• Authors:
    • Moorman, T.
    • Cambardella, C.
    • Singer, J.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 6
  • Year: 2008
  • Summary: Coupling winter small grain cover crops (CC) with liquid manure injection may increase manure nutrient capture. The objectives of this research were to quantify manure injection effects using target swine ( Sus scrofa) manure N rates of 112, 224, and 336 kg N ha -1 on CC plant density, fall and spring shoot biomass, N, P, and K uptake and subsequent corn ( Zea mays L.) yield. A winter rye ( Secale cereale L.)-oat ( Avena sativa L.) CC was established before fall manure injection. Manure injection lowered mean CC plant density 25% because of CC mortality in the injection zone. Fall CC dry matter (DM) was 26% lower in the manure treatments than the no manure CC control, although no difference was detected for N (9.4 kg ha -1) or P (1.4 kg ha -1) uptake. No difference was detected for spring DM between CC no manure and manure treatments. Shoot DM, N, P, and K uptake increased 29, 41, 31, and 25% from the CC manure 112 to CC manure 224 with no increase above CC manure 224. Cover crop N uptake was higher in CC manure vs. no manure (60.1 vs. 35.6 kg ha -1). Cover crop P and K uptake were also higher in CC manure vs. no manure (9.2 vs. 6.6 kg P ha -1 and 41.3 vs. 30.0 kg K ha -1). Corn grain yield was unaffected by CC and responded positively to manure application (11,022 with manure vs. 9,845 kg ha -1 without manure). Coupling manure injection and cover crops can increase nutrient capture without lowering corn yield.
  • Authors:
    • Stoffella, P.
    • Bayer, C.
    • Wilson, P.
    • He, Z.
    • Vieira, F.
    • Baligar, V.
  • Source: Australian Journal of Agricultural Research
  • Volume: 59
  • Issue: 1
  • Year: 2008
  • Summary: This study aimed to: (1) determine the effect of P depletion and presence of Al on root and shoot growth of representative cover crops, and on their nutrient uptake; (2) characterise the composition of root exudation under P and Al stress in nutrient solution; (3) evaluate the ability of aqueous extracts of composts in reducing Al phytotoxicity. Plants of cowpea ( Vigna unguiculata subsp. unguiculata), black oat ( Avena strigosa), and lablab ( Lablab purpureus) were cultivated in different nutrient solution compositions and concentrations for 3 weeks. It was found that Al at concentration of 20 and 200 mol/L increased citrate exudation at least 8 and 24 times, respectively, for cowpea and 18 and 36 times, respectively, for lablab, as compared with the blank. However, no release of organic acids occurred due to P deprivation, suggesting that citrate exudation was a specific response to excess Al. No response in organic acid release was observed for black oat under the stress of P deficiency or Al toxicity. Although the presence of Al in solution did not significantly affect chlorophyll content in leaves, it decreased root and shoot weight, as well as root length, surface area, volume, and number of tips. Organic extracts alleviated aluminum toxicity, improving plant growth and ameliorating plant nutrition status. Yard waste extract was more effective in enhancing plant growth than GreenEdge extract in plants under Al stress.
  • Authors:
    • Mamo, M.
    • Drijber, R.
    • Quincke, J.
    • Wortmann, C.
    • Franti, T.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 6
  • Year: 2008
  • Summary: Continuous no-till (NT) results in soil improvements, primarily in the surface 5 cm of soil. One-time tillage may improve NT systems by inverting surface soil with less improved deeper soil. Research was conducted to determine the change in abundance of soil microbial groups after a one-time tillage of NT and their recovery dynamics. Experiments were conducted under rainfed corn ( Zea mays L.) or sorghum [ Sorghum bicolor (L.) Moench] rotated with soybean [ Glycine max (L.) Merr.] in eastern Nebraska with one-time moldboard plow (MP) and mini-moldboard plow (mini-MP) tillage compared with continuous NT. Fatty acid methyl ester (FAME) profiles were used as biomarkers of soil microbial groups. The biomass of microbial groups within the soil profile was affected by tillage treatment, soil depth, and time after one-time tillage. Soil microbial biomass under NT was greatest at the 0- to 5-cm depth with 50% less in the 5- to 20-cm depth, and least in the 20- to 30-cm depth. Microbial group biomass was decreased by one-time MP tillage, and generally by mini-MP tillage, compared with NT. On an equivalent soil mass basis, the quantity of the arbuscular mycorrhizal (AM) biomarker C16:1(c11) in the second year after tillage was 22% less for tilled treatments compared with NT. In contrast, the fungal biomarker C18:2(c9,12) was 6% more in the second year after tillage for tilled compared with NT. Tillage affected biomass and recovery of microbial groups differently, with all except AM returning to the NT microbial biomass levels within 1 to 3 yr.
  • Authors:
    • Krupinsky, J. M.
    • Tanaka, D. L.
    • Merrill, S. D.
    • van Donk, S. J.
  • Source: Transactions of the ASABE
  • Volume: 51
  • Issue: 5
  • Year: 2008
  • Summary: Residue cover is very important for controlling soil erosion by water and wind. Thus, the wind erosion prediction system (WEPS) includes a model for the decomposition of crop residue. It simulates the fall rate of standing residue and the decomposition of standing and flat residue as a function of temperature and moisture. It also calculates residue cover from flat residue mass. Most of the data used to develop and parameterize this model have been collected in the southern USA. We compared WEPS-simulated residue cover with that measured in south-central North Dakota for 50 two-year cropping sequences from nine crops species that were grown using no-till management. Measured data included residue mass at the time of harvest and residue cover just after seeding the next spring.
  • Authors:
    • Jones, C. A.
    • Buschena, D. E.
    • Miller, P. R.
    • Holmes, J. A.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 3
  • Year: 2008
  • Summary: Transition to no-till (NT) and organic (ORG) farming systems may enhance sustainability. Our objectives were to compare transitional crop productivity and soil nutrient status among diversified NT and ORG cropping systems in Montana. Three NT systems were designed as 4-yr rotations, including a pulse (lentil [ Lens culinaris Medik.] or pea [ Pisum sativum L.]), an oilseed (canola [ Brassica napus L.] or sunflower [ Helianthus annuus L.]) and two cereal crops (corn [ Zea mays L.], proso millet [ Panicum miliaceum L.], or wheat [ Triticum aestivum L.]). No-till continuous wheat was also included. The ORG system included a green manure (pea), wheat, lentil, and barley ( Hordeum vulgare L.) and received no inputs. Winter wheat in the ORG system yielded equal or greater than in the NT systems, and had superior grain quality, even though 117 kg N ha -1 was applied to the NT winter wheat. After 4 yr, soil nitrate-N and Olsen-P were 41 and 14% lower in the ORG system, whereas potentially mineralizable N was 23% higher in the ORG system. After 4 yr, total economic net returns were equal between NT and ORG systems on a per-ha basis. Studying simultaneous transition to diversified NT and ORG cropping systems was instructive for increased sustainability.
  • Authors:
    • Nelson, R. G.
    • Larson, J. A.
    • De La Torre Ugarte, D. G.
    • Marland, g.
    • Tyler, D. D.
    • Hellwinckel, C. M.
    • Wilson, B. S.
    • Brandt, C. C.
    • West, T. O.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 2
  • Year: 2008
  • Summary: To manage lands locally for C sequestration and for emissions reductions, it is useful to have a system that can monitor and predict changes in soil C and greenhouse gas emissions with high spatial resolution. We are developing a C accounting framework that can estimate C dynamics and net emissions associated with changes in land management. One component of this framework integrates field measurements, inventory data, and remote sensing products to estimate changes in soil C and to estimate where these changes are likely to occur at a subcounty (30- by 30-m) resolution. We applied this framework component to a midwestern region of the United States that consists of 679 counties approximately centered around Iowa. We estimated the 1990 baseline soil C to a maximum depth of 3 m for this region to be 4117 Tg. Cumulative soil C accumulation of 70.3 Tg was estimated for this region between 1991 and 2000, of which 33.8 Tg is due to changes in tillage intensity. Without accounting for soil C loss following changes to more intensive tillage practices, our estimate increases to 45.0 Tg C. This difference indicates that on-site permanence of soil C associated with a change to less intensive tillage practices is approximately 75% if no additional economic incentives are provided for soil C sequestration practices. This C accounting framework offers a method to integrate inventory and remote sensing data on an annual basis and to transparently account for alternating annual trends in land management and associated C stocks and fluxes.
  • Authors:
    • Kay, B. D.
    • Wander, M. M.
    • Drury, C. F.
    • Yang, X. M.
  • Source: Pedosphere
  • Volume: 18
  • Issue: 4
  • Year: 2008
  • Summary: Three long-term field trials in humid regions of Canada and the USA were used to evaluate the influence of soil depth and sample numbers on soil organic carbon (SOC) sequestration in no-tillage (NT) and moldboard plow (MP) corn (Zea mays L.) and soybean (Glycine max L.) production systems. The first trial was conducted on a Maryhill silt loam (Typic Hapludalf) at Elora, Ontario, Canada, the second on a Brookston clay loam (Typic Argiaquoll) at Woodslee, Ontario, Canada, and the third on a Thorp silt loam (Argiaquic Argialboll) at Urbana, Illinois, USA. No-tillage led to significantly higher SOC concentrations in the top 5 cm compared to MP at all 3 sites. However, NT resulted in significantly lower SOC in sub-surface soils as compared to MP at Woodslee (10-20 cm, P = 0.01) and Urbana (20-30 cm, P < 0.10). No-tillage had significantly more SOC storage than MP at the Elora site (3.3 Mg C ha(-1)) and at the Woodslee site (6.2 Mg C ha(-1)) on an equivalent mass basis (1350 Mg ha(-1) soil equivalent mass). Similarly, NT had greater SOC storage than NIP at the Urbana site (2.7 Mg C ha(-1)) on an equivalent mass basis of 675 Mg ha-1 soil. However, these differences disappeared when the entire plow layer was evaluated for both the Woodslee and Urbana sites as a result of the higher SOC concentrations in NIP than in NT at depth. Using the minimum detectable difference technique, we observed that up to 1500 soil sample per tillage treatment comparison will have to be collected and analyzed for the Elora and Woodslee sites and over 40 soil samples per tillage treatment comparison for the Urbana to statistically separate significant differences in the SOC contents of sub-plow depth soils. Therefore, it is impracticable, and at the least prohibitively expensive, to detect tillage-induced differences in soil C beyond the plow layer in various soils.
  • Authors:
    • Archer, D. W.
    • Halvorson, A. D.
    • Reule, C. A.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 4
  • Year: 2008
  • Summary: Conversion of irrigated cropland from conventional tillage (CT) to no-till (NT) could have several environmental benefits including reduced erosion potential, reduction of greenhouse gas emissions, and conservation of water. However NT must be economically viable if it is to be adopted. Costs of production and economic returns were evaluated for an irrigated, continuous corn ( Zea mays L.) system under CT and NT over 6 yr on a clay loam soil in northern Colorado. Yield responses to N fertilization were included to determine economic optimum fertilization rates under each tillage system. Corn grain yields at economic optimum N fertilizer rates were 1.1 to 1.4 Mg ha -1 lower for NT than for CT. However, net returns were $46 to 74 ha -1 higher for NT than for CT due to reductions in operating costs of $57 to 114 ha -1 and reductions in machinery ownership costs of $87 to 90 ha -1. Operating cost savings were realized largely due to fuel and labor reductions of 75% and 71 to 72%, respectively, and in spite of higher N fertilizer requirements of 16 to 55 kg ha -1 for NT compared to CT. No-till, irrigated, continuous corn appears to be an economically viable option for replacing CT production systems in the central Great Plains, especially when combined with the environmental benefits of the NT system.
  • Authors:
    • Ahuja, L. R.
    • Saseendran, S. A.
    • Ma, L.
    • Trout, T.
    • Nielsen, D. C.
  • Source: World Environmental and Water Resources Congress 2008
  • Year: 2008
  • Summary: Most of the agriculture in the Great Plains and western U.S. is water-limited, consisting of rain-fed, dry-land, cropping systems or range-livestock systems and some irrigated cropping systems where irrigation water is available. Prolonged drought in the last few years has aggravated the situation, and greater frequency of severe droughts predicted by global climate change models is a cause for great concern, especially for dry-land systems. At the same time, the increasing water demands for drinking, sanitation, urban irrigation, industry, and environmental uses are outbidding and reducing the irrigation water available for agriculture. Similar situation exists in many other arid to semi-arid parts of the world. To obtain maximum return out of limited rainfall and irrigation water, with minimum environmental impact, the producers need whole-system and quantitative management tools to help them optimize the use of available water and minimize associated inputs on site-specific and field-specific basis. The tools should help determine appropriate crop sequences, and optimize the use of limited rainfall and irrigation water with respect to the amounts and timings of rainfall, critical growth stages of crop, soil fertility, and weather conditions; help determine an optimal selection of alternate crops during droughts; and an optimal allocation of limited water among crops. There is currently great excitement about growing bio-energy crops in the area, including the dry-land oil seed crops and irrigated corn or other biomass crops. The above tools should also be able to evaluate the long-term economics of bio-energy crops while leaving enough crop residues on the soil to maintain soil organic matter.
  • Authors:
    • Bridges, M.
    • Henry, W. B.
    • Shaner, D. L.
    • Khosla, R.
    • Westra, P.
    • Reich, R.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 6
  • Year: 2008
  • Summary: An area of interest in precision farming is variable-rate application of herbicides to optimize herbicide use efficiency and minimize negative off-site and non-target effects. Site-specific weed management based on field scale management zones derived from soil characteristics known to affect soil-applied herbicide efficacy could alleviate challenges posed by post-emergence precision weed management. Two commonly used soil-applied herbicides in dryland corn ( Zea mays L.) production are atrazine and metolachlor. Accelerated dissipation of atrazine has been discovered recently in irrigated corn fields in eastern Colorado. The objectives of this study were (i) to compare the rates of dissipation of atrazine and metolachlor across different soil zones from three dryland no-tillage fields under laboratory incubation conditions and (ii) to determine if rapid dissipation of atrazine and/or metolachlor occurred in dryland soils. Herbicide dissipation was evaluated at time points between 0 and 35 d after soil treatment using a toluene extraction procedure with GC/MS analysis. Differential rates of atrazine and metolachlor dissipation occurred between two soil zones on two of three fields evaluated. Accelerated atrazine dissipation occurred in soil from all fields of this study, with half-lives ranging from 1.8 to 3.2 d in the laboratory. The rapid atrazine dissipation rates were likely attributed to the history of atrazine use on all fields investigated in this study. Metolachlor dissipation was not considered accelerated and exhibited half-lives ranging from 9.0 to 10.7 d in the laboratory.