19952015
  • Authors:
    • Martius, C.
    • Lamers, J. P. A.
    • Ibragimov, N.
    • Kienzler, K.
    • Wassmann, R.
    • Scheer, C.
  • Source: Global Change Biology
  • Volume: 14
  • Issue: 10
  • Year: 2008
  • Summary: Land use and agricultural practices can result in important contributions to the global source strength of atmospheric nitrous oxide (N2O) and methane (CH4). However, knowledge of gas flux from irrigated agriculture is very limited. From April 2005 to October 2006, a study was conducted in the Aral Sea Basin, Uzbekistan, to quantify and compare emissions of N2O and CH4 in various annual and perennial land-use systems: irrigated cotton, winter wheat and rice crops, a poplar plantation and a natural Tugai (floodplain) forest. In the annual systems, average N2O emissions ranged from 10 to 150 mu g N2O-N m(-2) h(-1) with highest N2O emissions in the cotton fields, covering a similar range of previous studies from irrigated cropping systems. Emission factors (uncorrected for background emission), used to determine the fertilizer-induced N2O emission as a percentage of N fertilizer applied, ranged from 0.2% to 2.6%. Seasonal variations in N2O emissions were principally controlled by fertilization and irrigation management. Pulses of N2O emissions occurred after concomitant N-fertilizer application and irrigation. The unfertilized poplar plantation showed high N2O emissions over the entire study period (30 mu g N2O-N m(-2) h(-1)), whereas only negligible fluxes of N2O (< 2 mu g N2O-N m(-2) h(-1)) occurred in the Tugai. Significant CH4 fluxes only were determined from the flooded rice field: Fluxes were low with mean flux rates of 32 mg CH4 m(-2) day(-1) and a low seasonal total of 35.2 kg CH4 ha(-1). The global warming potential (GWP) of the N2O and CH4 fluxes was highest under rice and cotton, with seasonal changes between 500 and 3000 kg CO2 eq. ha(-1). The biennial cotton-wheat-rice crop rotation commonly practiced in the region would average a GWP of 2500 kg CO2 eq. ha(-1) yr(-1). The analyses point out opportunities for reducing the GWP of these irrigated agricultural systems by (i) optimization of fertilization and irrigation practices and (ii) conversion of annual cropping systems into perennial forest plantations, especially on less profitable, marginal lands.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Year: 2008
  • Authors:
    • Raper, R. L.
    • Wood, C. W.
    • Reeves, D. W.
    • Shaw, J. N.
    • Franzluebbers, A. J.
    • Causarano, H. J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 1
  • Year: 2008
  • Summary: Quantification of the impact of long-term agricultural land use on soil organic C (SOC) is important to farmers and policyrnakers, but few studies have characterized land use and management effects on SOC across physiographic regions. We measured the distribution and total stock of SOC to a depth of 20 cm under conventional tillage (CvT), conservation tillage (CsT), and pasture in 87 production fields from the Southern Piedmont and Coastal Plain Major Land Resource Areas. Across locations, SOC at a depth of 0 to 20 cm was: pasture (38.9 Mg ha(-1)) > CsT (27.9 Mg ha(-1)) > CvT (22.2 Mg ha(-1)) (P <= 0.02). Variation in SOC was explained by management (41.6%), surface horizon clay content (5.2%), and mean annual temperature (1.0%). Higher clay content and cooler temperature contributed to higher SOC. Management affected SOC primarily at the soil surface (0-5 cm). All SOC fractions (i.e., total SOC, particulate organic C, soil microbial biomass C, and potential C mineralization) were strongly correlated across a diversity of soils and management systems (r = 0.85-0.96). The stratification ratio (concentration at the soil surface/concentration at a lower depth) of SOC fractions differed among management systems (P <= 0.0001), and was 4.2 to 6.1 under pastures, 2.6 to 4.7 under CsT and 1.4 to 2.4 under CvT; these results agree with a threshold value of 2 to distinguish historically degraded soils with improved soil conditions from degraded soils. This on-farm survey of SOC complements experimental data and shows that pastures and conservation tillage will lead to significant SOC sequestration throughout the region, resulting in improved soil quality and potential to mitigate CO2 emissions.
  • Authors:
    • Leser, J. F.
    • Wheeler, T. A.
    • Keeling, J. W.
    • Mullinix, B.
  • Source: JOURNAL OF NEMATOLOGY
  • Volume: 40
  • Issue: 2
  • Year: 2008
  • Summary: Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log 10 (J2+1)/500 cm 3 soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log 10(J2+1)/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18°C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10°C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.
  • Authors:
    • Reddy, K. N.
    • Zablotowicz, R. M.
    • Locke, M. A.
  • Source: Pest Management Science
  • Volume: 64
  • Issue: 4
  • Year: 2008
  • Summary: BACKGROUND: Conservation practices often associated with glyphosate-resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate-resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate-resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate-resistant crops, and presents data from a Mississippi field trial comparing glyphosate-resistant and non-glyphosate-resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management. RESULTS: Results from the reduced-tillage study indicate differences in soil biological and chemical properties owing to glyphosate-resistant crops. Under continuous glyphosate-resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non-glyphosate-resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate-resistant crop following 5 years of continuous glyphosate-resistant crop as compared with the non-glyphosate-resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate-resistant crop, but many are transient and benign for the soil ecosystem. CONCLUSIONS: Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long-term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate-resistant crop and conservation practice interactions. Published in 2008 by John Wiley & Sons, Ltd.
  • Authors:
    • Balkcom, K. S.
    • Delaney, D. P.
    • Mitchell, C. C.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 5
  • Year: 2008
  • Summary: After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long-term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long-term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2-yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max. (L.) Merr.] in a 3-yr rotation produced little long-term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in-row subsoiling, high-residue, conservation tillage, and genetically modified cultivars; in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha(-1) in 2006, 14.8 Mg corn grain ha(-1) in 1999, 6.34 Mg wheat ha-1 in 2001, and 4.50 Mg soybean ha(-1) in 2004.
  • Authors:
    • Chikte, P.
    • Bhalkare, S. K.
    • Thakare, S. M.
    • Lande, G. K.
  • Source: Journal Of Cotton Research And Development
  • Volume: 22
  • Issue: 2
  • Year: 2008
  • Summary: The experiment was conducted during the kharif season of 2004-05 at Dr. PDKV, Akola to evaluate the effect of different possible intercrops on bollworm complex on cotton crop. The intercrops viz., cotton+greengram, cotton+blackgram, cotton+cowpea, cotton+sorghum, cotton+maize, cotton+marigold, cotton+soybean in 1:1 ratio alongwith a treatment of sole cotton crop were sown. The intercrop cotton+cowpea proved to be the best recording least population of spotted bollworm, American bollworm and pink bollworm as against the treatment of sole cotton crop. The highest seed cotton yield of 251 kg/ha was recorded in cotton+cowpea-intercropping system as against 160 kg/ha recorded in the sole cotton crop.
  • Authors:
    • Reddy, K. C.
    • Tazisong, I. A.
    • Nyakatawa, E. Z.
    • Senwo, Z. N.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 3
  • Year: 2008
  • Summary: Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0-to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH4NO3 and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions weresoil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cottoil-rye/cotton-corn than in cotton-cotton-corn and greater with NH4NO3 than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm, after 10 yr was greater with poultry litter than with NH4NO3 in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH4NO3. Poultry litter also increased PCM and MBC compared with NH4NO3. Cropping increased SOC, POC, and PCM compared with fallow in NT Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO2 levels, and improve soil and environmental quality.
  • Authors:
    • Suzuki, L. G. A. S.
    • Alves, M. C.
    • Suzuki, L. E. A. S.
    • Rodrigues, R. A. F.
  • Source: Científica, Jaboticabal
  • Volume: 36
  • Issue: 2
  • Year: 2008
  • Summary: The objective of this study was to verify the biomass yield potential of different cover crops in a Cerrado region, in Selviria, Mato Grosso do Sul, Brazil. The work was conducted in the Experimental University Farm of the Paulista State University (UNESP). The experimental design was the randomized complete blocks in strips with splitsplit plot: the plots were the cover crops Mucuna aterrima, Pennisetum americanum, Crotalaria juncea, Cajanus cajan and a fallow area; the split plots were the no-tillage and the conventional tillage, and the splitsplit plots were corn ( Zea mays L.), soybean ( Glycine max (L.) Merrill), and cotton ( Gossypium hirsutum L.) crops. In the winter irrigated Phaseolus vulgaris L. was the crop. In the spring/summer season the cover crop with the greatest biomass yield was Pennisetum americanum. Crotalaria juncea and the fallow area showed medium results while Mucuna aterrima and Cajanus cajan were those with the least yields. Pennisetum americanum was the crop cover with the biggest production potential of dry biomass. The cultivation systems did not influence the dry biomass of the cover crops. Only Pennisetum americanum production was influenced by crop sequence.
  • Authors:
    • Rao, K. C.
    • Bharathi, V.
    • Reddy, L. K.
  • Source: International Journal of Agricultural Sciences
  • Volume: 4
  • Issue: 2
  • Year: 2008
  • Summary: Plant root exudates are known to affect survival, reproduction and development of various microorganisms in soil through extremely complex phenomenon. Saprophytic and pathogenic activities such as competition and antibiosis of the root microflora are mediated by exudates. An analysis of the effect of different crop root exudates such as groundnut, castor, soybean, sunflower, maize, green gram, hybrid sorghum and resistant pigeon pea revealed high inhibitory effect on conidial germination and radial growth of fusarium udum. In contrast, the root exudates of local sorghum varieties had less influence on the radial growth of antagonistic fungi viz., Penicillium sp., Trichoderma sp. Aspergillus sp. in the increasing order (6.8, 9.8 and 10 per cent), in spite of promoting germination and radial growth of the wilt pathogen Fusarium udum. However, root exudates of some crops such as groundnut, cotton, hybrid sorghum and resistant pipeaonpea had stimulatory effect on antagonistic fungi such as Aspergillus sp. Pencillium sp. and Trichoderma sp. in the range of 39.8 to 47.5 per cent. Root exudates of cotton were, however, found to promote both the wilt pathogen, as well as antagonistic fungi. Groundnut and castor exudates were found to be at par with each other in the promotion of radial growth of antagonists. Identification of such biochemical compounds in the crop root exudates responsible for inhibition or stimulation of the fungi would be more useful.