• Authors:
    • Ferris, H.
    • DuPont, S. T.
    • Horn, M. van
  • Source: Applied Soil Ecology
  • Volume: 41
  • Issue: 2
  • Year: 2009
  • Summary: Soil food webs cycle nutrients and regulate parasites and pathogens, services essential for both agricultural productivity and ecosystem health. Nematodes provide useful indicators of soil food web dynamics. This study was conducted to determine if nematode soil food web indicators and crop yield can be enhanced by combinations of cover crops in a conservation tillage system. The effects of three cover crop treatments (vetch/pea, oat/wheat and oat/wheat/pea/vetch) with low, medium and high C:N and a bare fallow control were investigated in Davis, CA. Nematode fauna, soil properties and plant productivity were measured. Soil food web indices, including the Enrichment Index (EI), Structure Index (SI), Basal Index (BI), and Channel Index (CI), based on the composition of nematode assemblages, were calculated to infer soil food web condition. Cover cropped tomato/corn rotations had twice the number of enrichment opportunist bacterial feeding nematodes, active participants in nitrogen mineralization, than fallowed tomato/corn rotations (opportunist bacterial feeders=163 versus 98). In winter fallowed plots food webs were basal, common in disturbed, nutrient-poor conditions (BI=37). Total number of enrichment opportunist nematodes, soil NH 4-N levels, and inferred nitrogen mineralization, were higher in cover crop treatments with low to mid C:N ratios. Omnivore and predator nematodes were scarce, averaging less than 6 nematodes 100 g -1 in all treatments. In year one, plant productivity was highest after fallow. In contrast, in year two productivity was highest after cover crops with high nitrogen content and productivity significantly correlated with the structure of the soil fauna. Monitoring the abundance of enrichment opportunists may provide managers with a new tool to evaluate soil food web nitrogen mineralization and plant productivity.
  • Authors:
    • Ben-Hammouda, M.
    • Errouissi, F.
    • Moussa-Machraoui, S.
    • Nouira, S.
  • Source: Soil & Tillage Research
  • Volume: 106
  • Issue: 2
  • Year: 2009
  • Summary: No-tillage (NT) is becoming increasingly attractive to farmers worldwide because it clearly reduces production costs relative to conventional tillage (CT) and improves soil properties and crop yield. Currently, under semi-arid conditions in North Africa, modern no-tillage techniques are being practiced on several hectares of land. The effect of NT and CT management and crop rotation on soil properties under semi-arid Mediterranean conditions was studied, over a 4-year period at two locations in northern Tunisia. Data from a short-term (2000-2004) use of both no-tillage (NT) and conventional tillage (CT) at the ESAK (Tunisia) were used to evaluate the influence of the tillage systems on the physicochemical properties of soil at the 0-20 cm depth layers. Trial was set up in 2000, where the two tillage systems (CT and NT), and four crop types (durum wheat, barley, pea and oats) were implemented in two distinct sites close to two governorates: Kef (silt/clayey) and Siliana (sand/clay) in northwestern Tunisia. Four years after implementing the two different tillage systems, soil parameters (N, NO 32-, NH 4+ P, P 2O 5, K, K 2O, SOC, SOM and CEC) were determined and comparison between the two tillage systems was made. Our results showed that after 4 years the contents of some parameters for most crop types were greater under NT than under CT at 0-20 cm depth layers, the results varied depending on crop type and site. NT significantly improved soil content especially for K, K 2O, P 2O 5 and N. Under NT system SOM and SOC were enhanced, but without significant results. These enhancements were accompanied by the enhancement of the CEC and the decrease of the C/N ratio. Thus the mineralization process was slightly quicker under NT. Our results also indicate that residue cover combined with no-tillage appears to improve some agronomic parameters and biomass production (grain yield). Multivariate analyses indicate that the improvement of soil properties was dependant on tillage management, sites (climate and soil type) and crop succession (species and cover residue). It must be pointed out that a 4-year period was not sufficient to clearly establish some parameters used in the effects of the NT system on soil properties under semi-arid conditions in northwestern Tunisia.
  • Authors:
    • Komecki, T. S.
    • Balkcom, K. S.
    • Raper, R. L.
    • Arriaga, F. J.
    • Price, A. J.
    • Reeves, D. W.
  • Source: Journal of Cotton Science
  • Volume: 13
  • Issue: 4
  • Year: 2009
  • Summary: An integral component of conservation agriculture systems in cotton ( Gossypium hirsutum L.) is the use of a high-residue winter cover crop; however, terminating cover crops is an additional expense and planting into high-residue can be a challenge. An experiment was conducted using black oat ( Avena strigosa Schreb.), rye ( Secale cereale L.), and wheat ( Triticum aestivum L.) cover crops established in early November at three locations. In mid-April each year all winter cover crops were flattened with a straight-blade mechanical roller-crimper alone or followed by three rates of glyphosate (0.84, 0.42, 0.21 kg ae/ha). Additionally, glyphosate alone at each rate and a non-treated check were included to complete the factorial treatment arrangement. Cotton was then planted 3 weeks after treatments were administered following in-row sub-soiling at E.V. Smith and direct seeding at Tennessee Valley and Robertsdale. Results showed that rolling followed by reduced glyphosate rates as low as 0.42 kg ae/ha can effectively and reliably terminate mature cereal winter cover crops; thus maintaining cotton population and protecting growth. Additionally, reduced glyphosate rates applied as low as 0.84 kg ae/ha alone can effectively terminate immature cereal covers while conserving soil moisture. Rolling mature winter cereal cover crops will likely conserve more soil moisture compared to standing covers; however, rolling immature cereal cover crops provides no benefit. In 2005 at E.V. Smith and at Tennessee Valley in 2006, increasing glyphosate rate increased cotton yield likely due to less mature cereal covers at time of treatment application. However, the inclusion of glyphosate did not increase cotton yield for any other comparison.
  • Authors:
    • Vanderlinden, K.
    • Murillo, J. M.
    • Madejon, E.
    • Lopez-Garrido, R.
    • Melero, S.
    • Ordonez, R.
    • Moreno, F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 133
  • Issue: 1-2
  • Year: 2009
  • Summary: Long-term field experiments can provide relevant information regarding soil organic carbon sequestration under different soil tillage systems. Especially, conservation tillage (CT) has been proved to be a practice that highly contributes to improve soil quality. For that reason, the study of soil quality indicators, such as organic fractions, are useful tools to assess changes caused by different soil tillage systems in long-term field experiments. We evaluated long-term effects of conservation tillage on soil carbon fractions and biological properties in a sandy clay loam Entisol (soil A) and in a clay Vertisol (soil B) located in semi-arid SW Spain. Cereal-sunflower-legume rotations under rainfed conditions were used in both soils in which conservation tillage (CT) was compared to traditional tillage (TT). Soil samples were collected at three depths (0-5, 5-10 and 10-20 cm) four months after sowing a pea crop ( Pisum arvense L.) in the Entisol and a wheat crop ( Triticum aestivum L.) in the Vertisol. Labile fractions of the total organic carbon (TOC) were determined as active carbon (AC) and water soluble carbon (WSC). Biological status was evaluated using soil microbial biomass carbon (MBC) and enzymatic activities [dehydrogenase activity (DHA), o-diphenol oxidase activity (Dphox), and beta-glucosidase activity (beta-glu)]. As a rule, the contents of AC, WSC, MBC, beta-glu and Dphox in soil A and contents of TOC, AC and DHA in soil B were higher in CT than in TT, at the 0-5 cm depth. In both soils, the studied parameters decreased with depth under both tillage treatments (TT and CT). Values of AC, TOC, MBC and beta-glu were positively correlated with each other ( p
  • Authors:
    • Ruiz, J. C.
    • Vanderlinden, K.
    • Melero, S.
    • Madejon, E.
  • Source: The Journal of Agricultural Science
  • Volume: 147
  • Issue: 1
  • Year: 2009
  • Summary: Soil enzyme activities are widely utilized as rapid and sensitive indicators in discriminating among soil management effects. The objective of the present study was to compare the influence of conservation tillage, i.e. direct drilling (DD) (residue cover is left on the soil surface) v. conventional tillage (CT), on soil chemical and biochemical properties in a crop rotation (cereals-sunflower-legumes) under dryland production in a semi-arid Mediterranean Vertisol after 23 years. A randomized experimental design was established. Soil biological status was evaluated by measuring of enzymatic activities (dehydrogenase, beta-glucosidase, alkaline phosphatase and protease). Total organic carbon (TOC) contents were greater in soils managed by DD than those found by CT. Except for protease activity, enzymatic activity values were approximately 2-fold higher in soils under DD than in soils under CT. The beta-glucosidase, alkaline phosphatase and dehydrogenase values showed a high correlation (from r=0.481 to r=0.886, P≤0.01) with TOC contents and they were correlated with each other (from r=0.664 to r=0.923, P≤0.01). The coefficient of variation of biochemical properties was higher than those of chemical properties in both treatments. Principal component analysis (PCA) showed that two principal components explained 58% and 20% of the total variability. The first principal component was influenced mostly by beta-glucosidase, dehydrogenase and TOC, whereas the second was influenced by pH. The first component effectively differentiated managed soil under both agriculture practices. In general, long-term soil conservation management by DD in a dryland farming system improved the quality of this Vertisol by enhancing its organic matter content and biochemical activity.
  • Authors:
    • Lal,R.
    • Dubey,A.
  • Source: Journal of Crop Improvement
  • Volume: 23
  • Issue: 4
  • Year: 2009
  • Summary: Sustainability of agricultural systems depends on their carbon (C) footprint, and the C output:C input ratio. Thus, this study was conducted with the objectives to: (i) assess the agricultural C emissions in relation to predominant farming systems in Punjab, India, and Ohio, USA; (ii) evaluate C-use efficiency of production systems; and (iii) determine the relative sustainability of agronomic production systems as determined by their C footprints. The data collated on C-based input into the soil for predominant crops for both regions included the amounts of fertilizers (N, P, K), herbicides and pesticides used for each crop annually, tillage methods, cropland area, total production of each crop, area under different farming systems, water-management practices (e.g., tubewell irrigation), and total number of livestock. These data were used to compute C equivalent (CE) per hectare of input and output, and the relative sustainability indices as a measure of the C-production efficiency. There existed a linear relationship observed between C input and C output for Punjab, indicating that an increase of 1 Tg/yr (1 Tg=teragram=10 12 g=million ton) of C input resulted in the corresponding C output of ~12 Tg/yr. A similar linear relationship between input and net C output between the 1930s and 1980s was observed for Ohio, and the ratio reached a plateau during 1990s. The average C-sustainability index (increase in C output as % of C-based input) value for Ohio from 1990 to 2005 was 35-43, almost 2.5 times that of Punjab. Since 1989, there has been a major shift in Ohio from conventional tillage to reduced and conservation tillage along with a decline in fertilizer use. No-till farming is practiced on about 35% of the cultivated area, which involves elimination of plowing, retention of crop residue mulch, and judicious use of chemicals. In Punjab, crop residues are removed, resulting in loss of C from the soil organic carbon pool. Hence, the C-based sustainability index is much higher in Ohio than in Punjab. C-efficient systems are more sustainable than inefficient farming systems, and residue removal reduces agricultural sustainability by depleting the soil C pool.
  • Authors:
    • Bauer, P. J.
    • Watts, D. W.
    • Frederick, J. R.
    • Novak, J. M.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 2
  • Year: 2009
  • Summary: Long-term disk tillage (DT) for cotton (Gossypium hirsutum L.) production in the southeastern U.S. Coastal Plain has resulted in soil organic C (SOC) content reductions. Conservation tillage (CT) management in some studies can rebuild SOC levels. A field study, with two adjacent 3.5-ha fields, both containing soil series formed in upland and depressional areas, was conducted using a 6-yr rotation of corn (Zea mays L.) and cotton to determine the CT and DT effects on SOC contents and residue characteristics returned to the soil. Annual soil samples were collected from 50 locations per field at 0- to 3- and 3- to 15-cm. After 6 yr under CT, residue accumulation promoted a significant SOC increase in the 0- to 3-cm depth in the upland soil series (about 0.7 Mg SOC ha(-1)). The lack of residue mixing in the 3- to 15-cm depth in upland Soils under CT however, resulted in a significant SOC content decline at this depth (1.25-2.51 Mg SOC ha(-1)). There was no significant SOC content change in soils under CT formed in depressional areas or in all soils under DT During 6 yr, 14.8 Mg ha(-1) of organic C from both corn and cotton residues was returned to Soils under CT but <4% was incorporated into the SOC pool. Levels of SOC in sandy upland soils can be increased at the surface after 6 yr of CT under a corn and cotton rotation, with the increase coming at the expense of an SOC decline at a deeper topsoil depth.
  • Authors:
    • Oberholzer, H.
    • Reiser, R.
    • Leifeld, J.
  • Source: Agronomy Journal
  • Volume: 101
  • Issue: 5
  • Year: 2009
  • Summary: Organic farming practices are regarded as being beneficial for the environment by promoting soil quality and sequestering soil organic carbon (SOC). We studied SOC dynamics in the long-term field experiment DOK in Switzerland. The experiment compares three organically fertilized treatments under conventional (CONFYM), bioorganic (BIOORG), and biodynamic (BIO-DYN) management, and two systems with (CONMIN) or without (NOFERT) mineral fertilizer. We analyzed measured SOC time series from 1977 to 2004 and applied soil fractionation, radiocarbon dating, and modeling with the carbon model RothC. The SOC declined significantly in most parcels, but was not systematically different between systems. Initial SOC contents correlated with soil texture and were identified as being important with respect to the change rate. The SOC loss was at the expense of mineral-associated carbon whereas the more labile fractions increased. The overall decline was explained by reduced carbon inputs since commencement of the experiment and was most pronounced in NOFERT and CONMIN. The model satisfactorily simulated the dynamics of most of the treatments for both initialization with equilibrium runs or measured SOC fractions. Carbon loss in CONFYM was not fully captured by the model. Composition of organic fertilizers depended on the particular management, and a model adjustment of their relative stability improved the match between model and measurements. Model runs without management effects indicated that the observed increase in temperatures at the experimental site does not induce a change in SOC. Overall, the study does not support a benefit of organic farming on SOC contents compared with conventional systems with manure.
  • Authors:
    • Miller, M. J.
  • Year: 2009
  • Summary: Climate change is a worldwide environmental problem that will affect every citizen of the planet. Societies can respond to climate change by reducing greenhouse gas emissions and reducing the rate and the magnitude of effects caused by climate change. Agriculture is a major contributor to the problem of climate change, but also has the capacity to be a part of the solution. No-till practices are considered dual purpose in that it has potential as a climate change mitigation strategy as well as an adaptation strategy. Economists have proposed using a market system to aid in the mitigation of climate change because it creates financial incentives to innovate and conserve. Carbon markets have presented farmers with the opportunity to be paid for practices that decrease emissions and sequester carbon, such as no-till farming. No-till farming practices have been in use in the United States for decades by some farmers in order to reduce soil erosion. However, many farmers continue to use traditional tillage methods that release carbon into the atmosphere. In order to exploit the carbon sink capacity of agricultural soils and adapt to the effects of climate change, more farmers need to utilize carbon sequestering practices such as continuous no-till farming. Most research on the introduction of new practices focuses on the initial adoption decision, with little research focusing on the continued use of the practices. The present study focuses on the adoption of no-till practices and carbon credits, and considers continuous no-till farming as a gateway to the adoption of carbon credits. A survey of 228 farmers at the Conservation Tillage and Technology Conference in Ada, Ohio, provided data used in this study. Fifty-nine percent of the respondents practice continuous no-till on some or all of their land, which indicates eligibility for carbon credits. Yet only four survey respondents currently participate in carbon credit programs. Results indicate that the majority, 88 percent, of no-till farmers surveyed are aware of carbon credit programs, which signals that lack of awareness of the program is not the main reason for non-participation. Findings indicate that there is a substantial relationship between the use of no-till practices and satisfaction with them. Additionally, there is a relationship between the use of no-till practices and participation in other resource conservation programs. The study also finds that belief in anthropogenic climate change is strongly associated with liberal political beliefs, yet neither belief is associated with the use of continuous no-till practices. Additional findings suggest that older farmers tend to be more likely to adopt no-till practices and use of no-till practices is associated with smaller farm operations. The importance attributed to human practices as a cause for climate change, degree of familiarity with carbon-related topics, education, and dedication to farm activities were not found to be statistically related to the use of no-till practices.
  • Authors:
    • Six, J.
    • Howitt, R. E.
    • Catalá-Luque, R.
    • Albarracin, M. V.
    • De Gryze, S.
  • Source: California Agriculture
  • Volume: 63
  • Issue: 2
  • Year: 2009
  • Summary: Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.