• Authors:
    • Chambers, B. J.
    • Silgram, M.
  • Source: Journal of Agricultural Science
  • Volume: 139
  • Year: 2002
  • Summary: The effects of straw incorporation (early and late cultivation) and straw burning were contrasted in a split-plot study examining the impact of long-term straw residue management, and six fertilizer nitrogen (N) rates on soil mineral nitrogen, crop fertilizer N requirements and nitrate leaching losses. The experiments ran from 1984 to 1997 on light-textured soils at ADAS Gleadthorpe (Nottinghamshire, UK) and Morley Research Centre (Norfolk, UK). Soil incorporation of the straw residues returned an estimated 633 kg N/ha at Gleadthorpe and 429 kg N/ha at Morley on the treatment receiving 150 kg/ha per year fertilizer N since 1984. Straw disposal method had no consistent effect on grain and straw yields, crop N uptake, or optimal fertilizer N rates. In every year there was a positive response (Pearly incorporate >late plough. The incorporation of straw residues induced temporary N immobilization compared with the treatment where straw was burnt, while the earlier timing of tillage on the incorporate treatment resulted in slightly more mineral N compared with the later ploughed treatment. Fertilizer N rate increased (P < 0.001) soil mineral nitrogen at both sites. At Morley, there was more organic carbon in the plough layer where straw had been incorporated (mean 1.09 g/100 g) rather than burnt (mean 0.89 g/100 g), and a strong positive relationship between organic carbon and fertilizer N rate (r2 = 93.2%, P < 0.01). There was a detectable effect of fertilizer N on readily mineralizable N in the plough layer at both Gleadthorpe (P < 0.001) and Morley (P < 0.05). At Morley, there was a consistent trend (P = 0.06) for readily mineralizable N to be higher where straw had been incorporated rather than burnt, indicating that ploughing-in residues may contribute to soil nitrogen supply over the longer term.
  • Authors:
    • Petersen,SO
    • Frohne,PS
    • Kennedy,AC
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 3
  • Year: 2002
  • Summary: In arable systems, seasonal fluctuations of microbiological properties can be significant. We hypothesized that adaptation to soil environmental conditions may contribute to the variation observed, and this was examined by characterization of different microbial community attributes under a range of soil conditions. Soil was sampled from no-till and chisel-tilled fields within a long-term experiment in eastern Washington during growth of spring wheat (Triticum aestivum). The range of soil environmental conditions covered was extended by amendment of crop residues. Soil samples were characterized with respect to biomass N and biomass P, substrate utilization dynamics, phospholipid fatty acid (PLFA) profiles and whole-soil fatty acid (MIDI-FA) profiles, and with respect to soil environmental variables (bulk density, soil organic C [SOC], temperature, moisture, and inorganic N and P). Bacterial and fungal lipid biomarkers were negatively correlated (P < 0.001), confirming that these subsets of fatty acids are associated with contrasting components of the microbial biomass. Biomass N was closely associated with soil conditions, notably N availability. The proportion of substrates used with no apparent lag phase decreased during summer and was negatively correlated with lipid stress indicators. Cyclopropyl fatty acids accounted for more than 60% of the variation in bacteria] PLFA. These observations suggest that adaptation to environmental stresses was partly responsible for the microbial dynamics observed. Tillage practice had little effect on the relationships between soil conditions and microbiological properties. The results showed that MIDI-FA included a significant background of nonmicrobial material and was less sensitive to soil environmental conditions than PLFA.
  • Authors:
    • Ottow, J. C. G.
    • Benckiser, G.
    • Weiske, A.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 60
  • Issue: 1-3
  • Year: 2001
  • Summary: In a 3-year field experiment the effect of the new nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate, trade name ENTEC) on the release of N2O and on methane oxidation was examined in comparison to dicyandiamide (DCD). Soil samples were analysed for the concentrations of ammonium, nitrite, nitrate and for the degradation kinetics of DMPP as well as DCD. DMPP decreased the release of N2O by 41% (1997), 47% (1998) and 53%(1999) (with an average of 49%) while DCD reducedN2O emissions by 30%(1997), 22%(1998) and 29% (1999) (with an average of 26%), respectively. Both nitrification inhibitors (NI) failed to affect methane oxidation negatively. The plots that received DCD or DMPP, respectively, even seem to function as enhanced sinks for atmospheric methane. DMPP apparently stimulated methane oxidation by ca. 28% in comparison to the control. The concentrations of ammonium remained unaffected by nitrification inhibitors whereas the amounts of nitrite diminished in the plots treated with DCD by 25% and with DMPP by 20%, respectively. Nitrate concentrations in soil were in both NI treatments 23% lower than in the control. DMPP and DCD did not affect the yields of summer barley, maize and winter wheat significantly. Dicyandiamide was mineralized more rapidly than DMPP (data for the cropping season in 1997 as an example).
  • Authors:
    • Barrett, D. J.
    • Galbally, I. E.
    • Graetz, R. D.
  • Source: Global Change Biology
  • Volume: 7
  • Issue: 8
  • Year: 2001
  • Authors:
    • Lal, R.
    • Kimble, J. M.
    • Follett, R. F.
  • Year: 2001
  • Summary: Grazing lands represent the largest and most diverse land resource-taking up over half the earth's land surface. The large area grazing land occupies, its diversity of climates and soils, and the potential to improve its use and productivity all contribute to its importance for sequestering C and mitigating the greenhouse effect and other conditions brought about by climate change. The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect gives you an in-depth look at this possibility.
  • Authors:
    • Ruiz-Suárez, L. G.
    • González-Avalos, E.
  • Source: Bioresource Technology
  • Volume: 80
  • Issue: 1
  • Year: 2001
  • Authors:
    • Kayisoglu, B.
    • Yalcn, H.
    • Koc, F.
    • Gonulol, E.
    • Bayhan, Y.
  • Source: Farm work science facing the challenges of the XXI century. Proceedings XXIX CIOSTA-GIGR V Congress, Krakow, Poland, 25-27 June, 2001, p. 30-35
  • Volume: 10
  • Year: 2001
  • Summary: The effect of different tillage methods on silage quality in second crop maize for silage was determined in this study. For this purpose, second crop maize was planted by using the following tillage methods: (1) Direct drilling (no-till) (DRD); (2) Heavy duty disc harrow+pneumatic precision drill (DIS); (3) Plough+disc harrow+roller+pneumatic precision drill (PLO); (4) Rotary tiller+pneumatic precision drill (ROT); (5) Tillage combination+pneumatic precision drill (TIC); and (6) Irrigation+Plough+disc harrow+roller+pneumatic precision drill (conventional) (CON). After harvesting, plant samples were filled into PVC silos (with three replication for each treatment) for fermentation and kept in these silos for 75 days. Significant statistical differences were found between treatments (tillage methods) according to pH, DM (dry matter), CA (crude ash), CF (crude fibre), WSC (water soluble carbohydrate), NH 3-N 3 and LAB (lactic acid batteries). Quality parameters in all treatments remained between the desired levels. No-tillage method with DRD and minimum tillage methods with ROT and TIC can be suggested.
  • Authors:
    • Hulugalle, N. R.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 31
  • Issue: 5-6
  • Year: 2000
  • Authors:
    • Hunt, H. W.
    • Elliott, E. T.
    • Six, J.
    • Paustian, K.
  • Source: Biogeochemistry
  • Volume: 48
  • Issue: 1
  • Year: 2000
  • Summary: Crop-based agriculture occupies 1.7 billion hectares, globally, with a soil C stock of about 170 Pg. Of the past anthropogenic CO2 additions to the atmosphere, about 50 Pg C came from the loss of soil organic matter (SOM) in cultivated soils. Improved management practices, however, can rebuild C stocks in agricultural soils and help mitigate CO2 emissions. Increasing soil C stocks requires increasing C inputs and/or reducing soil heterotrophic respiration. Management options that contribute to reduced soil respiration include reduced tillage practices (especially no-till) and increased cropping intensity. Physical disturbance associated with intensive soil tillage increases the turnover of soil aggregates and accelerates the decomposition of aggregate-associated SOM. No-till increases aggregate stability and promotes the formation of recalcitrant SOM fractions within stabilized micro- and macroaggregate structures. Experiments using 13C natural abundance show up to a two-fold increase in mean residence time of SOM under no-till vs intensive tillage. Greater cropping intensity, i.e., by reducing the frequency of bare fallow in crop rotations and increasing the use of perennial vegetation, can increase water and nutrient use efficiency by plants, thereby increasing C inputs to soil and reducing organic matter decomposition rates. Management and policies to sequester C in soils need to consider that: soils have a finite capacity to store C, gains in soil C can be reversed if proper management is not maintained, and fossil fuel inputs for different management practices need to be factored into a total agricultural CO2 balance.
  • Authors:
    • Meijles, E. W.
    • van Essen, E. A.
    • Bouma, J.
    • Pulleman, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: A regional survey of management and crop type and soil organic matter (SOM) content was conducted in one soil series in the Netherlands (loamy, mixed, mesic, Fluventic Eutrudept). The objective was to determine the effects of land use history on SOM contents in a prime agricultural soil, using available soil survey information and statistical analyses. Soil organic matter content is a relatively stable, integrating soil characteristic that reflects long-term land use and is an important indicator of soil quality. The SOM contents and information about past land use were obtained from 45 fields. Land use history was expressed in terms of (i) tillage; (ii) crop type; and (iii) use of chemical fertilizers, (iv) manure, and (v) biocides, for six successive periods (63-31, 31-15, 15-7, 7-3, 3-1, and 1-0 yr before sampling). Only four land use types occurred: conventional-arable, conventional-grass, organic-arable, and organic-grass. The SOM contents ranged between 17 and 88 g kg-1. Regression models of the actual SOM content as a function of crop type and management in the different periods showed that SOM contents were increased under long-term grass or, to a lesser extent, by organic farming, when compared with conventional-arable use. The regression model depends on the nature of land use history in any particular region and on the length of the selected periods, but it provides an easy method to predict SOM content as a function of management in a given soil series. The method can be an alternative to simulation modeling in situations where detailed data records from long-term field experiments are not available.