• Authors:
    • Al-Kaisi, M.
  • Source: Integrated Crop Management
  • Volume: IC-496
  • Issue: 11
  • Year: 2006
  • Authors:
    • Benvenuti, S.
    • Macchia, M.
  • Source: Italian Journal of Agronomy
  • Volume: 1
  • Issue: 1
  • Year: 2006
  • Summary: Little information is available on the stale seedbed effect on seedbank reduction. This weed management is of increasing interest overall in organic agricultural systems where is no possible to use herbicides. The emergence dynamics and related seedbank reduction were evaluated following adoption of two different stale seedbed techniques (with or without irrigation), made during the spring-summer season in 2001 in organic agricultural systems. As expected, emergence was strongly stimulated by irrigation and soil tillage. When the no-tillage technique was adopted (control), the absence of soil disturbance resulted in extremely low emergence levels, associated with a reduction in the number of the relative species. Consequently, analysis of the residual seedbank of the shallow layer (0-10 cm) of the control (no-till) showed only small reduction (about 1%). In contrast, the tillage-only experiment led to a reduction of about 5% in the same soil layer. However only with the irrigation, a drastic reduction in the amount of seeds (roughly half) was achieved. In particular, grasses showed the highest seedbank reduction rates. Despite this different effectiveness of the stale seedbed techniques, the soil layers at greater depths (10-20 and 20-30 cm) were found to be completely unaffected, independently of the agronomic practices carried out. Qualitative analysis of exhumed seeds demonstrated that greatest "forcing of germination" (tillage+irrigation) resulted in a percentage increase of "deep-dormant" seeds as a consequence "non-dormant" seeds decrease. Although stale seedbed appeared to be only partially effective, we believe that if this agrotechnique is properly carried out and repeated at the appropriate times, it promises to be successful in agricultural systems where herbicides are excluded.
  • Authors:
    • Ndufa, J. K.
    • Chebii, J.
    • Baggs, E. M.
  • Source: Soil & Tillage Research
  • Volume: 90
  • Issue: 1-2
  • Year: 2006
  • Summary: Improved-fallow agroforestry systems are increasingly being adopted in the humid tropics for soil fertility management. However, there is little information on trace gas emissions after residue application in these systems, or on the effect of tillage practice on emissions from tropical agricultural systems. Here, we report a short-term experiment in which the effects of tillage practice (no-tillage versus tillage to 15 cm depth) and residue quality on emissions of N2O, CO2 and CH4 were determined in an improved-fallow agroforestry system in western Kenya. Emissions were increased following tillage of Tephrosia candida (2.1 g N2O-N ha-1 kg N applied-1; 759 kg CO2-C ha-1 t C applied-1; 30 g CH4-C ha-1 t C applied-1) and Crotalaria paulina residues (2.8 g N2O-N ha-1 kg N applied-1; 967 kg CO2-C ha-1 t C applied-1; 146 g CH4-C ha-1 t C applied-1) and were higher than from tillage of natural-fallow residues (1.0 g N2O-N ha-1 kg N applied-1; 432 kg CO2-C ha-1 t C applied-1; 14.7 g CH4-C ha-1 t C applied-1) or from continuous maize cropping systems. Emissions from these fallow treatments were positively correlated with residue N content (r = 0.62–0.97; P < 0.05) and negatively correlated with residue lignin content (r = -0.56, N2O; r = -0.92, CH4; P < 0.05). No-tillage of surface applied Tephrosia residues lowered the total N2O and CO2 emitted over 99 days by 0.33 g N2O-N ha-1 kg N applied-1 and 124 kg CO2-C ha-1 t C applied-1, respectively; estimated to provide a reduction in global warming potential of 41 g CO2 equivalents. However, emissions were increased from this treatment over the first 2 weeks. The responses to tillage practice and residue quality reported here need to be verified in longer term experiments before they can be used to suggest mitigation strategies appropriate for all three greenhouse gases.
  • Authors:
    • Marchetti, M.
    • Vitorino, A.
    • Souza, L.
    • Brandt, E.
  • Source: CIENCIA E AGROTECNOLOGIA
  • Volume: 30
  • Issue: 5
  • Year: 2006
  • Summary: The effects of crop rotation on the performance of soyabean were studied in Dourados, Mato Grosso do Sul, Brazil, during 1998, 1999 and 2000. The treatments were: maize/vetch/maize/vetch/soyabean, cotton/oat/cotton/sorghum/soyabean, soyabean/wheat/soyabean/maize/millet/soyabean, maize/grazing turnip/maize/sorghum/soyabean, maize/oat/maize/bean/millet/soyabean, rice/grazing turnip/rice/oat/soyabean, rice/sorghum/rice/bean/millet/soyabean, cotton/wheat/cotton/wheat/soyabean, and cotton/grazing turnip/cotton/oat/soyabean. Dry matter of aerial parts at the full flowering stage, plant height, first pod insertion, number of pods per plant, productivity and 1000-grain mass were evaluated. The rotation system had no significant effects on plant height, first pod insertion, and number of pods per plant. The highest grain yields were obtained under rice/sorghum/rice/bean/millet/soyabean and soyabean/wheat/soyabean/maize/millet/soyabean.
  • Authors:
    • Hons, F.
    • Dou, F.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 6
  • Year: 2006
  • Summary: Management practices that alter plant residue production and distribution influence SOC (soil organic carbon) dynamics. The objectives of this study were to investigate the impacts of tillage, cropping system, and N fertilizer application on SOC and soil N pools through physical fractionation of a central Texas soil after 20 years. Nitrogen fertilizer application and no-tillage (NT) significantly increased wheat ( Triticum aestivum) straw yield. Compared with conventional tillage (CT), SOC under NT in surface (0-5 cm) samples was 38, 69, and 68% greater for continuous wheat (CW), wheat-soyabean ( Glycine max)-sorghum ( Sorghum bicolor) rotation (SWS), and double-cropped wheat-soyabean (WS), respectively. The greatest SOC was observed in WS under NT with N fertilizer application, and the lowest occurred in CW under CT without N. Increased cropping intensity increased SOC compared with monoculture. Nitrogen fertilizer application only significantly increased SOC sequestration under NT. No-tillage increased SOC concentration in all physical size fractions compared with CT. Increased cropping intensity and N fertilizer application significantly increased SOC sequestration in most size fractions only under NT. Intraparticulate organic matter C (IPOM-C) was proportionally more affected by tillage than total SOC, indicating that this fraction was more sensitive to management. Carbon concentrations in all size fractions were significantly correlated with each other as well as SOC. Our results indicated that NT associated with enhanced cropping intensity and N fertilizer application sequestered greater SOC and soil total N.
  • Authors:
    • Derksen, D.
    • May, W.
    • Johnston, A.
    • Clayton, G.
    • Lafond, G.
    • Stevenson, F.
  • Source: Canadian Journal of Plant Science
  • Volume: 86
  • Issue: 2
  • Year: 2006
  • Summary: Surface residues and standing stubble protect soil against erosion and mitigate against crop water deficits by conserving additional moisture. However, residues and stubble can also present a dilemma for producers practising no-till in terms of nitrogen (N) fertilizer management and row spacing. The objective of this research was to determine how row spacing, N management using urea and two rates of post-emergent herbicide (66 and 100% of recommended) affect spring wheat establishment and plant development. The study was conducted using a no-till system and a canola-spring wheat cropping system at three locations over a 3-yr period. The N management and row spacing treatments were (1) 23-cm row spacing with fall banded N on 30 cm; (2) 23-cm row spacing with spring banded N on 30 cm; (3) 30-cm row spacing with the N side-banded; (4) 23-cm row spacing with the N side-banded; and (5) sweep on 23-cm spacing with seed and fertilizer scattered over a 20-cm width. Herbicide rates did not affect wheat development. Planting depth was greater for the sweep treatment, but only by 6 mm. Plant densities were at the low end of the optimal range of 200-250 plants m -2 for all treatments and were least for the 30 cm row spacing. Average frequencies for tillers T0, T1, T2 and T3 were 20, 81 61 and 10%, respectively. Fall and spring band treatments resulted in lower tiller frequencies than the sweep treatment, with intermediate levels for the side-band treatments. Tiller frequencies were identical between the 23-cm and 30-cm row spacings with N side-banded. Greater tiller frequencies for the sweep treatment likely resulted from the greater spread of seed, reducing inter-plant competition and closer proximity of the seed to fertilizer N. Spike density was not affected by N management. Expected spike density, calculated from tiller frequency and plant density data, was within 1% of the actual spikes recorded, when averaged over treatments. This means that tiller frequencies at the 5 to 5.5 leaf stage are a good predictor of expected spike density. Wider row spacings did not affect plant and tiller development but applying N fertilizer at time of seeding provided better spring wheat tiller development.
  • Authors:
    • Gamero, C.
    • Rodrigues, J.
  • Source: Energia na Agricultura
  • Volume: 21
  • Issue: 4
  • Year: 2006
  • Summary: The present study aimed to evaluate the energy demand and the effective field capacity in different soil management systems, and three kinds of vegetal covering for soyabean cultivation. The experiment was carried out at the Lageado Experimental Farm, School of Agronomical Sciences, UNESP, Botucatu, SP, Brazil. The experimental area soil was classified as Red Dystroferric Nitosol. The experiment consisted of nine treatments combining three soil management systems (conventional, reduced and no-tillage) and three vegetal covering (black oats, sorghum and spontaneous vegetation). The experimental design was in randomized blocks, 3*3 factorial scheme with 4 replications, using Tukey's test at 5% to compare means. The soil management systems presented significant differences in the effective field capacity, fuel consumption per hour and operational consumption; the no-tillage system presented the best results, regardless of soil vegetal covering.
  • Authors:
    • Spera, S.
    • Lhamby, J.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 36
  • Issue: 1
  • Year: 2006
  • Summary: A 6-year (1997/98-2002/03) study was undertaken in Passo Fundo, Rio Grande do Sul, Brazil, to assess the effects of soil tillage systems and crop rotation systems on soyabean grain yield and its components. The treatments comprised 4 soil tillage systems: (1) no-tillage, (2) minimum tillage in winter and no-tillage in summer, (3) conventional tillage with a disc plough in winter and no-tillage in summer, and (4) tillage using a mouldboard plough in winter and no-tillage in summer; and 3 crop rotation systems (I) wheat/soyabean, (II) wheat/soyabean and common vetch [ Vicia sativa]/maize or sorghum, and (III) wheat/soyabean, common vetch/maize or sorghum and white oats/soyabean. The yield and weight of 1000 kernels of soyabean grown under no-tillage and minimum tillage was higher than those grown under conventional soil tillage with a disc plough and a mouldboard plough. Plant height was greater in the no-tillage system. The yield of soyabean grown after wheat in system II was higher than in soyabean grown after white oats and wheat in system III and after wheat in system I. The lowest soyabean yield, grain weight per plant and weight of 1000 kernels were obtained in monoculture (wheat/soyabean).
  • Authors:
    • Avila, A.
    • Spera, S.
    • Lhamby, J.
    • Santos, H.
  • Source: Bragantia
  • Volume: 65
  • Issue: 4
  • Year: 2006
  • Summary: The effects of soil management system and winter crop rotation on wheat yield and root diseases were assessed. Four soil management systems: (1) no-tillage, minimum tillage, conventional tillage using a disc plough plus disc harrow, and conventional tillage using a mouldboard plough plus disc harrow; and 3 crop rotation systems: wheat/soyabean, wheat/soyabean and common vetch [ Vicia sativa]/maize or sorghum ( Sorghum bicolor), and wheat/soyabean, white oat/soyabean and common vetch/maize or sorghum, were compared. The yield and plant height of wheat grown under no-tillage and minimum tillage were higher than the yield of wheat grown under conventional soil tillage using either disk plough or mouldboard plough. Weight of 1000 kernels was highest in the no-tillage. Crop rotation was efficient in reducing root diseases and in increasing wheat yield. The lowest wheat yield, grain weight per plant, 1000-kernel weight and test weight were obtained in monoculture (wheat/soyabean).
  • Authors:
    • Sweeney, D.
    • Kilgore, G.
    • Whitney, D.
    • Schwab, G.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 3
  • Year: 2006
  • Summary: Reduced- and no-tillage seedbed preparation methods coupled with broadcast P applications lead to an accumulation of available P in the surface 0- to 5-cm soil layer and a depletion of available P deeper in the profile. A 3-yr study determined the effects of tillage and fertilizer P management on P uptake and grain yield for P-stratified soils. Tillage practices were moldboard plow (once at the start of the study followed by reduced tillage), reduced tillage (disk followed by field cultivation), and no-tillage. Four P management methods were imposed: (i) no P; (ii) 20 kg P ha -1 applied as a surface broadcast; (iii) 20 kg ha -1 applied as a banded starter, 5 cm to the side and 5 cm below the seed; or (iv) 20 kg ha -1 applied in a deep placed band, 13 to 15 cm on 0.7-m centers. The one-time moldboard plowing produced higher early season dry matter yields for corn ( Zea mays L.), wheat ( Triticum aestivum L.), and soybean [ Glycine max (L.) Merr.] compared with the no-tillage system, but tillage effects on final grain yield were inconsistent. Subsurface placement of P generally increased P uptake and grain yield of corn and sorghum [ Sorghum bicolor (L.) Moench], but had little effect on grain yield of soybean. Results indicate that subsurface applications of P fertilizers should be considered if soil test P is highly stratified within the surface 0- to 15-cm layer and the 15-cm composite is medium or below for available P.