation; S3, all N applied at maize sowing; S4, all N side-dressed when maize had five expanded leaves (V5 growth stage); S5, 1/3 of N rate applied at maize sowing and 2/3 at V5; and S6, 2/3 of nitrogen rate applied at maize sowing and 1/3 at V5. Maize response to the time and form of splitting N was not affected by the soil tillage system. Grain yield ranged from 6.0 to 11.8 t ha -1. The anticipation of N application (S2 and S3) decreased grain yield in two of three years. In the rainiest early spring season (2000/2001) of the experiment, S4 promoted an yield advantage of 2.2 t ha -1 over S2 and S3. Application of total N rate before or at sowing decreased the number of kernels produced per ear in 2000/01 and 2001/02 and the number of ears produced per area in 2001/02, resulting in reduced grain yield. The agronomic efficiency of applied N (kg grain increase/kg of N applied) ranged from 13.9 to 38.8 and was always higher in the S4 than in the S2 and S3 N systems. Short-term N immobilization did not reduce grain yield when no N was applied before or at maize sowing in a soil with high organic matter content, regardless of the soil tillage system.
  • Authors:
    • Rambo, L.
    • Strieder, M.
    • Argenta, G.
    • Suhre, E.
    • Silva, P.
    • Silva, A.
  • Source: Ciencia Rural
  • Volume: 37
  • Issue: 4
  • Year: 2007
  • Summary: The black oats use ( Avena strigosa) as species of soil covering in the winter, cause immobilization of the nitrogen (N), that reduces the plant development and grain yield of maize cultivated in succession. Thus, the black oat intercropped systems with leguminous as common vetch ( Vicia sativa) and brassicas as oilseed radish ( Raphanus sativus) is aimed at increasing nitrogen (N) disponibility in the system and the permanence timing of its residues in the soil. Two experiments were carried out in the growth seasons of 2001/2002 and 2002/2003, in Rio Grande do Sul, Brazil. The first one was aimed at evaluating the effect of three winter species of soil covering, grown as a single culture and as intercropped crops on maize grain yield, with and without nitrogen side-dressed. The second one was aimed at determining the most adequate seed ratio of oilseed radish and black oat in intercropped systems, as soil covering crops in the winter preceding maize, under different nitrogen levels side-dressed. In Experiment I, treatments were composed by N application of 180 kg ha -1, a control without N side-dressed and seven winter soil covering systems. In the Experiment II, treatments consisted of two levels of N side-dressing application in maize, a control without N side-dressed, and of three seed ratio of oilseed radish and black oat, as single and as intercropped crops and a control without crop in the winter. In all intercropped systems, independently of seed ratio used, the oilseed radish was mostly responsible for the yield of dry mass of the systems. The intercropped systems of common vetch or oilseed radish with black oat minimize the negative effect of oat on maize grain yield cultivated in succession in systems with low N availability and, even with high N supply, maize grain yield also increases when grown after common vetch.
  • Authors:
    • Santen, E. van
    • Price, A.
    • Shaw, J. N.
    • Sullivan, D. G.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Conservation tillage is a commonly adopted best management practice for reducing runoff and erosion, and increasing infiltration. Yet current methodologies in place to monitor conservation tillage adoption are largely inappropriate for regional or national assessments. A major goal of this study was to evaluate the spectral response properties of four alternative winter cover crops using remotely derived crop residue cover indices. Experimental plots were located in east-central Alabama on a coarse-loamy siliceous, subactive, thermic Plinthic Paleudult. The experiment was a randomized complete block design having four replications of each of the following treatments: one fallow conventional tillage treatment and four no-tillage treatments with black oat ( Avena strigosa Schreb.), crimson clover ( Trifolium incarnatum L.), turnip ( Brassica rapa L. subsp.rapa), or rye ( Secale cereale L.) cover crops. Remotely sensed data were acquired three times using a 14 d sampling interval beginning near planting and using a handheld multispectral radiometer (485-1650 nm) in 2005 and 2006. Three crop residue cover indices using combinations of middle-infrared and visible spectra were compared and evaluated. Rye, clover, and black oat were spectrally similar, having an overall spectral response ranging from 8 to 45% (440-1650 nm). Increasing soil water content between remotely sensed data acquisitions was evidenced by as much as a 24% decline in middle-infrared reflectance. Despite this variability, a normalized difference ratio of middle-infrared (1650 nm) and blue (445 nm) spectra (Crop Residue Cover Index) provided the most consistent differentiation between tillage systems, varying within 8% of benchmark conditions (low soil water and low canopy cover). Considering the impact that conservation tillage may have on soil and water resources, rapid, watershed scale assessments of conservation tillage adoption may facilitate natural resource inventories, carbon sequestration estimates, and improved agricultural water management regimes.
  • Authors:
    • Mangum, R. W.
    • Coffman, C. B.
    • Teasdale, J. R.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 5
  • Year: 2007
  • Summary: There have been few comparisons of the performance of no-tillage cropping systems vs. organic farming systems, particularly on erodible, droughty soils where reduced-tillage systems are recommended. In particular, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A 9-yr comparison of selected minimum-tillage strategies for grain production of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) was conducted on a sloping, droughty site in Beltsville, MD, from 1994 to 2002. Four systems were compared: (i) a standard mid-Atlantic no-tillage system (NT) with recommended herbicide and N inputs, (ii) a cover crop-based no-tillage system (CC) including hairy vetch (Vicia villosa Roth) before corn, and rye (Secale cereale L.) before soybean, with reduced herbicide and N inputs, (iii) a no-tillage crownvetch (Coronilla varia L.) living mulch system (CV) with recommended herbicide and N inputs, and (iv) a chisel-plow based organic system (OR) with cover crops and manure for nutrients and postplanting cultivation for weed control. After 9 yr, competition with corn by weeds in OR and by the crownvetch living mulch in CV was unacceptable, particularly in dry years. On average, corn yields were 28 and 12% lower in OR and CV, respectively, than in the standard NT, whereas corn yields in CC and NT were similar. Despite the use of tillage, soil combustible C and N concentrations were higher at all depth intervals to 30 cm in OR compared with that in all other systems. A uniformity trial was conducted from 2003 to 2005 with corn grown according to the NT system on all plots. Yield of corn grown on plots with a 9-yr history of OR and CV were 18 and 19% higher, respectively, than those with a history of NT whereas there was no difference between corn yield of plots with a history of NT and CC. Three tests of N availability (corn yield loss in subplots with no N applied in 2003-2005, presidedress soil nitrate test, and corn ear leaf N) all confirmed that there was more N available to corn in OR and CV than in NT. These results suggest that OR can provide greater long-term soil benefits than conventional NT, despite the use of tillage in OR. However, these benefits may not be realized because of difficulty controlling weeds in OR.
  • Authors:
    • Mitchell, J. P.
    • Horwath, W. R.
    • Veenstra, J. J.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 2
  • Year: 2007
  • Summary: Conservation tillage (CT) and cover cropping (CC) are agricultural practices that may provide solutions to address water and air quality issues arising from intensive agricultural practices. This study investigated how CT and CC affect soil organic matter dynamics in a cotton(Gossypium hirsutum L.)-tomato (Lycopersicon esculentum Mill.) rotation in California's San Joaquin Valley. There were four treatments: conservation tillage, no cover crop (CTNO); conservation tillage with cover crop (CTCC); standard tillage, no cover crop (STNO); and standard tillage with cover crop (STCC). After 5 yr, the top 30 cm of soil in CTCC had an increase of 4500 kg C ha(-1), compared with an increase of 3800 kg C hat in STCC from initial soil C content in 1999. To enhance our understanding of C dynamics in CT systems, we pulse-labeled cotton with (CO2)-C-13 in the field and followed the decomposition of both the roots and the shoots through three physical fractions: light fraction (LF), which tends to turnover quickly, and two relatively stable C pools-intraaggregate LF (iLF) and mineral-associated carbon (mC). Soil under CT treatments retained more of the cotton-residue-derived C in LF and iLF than ST 3 mo after placement in the field. These differences disappeared after 1 yr, however, with no discernable differences between CT and ST regardless of CC. In California's Mediterranean climate, CT alone does not accumulate or stabilize more C than ST in tomato-cotton rotations, and the addition of cover crop biomass is more important than tillage reduction for total soil C accumulation.
  • Authors:
    • Boast, C. W.
    • Ellsworth, T. R.
    • Mulvaney, R. L.
    • Khan, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 36
  • Issue: 6
  • Year: 2007
  • Summary: Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. These are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO2 enrichment, and NO3- pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N managment practices, if combined with corn stover removal for bioenergy production; exacerbate soil C loss.
  • Authors:
    • Hao,X.
    • Kravchenko,A. N.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 1
  • Year: 2007
  • Summary: Management practice and soil texture are known to affect soil C. Relatively little information exists, however, on interactions between textural and management effects. The objective of this study was to evaluate management effects on soil total C along a textural gradient in well-drained Typic Hapludalfs in southwest Michigan. Three management practices considered in this study were conventional tillage (CT) and no-till (NT) both with conventional chemical inputs, and conventional tillage with leguminous cover crops and no chemical inputs (CT-cover). Four replicate plots were sampled for each practice, with approximately 100 soil samples taken at the 0- to 5-cm depth in each plot. In all management practices, the relationships of total C and N with clay + silt varied depending on the range of clay + silt values, with regression slopes at clay + silt 570 g kg-1. Total C in the CT-cover and NT treatments was higher than that in the CT treatment across the whole range of studied textures; however, a greater difference in total C between NT and CT occurred at greater clay + silt contents. Total C in the CT-cover and NT treatments were not different when clay + silt was 600 g kg-1. The results indicate that the potential for C accumulation in surface soils via NT treatment depends on soil texture.
  • Authors:
    • Tourdonnet, S. D.
    • Carof, M.
    • Coquet, Y.
    • Hallaire, V.
    • Roger-Estrade, J.
  • Source: Soil Use and Management
  • Volume: 23
  • Issue: 3
  • Year: 2007
  • Summary: We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no-till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's-foot-trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (22120.6, 22120.2 and 22120.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0201310 cm layer and in the 10201320 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0201310 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous-root type) and the leguminous ones (tap-root type). However, we recorded larger functional pores and more tubules in the no-till treatments with a cover crop, compared with the no-till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time.
  • Authors:
    • Borghi, E.
    • Crusciol, C.
    • Mateus, G.
  • Source: Acta Scientiarum Agronomy
  • Volume: 29
  • Issue: 4
  • Year: 2007
  • Summary: The effects of cover plants on the performance of annual crops under no-tillage systems are not well defined yet. A field trial was carried out on a Rhodic Kandiudalf soil in Botucatu, state of Sao Paulo, Brazil, aiming to evaluate the effect of the amount of Gigante guinea sorghum straw on soybean nutrient uptake and its consequent performance of grain yield in no-tillage area. The experimental design was developed in randomized blocks with four replications. The treatments consisted of 6.1, 7.1, 19.5, 26.7, 28.1 e 30.2 ton ha -1 of guinea sorghum straw. The increase of straw provided increment of N and P plant levels until the amount of 25.0 and 17.5 ton ha -1, respectively. Thus, the highest soybean grain yields reported in soils under no-tillage systems might be related to the proper water and nutrient uptakes due to higher soil moisture availability.