• Authors:
    • Alvarez, R.
  • Source: Soil Use and Management
  • Volume: 21
  • Issue: 1
  • Year: 2005
  • Summary: The effects of nitrogen fertilizer and tillage systems on soil organic carbon (SOC) storage have been tested in many field experiments worldwide. The published results of this research are here compiled for evaluation of the impact of management practices on carbon sequestration. Paired data from 137 sites with varying nitrogen rates and 161 sites with contrasting tillage systems were included. Nitrogen fertilizer increased SOC but only when crop residues were returned to the soil; a multiple regression model accounted for just over half the variance (R2=0.56, P=0.001). The model included as independent variables: cumulative nitrogen fertilizer rate; rainfall; temperature; soil texture; and a cropping intensity index, calculated as a combination of the number of crops per year and percentage of corn in the rotation. Carbon sequestration increased as more nitrogen was applied to the system, and as rainfall or cropping intensity increased. At sites with higher mean temperatures and also in fine textured soils, carbon sequestration decreased. When the carbon costs of production, transportation and application of fertilizer are subtracted from the carbon sequestration predicted by the model, it appears that nitrogen fertilizer-use in tropical regions results in no additional carbon sequestration, whereas in temperate climates, it appears to promote net carbon sequestration. No differences in SOC were found between reduced till (chisel, disc, and sweep till) and no-till, whereas conventional tillage (mouldboard plough, disc plough) was associated with less SOC. The accumulation of SOC under conservation tillage (reduced and no till) was an S-shape time dependent process, which reached a steady state after 25201330 years, but this relationship only accounted for 26% of the variance. Averaging out SOC differences in all the experiments under conservation tillage, there was an increase of 2.1 t C ha22121 over ploughing. However, when only those cases that had apparently reached equilibrium were included (all no till vs. conventional tillage comparisons from temperate regions), mean SOC increased by approximately 12 t C ha22121. This estimate is larger than others previously reported. Carbon sequestration under conservation tillage was not significantly related to climate, soil texture or rotation.
  • Authors:
    • Saggin, A.
    • Santos, D.
    • Gatiboni, L.
    • Brunetto, G.
    • Kaminski, J.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 29
  • Issue: 4
  • Year: 2005
  • Summary: The critical potassium level for fertilizer recommendation for soils in the State of Rio Grande do Sul (RS) and Santa Catarina (SC), Brazil, with cation exchange capacity (CEC) from 5.1 to 15 cmol c dm -3 is 60 mg dm -3. However, until 2002 concentrations of 80 mg dm -3 had been used. Two experiments were carried out on an experimental area of the Department of Soil Science of the Federal University of Santa Maria (RS-Brazil) on a sandy Typic Hapludalf under no-tillage. The objective of the study was to evaluate critical potassium levels for fertilizer recommendations for soyabean, maize and sorghum. The first experiment was set up in 1991 and carried out until 2002. The main plot treatments were the application of 0, 60, 120, and 180 kg ha -1 K 2O every four years, and split-plot treatments were the reapplication of 60 kg of K 2O in 0, 1, 2, or 3 years. The second experiment was carried out from 1995 to 2002 and the treatments were 0, 50, 100, 150, and 200 kg ha -1 year -1 K 2O. Results showed that the critical potassium level extracted with Mehlich-1 solution is 42 mg dm -3. When using the critical potassium level established by the Regional Soil Chemistry and Fertility Commission in these soils it is possible to reach over 95% of the maximum crop yield.
  • Authors:
    • Irvine, B.
    • Chen, Y.
    • Doan, V.
  • Source: Canadian Biosystems Engineering
  • Volume: 47
  • Year: 2005
  • Summary: A two-year field study was conducted to investigate the performance of seeding canola crop as influenced by types of residue (canola, wheat, and pea) and types of seed opener (disc and hoe). Seed placement (seeding depth and seed scattering index), speed of crop emergence, and plant populations were used to evaluate the seeding performance. Seeding placement as affected by field wheel tracks (inside and outside wheel tracks) was also examined. The results showed that the disc opener produced a greater seeding depth and faster emergence than the hoe opener. The two openers resulted in the same level of plant population. In the first year, plots with pea residue resulted in greater and more uniform seeding depth, faster emergence, and higher plant population than plots with wheat and canola residues. In the second year, a better uniformity of seeding depth was observed for pea residue than the other two types of residue, while there were no significant differences between residue types in the other measured variables due to the extremely dry soil condition in the spring of that year. Seeds were placed more uniformly outside the wheel track than inside the wheel track, while the mean seeding depths were similar inside and outside the wheel track.
  • Authors:
    • Sweeney, D.
    • Kelley, K.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 3
  • Year: 2005
  • Summary: In the eastern Great Plains, winter wheat ( Triticum aestivum L.) is often rotated with other crops to diversify cropping systems. In these multicropping systems, wheat typically is planted with conservation tillage methods, but previous crop residues influence fertilizer N management. This field study was conducted from 1992 through 2001 in southeastern Kansas on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf). The objectives were to determine effects and interactions of previous crop {grain sorghum [ Sorghum bicolor (L.) Moench] and soybean [ Glycine max (L.) Merr.]}, tillage system [reduced tillage (RT) and no-tillage (NT)], N rate (67 and 134 kg ha -1), and preplant placement (surface-broadcast and subsurface-knife) of urea ammonium nitrate solution (UAN, 280 g kg -1) on wheat grain yield, yield components, and plant N uptake in a 2-yr cropping rotation. Wheat yields averaged 3.39 Mg ha -1 following soybean compared with 2.90 Mg ha -1 following grain sorghum. Tillage effects on grain yield were smaller than other treatment factors, averaging 3.23 Mg ha -1 for RT and 3.06 Mg ha -1 for NT. Grain yields were greatest in all cropping systems for the high-N-rate subsurface-knife treatment. Plant N uptake responses indicated that grain yield differences were primarily related to greater immobilization of both fertilizer and soil N following grain sorghum, compared with soybean, and to better utilization of subsurface-knifed N than surface-broadcast N. Results indicate that wheat yield potential is more strongly influenced by previous crop, fertilizer N rate, and N placement method than tillage system.
  • Authors:
    • Johnston, A.
    • Turkington, T.
    • Harker, K.
    • Clayton, G.
    • Lupwayi, N.
  • Source: Better Crops with Plant Food
  • Volume: 89
  • Issue: 3
  • Year: 2005
  • Summary: A field experiment was conducted at Fort Vermilion in northwestern Alberta, Canada, during 1998-99 and 1999-2000 to determine the amount of potassium (K) released from crop residues of four different crop rotations that included red clover [ Trifolium pratense] green manure, field pea, canola [rape] and spring wheat, under conventional and no-till seeding systems. Crops were grown on soils that had soil test levels of 150 ppm K (0.5M NaHCO 3-extractable), and no fertilizer K was added. Crop residues dry matter returned to the soil by the different crops were considerably higher in 1999-2000 relative to 1998-1999, reflecting the higher crop production during the 1999 growing season. Crop residue yield showed a large difference between the two study periods in the amount of total K being returned to the field. The results illustrate that all crop residues considered released more than 90% of their accumulated K in the 52-week period. The tillage system had no effect on the release of K from the crop residues.
  • Authors:
    • Rodrigues, L.
    • Lazarini, E.
    • Leal, A.
    • Muraishi, C.
    • Gomes Junior, F.
  • Source: Acta Scientiarum Agronomy
  • Volume: 27
  • Issue: 2
  • Year: 2005
  • Summary: This experiment aimed to verify the reaction of soyabean and maize cultures sown 38 days near or after chemical or mechanical handling of different soil coverings. The experiment was carried out at the experimental Station of Unesp, Ilha Solteira Campus, in the municipality of Selviria, state of Mato Grosso do Sul, Brazil, during the agricultural year of 2001/02. The covering cultures used were: rice, sorghum, Brachiaria decumbens [ Urochloa decumbens] and B. brizantha [ U. brizantha], millet [ Pennisetum glaucum] and Eleusine coracana. It was observed that the covering cultures showed good environment adaptation in dry mass production. The maize productivity was larger when the covering cultures handling was mechanically accomplished. The interval between handling and sowing of soyabean and maize culture is important only for rice or Brachiaria decumbens covering cultures; in this case, a 38-day previous handling is recommended. Maize yield was inferior when sown on sorghum residues.
  • Authors:
    • Sarpe,N.
    • Poienaru,S.
  • Source: Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara "Ion Ionescu de la Brad" Iasi, Seria Agronomie, Romania
  • Volume: 48
  • Year: 2005
  • Summary: Results are presented of an experiment in the Plain of Danube (Romania) with genetically modified soyabean (0094RR) in successive culture after barley under no-stripping system. Roundup Ready (containing 360 g glyphosate/l) was used to control grassy weeds, including Sorghum halepense. Roundup Ready at 3+3 l/ha resulted in 100% control of annual and perennial grasses. It also recorded the highest yield of 2800 kg/ha under 2 irrigations with a watering rate of 400 m 3/ha. With barley culture+soyabean in successive culture on the traditional system, 122 l of fuel oil was consumed for mechanical work, whereas on the system of no-stripping only 48 l/ha. Calculations concerning economic efficiency revealed that barley culture+soyabean in successive culture recorded a profit of ~28 million lei/ha.
  • Authors:
    • Arshad, M.
    • Soon, Y.
  • Source: Soil & Tillage Research
  • Volume: 80
  • Issue: 1/2
  • Year: 2005
  • Summary: Limited information is available on soil management effects on crop production and nitrogen (N) cycling in acid soils. The effects of conventional tillage (CT) versus no-till (NT) and liming (0 versus 7.5 Mg ha -1), and their interaction, on labile N pools in an acid soil were evaluated during the 7th to 10th year of a 3-course small grain rotation. Crop production and N uptake, N 2 fixation by pea ( Pisum sativum L.), and labile soil N were determined. Liming increased the pH from 5.3 to 6.0 in the top 10 cm of soil and had no influence below 10 cm depth. No-till increased average crop yield and N uptake by 12 and 14%, respectively, compared to CT. The corresponding increases due to lime application were 13 and 20%. There was no treatment effect on N concentrations in plant tissues (probably because of adequate N fertilizer application), or on N 2 fixation in pea. The percent N derived from the atmosphere varied from 12% in one dry year to 68% in a moister year. Soil NO 3 in spring and autumn was significantly higher where the preceding crop was field pea, particularly in the surface soil layer. Soil inorganic N was little influenced by tillage and liming. In contrast, soil microbial biomass N concentration was consistently greater with liming than without (30-64% difference) and with NT than with CT (7-36% difference), but little affected by crop sequence. Liming enhanced the positive effect of NT on soil microbial biomass N. Crop total N uptake was significantly correlated with microbial biomass N ( r=0.69* for barley ( Hordeum vulgare L.), and 0.70** for canola ( Brassica rapa L.)). Liming with NT can be effective in increasing N turnover and crop growth in acid soils.
  • Authors:
    • Arshad, M.
    • Klein-Gebbinck, H.
    • Soon, Y.
  • Source: Canadian Journal of Plant Science
  • Volume: 85
  • Issue: 1
  • Year: 2005
  • Summary: Brown girdling root rot (BGRR) is a serious and widespread disease of canola ( Brassica rapa L.) in the Peace River region of northwestern Canada. There is no chemical control treatment for the pathogen, and farmers have observed that the disease is more severe when canola follows red fescue ( Festuca rubra L.) or clover ( Trifolium spp.) compared to summer fallow. A field study was conducted to determine how crop sequences following red fescue termination can be combined with residue and tillage management to reduce BGRR infection and increase canola yield. The five treatments consisted of rotations of: continuous canola (CCC) and oat ( Avena sativa L.)-oat-canola (OOC), both managed using reduced tillage (RT), and wheat ( Triticum aestivum L.)-wheat-canola (WWC), managed using RT, conventional tillage (CT) or no-till (NT). Canola yield followed the trend: OOC(RT)=WWC(RT) > WWC(CT) > CCC(RT)=WWC(NT). BGRR infection increased with tillage intensity: WWC(CT) > CCC(RT)=WWC(RT)=OOC(RT) > WWC(NT), and was reduced when canola followed two cereal break crops. Yield was highest when canola was preceded by a cereal crop and lowest without a break crop. The low yield with NT was attributed to poor crop emergence from a hard seed bed with unbroken turf and to competition from re-emerged fescue in the third year after fescue breaking. This study demonstrated that the cropping sequence and tillage system used influenced canola yield to a greater extent than did BGRR infection.
  • Authors:
    • Álvaro-Fuentes, J.
    • Arrúe, J. L.
    • López, M. V.
    • Moret, D.
  • Source: European Journal of Agronomy
  • Volume: 23
  • Issue: 1
  • Year: 2005
  • Summary: Most of the benefits from conservation tillage are attained by maintaining crop residues on the soil surface. However, the effectiveness of crop residues depends on their persistence in time and maintenance of sufficient residue cover can become difficult, especially when a long-fallow period is involved. In this study, we evaluate the effects of conventional tillage (CT) and two conservation tillage systems (reduced tillage, RT, and no-tillage, NT), under both continuous cropping (CC) and cereal-fallow rotation (CF), on the dynamics of surface barley residues during four fallow periods in a dryland field of semiarid Aragon. The CC system involves a summer fallow period of 5-6 months and the CF rotation a long-fallow of 17-18 months. Results indicate that the lack of residue-disturbing operations in NT makes this practice the best strategy for fallow management. With this tillage system, the soil surface still conserved a residue cover of 10-15% after long-fallowing and percentages of standing residues ranging from 20 to 40% of the total mass after the first 11-12 months. In both CT and RT, primary tillage operations had the major influence on residue incorporation, with percentages of cover reduction of 90-100% after mouldboard ploughing (CT) and 50-70% after chiselling (RT). Two decomposition models were tested, the Douglas-Rickman and the Steiner models. Our data indicate that the Steiner model described more accurately the decline of surface residue mass over the long-fallow period in the NT plots. Measured and predicted data indicate that, under NT, 80-90% of the initial residue mass is lost at the end of fallow and that 60-75% of this loss occurs during the first 9-10 months. Finally, the mass-to-cover relationship established in this study for barley residues could be used to predict soil cover from flat residue mass through the fallow period by using a single A(m) coefficient (0.00208 ha kg(-1)). (C) 2004 Elsevier B.V. All rights reserved.