• 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:
    • Sayre, K. D.
    • Govaerts, B.
    • Deckers, J.
  • Source: Field Crops Research
  • Volume: 94
  • Issue: 1
  • Year: 2005
  • Summary: Subtropical highlands of the world have been densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen throughout this agro-ecological zone. This article considers practices that would sustain higher and stable yields for wheat and maize in such region. A long-term field experiment under rainfed conditions was started at El Batan, Mexico (2240 m a.s.l.; 19.31 degrees N, 98.50 degrees W;fine, mixed, thermic, Cumulic Haplustoll) in 1991. It included treatments varying in: (1) rotation (continuous maize (Zea mays) or wheat (Triticum aestivum) and the rotation of both); (2) tillage (conventional, zero and permanent beds); (3) crop residue management (full, partial or no retention). Small-scale maize and wheat farmers may expect yield improvements through zero tillage, appropriate rotations and retention of sufficient residues (average maize and wheat yield of 5285 and 5591 kg ha(-1)), compared to the common practices of heavy tillage before seeding, monocropping and crop residue removal (average maize and wheat yield of 3570 and 4414 kg ha(-1)). Leaving residue on the field is critical for zero tillage practices. However, it can take some time-roughly 5 years-before the benefits are evident. After that, zero tillage with residue retention resulted in higher and more stable yields than alternative management. Conventional tillage with or without residue incorporation resulted in intermediate yields. Zero tillage without residue drastically reduced yields, except in the case of continuous wheat which, although not high yielding, still performed better than the other treatments with zero tillage and residue removal. Zero tillage treatments with partial residue removal gave yields equivalent to treatments with full residue retention (average maize and wheat yield of 5868 and 5250 kg ha(-1)). There may be scope to remove part of the residues for fodder and still retain adequate amounts to provide the necessary ground cover. This could make the adoption of zero tillage more acceptable for the small-scale, subsistence farmer whose livelihood strategies include livestock as a key component. Raised-bed cultivation systems allow both dramatic reductions in tillage and opportunities to retain crop residues on the soil surface. Permanent bed treatments combined with rotation and residue retention yielded the same as the zero tillage treatments, with the advantage that more varied weeding and fertilizer application practices are possible. It is important small-scale farmers have access to, and are trained in the use of these technologies. (c) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Anderson, R. L.
  • Source: Weed Technology
  • Volume: 18
  • Issue: 1
  • Year: 2004
  • Summary: Dryland rotations are changing in the semiarid Great Plains because of no-till systems. Producers now rotate summer annual crops such as corn with winter wheat and fallow, which can disrupt weed population growth because of diverse life cycles among crops. This study estimated changes in weed populations as affected by rotation design, with the goal of suggesting crop sequences that lower weed community density. We used an empirical life-cycle simulation based on demographics of jointed goatgrass and green foxtail to compare various rotations consisting of winter wheat, corn, proso millet, and fallow across a 12-yr period. The simulation indicated that designing rotations to include a 2-yr interval when seed production of either jointed goatgrass or green foxtail is prevented will drastically reduce weed populations. Arranging four different crops in sequences of two cool-season crops, followed by two warm-season crops was the most beneficial for weed management. Fallow, if used, serves in either life-cycle category. However, if the same crop is grown 2 yr in a row, such as winter wheat, the benefit of rotation design on weed density is reduced considerably. Impact of rotation design on weed density was enhanced by improving crop competitiveness with cultural practices. Rotations with balanced life-cycle intervals not only reduce weed density but enable producers to use alternative weed management strategies, improve effectiveness of herbicides used, and minimize herbicide resistance.
  • Authors:
    • Wienhold, B. J.
    • Tanaka, D. L.
    • Liebig, M. A.
  • Source: Soil & Tillage Research
  • Volume: 78
  • Issue: 2
  • Year: 2004
  • Summary: The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA1: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0-7.5, 7.5-15, and 15-30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop-fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mgha-1), particulate organic matter C (POM-C) (by 4.98Mgha-1), potentially mineralizable N (PMN) (by 32.4 kg ha-1), and microbial biomass C (by 586 kg ha-1), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h-1) relative to the crop-fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha-1 for PMN; 792 kg ha-1 for microbial biomass C) as compared with sequences with fallow (SW-S-F and SW-F) (Average = 15.9 kg ha-1 for PMN; 577 kg ha-1 for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.
  • Authors:
    • Carmo, C.
    • Lhamby, J.
    • Ambrosi, I.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 34
  • Issue: 1
  • Year: 2004
  • Summary: Soil tillage and crop rotation and succession systems were assessed in Passo Fundo, Rio Grande do Sul, Brazil, from 1994/95 to 1997/98. Four soil tillage systems, i.e. no-tillage, minimum tillage, conventional tillage using a disc plough, and conventional tillage using a mouldboard plough, and three crop rotation and succession systems, i.e. system I (wheat/soyabean), system II (wheat/soyabean and common vetch [ Vicia sativa]/sorghum or maize) and system III (wheat/soyabean, common vetch/sorghum or maize, and white oats/soyabean), were compared. An experimental design of randomized blocks with split-plots and three replications was used. The main plot was formed by the soil tillage systems, while the split-plots consisted of the crop rotation and succession systems. Two types of analysis were applied to the net return of soil tillage and crop rotation and succession systems: mean-variance and risk analysis. By the mean-variance analysis, no-tillage and minimum tillage, which presented higher net returns, were the best alternatives to be offered to the farmer. By the stochastic dominance analysis, no-tillage and crop rotation with two winters without wheat showed the highest profit and the lowest risk.
  • Authors:
    • Arshad, M.
    • Soon, Y.
  • Source: Canadian Journal of Soil Science
  • Volume: 84
  • Issue: 4
  • Year: 2004
  • Summary: A field study was conducted to determine the effects and interactions of crop sequence, tillage and residue management on labile N pools and their availability because such information is sparse. Experimental treatments were no-till (NT) vs. conventional tillage (CT), and removal vs. retention of straw, imposed on a barley ( Hordeum vulgare L.)-canola ( Brassica rapa L.)-field pea ( Pisum sativum L.) rotation. 15N-labelling was used to quantify N uptake from straw, below-ground N (BGN), and fertilizer N. Straw retention increased soil microbial biomass N (MBN) in 2 of 3 yr at the four-leaf growth stage of barley, consistent with observed decreases in extractable soil inorganic N at seeding. However, crop yield and N uptake at maturity were not different between straw treatments. No tillage increased soil MBN, crop yield and N uptake compared to CT, but had no effect on extractable soil inorganic N. The greater availability of N under NT was probably related to soil moisture conservation. Tillage effects on soil and plant N were mostly independent of straw treatment. Straw and tillage treatments did not influence the uptake of N from its various sources. However, barley following pea (legume/non-legume sequence) derived a greater proportion of its N from BGN (13 to 23% or 9 to 23 kg N ha -1) than canola following barley (non-legumes) (6 to 16% or 3 to 9 kg N ha -1). Fertilizer N constituted 8 to 11% of barley N uptake and 23 to 32% of canola N uptake. Straw N contributed only 1 to 3% of plant N uptake. This study showed the dominant influence of tillage on N availability, and of the preceding crop or cropping sequence on N uptake partitioning among available N sources.
  • Authors:
    • Mosier, A. R.
    • Burke, I. C.
    • Kaye, J. P.
    • Guerschman, J. P.
  • Source: Ecological Applications
  • Volume: 14
  • Issue: 4
  • Year: 2004
  • Summary: Land-use change is an important driver of soil-atmosphere gas exchange, but current greenhouse-gas budgets lack data from urban lands. Field comparisons of urban and non-urban ecosystems are required to predict the consequences of global urban-land expansion for greenhouse-gas budgets. In a rapidly urbanizing region of the U.S. Great Plains, we measured soil-atmosphere exchange of methane (CH 4) and nitrous oxide (N 2O) for one year in replicated ( n=3) urban lawn, native shortgrass steppe, dryland wheat-fallow, and flood-irrigated corn ecosystems. All soils were net sinks for atmospheric CH 4, but uptake by urban, corn, and wheat-fallow soils was half that of native grasslands (-0.300.04 g C.m -2.yr -1 [mean1 Se]). Urban (0.240.03 g N.m -2.yr -1) and corn (0.200.02 g N.m -2.yr -1) soils emitted 10 times more N 2O to the atmosphere than native grassland and wheat-fallow soils. Using remotely sensed land-cover data we calculated an upper bound for the contribution of lawns to regional soil-atmosphere gas fluxes. Urban lawns occupied 6.4% of a 1578-km 2 study region, but contribute up to 5% and 30% of the regional soil CH 4 consumption and N 2O emission, respectively, from land-use types that we sampled. Lawns that cover small portions of the landscape may contribute significantly to regional soil-atmosphere gas exchange.
  • Authors:
    • Sherrod,L. A.
    • Shaver,T. M.
    • Peterson,G. A.
  • Source: Geoderma
  • Volume: 116
  • Issue: 1-2
  • Year: 2003
  • Summary: Great Plains dryland agriculture is a risky venture because of large annual fluctuations in precipitation and high evaporation potentials. Water capture is limited by low water infiltration rates because many of our soils have relatively small aggregate size distributions, which limit infiltration, and are also susceptible to crusting and sealing. No-till management has permitted cropping intensification, which via improved water storage, has increased crop residue returned to the soil, decreased surface bulk density, and increased surface soil porosity. Our objective was to quantify the relationship between crop residue biomass generated by cropping system intensification and the physical properties of the surface soil (0-2.5-cm depth). This study was conducted within an existing long-term dryland experiment consisting of three sites in eastern Colorado that transect an evapotranspiration gradient. Each site transects a soil catena with three distinct soils arranged along a slope gradient. Only soils at the summit and toe slopes were sampled for this study. Soils are Argiustolls and Ustochrepts. Three no-till cropping systems, Wheat-Fallow (WF), Wheat-Corn-Fallow (WCF), and Continuous Cropping (CC), were sampled in the summer of 1998 after the cropping systems had been in place for 12 years. Bulk density, effective porosity, aggregate size distribution, sorptivity, and soil aggregate organic C content were measured at the surface 2.5 cm of the soil in each cropping system at the two soil positions at each site. Bulk density was reduced by 0.01 g cm(-3) for each 1000 kg ha(-1) of residue addition over the 12-year period. Each 1000 kg ha(-1) of residue addition increased effective porosity by 0.3%. Increases in macroaggregation were associated with linear increases in the C content of the aggregates; each g kg(-1) of organic C in the macroaggregates increased the proportion of macroaggregates by 4.4%. Implementation of no-till intensive cropping systems under this semiarid environment increased, residue biomass, which has ultimately increased effective porosity, and thus water capture potential was increased.
  • Authors:
    • Acosta-Martinez, V.
    • Gill, T. E.
    • Zobeck, T. M.
    • Kennedy, A. C.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 4
  • Year: 2003
  • Summary: Microbes (i.e., fungi and bacteria) are needed to maintain the quality of semiarid soils and crop production. Enzyme (produced by microbes) activities were increased in the soil when cotton was rotated with sorghum or wheat under reduced or no-tillage in comparison to continuous cotton under tillage. Soil bacteria and fungi did not change, according to one analysis conducted, due to crop rotation under reduced or no-tillage in comparison to continuous cotton under tillage. The increases in enzyme activities, however, are indicating that microbes and their enzymes will be increased, and thus nutrients will be more available to plants, more organic matter will be formed, and other soil properties will also positively change if crop rotations with reduced or no-tillage are applied to semiarid soils in comparison to the typical current practice of continuous cotton with tillage.
  • Authors:
    • Wiemken, A.
    • Boller, T.
    • Mader, P.
    • Ineichen, K.
    • Sieverding, E.
    • Oehl, F.
  • Source: Applied and Environmental Microbiology
  • Volume: 69
  • Issue: 5
  • Year: 2003
  • Summary: The impact of land use intensity on the diversity of arbuscular mycorrhizal fungi (AMF) was investigated at eight sites in the "three-country corner" of France, Germany, and Switzerland. Three sites were low-input, species-rich grasslands. Two sites represented low- to moderate-input farming with a 7-year crop rotation, and three sites represented high-input continuous maize monocropping. Representative soil samples were taken, and the AMF spores present were morphologically identified and counted. The same soil samples also served as inocula for "AMF trap cultures" with Plantago lanceolata, Trifolium pratense, and Lolium perenne. These trap cultures were established in pots in a greenhouse, and AMF root colonization and spore formation were monitored over 8 months. For the field samples, the numbers of AMF spores and species were highest in the grasslands, lower in the low- and moderate-input arable lands, and lowest in the lands with intensive continuous maize monocropping. Some AMF species occurred at all sites ("generalists"); most of them were prevalent in the intensively managed arable lands. Many other species, particularly those forming sporocarps, appeared to be specialists for grasslands. Only a few species were specialized on the arable lands with crop rotation, and only one species was restricted to the high-input maize sites. In the trap culture experiment, the rate of root colonization by AMF was highest with inocula from the permanent grasslands and lowest with those from the high-input monocropping sites. In contrast, AMF spore formation was slowest with the former inocula and fastest with the latter inocula. In conclusion, the increased land use intensity was correlated with a decrease in AMF species richness and with a preferential selection of species that colonized roots slowly but formed spores rapidly.