• Authors:
    • Daughtry, C. S. T.
    • Vigil, M.
    • Evans, R.
    • Aguilar, J.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 2
  • Year: 2012
  • Summary: Crop residue is important for erosion control, soil water storage, filling gaps in various agroecosystem-based modeling, and sink for atmospheric carbon. The use of remote sensing technology provides a fast, objective, and efficient tool for measuring and managing this resource. The challenge is to distinguish the crop residue from the soil and effectively estimate the residue cover across a variety of landscapes. The objective of this study is to assess a select Landsat Thematic Mapper (TM) and hyperspectral-based indices in estimating crop residue cover and amount for both standing and laid flat, and between two winter wheat ( Triticum aestivum L.) harvest managements (i.e., stripper-header and conventional header) and fallow following proso-millet ( Panicum miliaceum L.) plots. The primary plots were located in Colorado with additional plots in eastern Montana, Oregon, and Washington states. Data collected include hyperspectral scans, crop residue amount (by weight) and residue cover (by photo-grid). Mean analyses, correlation tests, and spectral signature comparison show that the relative position of the crop residues affected the values of some remote sensing indices more than harvest management. Geographical location did not seem to influence the results. There was not enough evidence to support the use of these indices to accurately estimate the amount of residue. Hyperspectral data may deliver better estimates, but in its absence, the use of two or more of these datasets might improve the estimation of residue cover. This information will be useful in guiding analysis of remotely sensed data and in planning data acquisition programs for crop residue, which are essentially nonexistent at present.
  • Authors:
    • Urquiaga, S.
    • Martellotto, E. E.
    • Jantalia, C. P.
    • Alves, B. J. R.
    • Alvarez, C. R.
    • Costantini, A.
    • Alvarez, C.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: The aim of this study was to analyze the influence of different crop sequences (soybean-corn and soybean-soybean) and tillage systems (no tillage and reduced tillage) on nitrous oxide (N2O) soil emissions under field conditions. The experiment was carried out in Manfredi, Crdoba province, Argentina on an Entic Haplustoll and N2O emissions were measured in the field during a year. N2O fluxes were low during winter, but in late spring it peaked. For fallow, N-NO3-content was the most important variable to explain N2O emissions. For growing period water-filled pores was the main variable explaining N2O emissions. Nitrogen fertilization of corn crop increased N2O-N emissions, whereas no significant differences were found due to the tillage system. Measured annual N2O-N emissions were generally lower than those calculated using the methodology proposed by the Intergovernmental Panel on Climate Change.
  • Authors:
    • Azooz, R. H.
    • Soon, Y. K.
    • Arshad, M. A.
    • Lupwayi, N. Z.
    • Chang, S. X.
  • Source: AGRONOMY JOURNAL
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Wood ash has the properties to be an effective liming material, and research is needed to compare its effectiveness relative to agricultural lime on acidic agricultural soils. Wood ash at a calcium carbonate rate of 6.72 t ha -1 was compared with an equivalent rate of agricultural lime on a clay loam soil with an initial pH of 4.9. Replicated plots were managed under a barley ( Hordeum vulgare L.)-canola ( Brassica rapa L.)-pea ( Pisum sativum L.) rotation for 4 yr (2002-2005). Soil pH increased in the order of: wood ash=lime > control (without lime or wood ash). Available soil P increased in the order of: wood ash > lime ≥ control. The effect of wood ash and lime application on pH and available P was greatest in the 0- to 5-cm depth, less but still significant in the 5- to 10-cm depth, and not significant below 10 cm. The effect on soil aggregation was: wood ash > lime > control. Averaged over 4 yr, application of wood ash increased grain yields of barley, canola, and pea by 49, 59, and 55%, respectively, compared to a corresponding increase of 38, 31, and 49% by agricultural lime. The increase in crop yield with wood ash compared with lime is attributed partly to increased P availability in wood ash-amended plots. It is concluded that wood ash applied at rates equivalent to agricultural lime improved some soil chemical and physical properties and increased crop production relative to agricultural lime.
  • Authors:
    • Huggins, D. R.
    • Brown, T. T.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Knowledge of soil organic carbon (SOC) changes that occur under different agricultural practices is important for policy development, carbon (C) marketing, and sustainable land management. Our objective was to quantify agricultural impacts on SOC sequestration for dryland cropping systems in different agroclimatic zones (ACZs) of the Pacific Northwest (PNW). Data from 131 SOC studies were analyzed to assess land management-induced changes in SOC, including the conversion of native ecosystems to agricultural crops, conversion from conventional tillage (CT) to no-tillage (NT), and alternative crop rotations and management practices. Cumulative probabilities of SOC change were developed for assessing uncertainties inherent in SOC studies and for informing SOC markets. These analyses showed that 75% of converted native land lost at least 0.14 to 0.70 Mg C ha(-1) y(-1) (0.06 to 0.31 tn C ac(-1) yr(-1)) over an average of 55 to 74 years depending on ACZ. Converting from CT to NT was predicted to increase SOC at least 0.12 to 0.21 Mg C ha(-1) y(-1) (0.05 to 0.09 tn C ac(-1) yr(-1)) over 10 to 12 years in 75% of studies analyzed and was also ACZ specific. Compared to annual cropping, mixed perennial-annual systems would be expected to gain at least 0.69 Mg C ha(-1) y(-1) (0.31 tn C ac(-1) ha(-1)) over 12 years in 75% of ACZ 2 sites. Other conclusions were that (1) SOC databases are lacking for low precipitation areas of the PNW; such as the dryland wheat-fallow region; (2) baseline sampling of SOC prior to management change is largely nonexistent for PNW databases except for a few notable cases; (3) soil erosion processes have likely impacted SOC and contributed to large variability among studies; (4) sampling methodologies and analyses for SOC have been inconsistent, thereby contributing to SOC variability; and (5) a validated C model for the PNW would aid evaluation of SOC changes due to management, particularly for specific farms and sites with unique SOC history and circumstances.
  • Authors:
    • Wu,
    • Zhang, Y. M.
    • Hu, C. S.
    • Dong, W. X.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: No-tillage cropping can increase soil carbon (C) stocks and aggregation, and subsequently impact the internal nitrogen (N) cycle and gas loss. The N-15 pool dilution method was used to study gross N transformations, and relative proportions of nitrous oxide (N2O) emissions derived from denitrification versus nitrification-related processes under long-term tillage systems (no-tillage, rotary tillage and conventional tillage) in the North China Plain. In-field incubation experiments were repeated in successive growing seasons during April-November in 2007. Gross mineralization rates for rotary and mouldboard plough tillage (3.6 +/- A 0.3-10.6 +/- A 1.5 mg N kg(-1) days(-1)) were significantly higher than for no-tillage (1.7 +/- A 0.8-6.8 +/- A 1.1 mg N kg(-1) days(-1)). Gross mineralization was positively correlated with soil moisture and temperature, as well as with microbial biomass N and C. However, there was no consistent tillage effect on gross nitrification, and gross nitrification was positively correlated with soil moisture, but not with gross mineralization and microbial biomass. N2O emissions were higher in no-tillage (NT) than for conventional tillage (CT) during May-August. The N-15 labelling indicated that 26-92 % of the N2O was directly derived from the soil ammonium (NH4 (+)) pool. Emission rates of N2O from both nitrification and denitrification were positively correlated with NH4 (+) supply as expressed by gross mineralization, but not correlated with supply of nitrate as expressed by gross nitrification. The fraction of nitrified N emitted as N2O was positively correlated with changes in soil moisture and varied within 0.01-2.51 aEuro degrees. Our results showed that the tillage management impact on gross N transformation was not consistent with N2O emission, and more detailed information on the controls over N2O formation needs to be sought.
  • Authors:
    • Ahuja, L. R.
    • Hatfield, J. L.
    • Ma, L.
    • Malone, R. W.
    • Heiman, P.
    • Boyle, K. P.
    • Kanwar, R. S.
  • Source: Agricultural Systems
  • Volume: 106
  • Issue: 1
  • Year: 2012
  • Summary: A 45% reduction in riverine total nitrogen flux from the 1980-1996 time period is needed to meet water quality goals in the Mississippi Basin and Gulf of Mexico. This paper addresses the goal of reducing nitrogen in the Mississippi River through three objectives. First, the paper outlines an approach to the site-specific quantification of management effects on nitrogen loading from tile drained agriculture using a simulation model and expert review. Second, information about the net returns to farmers is integrated with the nitrogen loading information to assess the incentives to adopt alternative management systems. Third, the results are presented in a decision support framework that compares the rankings of management systems based on observed and simulated values for net returns and nitrogen loading. The specific question addressed is how information about the physical and biological processes at Iowa State University's Northeast Research Farm near Nashua, Iowa, could be applied over a large area to help farmers select management systems to reduce nitrogen loading in tile drained areas. Previous research has documented the parameterization and calibration of the RZWQM model at Nashua to simulate 35 management system effects on corn and soybean yields and N loading in tileflow from 1990 to 2003. As most management systems were studied for a 6 year period and in some cases weather had substantial impacts, a set of 30 alternative management systems were also simulated using a common 1974-2003 input climate dataset. To integrate an understanding of the economics of N management, we calculated net returns for all management systems using the DevTreks social budgeting tool. We ranked the 35 observed systems in the Facilitator decision support tool using N loading and net returns and found that rankings from simulated results were very similar to those from the observed results from both an onsite and offsite perspective. We analyzed the effects of tillage, crop rotation, cover crops, and N application method, timing, and amount for the 30 long term simulations on net returns and N loading. The primary contribution of this paper is an approach to creating a quality assured database of management effects on nitrogen loading and net returns for tile drained agriculture in the Mississippi Basin. Such a database would systematically extend data from intensively monitored agricultural fields to the larger area those fields represent. Published by Elsevier Ltd.
  • Authors:
    • Takebe, M.
    • Karasawa, T.
  • Source: Plant and Soil
  • Volume: 353
  • Issue: 1-2
  • Year: 2012
  • Summary: Aims A field experiment was conducted where maintenance of indigenous arbuscular mycorrhizal (AM) fungal populations was attempted using AM host cover crops arranged temporally or spatially during growth of nonmycorrhizal crops. Methods To arrange AM hosts temporally, sunflower or oat was grown as a cover crop after non-host cropping (cabbage) or fallowing. In order to arrange AM hosts spatially, red clover, white clover or vetch was intercropped during growth of non-host cabbage. Results The AM colonization and growth of maize with previously introduced sunflower or oat were much greater than those without introduction of cover crops or those with introduction of non-host cover crops. The AM colonization and yield of winter wheat grown after cabbage with AM host intercropping were greater than those after cabbage only cropping, suggesting that arrangement of AM hosts between cabbage rows is effective for maintaining the AM fungal population in soil during non-host cropping. Conclusions Mycorrhizal hosts cropped after or during non-host cropping is an effective means to increase indigenous AM fungal populations. The results show that AM colonization, P uptake and productivity of crops after cultivation of nonmycorrhizal crops can be improved by arranging AM hosts temporally or spatially as cover crops.
  • Authors:
    • Okeyo, J.
    • Vanlauwe, B.
    • Kimetu, J. M.
    • Waswa, B.
    • Bationo, A.
    • Kihara, J.
    • Mukalama, J.
    • Martius, C.
  • Source: Experimental Agriculture
  • Volume: 48
  • Issue: 2
  • Year: 2012
  • Summary: Reduced tillage is said to be one of the potential ways to reverse land degradation and ultimately increase the productivity of degrading soils of Africa. We hypothesised that crop yield following a modest application of 2 t ha(-1) of crop residue in a reduced tillage system is similar to the yield obtained from a conventional tillage system, and that incorporation of legumes in a cropping system leads to greater economic benefits as opposed to a cropping system involving continuous maize. Three cropping systems (continuous maize monocropping, legume/maize intercropping and rotation) under different tillage and residue management systems were tested in sub-humid western Kenya over 10 seasons. While soybean performed equally well in both tillage systems throughout, maize yield was lower in reduced than conventional tillage during the first five seasons but no significant differences were observed after season 6. Likewise, with crop residue application, yields in conventional and reduced tillage systems are comparable after season 6. Nitrogen and phosphorus increased yield by up to 100% compared with control. Gross margins were not significantly different among the cropping systems being only 6 to 39% more in the legume-cereal systems relative to similar treatments in continuous cereal monocropping system. After 10 seasons of reduced tillage production, the economic benefits for our cropping systems are still not attractive for a switch from the conventional to reduced tillage.
  • Authors:
    • Brainard, D.
  • Source: Acta Horticulturae
  • Issue: 950
  • Year: 2012
  • Summary: In response to declines in yield and stand longevity, Michigan asparagus growers are experimenting with multiple cultural practices including irrigation, shallow tillage, and "living-mulches" sown immediately following harvest in late June. Drought stress may play an important role in limiting fern growth and increasing fern susceptibility to pests. Living mulches are thought to reduce soil degradation and suppress weeds, but may also suppress asparagus through competition for water. Research was initiated in Hart, Michigan, USA, in 2008 with the following long-term objectives: (1) to evaluate the effects of irrigation on asparagus yields and weed management under two cropping systems; and (2) to determine the effects of cereal rye ( Secale cereal) living-mulch on soil moisture, weed growth, and asparagus yield. In a research farm field experiment, 4 treatments were examined: (1) no-till with standard herbicides; (2) no-till with standard herbicides plus irrigation; (3) shallow-tillage with rye living-mulch; (4) shallow tillage with rye living-mulch plus irrigation. Irrigation increased weed density and weed dry weight but had no detectable effect on asparagus yields. Rye living mulch (1) reduced soil volumetric water content by approximately 2-3% at 60 cm; (2) suppressed weeds compared to weedy control treatments, but resulted in increased weed density and dry weight compared to conventional herbicide treatments; and (3) had no detectable effect on asparagus yield.
  • Authors:
    • Kutu, F. R.
  • Source: African Journal of Agricultural Research
  • Volume: 7
  • Issue: 26
  • Year: 2012
  • Summary: Conservation agriculture experiment was conducted under irrigated and dryland conditions during 2007/2008-summer cropping season to determine a suitable soil-crop management practice for increase maize yield. The study consisted of tillage practices (conventional, minimum and zero), cropping systems (sole and intercrop plots) and fertilizer regimes (unfertilized control, low, adjusted low and optimum) as treatments. Minimum and zero tillage practices constituted the conservation agriculture tillage practices while supplementation of low fertilizer rate with seed inoculation using growth enhancing microbial inoculant constituted the adjusted low fertilizer rate. Fertilizer application gave a significant (P