19862015
  • Authors:
    • Dobermann, A.
    • Walters, D. T.
    • Binder, D. L.
    • Haddix, M. L.
    • Adviento-Borbe, M. A. A.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 9
  • Year: 2007
  • Summary: Crop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC-rec) or intensive management (CC-int) and maize-soybean rotation with recommended (CS-rec) or intensive management (CS-int). Grain yields of maize and soybean were generally within 80-100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS-rec or remained unchanged in CS-int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3-N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC-rec and CS-rec systems. Fertilizer-induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize-soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol-based gasoline by 33-38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build-up of soil organic matter from large amounts of crop residues returned.
  • Authors:
    • Myers, L.
    • Sherwood, J.
    • Edelson, J.
    • Damicone, J.
    • Motes, J.
  • Source: Plant Disease
  • Volume: 91
  • Issue: 5
  • Year: 2007
  • Summary: In five field trials over 3 years, control of aphid-transmitted, nonpersistent virus diseases on pumpkin, caused mostly by the potyviruses Watermelon mosaic virus (WMV) and Papaya ringspot virus type-W (PRSV-W), was achieved by intercropping with grain sorghum, as opposed to clean tillage. Reductions in disease incidence ranged from 43 to 96% ( P≤0.05). Surrounding pumpkin plots with borders of peanut, soybean, or corn was not effective. Borders of grain sorghum were effective, but disease control was generally less than for the intercrop treatment. Intercropping soybean and peanut with pumpkin reduced disease incidence by 27 to 60% ( P≤0.05), but disease control generally was less than for grain sorghum. Peak periods of alate aphid immigration generally preceded virus disease outbreaks by 7 to 14 days. However, alate landing rates, as measured in green tile traps, did not differ among treatments. Marketable yield was not increased by the intercrop treatments, and yield was reduced by up to 50% for the intercrop treatment with grain sorghum in two trials. The use of grass-selective herbicide applied along pumpkin rows, reduced seeding rates of the intercrops, or mowing did not alleviate the adverse effects of competition between pumpkin and the grain sorghum intercrop on yield.
  • Authors:
    • Hons, F.
    • Wright, A.
    • Dou, F.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Crop management practices have potential to enhance subsoil C and N sequestration in the southern U.S., but effects may vary with tillage regime and cropping sequence. The objective of this study was to determine the impacts of tillage and soyabean cropping sequence on the depth distribution of soil organic C (SOC), dissolved organic C (DOC), and total N after 20 years of treatment imposition for a silty clay loam soil in central Texas. A continuous soyabean monoculture, a wheat-soybean doublecrop, and a sorghum-wheat-soybean rotation were established under both conventional (CT) and no tillage (NT). Soil was sampled after soyabean harvest and sectioned into 0-5, 5-15, 15-30, 30-55, 55-80, and 80-105 cm depth intervals. Both tillage and cropping intensity influenced C and N dynamics in surface and subsurface soils. No tillage increased SOC, DOC, and total N compared to CT to a 30 cm depth for continuous soyabean, but to 55 cm depths for the more intensive sorghum-wheat-soybean rotation and wheat-soybean doublecrop. Averaged from 0 to 105 cm, NT increased SOC, DOC, and total N by 32, 22, and 34%, respectively, compared to CT. Intensive cropping increased SOC and total N at depths to 55 cm compared to continuous soyabean, regardless of tillage regime. Continuous soyabean had significantly lower SOC (5.3 g kg -1) than sorghum-wheat-soybean (6.4 g kg -1) and wheat-soybean (6.1 g kg -1), and 19% lower total N than other cropping sequences. Dissolved organic C was also significantly higher for sorghum-wheat-soybean (139 mg C kg -1) than wheat-soybean (92 mg C kg -1) and continuous soyabean (100 mg C kg -1). The depth distribution of SOC, DOC, and total N indicated treatment effects below the maximum tillage depth (25 cm), suggesting that roots, or translocation of dissolved organic matter from surface soils, contributed to higher soil organic matter levels under NT than CT in subsurface soils. High-intensity cropping sequences, coupled with NT, resulted in the highest soil organic matter levels, demonstrating potential for C and N sequestration for subsurface soils in the southern U.S.
  • Authors:
    • Silva, A. C.
    • Duarte, A. P.
    • Deuber, R.
  • Source: PLANTA DANINHA
  • Volume: 25
  • Issue: 2
  • Year: 2007
  • Summary: A weed infestation survey was performed in 20 second maize crop areas in 1997 and in 40 areas in 1998 and 1999 after soyabean planting in the Medio Paranapanema Region, Sao Paulo, Brazil. The survey was conducted in the counties of Assis, Campos Novos, Candido Mota, Cruzalia, Florinea, Maracai, Palmital, Pedrinhas Paulista and Platina. When the maize reached the grain filling stage, the crop weeds were evaluated by zigzag walking through the areas starting from different points to represent the whole area. The crops were classified in three types, according to the system applied: no-tillage, conventional system with disc plowing, and second maize crop in the soyabean straw only. Infestation level and occurring weed species were evaluated in each crop. The weed control systems adopted were also considered, according to the herbicides applied. The most important weed species occurring in the areas were: Cenchrus echinatus, Bidens pilosa, Euphorbia heterophylla, Raphanus sativus, Digitaria horizontalis, Commelina benghalensis, Amaranthus sp., Achyrocline satureioides, Sinapis arvensis, Sida sp., Glycine max, Avena strigosa [ Avena nuda], Eleusine indica and Sorghum halepense. The results showed a strong infestation increase of C. echinatus, which turned out to be the most important weed species in the area evaluated. R. sativus was also important and showed an expressive increase from 1997 to 1999. Weed infestations were higher in the conventional system areas, showing that this system is inferior to the others, concerning weed control. The chemical weed control most used was the mixture of (atrazine+oil) plus 2,4-D, followed by (atrazine+oil) and atrazine alone. No weed control was used in 22% of the crops, which were the most infested. The infestation level varied from year to year for the different weed control systems, depending on climate conditions.
  • Authors:
    • Drijber, R.
    • Mamo, M.
    • Wortmann, C.
    • Garcia, J.
    • Tarkalson, D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Stratification of nutrient availability, especially of P, that develops with continuous no-till (NT) can affect runoff nutrient concentration and possibly nutrient uptake. The effects of composted manure application and one-time tillage of NT on the distribution of soil chemical properties, root colonization by arbuscular mycorrhizae (AM), and plant P uptake were determined. Research was conducted on Typic Argiudoll and Mollic Hapludalf soils under rainfed corn ( Zea mays L.) or sorghum [ Sorghum bicolor (L.) Moench.] rotated with soybean [ Glycine max (L.) Merr.] in eastern Nebraska. Tillage treatments included NT, disk, chisel, moldboard plow (MP), and mini-moldboard plow (MMP). Subplots had either 0 or 87.4 kg P ha -1 applied in compost before tillage. Bray-P1 was five to 21 times as high for the 0- to 5-cm as compared with the 10- to 20-cm soil depth. Greater redistribution of nutrients and incorporation of compost P resulted from MP tillage than from other tillage treatments. One-time chisel or disk tillage did not effectively redistribute nutrients while MMP tillage had an intermediate effect. Compost application reduced AM colonization of roots at R6 for all crops. Tillage reduced AM colonization with reductions at R6 due to MP tillage of 58 to 87%. The tillage effect on colonization persisted through the second year with no indication of AM recovery. Root P concentration was increased by MP and was negatively correlated to colonization. Decreased colonization did not result in decreased plant P uptake. Infrequent MP tillage can reduce surface soil P and the potential for P loss in runoff, but may reduce AM colonization of the roots, possibly reducing P uptake with some low P soils. The results do not indicate any advantage to one-time tillage of NT if runoff P loss is not a concern.
  • Authors:
    • Borghi, E.
    • Crusciol, C.
    • Mateus, G.
  • Source: Acta Scientiarum Agronomy
  • Volume: 29
  • Issue: 4
  • Year: 2007
  • Summary: The effects of cover plants on the performance of annual crops under no-tillage systems are not well defined yet. A field trial was carried out on a Rhodic Kandiudalf soil in Botucatu, state of Sao Paulo, Brazil, aiming to evaluate the effect of the amount of Gigante guinea sorghum straw on soybean nutrient uptake and its consequent performance of grain yield in no-tillage area. The experimental design was developed in randomized blocks with four replications. The treatments consisted of 6.1, 7.1, 19.5, 26.7, 28.1 e 30.2 ton ha -1 of guinea sorghum straw. The increase of straw provided increment of N and P plant levels until the amount of 25.0 and 17.5 ton ha -1, respectively. Thus, the highest soybean grain yields reported in soils under no-tillage systems might be related to the proper water and nutrient uptakes due to higher soil moisture availability.
  • Authors:
    • Verma, S.
    • Ranade, D.
  • Source: Soybean Research
  • Volume: 5
  • Year: 2007
  • Summary: Studies conducted between 2003 and 2005 on black soils of Malwa region brought out that deep tillage plays a vital role in increasing the productivity of the crops through reduced infestation of weeds and increased water retention capacity of soil consequent upon improvement in its physical environment as indicated by lower values in bulk density of soil. This not only led to increasing productivity of soybean but also made the planting of rabi crops feasible without pre-sowing irrigation. The studies further revealed that the waste land reclaimed by spreading excavated soil from tank can immediately be brought under cultivation for soybean based cropping system. Successful raising of rainfed soybean ( kharif) followed by gram ( rabi) has been demonstrated on such reclaimed land.
  • Authors:
    • Avila, A.
    • Spera, S.
    • Tomm, G.
    • Santos, H.
  • Source: Bragantia
  • Volume: 66
  • Issue: 2
  • Year: 2007
  • Summary: The effects of soil management systems and crop rotations were assessed from 1997 to 2003, in Passo Fundo, Rio Grande do Sul State, Brazil. Four soil management systems (no-tillage, minimum tillage, conventional tillage using disc plough, and conventional tillage using mouldboard plough) and three crop rotation systems (system I (wheat/soyabean), system II (wheat/soyabean and common vetch/maize or sorghum), and system III (wheat/soyabean, common vetch/maize or sorghum and white oats/soyabean)) were compared. The main plot consisted of soil management systems, while the split-plots consisted of crop rotation systems. Energy conversion (energy available/energy consumed) and balance (energy available-energy consumed) during the seven-year period is presented. No-tillage resulted in higher energy conversion and balance (72.44 and 190 766 MJ/ha) than minimum tillage (64.06 and 167 349 MJ/ha), conventional tillage using disc plough (54.35 and 134 982 MJ/ha), and conventional tillage using mouldboard (52.02 and 128 159 MJ/ha), respectively. Wheat in crop rotations presented higher energy efficiency than that in monoculture. Maize had the highest energy efficiency among the crops.
  • Authors:
    • An, M.
    • Cheema, Z. A.
    • Iqbal, J.
  • Source: Plant and Soil
  • Volume: 300
  • Issue: 1/2
  • Year: 2007
  • Summary: A 2-year field investigation was carried out during 2003-2004 to determine the effectiveness of intercropping single and double rows of sorghum, soybean and sesame in a cotton crop on the suppression of purple nutsedge ( Cyperus rotundus L.). Results revealed that all three intercrops were effective in inhibiting purple nutsedge density (70-96%) and dry matter production (71-97%) during both years of experimentation. Control in the second year was more effective than in the first year. The seed cotton yield was also depressed by the intercrops but its suppression (8-23%) was far less severe than that of purple nutsedge and its loss was compensated by greater total economic returns. Intercropping of sorghum and sesame produced greater than 20% net benefits (up to 60%) in comparison with the control (cotton alone). Soybean intercropping produced comparable net benefits (95-103%). Sesame two rows intercrop treatment appeared the most profitable with net benefit of 51-59% with good purple nutsedge control (73-92% density suppression, 77-95% dry weight suppression) during both years of experimentation.
  • Authors:
    • McGawley, E. C.
    • Pontif, M. J.
  • Source: Nematropica
  • Volume: 37
  • Issue: 2
  • Year: 2007
  • Summary: Reniform nematodes that parasitize cotton and soybean can also reproduce on a wide spectrum of weed species, thereby maintaining nematode populations during the off-season. Microplot studies were conducted to evaluate the effects of three endemic weed species, morningglory ( Ipomoea lacunosa), hemp sesbania ( Sesbania exaltata), and johnsongrass ( Sorghum halepense), on reproduction of the reniform nematode, Rotylenchulus reniformison cotton (LA. 887) and soybean (Pioneer 96B21). Over two years of microplot trials, the co-culture of cotton with any of the three weed species suppressed numbers of reniform nematode juveniles in soil significantly. When grown singly, reproductive values of R. reniformis after 60 days on cotton averaged 69.0, while those for morningglory, hemp sesbania, and johnsongrass averaged 42.0, 23.5, and 18.0, respectively. Reproductive values on cotton co-cultured with morningglory averaged 38.5. Those for the cotton-hemp sesbania and cotton-johnsongrass combinations averaged 23.5 and 26.0, respectively. Nematode reproduction on soybean alone, and co-cultured with each of the three weeds, reduced reproduction of reniform nematode only in the presence of johnsongrass in two trials. Data from two subsequent 45-day duration greenhouse experiments conducted with cotton and leachates from each of the three weed species support the hypothesis that suppression of reniform nematode reproduction likely resulted from the secretion of allelopathic compounds by weed roots.