• 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:
    • 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:
    • Edwards, J.
    • Godsey, C.
    • Vitale, J. D.
    • Taylor, R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 4
  • Year: 2011
  • Summary: Conservation tillage had initial roots in the Great Plains, but the current adoption of conservation tillage, especially no-till, lags behind in the rest of the United States. This paper documents the results of a recent survey of Oklahoma producers, which was conducted to assess the current status of conservation tillage in the state. Based on responses from 1,703 producers, econometric analysis was conducted to identify factors explaining the observed use of conservation tillage practices in Oklahoma. The survey found that conventional tillage remains the most common tillage practice among Oklahoma producers. According to the survey, conventional tillage is used on 43.2% of the state's total acreage, conservation tillage on 26.7% of the total acreage, and reduced tillage on the remaining 30.1% of the crop acreage. A Tobit model was developed to explain patterns of tillage use based on producer characteristics and their perceptions on how conservation tillage performs relative to conventional tillage according to various economic and agronomic factors. The Tobit model identified operator age, farm size, crop rotation, knowledge, and erosion control as highly significant factors explaining the observed use of conservation tillage. The model results also identified potential constraints to conservation tillage adoption and use in the Southern Plains, suggesting that the unique needs of mixed crop-livestock farming systems, and the dominant winter wheat ( Triticum aestivum L.) monoculture, hinder further diffusion of conservation tillage. Future policy should consider addressing the needs of Oklahoma producers, particularly crop producers heavily engaged in livestock activities, as well as finding viable rotation crops to provide alternatives for the winter wheat monoculture.
  • Authors:
    • Hoogmoed, W. B.
    • Cai, D.
    • Zhao, Q.
    • Wang, Y.
    • Zhang, X.
    • Zhang, D.
    • Dai, K.
    • Wang, X.
    • Oenema, O.
  • Source: Field Crops Research
  • Volume: 120
  • Issue: 1
  • Year: 2011
  • Summary: Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage/crop residue and nutrient management practices on maize ( Zea mays L.) yield, water use efficiency (WUE), and N agronomic use efficiency (NAE) at Shouyang Dryland Farming Experimental Station in northern China during 2003-2008. The experiment was set-up using a split-plot design with 3 tillage/crop residue methods as main treatments: conventional, reduced (till with crop residue incorporated in fall but no-till in spring), and no-till (with crop residue mulching in fall). Sub-treatments were 3 NP fertilizer rates: 105-46, 179-78 and 210-92 kg N and P ha -1. Maize grain yields were greatly influenced by the growing season rainfall and soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage/crop residue treatments were 5604, 5347 and 5185 kg ha -1, under reduced, no-till and conventional tillage, respectively. Grain yields under no-till, were generally higher (+19%) in dry years but lower (-7%) in wet years. Mean WUE was 13.7, 13.6 and 12.6 kg ha -1 mm -1 under reduced, no-till, and conventional tillage, respectively. The no-till treatment had 8-12% more water in the soil profiles than the conventional and reduced tillage treatments at sowing and harvest time. Grain yields, WUE and NAE were highest with the lowest NP fertilizer application rates (at 105 kg N and 46 kg P ha -1) under reduced tillage, while yields and WUE tended to be higher with additional NP fertilizer rates under conventional tillage, however, there was no significant yield increase above the optimum fertilizer rate. In conclusion, maize grain yields, WUE and NAE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P ha -1. No-till increased soil water storage by 8-12% and improved WUE compared to conventional tillage, thus showing potentials for drought mitigation and economic use of fertilizers in drought-prone rainfed conditions in northern China.
  • Authors:
    • Wu, Z. J.
    • Zhu, A. N.
    • Chen, L. J.
    • Chen, Z. H.
    • Wang, J. B.
  • Source: Plant, Soil and Environment
  • Volume: 57
  • Issue: 6
  • Year: 2011
  • Summary: The effects of tillage and residue input amounts on soil phosphatase (alkaline phosphomonoesterase ALP, acid phosphomonoesterase ACP, phosphodiesterase PD, and inorganic pyrophosphatase IPP) activities and soil phosphorus (P) forms (total P, organic P, and available P) were evaluated using soils collected from a three-year experiment. The results showed that no-till increased soil total and organic P, but not available P as compared to conventional tillage treatments. Total P was increased as inputs of crop residue increased for no-till treatment. There were higher ALP and IPP activities in no-till treatments, while higher PD activity was found in tillage treatments and tillage had no significant effect on ACP activity. Overall phosphatase activities increased with an increase of crop residue amounts. Soil total P was correlated negatively with PD activity and positively with other phosphatase activities. Organic P had a positive correlation with ACP activity, but a negative correlation with PD activity. Available P had no significant correlation with phosphatase activities. Our data suggests that no-till and residue input could increase soil P contents and enhance the activities of phosphatase.
  • Authors:
    • Miller, P.
    • Lawrence, R. L.
    • Watts, J. D.
    • Montagne, C.
  • Source: Climactic Change
  • Volume: 108
  • Issue: 1/2
  • Year: 2011
  • Summary: A pilot cropland carbon sequestration program within north central Montana has allowed farmers to receive carbon credit for management adjustments associated with changing from tillage-based agricultural systems to no-till. Carbon credit can also be obtained by adopting conservation reserve, where cropland is planted into perennial vegetation. Summer fallowing is also considered within the crediting process as credit is not given in years that a field is left un-vegetated. The carbon sequestration program has been advocated as a means to mitigate climate change while providing an added source of income for Montana farmers. There is lack of data, however, pertaining to the percentage of lands within this region that have not converted to no-till management, lands under certain crop intensities (e.g. those that are cropped every growing season vs. those that use a fallow-crop-fallow system), or cropland that have converted to perennial vegetation outside of the popular Conservation Reserve Program. Data is also sparse concerning the amount of soil organic carbon that might be sequestered given a conversion to no-till or conservation reserve. This study established regional percentage estimates of cropland under no-till, various degrees of crop intensity, and conservation reserve within north central Montana. Literature-based carbon sequestration estimates were used to generate carbon gain data associated with the conversation to no-till and to conservation reserve. These estimates were then applied to the area-based cropland statistics to estimate potential regional carbon sequestration associated with these management changes.
  • Authors:
    • Hilker, T.
    • Lawrence, R. L.
    • Powell, S. L.
    • Watts, J. D.
  • Source: Remote Sensing of Environment
  • Volume: 115
  • Issue: 1
  • Year: 2011
  • Summary: Conservation tillage management has been advocated for carbon sequestration and soil quality preservation purposes. Past satellite image analyses have had difficulty in differentiating between no-till (NT) and minimal tillage (MT) conservation classes due to similarities in surface residues, and may have been restricted by the availability of cloud-free satellite imagery. This study hypothesized that the inclusion of high temporal data into the classification process would increase conservation tillage accuracy due to the added likelihood of capturing spectral changes in MT fields following a tillage disturbance. Classification accuracies were evaluated for Random Forest models based on 250-m and 500-m MODIS, 30-m Landsat, and 30-m synthetic reflectance values. Synthetic (30-m) data derived from the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) were evaluated because high frequency Landsat image sets are often unavailable within a cropping season due to cloud issues. Classification results from a five-date Landsat model were substantially better than those reported by previous classification tillage studies, with 94% total and >= 88% class producer's accuracies. Landsat-derived models based on individual image scenes (May through August) yielded poor MT classifications, but a monthly increase in accuracy illustrated the importance of temporal sampling for capturing regional tillage disturbance signatures. MODIS-based model accuracies (90% total; >= 82% class) were lower than in the five-date Landsat model, but were higher than previous image-based and survey-based tillage classification results. Almost all the STARFM prediction-based models had classification accuracies higher than, or comparable to, the MODIS-based results (>90% total; >= 84% class) but the resulting model accuracies were dependent on the MODIS/Landsat base pairs used to generate the STARFM predictions. Also evident within the STARFM prediction-based models was the ability for high frequency data series to compensate for degraded synthetic spectral values when classifying field-based tillage. The decision to use MODIS or STARFM-based data within conservation tillage analysis is likely situation dependent. A MODIS-based approach requires little data processing and could be more efficient for large-area mapping; however a STARFM-based analysis might be more appropriate in mixed-pixel situations that could potentially compromise classification accuracy.
  • Authors:
    • Schillinger, W.
    • Wuest, S.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Farmers in the low-precipitation (<300 mm annual) region of the Inland Pacific Northwest of the USA practice summer fallow to produce winter wheat ( Triticum aestivum L.) in a 2-yr rotation. No-till fallow (NTF) is ideal for wind erosion control but is not widely practiced because of seed-zone soil drying during the summer, whereas adequate seed-zone water for germination and emergence of deep-sown winter wheat can generally be retained with tilled fallow (TF). Successful establishment of winter wheat from late August- early September planting is critical for optimum grain yield potential. A 6-yr field study was conducted to determine if accumulations of surface residue under long-term NTF might eventually be enough to substitute for TF in conserving seed-zone water over summer. Averaged over the 6 yr, residue rates of 1500, 6000, and 10 500 kg ha -1 (1*, 4*, and 7* rates, respectively) on NTF produced incrementally greater seed-zone water but were not capable of conserving as much as TF. Total root zone (0-180 cm) over-summer water loss was greatest in the 1 * NTF whereas there were no significant differences in the 4* and 7* NTF versus TF. Average precipitation storage efficiency ranged from 33% for 1* NTF to 40% for TF. We conclude that for the low-precipitation winter wheat-summer fallow region of the Inland Pacific Northwest: (i) Cumulative water loss during the summer from NTF generally exceeds that of TF; (ii) there is more extensive and deeper over-summer drying of the seed-zone layer with NTF than with TF; (iii) increased quantities of surface residue in NTF slow the rate of evaporative loss from late-summer rains, and (iv) large quantities of surface residue from April through August will marginally enhance total-profile and seed-zone water in NTF, but will not retain adequate seed-zone water for early establishment of winter wheat except sometimes during years of exceptionally high precipitation or when substantial rain occurs in mid-to-late August.
  • Authors:
    • Gurjeet, G.
    • Malik, R.
    • Ashok, Y.
    • Kamboj, B.
    • Yadav, D.
  • Source: Environment and Ecology
  • Volume: 29
  • Issue: 4
  • Year: 2011
  • Summary: Two field experiments were conducted during kharif of 2009, to optimize ground cover by green manure cover crops before taking no-till direct seeded basmati rice and mechanical transplanted coarse grain rice. The treatments included three cover crops ( Sesbania, mungbean and cowpea) with two seed rates (X and 2X) along with check (without cover crop) under no-till after wheat harvest. The X seed rates for Sesbania, mungbean and cowpea were 30, 20 and 50 kg/ha, respectively. Farmers' field trails on the issue in question were also conducted at three locations. Weed infestation until cover crops were knocked down, was significantly reduced due to growing of cover crops as compared to plots where no cover crop was included. Minimum density and dry weight of weeds was recorded with Sesbania at 60 kg/ha seed rate which was superior to all other treatments. This could be due to ample ground cover and heavy biomass production by Sesbania. In general biomass production among green manure cover crops was followed the sequence of Sesbania > cowpea > mungbean. Due to lower cost of seed, Sesbania at 60 kg/ha was realized more economical than other cover crops. Infestation of Echinochloa sp. in rice was lowest in the plots where Sesbania was taken as preceding cover crop and it was superior to other two cover crops. There was no infestation of sedges in rice in the plots where cover crops were grown but there was infestation of sedges in check plots. There was no significant impact of different cover crops on the yield and yield attributed of rice; however, to attain higher returns, inclusion of green manure cover crops on long-term basis could be more meaningful.
  • Authors:
    • Xie, J.
    • Li, L.
    • Huang, G.
    • Cai, L.
    • Luo, Z.
    • Zhang, R.
  • Source: Acta Prataculturae Sinica
  • Volume: 20
  • Issue: 4
  • Year: 2011
  • Summary: Long-term field experiments on soil physical quality in rainfed farming systems were conducted in Dingxi on the western Loess Plateau. The effects of conventional tillage and five conservation agriculture patterns [conventional tillage (T), conventional tillage with stubble incorporation (TS), no till with no stubble (NT), no till with stubble retention (NTS), conventional tillage with plastic mulching (TP) and no till with plastic mulching (NTP)] were studied. The experiment was fully-phased with two rotation sequences. Phase 1 started with field pea ( Pisum sativum) followed by spring wheat ( Triticum aestivum) (P->W) whereas phase 2 started with spring wheat followed by field pea (W->P). There were highly significant differences between the six tillage measures in soil properties including soil aggregates, available water content, water use efficiency and saturation conductivity. There were also significant differences in some soil properties including soil bulk density, total porosity, capillary porosity, non-capillary porosity, soil strength and saturation capacity. There were no significant differences in soil properties such as soil temperature and field capacity. Using the addition and multiplication method, and weighted integrated method, quantitative assessments of soil physical quality in different tillage systems were carried out. The order of soil physical quality index from high to low was NTS, NTP, NT, TS, T(TP) and TP(T) in P->W rotation, and NTS, NTP, TS, NT, TP and T in W->P rotation. The various tillage measures resulted in very different soil physical quality levels. Improved soil structure arose from tillage reduction or residue retention which improved soil structure, enhanced water infiltration, reduced soil and water loss, and hence improved soil physical quality.