• Authors:
    • Blanco-Canqui, H.
  • Source: Soil Use and Management
  • Volume: 27
  • Issue: 1
  • Year: 2011
  • Summary: Soil water repellency (SWR) is an intrinsic and dynamic soil property that can influence soil hydrology and crop production. Although several land use systems have been shown to induce water repellency in soil, the specific effects of no-till cropping on SWR are poorly understood. This article reviews the impacts of no-till on SWR and identifies research needs. No-till cropping generally induces 1.5 to 40 times more SWR than conventional tillage, depending on soil type. This may result from near-surface accumulation of hydrophobic organic C compounds derived from crop residues, microbial activity and reduced soil disturbance. While large SWR may have adverse impacts on soil hydrology and crop production, the level of SWR under no-till relative to conventional tillage may contribute to aggregate stabilization and intra-aggregate C sequestration. More research is needed to discern the extent and relevance of no-till induced SWR. This includes: (1) further assessment of SWR under different tillage systems across a wide range of soil textures and climates, (2) comparison of the various methods for measuring SWR over a range of water contents, (3) inclusion of SWR in routine soil analysis and its use as a parameter to evaluate management impacts, (4) assessment of the temporal and spatial changes in SWR under field conditions, (5) further assessment of the impacts of the small differences in SWR between no-till and conventionally tilled soils on crop production, soil hydrology and soil C sequestration, and (6) development of models to predict SWR for different tillage systems and soils.
  • Authors:
    • Blanco-Canqui, H.
    • Mikha, M. M.
    • Presley, D. R.
    • Claassen, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Inclusion of cover crops (CCs) may be a potential strategy to boost no-till performance by improving soil physical properties. To assess this potential, we utilized a winter wheat ( Triticum aestivum L.)-grain sorghum [ Sorghum bicolor (L.) Moench] rotation, four N rates, and a hairy vetch (HV; Vicia villosa Roth) CC after wheat during the first rotation cycles, which was replaced in subsequent cycles with sunn hemp (SH; Crotalaria juncea L.) and late-maturing soybean [LMS; Glycine max (L.) Merr.] CCs in no-till on a silt loam. At the end of 15 yr, we studied the cumulative impacts of CCs on soil physical properties and assessed relationships between soil properties and soil organic C (SOC) concentration. Across N rates, SH reduced near-surface bulk density (rho b) by 4% and increased cumulative infiltration by three times relative to no-CC plots. Without N application, SH and LMS reduced Proctor maximum rho b, a parameter of soil compactibility, by 5%, indicating that soils under CCs may be less susceptible to compaction. Cover crops also increased mean weight diameter of aggregates (MWDA) by 80% in the 0- to 7.5-cm depth. The SOC concentration was 30% greater for SH and 20% greater for LMS than for no-CC plots in the 0- to 7.5-cm depth. The CC-induced increase in SOC concentration was negatively correlated with Proctor maximum rho b and positively with MWDA and cumulative infiltration. Overall, addition of CCs to no-till systems improved soil physical properties, and the CC-induced change in SOC concentration was correlated with soil physical properties.
  • Authors:
    • Blanco-Canqui, H.
    • Schlegel, A. J.
    • Heer, W. F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 144
  • Issue: 1
  • Year: 2011
  • Summary: No-till (NT) farming is considered as a potential strategy for sequestering C in the soil. Data on soil-profile distribution of C and related soil properties are, however, limited, particularly for semiarid regions. We assessed soil C pool and soil structural properties such as aggregate stability and strength to 1 m soil depth across three long-term (≥21 year) NT and conventional till (CT) experiments along a precipitation gradient in the central Great Plains of the USA. Tillage systems were in continuous winter wheat ( Triticum aestivum L.) on a loam at Hutchinson and winter wheat-sorghum [ Sorghum bicolor (L.) Moench]-fallow on silt loams at Hays and Tribune, Kansas. Mean annual precipitation was 889 mm for Hutchinson, 580 mm for Hays, and 440 mm for Tribune. Changes in profile distribution of soil properties were affected by differences in precipitations input among the three sites. At Hutchinson, NT had 1.8 times greater SOC pool than CT in the 0-2.5-cm depth, but CT had 1.5 times greater SOC pool in the 5-20-cm. At Hays, NT had 1.4 times greater SOC pool than CT in the 0-2.5-cm depth. Differences in summed SOC pool for the whole soil profile (0-1 m depth) between NT and CT were not significant at any site. The summed SOC pool with depth between NT and CT were only significant above the 5 cm depth at Hutchinson and 2.5 cm depth at Hays. At Hutchinson, NT stored 3.4 Mg ha -1 more SOC than CT above 5 cm depth. At Hays, NT stored 1.35 Mg ha -1 more SOC than CT above 2.5 cm depth. Moreover, NT management increased mean weight diameter of aggregates (MWDA) by 3 to 4 times for the 0-5-cm depth at Hutchinson and by 1.8 times for the 0-2.5-cm depth at Hays. It also reduced air-dry aggregate tensile strength (TS) for the 0-5-cm depth at Hutchinson and Hays and for the 0-2.5-cm depth at Tribune. The TS ( r=-0.73) and MWDA ( r=0.81) near the soil surface were more strongly correlated with SOC concentration at Hutchinson than at Hays and Tribune attributed to differences in precipitation input. Results suggested NT impacts on increasing SOC pool and improving soil structural properties decreased with a decrease in precipitation input. Changes in soil properties were larger at Hutchinson (880 mm of precipitation) than at Hays and Tribune (≤580 mm). While NT management did not increase SOC pool over CT for the whole soil profile, the greater near-surface accumulation of SOC in NT than in CT was critical to the improvement in soil structural properties. Overall, differences in precipitation input among soils appeared to be the dominant factor influencing NT impacts on soil-profile distribution of SOC and soil structural properties in this region.
  • Authors:
    • Blanke, M. M.
  • Source: Acta Horticulturae
  • Issue: 916
  • Year: 2011
  • Summary: Technological innovations appear under-utilised in many fruit tree crops, whereas viticulture, citriculture and vegetable crops have largely automated planting, pruning, thinning and harvesting and integrated GPS and/or GIS in their cultivation practises. As a consequence of the trend from pedestrian to tall orchards, innovation and technology is required to overcome shading, particularly in the lower part of the tree canopy. Types, properties and prices are presented of reflective ground covers (textile, aluminium and paper) as well as organic alternatives (lime, straw) as well as titanium dioxide and bio-degradable white line marker paint with additives. To combat sunburn, kaolin, carnauba-wax and other products are available, which can be combined with evaporative cooling. Mechanisation includes new machinery for mechanical thinning, pruning and harvesting to save labour. An autonomous prime mover (APM) is being developed for camera systems for assessment of flowering intensity, alternate bearing, fruit set, June drop, leaf nutrient status, pest and disease control and yield estimation/prediction. The two approaches for better light utilisation in row systems include reducing the spacing of every row from the current 14 feet (4.3 m) to 10-12 feet (3.0 to 2.6 m) or maintaining the spacing of a centre row at 14 feet (4.3 m) or ease of access, but narrower row spacing either side to less than 10 feet (3.0 m) The OTR (over the tree rows) developed by Washington State University and two commercial European multi-row sprayers are presented and new harvesting techniques with pre-sorting in the orchard.
  • Authors:
    • Caesar-TonThat, T.
    • Sainju, U. M.
    • Wright, S. F.
    • Shelver, W. L.
    • Kolberg, R. L.
    • West, M.
  • Source: Biology and Fertility of Soils
  • Volume: 47
  • Issue: 2
  • Year: 2011
  • Summary: Little is known about the long-term tillage and cropping management effects on the microbiologically derived factors that influence macroaggregates in semi-arid soil. We tested the hypothesis that differences in macro-aggregation are due to changes in soil structure related to management treatment-induced microbiological changes. In an experiment, microbiological factors consisting of aggregate stability, glomalin, russuloid basidiomycete fungi, uronic acids, total organic C (TOC), and total N (TN) were quantified in macroaggregate-size classes ranging from 4.75 to 0.25 mm, collected at 0-5 cm depth for the following treatments: (1) 12th year of fallow phase after 11 years of conventional- and no-tilled spring wheat-fallow (CTF and NTF), (2) 12th year of lentil phase after 11 years of conventional- and no-tilled spring wheat-lentil (CTL and NTL), (3) 12 years no-tilled continuous spring wheat (NTCW), and (4) 16 years uncultivated pasture (P) used as a baseline treatment. Immunoreactive easily extractable glomalin concentration was five to six times greater under P, NTCW, or NTL in the 2.00-1.00- and 1.00-0.50-mm macroaggregate-size classes than the other treatments and these results corroborated well with the results from aggregate stability assays. Russuloid basidiomycetes were highest in all NTCW macroaggregate-size classes, suggesting that annual input of lignin-containing wheat residues may influence the growth and survival of these fungi. Uronic acid amounts were highest in P but did not differ among the other treatments. In all macroaggregate-size classes, TOC content was greater in NTCW compared to CTF, and TN was about three times higher in NTL than NTF or CTF. In conclusion, 12 years of NTCW management in semi-arid soil has resulted in higher macroaggregate stability, glomalin concentration, russuloid basidiomycete populations, and TOC in macroaggregates compared to alternate-year fallow. Lentil can be used to replace fallow in dryland wheat rotation under no-till to enhance TN content and improve soil macro-aggregation.
  • Authors:
    • Chamberlain, J. F.
    • Miller, S. A.
    • Frederick, J. R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 3-4
  • Year: 2011
  • Summary: Use of a simulation model to predict long-term yield, greenhouse gas (GHG) emissions, and water quality impacts can be valuable for assessing land use conversion to bioenergy crops. The objective of this study is to assess the usability of DAYCENT for measuring environmental impacts due to land conversions from cotton and CRP lands (as unmanaged grasses) to switchgrass in the Southern U.S. We use published yield data to calibrate the crop growth parameters and test the calibrated model on independent data sets. We then apply the model to predict other relevant C and N parameters. In the case of cotton, the model simulates long-term mean cotton lint yield within 25% of observed yields across the South and within 4% of yields in the case study area of Darlington County, SC. DAYCENT also matches observed mature switchgrass yields within 25% of the mean in the range of expected fertilization rates across the region and within 6% in the case study area. Long-term simulations predict a decrease in GHG emissions (1.0-3.8 MtCO 2-e/ha-yr) and a reduction of nitrate runoff (up to 95%) for conversions from cotton to switchgrass at N application rates of 0-135 kgN/ha. Conversely, conversion from unmanaged grasses to switchgrass resulted in annual increases of net GHG emissions (0.2-1.4 MtCO 2-e/ha-yr) for switchgrass at no and low (45 kgN/ha) fertilization rates. Sequestration occurs due to increased soil organic C when higher levels of N are applied. At all levels of fertilization, a reduction of nitrate (50-70%) occurs when converting from unmanaged, unharvested grasses. The amount of nitrate leaching is only slightly sensitive to the fertilization rate applied to the perennial switchgrass. DAYCENT sufficiently models the "carbon debt" from land use conversion from CRP grasslands to managed switchgrass and highlights the importance of fertilization rate. Both C and N parameter results fall within published observed ranges. Thus, the long-term (10-15-year) accuracy of the model for both cotton and switchgrass offers promise as a tool for analyzing land use conversions in terms of N-managed yields and subsequent environmental impacts and benefits.
  • Authors:
    • Chen, G.
    • Weil, R. R.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: The yield of rainfed crops is commonly limited by the availability of soil water during the summer growing season. Channels produced by cover crop roots in fall/winter when soils are relatively moist may facilitate the penetration of compacted soils by subsequent crop roots in summer when soils are relatively dry and hard. Our objective was to determine the effects of fall cover crops on maize (Zea mays) growth and soil water status under three levels (high, medium, and no) of imposed traffic compaction. The study was conducted on coastal plain soils (fine-loamy Typic/Aquic hapludults and siliceous, Psammentic hapludults) in the mid-Atlantic region of the United States from 2006 to 2008. Cover crop treatments were FR (forage radish: Raphanus sativus var. longipinnatus, cv. 'Daikon'), rapeseed (Brassica napus, cv. 'Essex'), rye (cereal rye: Secale cereale L, cv. 'Wheeler') and NCC (no cover crop). Maize under high compaction achieved more deep-roots following FR and rapeseed than following rye or NCC. However, maize had greater yield following all cover crops than NCC control regardless of compaction levels and soil texture. Compaction reduced maize yield only under the high compaction in the lightly textured soils. During 24 June-24 July 2008, soils at 15 and 50 cm depths were drier under no compaction than high compaction and drier following FR than other cover crop treatments. Our results suggest that FR benefited maize root penetration in compacted soils while rye provided the best availability of surface soil water; rapeseed tended to provide both benefits. However, as rapeseed is relatively difficult to kill in spring, a mixture of FR and rye cover crops might be most practical and beneficial for rainfed summer crops under no-till systems in regions with cool to temperate, humid climates.
  • Authors:
    • Cheng, L.
    • Booker, F. L.
    • Burkey, K. O.
    • Tu, C.
    • Shew, H. D.
    • Rufty, T. W.
    • Fiscus, E. L.
    • Deforest, J. L.
    • Hu, S. J.
  • Source: PLOS ONE
  • Volume: 6
  • Issue: 6
  • Year: 2011
  • Summary: Climate change factors such as elevated atmospheric carbon dioxide (CO 2) and ozone (O 3) can exert significant impacts on soil microbes and the ecosystem level processes they mediate. However, the underlying mechanisms by which soil microbes respond to these environmental changes remain poorly understood. The prevailing hypothesis, which states that CO 2- or O 3-induced changes in carbon (C) availability dominate microbial responses, is primarily based on results from nitrogen (N)-limiting forests and grasslands. It remains largely unexplored how soil microbes respond to elevated CO 2 and O 3 in N-rich or N-aggrading systems, which severely hinders our ability to predict the long-term soil C dynamics in agroecosystems. Using a long-term field study conducted in a no-till wheat-soybean rotation system with open-top chambers, we showed that elevated CO 2 but not O 3 had a potent influence on soil microbes. Elevated CO 2 (1.5 * ambient) significantly increased, while O 3 (1.4 * ambient) reduced, aboveground (and presumably belowground) plant residue C and N inputs to soil. However, only elevated CO 2 significantly affected soil microbial biomass, activities (namely heterotrophic respiration) and community composition. The enhancement of microbial biomass and activities by elevated CO 2 largely occurred in the third and fourth years of the experiment and coincided with increased soil N availability, likely due to CO 2-stimulation of symbiotic N 2 fixation in soybean. Fungal biomass and the fungi:bacteria ratio decreased under both ambient and elevated CO 2 by the third year and also coincided with increased soil N availability; but they were significantly higher under elevated than ambient CO 2. These results suggest that more attention should be directed towards assessing the impact of N availability on microbial activities and decomposition in projections of soil organic C balance in N-rich systems under future CO 2 scenarios.
  • Authors:
    • Daigh, A. L.
  • Source: Soil Survey Horizons
  • Volume: 52
  • Issue: 2
  • Year: 2011
  • Summary: Bioenergy cropping systems will supply 16 billion gallons of cellulosic ethanol by the year 2022 in an attempt to reduce U.S. dependence on gasoline. To obtain long-term energy security, bioenergy systems will need to be sustainable, especially with regard to soil. Corn stover, as a bioenergy feedstock, is of great interest due to its immediate availability for harvest with minimal change to current corn-grain cropping systems. However, traditional row crop agriculture of the United States Corn Belt has reduced soil organic matter contents, an indicator of soil quality, by as much as 40 to 60% over the last 150 yr. The harvest of corn stover will directly remove a portion of the soil organic matter input, thus further reducing soil organic matter contents. The reduction in soil organic matter contents produce direct and indirect consequences unfavorable to soil quality and productivity. Therefore, the harvest of corn stover as a long-term bioenergy feedstock is detrimental to soil, impacting soil structure and stability, erodibility, A horizon depth, and physicochemical properties. Perennial biofuel systems, in contrast, have the potential to add soil organic matter to the soil, thus offering long-term enhancement of soil quality, productivity, and formation.
  • Authors:
    • Dawson, J. C.
    • Murphy, K. M.
    • Huggins, D. R.
    • Jones, S. S.
  • Source: Organic Agriculture
  • Volume: 1
  • Issue: 2
  • Year: 2011
  • Summary: There is growing interest in breeding crop cultivars specifically for organic agriculture, based on recognized differences in environmental conditions and management in organic systems compared to conventional systems, and especially due to environmental heterogeneity among and within individual organic systems. There is a need to develop effective strategies for improving crop performance in organic systems through plant breeding. This study evaluated 12 diverse winter wheat breeding lines chosen from conventional and organic breeding nurseries, six historic varieties, and an experimental perennial wheat population under organic management in the Inland Pacific Northwest region of the USA. A randomized complete block design with three replications in two locations over 2 years was used. Based on an analysis of variance, significant genetic differences and crossover interactions across years were found for grain yield, grain percent nitrogen, grain total nitrogen, and aboveground biomass. There were no main effects of locations or location-by-genotype effects for these traits. Based on comparisons among these breeding lines, it appears that there is a possibility of selecting for performance across a limited ecological zone as top-yielding lines were the same in both locations. However, individual entries may have variable performance across years within a single location so selection for stability of performance over years is also necessary. Using an analysis of direct measures of grain yield and grain %N in each location-year combination and overall, we identified breeding lines with relatively high yield, acceptable grain protein, and stable performance over all four location-year combinations. The use of indirect measures or index selection to simultaneously select for grain yield and protein did not appear to be more effective than direct selection based on yield and grain %N measured under organic management.