• Authors:
    • Arnold, J. G.
    • Jin, V. L.
    • Johnson, M. V. V.
    • Haney, R. L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 3-4
  • Year: 2011
  • Summary: The effects of biosolids application rate and history on soil potential C and N mineralization were measured over a 112-day laboratory incubation. Soils were collected from a large-scale biosolids recycling operation that surface-applies anaerobically digested Class B biosolids for commercial forage production. Five treatments were evaluated: unamended control; 22 Mg dry biosolids ha -1 y -1 applied for 25 years; 22, 45, and 67 Mg ha -1 y -1 applied for 8 years. Biosolids additions enhanced total soil organic C by 32-92% and total N by 30-157% compared to unamended soils. Total N increased with application rate and was dominated by nitrate-N. Potential C mineralization (cumulative CO 2 produced) was 11-62% greater in amended soils compared to controls and highest at 67 Mg ha -1 y -1. Net N mineralization and immobilization were highest early in the incubation for 45 and 67 Mg ha -1 y -1 treatments. No significant differences in potential C and N mineralization between controls and soils amended at the lowest rate for 8 or 25 years suggests that biosolids applications at 22 Mg ha -1 y -1 are sustainable over the long-term. Higher potential N mineralization rates and soil nitrate concentrations under higher application rates may increase the risk of off-site nutrient transport and requires further evaluation.
  • Authors:
    • Kaspar, T. C.
    • Parkin, T. B.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 6
  • Year: 2011
  • Summary: Measurements of soil CO 2 flux in the absence of living plants can be used to evaluate the effectiveness of soil management practices for C sequestration, but field CO 2 flux is spatially variable and may be affected by soil compaction and the percentage of total pore space filled with water (%WFPS). The objectives of our study were: (i) to evaluate the effect of wheel traffic compaction on CO 2 flux at two landscape positions with differing soil properties; and (ii) to examine the relationship of CO 2 flux and %WFPS under field conditions and a wide range of soil porosities. Carbon dioxide flux was measured near Ames, IA, in a no-till system without living plants using the closed chamber method on nine cylinders inserted into the soil at each measurement site and evenly spaced across three rows, an untracked interrow, and a tracked interrow. Flux, volumetric water contents, and soil temperature were measured on 12 or 13 d between day of the year (DOY) 164 and 284 in 2001, 2004, and 2005. Bulk density, soil organic C concentration, and soil texture were determined after DOY 284. On most days, CO 2 flux was less in the tracked interrow than in the row or untracked interrow positions. In all 3 yr, the cumulative flux of the tracked position was significantly less than one or both of the other positions. Landscape position did not affect the response of CO 2 flux to traffic. Percentage water-filled pore space was not a good predictor of surface CO 2 flux in the field. The effect of wheel traffic compaction on CO 2 flux should be considered when soil CO 2 flux is used to compare management practices.
  • Authors:
    • Kocyigit, R.
    • Rice ,C. W.
  • Source: Bulgarian Journal of Agricultural Science
  • Volume: 17
  • Issue: 4
  • Year: 2011
  • Summary: The soil surface CO 2 flux is the second largest flux in the terrestrial carbon budget after photosynthesis. Plant root and microbial respiration produce CO 2 in soils, which are important components of the global C cycle. This study determined the amount of CO 2 released during spring wheat ( Triticum aestivum L.) growth under no-till (NT) and conventional tillage (CT) systems. This experiment was conducted at Kansas State University North Agronomy Farm, Manhattan, KS, on a Kennebec silt loam. This study site was previously under dry land continuous corn production with NT and CT for more than 10 years. Spring wheat ( Triticum aestivum L.) was planted with two tillage systems (NT and CT) as four replicates in March. Surface CO 2 flux was measured weekly during plant growth. Soil water content at the surface (5 cm) tended to be greater in NT and decreased from planting to harvest. Soil microbial activity at the surface was usually higher in NT and decreased from planting to harvest, while activity was constant in the deeper depths. The higher microbial activity at the surface of NT occurred after 60 days of planting where soil water content was the most limiting factor on microbial activity. Soil CO 2 flux varied in response to changes in soil water content and the variation and magnitude of the increase was greater at higher soil water contents. Conventional tillage released 20% more CO 2 to the atmosphere compare to NT after 10 years in the North American Great Plains Regions.
  • Authors:
    • Kussman, R. D.
    • Kremer, R. J.
  • Source: Agroforestry Systems
  • Volume: 83
  • Issue: 2
  • Year: 2011
  • Summary: Intercropping alleys in agroforestry provides an income source until the tree crop produces harvestable yields. However, cultivation of annual crops decreases soil organic matter and increases soil erosion potential, especially on sloping landscapes. Perennial crops maintain a continuous soil cover, increase water infiltration, reduce soil erosion, and improve overall soil quality. The objective of this on-farm study was to assess the effects of a perennial legume, kura clover ( Trifolium ambiguum M. Bieb.), on soil quality in a recently established pecan ( Carya illinoinensis Wangenh. C. Koch) orchard. The pecan-kura clover agroforestry practice was established on deep loess soils of the Missouri River hills landscape. These silt loams are on 2-20% slopes and can be highly erosive. Kura clover, introduced as the alley crop 5 years after pecan planting, was selected based on its perennial growth habit, nitrogen-fixing ability, winter hardiness, high forage quality, and soil conservation properties. Kura clover was seeded in 2001 and harvested for hay annually beginning 2003. Soil quality indicators of total organic C, total N, water-stable aggregates, and selected soil enzymes were determined on surface soil samples collected annually after kura clover establishment. Soil organic C and activities of soil enzymes increased compared with cultivated and grass pasture control soils by the eighth year of establishment. Water-stable aggregation improved by 50% and surface soil shear strength improved significantly ( P<0.05) in alleys compared with control sites. Results illustrate that kura clover as the alley-cropped component improved soil fertility and biological activity through increased organic matter and improved soil structure, and yielded high quality forage valuable for the cattle-feeding operation. Kura clover maintained or improved soil quality, reduced soil erosion potential, and benefited pecan growth by providing a source of soil nitrogen and improving soil structure for adequate water infiltration and aeration.
  • Authors:
    • Lewis, D. B.
    • Kaye, J. P.
    • Jabbour, R.
    • Barbercheck, M. E.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 26
  • Issue: 4
  • Year: 2011
  • Summary: Weed management is one of the primary challenges for producers transitioning from conventional to organic agriculture. Tillage and the use of cover crops are two weed control tactics available to farmers transitioning to organic management, but little is known about their interactive effects on soil quality during the transition period. We investigated the response of soils to tillage and initial cover crop during the 3-year transition to organic in a cover crop-soybean ( Glycine max)-maize ( Zea mays) rotation in the Mid-Atlantic region of the USA. The tillage treatment contrasted full, inversion tillage with moldboard plowing (FT) versus reduced tillage with chisel plowing (RT). The cover crop treatment contrasted annual versus mostly perennial species during the first year of the rotation. The experiment was initiated twice (Start 1 and Start 2), in consecutive years in adjacent fields. By the end of the experiment, labile carbon, electrical conductivity, pH and soil moisture were all greater under RT than under FT in both starts. Soil organic matter and several other soil attributes were greater under RT than under FT in Start 1, but not in Start 2, perhaps owing to differences between starts in initial field conditions and realized weather. Soil attributes did not differ between the two cover crop treatments. Combining our soils results with agronomic and economic analyses on these plots suggests that using RT during the organic transition can increase soil quality without compromising yield and profitability.
  • Authors:
    • Liesch, A. M.
    • Krueger, E. S.
    • Ochsner, T. E.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Soils under continuous corn (Zea mays L.) silage production are oft en subjected to heavy traffic and tillage, which can degrade soil structure and physical properties. Cover crops have been shown to benefit soil structure, but the effects of double-cropping on soil structure and physical properties are unknown. Our objective was to compare the soil structure and physical properties under rye (Secale cereale L.) and corn silage double-cropping with those under continuous corn silage in Minnesota during the 2007-2008 cropping year. A conventional tillage corn silage system served as the control. Double-crop treatments were conventional tillage winter rye harvested in May or June followed by no-till corn silage. Relative to the control, the double-cropping systems exhibited superior soil structure with up to 57% better visual soil structure scores and up to 16% smaller mean weight aggregate diameter. Visual soil structure scores exhibited seasonal dynamics with significant treatment effects in November and June but not in May when the structural assessment was conducted shortly after preplant tillage in the control. The double-cropping system increased the resilience of the soil to traffic. The saturated hydraulic conductivity in wheel-tracked interrows was 375% higher in the double-cropping system relative to the control in July. Both the rye and the absence of tillage before corn planting may have contributed to this improved resilience. Heavy traffic and tillage in continuous corn silage production systems can degrade soil structure and physical properties; however, the rye-corn silage double-cropping system provided a measure of protection.
  • Authors:
    • Liu, K.
    • Wiatrak, P.
  • Source: International Journal of Plant Production
  • Volume: 5
  • Issue: 4
  • Year: 2011
  • Summary: Nitrogen (N) application management needs to be refined for low yielding environments under dryland conditions. This 3-yr study examined nitrogen fertilization management effects on corn ( Zea mays L.) plant characteristics and grain yield in rain fed environment under conventional tillage system. Nitrogen fertilization management consisted of two timing methods of N application [all N at planting and as split with 35 kg N ha -1 applied at planting and remaining N applied at vegetative (V) 6 growth stage] and five N rates (0, 45, 90, 135, and 180 kg N ha -1). Insufficient rainfall at reproductive stage in 2008 and 2009 likely resulted in significant reduction of grain yield compared with grain yield in 2007, average 2.9 vs. 5.9 Mg ha -1. Grain yield increased with N application up to 45 kg ha -1; however, no further increase in N application resulted in increased yields. Plant height, ear height, relative chlorophyll (SPAD) content, and normalized difference vegetation index (NDVI) at reproductive (R 1) stage increased with increasing N rate up to 90, 90, 135, and 90 kg N ha -1, respectively. Corn grain yield significantly correlated with plant height at R 1, SPAD at V 8, NDVI and LAI at V 8 and R 1 stage. The combination of plant height, NDVI, and LAI of R 1 stage explained most of the variability of grain yield (r-square=0.71). The fertilization timing had no effect on corn grain yield and plant characteristics. These observations showed that applying more than 45 kg N ha -1 to corn under dryland conditions with insufficient rainfall, especially during corn pollination, may not significantly increase grain yields.
  • Authors:
    • Machado, S.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: Use of crop residues for biofuel production raises concerns on how removal will impact soil organic carbon (SOC). Information on the effects on SOC is limited and requires long-term experimentation. Fortunately, Pendleton long-term experiments (LTEs), dating to the 1930s, provide some answers. This study compared crop residue inputs and SOC balance in conventional tillage (CT) winter wheat ( Triticum aestivum L.)-summer fallow (WW-SF) systems with annual rotation of WW and spring pea ( Pisum sativum L.). The WW-SF consisted of crop residue (CR-LTE) (0-90 N ha -1 yr -1, 11.2 Mg ha -1 yr -1 of steer ( Bos taurus) manure and 1.1 Mg ha -1 yr -1) of pea vines additions, residue burning, and tillage fertility (TF-LTE) (tillage-plow, disc, sweep, and N (0-180 kg ha -1)). Winter wheat-pea (WP-LTE) rotation treatments included maxi-till (MT-disc/chisel), fall plow (FP), spring plow (SP), and no-till (NT). Soils were sampled (0-60-cm depth) at 10-yr intervals, and grain yield and residue data collected every year. In WW-SF systems, SOC was maintained only by manure addition and depleted at a rate of 0.22 to 0.42 Mg ha -1 yr -1 in other treatments. In WP-LTE, MT, FP, SP, and NT treatments increased SOC at the rate of 0.10, 0.11, 0.02, and 0.89 Mg ha -1 yr -1, respectively. Minimum straw biomass to maintain soil organic carbon (MSB) in the CR-LTE, TF-LTE, and WP-LTE was 7.8, 5.8, and 5.2 Mg ha -1 yr -1, respectively. Winter wheat-SF straw production was lower than MSB, therefore residue removal exacerbated SOC decline. Harvesting straw residues under NT continuous cropping systems is possible when MSB and conservation requirements are exceeded.
  • Authors:
    • Miyamoto, S.
    • Nesbitt, M.
  • Source: HortTechnology
  • Volume: 21
  • Issue: 5
  • Year: 2011
  • Summary: Soil salinity management is a factor for successful production of pecan ( Carya illinoinensis) in arid southwestern United States. An exploratory study was performed to evaluate the effect of various soil management practices on salt leaching in basin-irrigated orchards developed on alluvial soils (Torrifluvents, Entisols) of the middle Rio Grande Basin. The practices evaluated were ripping, minimum-till chiseling, and soil profile modification. For ripping, parabolic shanks were passed through the center section (4 to 8 ft wide) between each tree row to a depth ranging from 18 to 36 inches. Minimum-till chisels included 7- and 30-inch shanks, equipped with coulters to reduce break up of the ground surface. Soil profile modification consisted of trenching with a backhoe and profile mixing with a large excavator. The effectiveness of these methods was evaluated by measuring soil salinity and moisture in treated and untreated zones at 17 test sites. Both ripping and minimum-till deep chiseling helped improve salt leaching, and the effectiveness of salt leaching increased as working depths approach the thickness of the clayey layer. However, annual ripping of the center section of each tree row space may not provide wide enough zones to alleviate salt stress to the trees. Straight shanks prune but do not lift tree roots, thus appearing to be better suited for chiseling closer to tree rows. Soil profile modification was highly effective in leaching salts. From the view of minimizing soil aggregate destruction and of maintaining a leveled floor, minimum-till deep chiseling, followed by the use of sand-topdressing and minimum-till shallow chisels for maintenance may prove to be more desirable than conventional ripping, especially in soil types consisting of silty clay loam.
  • Authors:
    • Wood,C. W.
    • Price,A. J.
    • Mulvaney,M. J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Limited input producers may adopt no-till production if sufficient weed suppression can be achieved. High-biomass producing cover crops used in conjunction with organic mulches may provide sufficient weed control in no-till vegetable production. Our objective was to quantify weed suppression from a forage soybean summer cover crop and three types of organic mulches applied after collard ( Brassica oleracea L.) planting. Forage soybean residue did not suppress weeds, but mulches were generally effective. Broadleaf and sedge weeds decreased in population size over the three-year period, but grass weed management remained problematic until three years after conversion to no-till. Grass suppression was greater when mulches were applied after the first year. Collard yield, averaging 17,863 kg ha -1, was not affected by any cover crop or mulch treatment.