• Authors:
    • Konopatzki, M. R. S.
    • Lima, G. P. de
    • Nobrega, L. H. P.
    • Pickler, E. P.
    • Pacheco, F. P.
  • Source: Engenharia na Agricultura
  • Volume: 20
  • Issue: 1
  • Year: 2012
  • Summary: The increased mechanization, without adequate management, contributes to changes in soil structure, which facilitate erosive processes and soil degradation. The cover crops help protect soil surface, enhance physical, chemical, biological and productive potential of a soil and minimize degradation. This trial was done to analyze the influence of winter cover crop on the soil density, water content, macro and microporosity of soil cultivated to soybean and corn under no-tillage system. The experiment was conducted in a field with 24 plots, having six treatments of cover crops (forage turnip, pearl millet, oilseed rape, black oat, wheat and fallow) with four replications. After cover crop management, twelve plots were planted with corn and the other twelve with soybeans. It was observed that the soil under corn had better macroporosity, porosity and density compared to the soil cultivated to soybean. The crop cover with forage turnip increased soil macroporosity. However, cover crops did not influence water content, density, microporosity and porosity.
  • Authors:
    • Baade, E.
    • Tramontin, A.
    • Sturmer, S.
    • Grossklaus, F.
    • Valicheski, R.
  • Source: REVISTA BRASILEIRA DE ENGENHARIA AGRICOLA E AMBIENTAL
  • Volume: 16
  • Issue: 9
  • Year: 2012
  • Summary: With the intense use of technologies geared toward the mechanization of agricultural operations, soil compaction is a factor limiting productivity. To mitigate this problem, the use of ground cover crops is frequently recommended. With the objective to determine the effect of compaction on the soil physical properties, an experiment was carried out using randomized block design in a 2*5 factorial scheme. Two cover crop species (black oat - Avena strigosa and forage radish - Raphanus sativus), five levels of compaction (0, 2, 4, 6 and 8 tractor passes with 5.0 Mg on the soil surface), with four repetitions were studied. Traffic intensities greater than 2 tractor passes change soil density, total porosity, and mechanical penetration resistance at a depth of 0-0,10 m, as well as linearly reduce the height and dry matter production of the above-ground parts of the cover crops. The cultivation of black oat or forage radish preceding the soybeans, associated with the use of a furrower during soybean sowing minimizes the effects of soil compaction, permitting to obtain productivity greater than 3,5 t ha -1.
  • Authors:
    • Wan, Y.
    • Chen, X.
    • Xiang, D.
    • Yang, W.
    • Yong, T.
  • Source: Acta Prataculturae Sinica
  • Volume: 21
  • Issue: 1
  • Year: 2012
  • Summary: The aim of this paper was to study the variation of interspecies competitiveness in two relay strip intercropping system; wheat-maize-soybean and wheat-maize-sweet potato. The character of biomass accumulation and nitrogen uptake were examined for five cropping systems using years of field experiment. The cropping systems included three sole cropping systems (wheat-soybean, wheat-sweet potato and maize) and two relay strip intercropping systems (wheat/maize/soybean and wheat/maize/sweet potato). Land equivalent ratio (LER), aggressiveness (A), and nutrition competition ratio (NCR) were introduced as indexes to evaluate the interspecies competitiveness in each treatment. The results showed that there was obvious relay strip intercropping advantage ( LER >1, Awc 1) in the wheat-maize-soybean relay strip intercropping system, maize occupied the dominant niche for the whole growing stage in the relay strip intercropping systems, and the interspecies competitiveness of wheat and soybean were lower than that of the maize. Comparing with the sole cropping systems and wheat-maize-sweet potato relay strip intercropping system, the grain yield and nitrogen uptake, total biomass and total nitrogen uptake above ground of crops were increased significantly at both flowering (or spinning) and maturity stages in the wheat-maize-soybean relay strip intercropping system. The values of biomass and nitrogen uptake for the relay strip intercropping system were greater than the sole cropping systems, and that of soybean stubble were greater than sweet potato stubble. The total economic returns of crops in the wheat/maize/soybean relay strip intercropping system was higher 28.02% than those of crops in the wheat/maize/sweet potato relay strip intercropping system.
  • Authors:
    • Zhu, Z.
    • Xiang, D.
    • Yang, W.
    • Yong, T.
  • Source: Acta Agronomica Sinica
  • Volume: 38
  • Issue: 2
  • Year: 2012
  • Summary: The aim of this study was to understand the relationship between diversity of rhizosphere bacterial community and nitrogen uptake of crops in two relay strip intercropping systems: wheat/maize/soybean and wheat/maize/sweet potato. We analyzed the diversities of rhizosphere bacterial community in five cropping systems using denaturing gradient gel electrophoresis (DGGE) based on 16S rDNA. The cropping systems included wheat-soybean (A1), wheat-sweet potato (A2), maize single cropping (A3), wheat/maize/soybean (A4), and wheat/maize/sweet potato (A5). Compared to the sole cropping systems (A1, A2, and A3 treatments), the A4 treatment showed increases in grain nitrogen uptake and total nitrogen uptake amounts of aboveground of crops at both flowering (or silking) and maturity stages, and the Shannon-Weiner indices for rhizosphere bacterial community diversity was also increased significantly. The values of nitrogen uptake and the Shannon-Weiner index in the relay strip intercropping systems were greater than those in sole cropping systems, and the values in the treatment with soybean stubble were greater than those in the treatment with sweet potato stubble. The number and strength of the DNA bands from DGGE profiles varied with the cropping systems, especially for the distinguished bands. The comparability of rhizosphere bacterial community composition was low among different cropping systems. The similarity coefficient ( Cs) was higher between two relay strip intercropping systems than between relay strip intercropping system and sole cropping system, but the Cs value was low between A4 and A5 treatments. However, there was obvious difference of rhizosphere bacterial community composition between A4 and A5 treatments, and the A4 treatment was propitious to enhancing rhizosphere bacterial community diversity and increasing nitrogen uptakes of crops.
  • Authors:
    • Franchini, J.
    • Jantalia, C.
    • Urquiaga, S.
    • Boddey, R.
    • Zatorre, N.
    • Zotarelli, L.
    • Alves, B.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: The sustainability of crop production systems depends on the adoption of practices that allow the balancing of nutrient output and the preservation of soil organic matter. In Brazil, no-tillage (NT) is widely adopted for soybean-based cropping systems. In the Southern region, soybean alternates with maize in the summer and black-oats or wheat in the winter. Green-manure legumes are occasionally introduced in the crop rotation to break the continuous use of wheat in the winter. The objective of the present study was to evaluate if NT adoption would increase biological nitrogen fixation to soybean and other legumes. The hypothesis that a system richer in N would bring about positive effects on soil C stocks, was also tested. The study was carried out in Londrina, Parana State, in Southern Brazil on a clayey Ferralsol that was cropped under NT with soybean as the main crop for more than 25 years. In 1997, three different crop rotations under both NT and conventional plough tillage (CT) were introduced. The crop rotations were composed of soybean, maize, wheat, black-oats and white lupins, but differed from each other in the frequency that each crop appeared in the rotation. Crop yields and the biomass of lupins and black-oats were quantified at every harvest during the 12 years of this study. Conversion factors of measured yield and biomass into C and biologically fixed N inputs to the crop system were developed from whole plant measurements performed in four of the twelve years of the study. The contribution of biological N 2 fixation (BNF) to the legumes was determined using the ureide abundance and the 15N natural abundance techniques in 1998, 1999, 2005 and 2007. From these data, the calculation of N balance for each rotation (input N minus output N in harvested grain) was carried out. Soil C and N stocks to 80 cm depth were quantified in 1997, 2003 and 2009. Grain yields were higher under NT for soybean and under CT for maize, in the rotation with the lowest frequency of legume crops. Soybean reliance on BNF was higher under NT (76%) than under CT (68%) whilst for lupins the reliance was 68% under NT and 60% under CT. The use of lupins as a green manure represented an extra contribution to soil N of approximately 300 kg N ha -1 and this was essential to maintain a positive N balance for the system. The comparison of soil C stocks between 1997 and 2009 revealed almost no gain in soil C under NT, but a C loss of 19 Mg C ha -1 after 12 years of CT. Significant soil C and N losses were recorded in the rotation where lupins were planted more frequently and fertilizer N application to maize was suspended, which resulted in a very negative N balance for the system. The results highlight the importance of NT to enhance BNF inputs to the system and the need to recognize the N balance as a key driver of C stock changes in the soil. In addition, it suggests NT in this study had the consequence of avoiding soil C loss rather than increasing soil C stocks.
  • Authors:
    • Assis, C. P.
    • Jucksch, I.
    • Mendonça, E. S.
    • Neves, J. C. L.
    • Silva, L. H. M.
    • Wendling, B.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 43
  • Issue: 5
  • Year: 2012
  • Summary: The objective of this study was to evaluate changes in distribution and quality of organic matter in light and heavy fractions of a medium-texture Red Latosol under different uses and management practices in Capinopolis, Brazil. Soil samples were collected from different layers in the profile (0-5, 5-10, and 10-20 cm). The following treatments were evaluated: NTs, no till (no tillage) for 4 years with maize (silage)/soybean in succession; NTg, no till for 4 years with maize/maize/maize/soybean in succession; NTtf, no till for 3 years with tifton (hay) and soybeans in the last year; CS, about 30 years with conventional cultivation system (maize/soybean) with only soybean in the past 4 years; and NF, native forest. The heavy fraction contributed 75-98% of total carbon and 94-99% of total nitrogen, indicating that most carbon and nitrogen in the soil are associated with the mineral fraction, which is fundamental for the maintenance of their stocks. Tifton grass in no tillage was efficient in increasing the amounts of light fraction (free and occluded). Increases of occluded light fraction in no-till systems were greater than in conventional cultivation system. The light fraction was shown to be sensitive to soil cultivation and can be considered indicative of soil degradation. Light-fraction analysis by Fourier transform infrared spectroscopy (FTIR) allowed the study of changes in the chemical structure of these fractions under different uses and management practices. Occluded light fraction was shown to be more recalcitrant and condensed than the free light fraction. The surface layer in the conventional cultivation system has a more aromatic and condensed free light fraction than in no-tillage system. In general, the upper layers were less aromatic than the deepest ones.
  • Authors:
    • Antle, J. M.
    • Ogle, S. M.
  • Source: Climatic Change
  • Volume: 111
  • Issue: 3/4
  • Year: 2012
  • Summary: Previous research has demonstrated that soil carbon sequestration through adoption of conservation tillage can be economically profitable depending on the value of a carbon offset in a greenhouse gas (GHG) emissions market. However adoption of conservation tillage also influences two other potentially important factors, changes in soil N2O emissions and CO2 emissions attributed to changes in fuel use. In this article we evaluate the supply of GHG offsets associated with conservation tillage adoption for corn-soy-hay and wheat-pasture systems of the central United States, taking into account not only the amount of carbon sequestration but also the changes in soil N2O emission and CO2 emissions from fuel use in tillage operations. The changes in N2O emissions are derived from a meta-analysis of published studies, and changes in fuel use are based on USDA data. These are used to estimate changes in global warming potential (GWP) associated with adoption of no-till practices, and the changes in GWP are then used in an economic analysis of the potential supply of GHG offsets from the region. Simulation results demonstrate that taking N2O emissions into account could result in substantial underestimation of the potential for GHG mitigation in the central U.S. wheat pasture systems, and large over-estimation in the corn-soy-hay systems. Fuel use also has quantitatively important effects, although generally smaller than N2O. These findings suggest that it is important to incorporate these two effects in estimates of GHG offset potential from agricultural lands, as well as in the design of GHG offset contracts for more complete accounting of the effect that no-till adoption will have on greenhouse gas emissions.
  • Authors:
    • Blanco-Canqui, H.
    • Claassen, M. M.
    • Presley, D. R.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Impact of cover crops (CCs) on winter wheat ( Triticum aestivum L.) and grain sorghum [ Sorghum bicolor (L.) Moench] yields is not well understood. We assessed crop yield and its relationships with CC-induced changes in soil properties for a 15-yr CC experiment in wheat-sorghum rotation at 0, 33, 66, and 100 kg ha -1 of N application in south central Kansas. Hairy vetch ( Vicia villosa Roth) was used as a winter CC from 1995 to 2000, while sunn hemp (SH; Crotalaria juncea L.) and late-maturing soybean [LMS; Glycine max (L.) Merr.] were used as summer CCs in no-till from 2002 to 2008. Summer CCs increased crop yields particularly at low rates of N application. At 0 kg N ha -1, SH increased sorghum yield by 1.18 to 1.54 times, while wheat yield increased by 1.60 times in the first year (2004) after CC establishment relative to non-CC plots. At 66 kg N ha -1, SH had no effects on sorghum yield, but it increased wheat yield in 2 of 3 yr. Cover crops increased soil total N pool by 270 kg ha -1 for the 0- to 7.5-cm depth. Crop yield increased with the CC-induced decrease in soil maximum compactibility (soil's susceptibility to compaction) and soil temperature, and increase in soil aggregate stability, soil organic carbon (SOC) and total N concentration, and soil water content, particularly at 0 kg N ha -1. Principal component analysis (PCA) selected soil compactibility and total N as the best yield predictors. Inclusion of summer legume CCs in no-till fixes N, increases crop yield, and improves soil-crop relationships.
  • Authors:
    • Gibson,Lance R.
    • Singer,Jeremy W.
    • Blaser,Brock C.
  • Source: Crop Science
  • Volume: 52
  • Issue: 1
  • Year: 2012
  • Summary: Frost-seeding red clover (Trifolium pratense L.) into winter cereals is an efficient establishment method, although performance under contrasting soil management practices remains unclear. Wheat and intercropped red clover productivity were evaluated in intensive tillage (IT), moderate tillage (MT), and no tillage (NT) with and without compost amendment in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-winter wheat (Triticum aestivum L.) and red clover rotation between 2005 and 2010. Wheat yields were not affected by tillage system and averaged 3.80 Mg ha(-1) but were 10% higher in compost amended soil compared to no compost. Red clover plant density and dry matter (DM) at cereal grain harvest averaged 127 plants m(-2) and 32 g m(-2) and were not affected by tillage or amendment treatments. Maximum wheat canopy light interception was attained in late May to early June and ranged from 84 to 91% and typically exceeded 77% light interception for at least 22 d. Red clover root DM increased on average 378% between wheat harvest and 40 d after harvest compared with a 64% average increase in red clover root length. Red clover shoot: root averaged 8.5 at wheat harvest compared with 11.2 40 d after wheat harvest. Producers using this wheat and red clover intercrop should expect no difference in wheat yield or red clover productivity when using IT, MT, or NT.
  • Authors:
    • Briedis, C.
    • Sa, J. C. de M.
    • Caires, E. F.
    • Navarro, J. de F.
    • Inagaki, T. M.
    • Boer, A.
    • Ferreira, A. de O.
    • Quadros Neto, C.
    • Canalli, L. B.
    • Santos, J. B. dos
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 1
  • Year: 2012
  • Summary: In a no-till system (NTS) on naturally acidic soils, surface liming is essential to neutralize soil acidity and increases crop productivity. As a result, the soil organic matter (SOM) pools of the soil surface layers may change, reflecting increased C inputs by crop residues. The objective of this study was to quantify changes in SOM pools and the rate of C sequestration that occur in response to surface liming in a long-term NTS experiment. The experiment was conducted in an Oxisol in southern Brazil. The treatments consisted of the application of 0 or 6 Mg ha -1 of dolomitic lime on the soil surface in 1993 and a reapplication of 0 or 3 Mg ha -1 of dolomitic lime in 2000 to plots with or without the previous lime application. Liming caused total organic C (TOC) accumulation, especially in the 0- to 2.5-cm layer. The amount of TOC stored in the 20-cm layer was 49.9, 52.9, 52.7, and 57.5 Mg ha -1 in the control, 6+0, 0+3, and 6+3 Mg ha -1 treatments, respectively. The levels of particulate organic C (POC) and mineral-associated organic C (MAOC) in the SOM were also enhanced by liming. The increase in POC was directly related ( R2=0.99, P=0.002) to the accumulation of C from crop residues, which was greater in the plots receiving lime treatment. There were positive correlations between TOC and C extractable with hot water, total polysaccharides, and labile polysaccharides. The correlation analysis also demonstrated that TOC was more tightly correlated with POC than with MAOC, indicating a greater influence of the labile fraction on the increase in TOC with surface liming.