• Authors:
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 5
  • Year: 2011
  • Summary: Soil organic matter (SOM) is commonly used as an indicator of soil quality, with different fractions being used as indices to measure changes in SOM caused by management. The objective of this study was to compare whether selected SOM fractions exhibited sensitivity to short-term changes in management. The experiment was conducted for similar to 3 yr as a split-split-plot design with crop rotation as the whole-plot treatment factor, tillage as the subplot treatment factor, and cover crop management as the sub-subplot treatment factor. Soil samples were collected at the 0- to 15-cm depth. Soil organic C (SOC) and N, particulate organic matter (POM), free light fraction (FLF), Illinois soil N test (ISNT), and easily oxidizable C (EOC) were tested as possible sensitive indices to changes in management. The stable fraction SOC was only affected by cover crop management, while C and N contents and C/N ratio of the labile POM and FLF fractions were affected by additional management practices. Between POM and FLF, the latter was the most sensitive, with cover crop management having the greatest effect. Because FLF is chemically and structurally closer to plant residues than POM, the sensitivity rank position of these fractions would probably be at least more similar if only tillage management was considered. In addition, the lack of sensitivity of ISNT and EOC to any tested management practice is added to previous studies that have raised questions of the representation of the labile SOM pool through these fractions.
  • Authors:
    • Maul, J. E.
    • Meisinger, J. J.
    • Cavigelli, M. A.
    • Spargo, J. T.
    • Mirsky, S. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 90
  • Issue: 2
  • Year: 2011
  • Summary: Sustainable soil fertility management depends on long-term integrated strategies that build and maintain soil organic matter and mineralizable soil N levels. These strategies increase the portion of crop N needs met by soil N and reduce dependence on external N inputs required for crop production. To better understand the impact of management on soil N dynamics, we conducted field and laboratory research on five diverse management systems at a long-term study in Maryland, the USDA- Agricultural Research Service Beltsville Farming Systems Project (FSP). The FSP is comprised of a conventional no-till corn ( Zea mays L.)-soybean ( Glycine max L.)-wheat ( Triticum aestivum L.)/double-crop soybean rotation (NT), a conventional chisel-till corn-soybean-wheat/soybean rotation (CT), a 2 year organic corn-soybean rotation (Org2), a 3 year organic corn-soybean-wheat rotation (Org3), and a 6 year organic corn-soybean-wheat-alfalfa ( Medicago sativa L.) (3 years) rotation (Org6). We found that total potentially mineralizable N in organic systems (average 315 kg N ha -1) was significantly greater than the conventional systems (average 235 kg N ha -1). Particulate organic matter (POM)-C and -N also tended to be greater in organic than conventional cropping systems. Average corn yield and N uptake from unamended (minus N) field microplots were 40 and 48%, respectively, greater in organic than conventional grain cropping systems. Among the three organic systems, all measures of N availability tended to increase with increasing frequency of manure application and crop rotation length (Org2 < Org3 ≤ Org6) while most measures were similar between NT and CT. Our results demonstrate that organic soil fertility management increases soil N availability by increasing labile soil organic matter. Relatively high levels of mineralizable soil N must be considered when developing soil fertility management plans for organic systems.
  • Authors:
    • Lal, R.
    • Stavi, I.
  • Source: Geomorphology
  • Volume: 125
  • Issue: 1
  • Year: 2011
  • Summary: Erosion and deposition processes affect the physical quality of the soil. Thus, the objective of this study was to assess the effects of these processes on a long-term no-till corn agroecosystem in a humid-temperate region of the Midwest U.S. The study was conducted under on-farm conditions, in a field which experiences erosional and depositional processes. At the end of the dormant season, soil characteristics were tested for two depths (0-5 and 5-10 cm) in uneroded (UN), eroded (ER), and depositional (DP) sites. The data showed that UN and ER were characterized by the highest and lowest soil shear strength (137.3 and 78.1 KPa, respectively) and organic carbon concentration (35.6 and 30.3 g kg -1, respectively). The highest and lowest aggregate stability (85.4% and 73.6%, respectively) and mean weight diameter (2.9 and 1.6 mm, respectively) were observed in UN and DP. The highest and lowest penetration resistance (4.82 and 4.57 MPa, respectively) and bulk density (1.49 and 1.33 Mg m -3, respectively) were measured in ER and DP. An opposite trend was observed for the C:N ratio (8.2 and 9.6, respectively), and the value's color variable (4.6 and 4.9, respectively). No significant differences among the erosional phases were measured in the soil's total nitrogen concentration, hue and chroma color variables, texture, hydraulic conductivity, and intrinsic permeability. The erodibility factor was the lowest and highest in DP and ER (0.00326 and 0.00397 Mg ha h ha -1 MJ -1 mm -1, respectively), and the effect of erosional phase on this factor was close to significant. In general, the effect of erosion and deposition on soil characteristics decreased with an increase in soil depth. This study suggests that the occurrence of positive feedbacks in ER and DP have led to accelerated erosional and depositional processes and the continuous degradation of the soil quality. A range of management practices should be considered in order to mitigate these processes and reduce negative impact on crop yields in such agroecosystems.
  • Authors:
    • Stavi,I.
    • Lal,R.
    • Owens,L. B.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 3
  • Year: 2011
  • Summary: Contrary to earlier studies, this study suggests that even one year of tillage within a long-term no-till agroecosystem adversely affected the soil quality, with possible negative impact on crop yields. Worldwide interest in conservation tillage is increasing, because conventional tillage adversely impacts the long-term quality of the soil and its vulnerability to erosion. No-till agriculture minimizes adverse impacts of an intensive arable land use. In some cases, occasional tillage is used as a means of weed or pathogen control. Therefore, this study was conducted in eastern Ohio to examine soil quality as affected by occasional tillage, i.e. disk plowed every 3-4 years, within a long-term no-till agroecosystem. The study compared the soil characteristics between two fields, both under corn ( Zea mays L.) at the time of the study. Soil properties were studied for three depths of 0-6, 6-12, and 12-18 cm. Compared with the continuous no-till field, the field under occasional tillage had significantly higher bulk density of 1.45 versus 1.31 gcm -3, and somewhat higher soil penetration resistance of 1.77 versus 1.56 MPa. Also, compared with the no-till field, the field under occasional tillage had significantly lower water stable aggregate of 475 versus 834 gkg -1, mean weight diameter of 1.4 versus 3.4 mm, field moisture capacity of 293 versus 360 gkg -1, equilibrium infiltration rate of 2.0 versus 6.7 mm min -1, and cumulative infiltration of 353.4 versus 1,211.8 mm. The field under occasional tillage had somewhat lower soil organic carbon of 16.0 versus 19.2 gkg -1, soil water sorptivity of 16.3 versus 36.5 mm min -0.5, and transmissivity of 2.1 versus 4.9 mm min -1. The occasional tillage had no effect on the soil shear strength. In general, the effect of tillage on soil properties decreased with increase in soil depth. Also corn yields were compared between the two agroecosystems. Compared with the no-till field, the field under occasional tillage had significantly lower grain moisture content of 22.4 versus 28.2%, and somewhat lower wet stover biomass of 14.6 versus 20.2 Mg ha -1, wet corn ear yield of 10.0 versus 11.4 Mg ha -1, and dry grain yield of 8.2 versus 9.4 Mg ha -1. As contrasted with earlier studies which were conducted under controlled research plots, this study was conducted under on-farm conditions.
  • Authors:
    • Shah, Z.
    • Stromberger, M. E.
    • Westfall, D. G.
  • Source: Soil Biology and Biochemistry
  • Volume: 43
  • Issue: 1
  • Year: 2011
  • Summary: The need to identify microbial community parameters that predict microbial activity is becoming more urgent, due to the desire to manage microbial communities for ecosystem services as well as the desire to incorporate microbial community parameters within ecosystem models. In dryland agroecosystems, microbial biomass C (MBC) can be increased by adopting alternative management strategies that increase crop residue retention, nutrient reserves, improve soil structure and result in greater water retention. Changes in MBC could subsequently affect microbial activities related to decomposition, C stabilization and sequestration. We hypothesized that MBC and potential microbial activities that broadly relate to decomposition (basal and substrate-induced respiration, N mineralization, and beta-glucosidase and arylsulfatase enzyme activities) would be similarly affected by no-till, dryland winter wheat rotations distributed along a potential evapotranspiration (PET) gradient in eastern Colorado. Microbial biomass was smaller in March 2004 than in November 2003 (417 vs. 231 g g -1 soil), and consistently smaller in soils from the high PET soil (191 g g -1) than in the medium and low PET soils (379 and 398 g g -1, respectively). Among treatments, MBC was largest under perennial grass (398 g g -1). Potential microbial activities did not consistently follow the same trends as MBC, and the only activities significantly correlated with MBC were beta-glucosidase ( r=0.61) and substrate-induced respiration ( r=0.27). In contrast to MBC, specific microbial activities (expressed on a per MBC basis) were greatest in the high PET soils. Specific but not total activities were correlated with microbial community structure, which was determined in a previous study. High specific activity in low biomass, high PET soils may be due to higher microbial maintenance requirements, as well as to the unique microbial community structure (lower bacterial-to-fungal fatty acid ratio and lower 17:0 cy-to-16:1omega7c stress ratio) associated with these soils. In conclusion, microbial biomass should not be utilized as the sole predictor of microbial activity when comparing soils with different community structures and levels of physiological stress, due to the influence of these factors on specific activity.
  • Authors:
    • Kravchenko, A. N.
    • Mokma, D. L.
    • Corbin, A. T.
    • Syswerda, S. P.
    • Robertson, G. P.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 1
  • Year: 2011
  • Summary: Soil C sequestration research has historically focused on the top 0 to 30 cm of the soil profile, ignoring deeper portions that might also respond to management. In this study we sampled soils along a 10-treatment management intensity gradient to a 1-m depth to test the hypothesis that C gains in surface soils are offset by losses lower in the profile. Treatments included four annual cropping systems in a corn ( Zea mays)-soybean ( Glycine max)-wheat ( Triticum aestivum) rotation, perennial alfalfa ( Medicago sativa) and poplar ( Populus * euramericana), and four unmanaged successional systems. The annual grain systems included conventionally tilled, no-tillage, reduced-input, and organic systems. Unmanaged treatments included a 12-yr-old early successional community, two 50-yr-old mid-successional communities, and a mature forest never cleared for agriculture. All treatments were replicated three to six times and all cropping systems were 12 yr post-establishment when sampled. Surface soil C concentrations and total C pools were significantly greater under no-till, organic, early successional, never-tilled mid-successional, and deciduous forest systems than in the conventionally managed cropping system ( p≤0.05, n=3-6 replicate sites). We found no consistent differences in soil C at depth, despite intensive sampling (30-60 deep soil cores per treatment). Carbon concentrations in the B/Bt and Bt2/C horizons were lower and two and three times more variable, respectively, than in surface soils. We found no evidence for C gains in the surface soils of no-till and other treatments to be either offset or magnified by carbon change at depth.
  • Authors:
    • Sirrine, J. R.
    • Simonson, P.
    • Hoagland, L. A.
    • Darby, H.
    • Benedict, C. A.
    • Turner, S. F.
    • Murphy, K. M.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Hop cones grown on the female plant of the perennial crop ( Humulus lupulus L.) are an integral component of the brewing process and provide flavor, bitterness, aroma, and antimicrobial properties to beer. Demand for organically grown hops from consumers via the brewing industry is on the rise; however, due to high N requirements and severe disease, weed, and arthropod pressures, hops are an extremely difficult crop to grow organically. Currently, the majority of the world's organic hops are grown in New Zealand, while other countries, including China, are beginning to increase organic hop production. Land under organic hop production in Washington State, where 75% of the hops in the United States are grown, increased from 1.6 ha to more than 26 ha from 2004 to 2010, and other hop-producing states demonstrate a similar trend. Removing hops from the USDA Organic Exemption list in January 2013 is expected to greatly increase organic hop demand and will require corresponding increases in organic hop hectarage. Current challenges, including weed management, fertility and irrigation management, insect and disease pressures, and novel practices that address these issues will be presented. Here, we discuss current and future research that will potentially impact organic hop production in the United States.
  • Authors:
    • Zahoor, A.
    • Fujimaki, H.
    • Andry, H.
    • Inoue, M.
    • Uzoma, K. C.
    • Nishihara, E.
  • Source: Soil Use and Management
  • Volume: 27
  • Issue: 2
  • Year: 2011
  • Summary: In this study, we performed a greenhouse experiment to investigate the effect of cow manure biochar on maize yield, nutrient uptake and physico-chemical properties of a dryland sandy soil. Biochar was derived from dry cow manure pyrolysed at 500 degrees C. Cow manure biochar was mixed with a sandy soil at the rate equivalent to 0, 10, 15 and 20 t biochar per hectare. Maize was used as a test crop. Results of the study indicated that cow manure biochar contains some important plant nutrients which significantly affected the maize crop growth. Maize yield and nutrient uptake were significantly improved with increasing the biochar mixing rate. Application of biochar at 15 and 20 t/ha mixing rates significantly increased maize grain yield by 150 and 98% as compared with the control, respectively. Maize net water use efficiency (WUE) increased by 6, 139 and 91% as compared with the control, with the 10, 15 and 20 t/ha mixing rate, respectively. Nutrient uptake by maize grain was significantly increased with higher biochar applications. Application of cow manure biochar improved the field-saturated hydraulic conductivity of the sandy soil, as a result net WUE also increased. Results of the soil analysis after the harvesting indicated significant increase in the pH, total C, total N, Oslen-P, exchangeable cations and cation exchange capacity. The results of this study indicated that application of cow manure biochar to sandy soil is not only beneficial for crop growth but it also significantly improved the physico-chemical properties of the coarse soil.
  • Authors:
    • Strickland, G. L.
    • Epplin, F. M.
    • Varner, B. T.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: The majority of cropland in the Southwest Oklahoma Agricultural Statistics District is tilled and seeded to continuous monoculture winter wheat (Triticum aestivum L.). This study was conducted to determine the expected yield and expected net returns of wheat, cotton (Gossypium hirsutum L.), and grain sorghum [Sorghum bicolor (L.) Moench], under two production systems, no-till (NT) and tilled (TL), and to determine the most risk-efficient system. The effect of tillage was investigated over 6 yr at Altus, OK, on a Hollister silty clay loam (fine, smectitic, thermic Typic Haplusterts) soil. Wheat and cotton yields were not different between tillage systems. Sorghum NT yielded significantly more than TL sorghum (P <= 0.05). Wheat NT produced the greatest expected net return to land, labor, overhead, and management ($217 ha(-1) yr(-1)). Tilled grain sorghum was the least profitable system (-$42 ha(-1) yr(-1)). Wheat NT required additional expenditures for herbicides ($15 ha(-1)), less for machinery fuel, lube, and repairs ($22 ha(-1)), and less ($23 ha(-1)) for machinery fixed costs. Net returns were slightly greater ($18 ha(-1)) for NT wheat than for TL wheat. However, since NT wheat yields were more variable, TL wheat may be preferred by risk-averse producers. Estimated machinery labor savings from switching from TL to NT wheat were 0.588 h ha(-1) or 609 h yr(-1) for a 1036 ha farm. The decision to switch from TL to NT wheat depends on risk preferences, and on the potential to use saved labor productively elsewhere, or to farm more land.
  • Authors:
    • Wilhelm, W. W.
    • Varvel, G. E.
  • Source: Soil & Tillage Research
  • Volume: 114
  • Issue: 1
  • Year: 2011
  • Summary: Emphasis and interest in carbon (C) and nitrogen (N) storage (sequestration) in soils has greatly increased in the last few years, especially C with its' potential to help alleviate or offset some of the negative effects of the increase in greenhouse gases in the atmosphere. Several questions still exist with regard to what management practices optimize C storage in the soil profile. A long-term rainfed study conducted in eastern Nebraska provided the opportunity to determine both the effects of different tillage treatments and cropping systems on soil N and soil organic C (SOC) levels throughout the soil profile. The study included six primary tillage systems (chisel, disk, plow, no-till, ridge-till, and subtill) with three cropping systems [continuous corn (CC), continuous soybean (CSB), and soybean-corn (SB-C)]. Soil samples were collected to a depth of 150-cm in depth increments of 0-15-, 15-30-, 15-30-, 30-60-, 60-90-, 90-120-, and 120-150-cm increments and composited by depth in the fall of 1999 after harvest and analyzed for total N and SOC. Significant differences in total N and SOC levels were obtained between tillage treatments and cropping systems in both surface depths of 0-15-, 15-30-cm, but also in the 30-60-cm depth. Total N and SOC accumulations throughout the profile (both calculated by depth and for equivalent masses of soil) were significantly affected by both tillage treatment and cropping system, with those in no-till the greatest among tillage treatments and those in CC the greatest among cropping systems. Soil N and SOC levels were increased at deeper depths in the profile, especially in those tillage systems with the least amount of soil disturbance. Most significant was the fact that soil N and SOC was sequestered deeper in the profile, which would strongly suggest that N and C at these depths would be less likely to be lost if the soil was tilled.