• Authors:
    • Pauletti, V.
    • Favaretto, N.
    • Molin, R.
    • Mellek, J. E.
    • Dieckow, J.
    • Da-Silva, V. L.
    • Vezzani, F. M.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 36
  • Issue: 3
  • Year: 2012
  • Summary: The quality of no-tillage systems depends on an adequate soil management that promotes soil structure improvements. This is associated to the cropping system adopted. This study investigated the effect of long-term no-tillage systems (18 years) on the structural quality of a sandy-clay to clay Oxisol (Latossolo Vermelho) in the region of Campos Gerais, Parana, Brazil. Five cropping systems were assessed: wheat-soybean [Wt-So], black oat-maize-wheat-soybean [Ot-Mz-Wt-So], vetch-maize-wheat-soybean [Vt-Mz-Wt-So], ryegrass-maize-ryegrass-soybean [Rg-Mz-Rg-So]; and alfalfa-maize [Alf-Mz]. Soil was sampled from the layers 0-5, 5-10 and 10-20 cm, in cylinders and in blocks with undisturbed structure. In the 0-5 cm layer, bulk density was lowest in the Ot-Mz-Wt-So (0.96 Mg m -3) and Vt-Mz-Wt-So systems (0.93 Mg m -3). In the 5-10 and 10-20 cm layers, the bulk density tended to be lowest in Alf-Mz systems (1.14 and 1.17 Mg m -3, respectively). A similar trend was observed for macroporosity, which in the top layer was greater in Ot-Mz-Wt-So (0.29 m 3 m -3) and Vt-Mz-Wt-So (0.30 m 3 m -3) and in the 5-10 and 10-20 cm layers tended to be greater in the Alf-Mz system (0.19 m 3 m -3). No clear trend was observed for microporosity. The saturated hydraulic conductivity was directly related with macroporosity, and was highest for Vt-Mz-Wt-So in the 0-5 cm layer (224 mm h -1) and Alf-Mz in the layers 5-10 (170 mm h -1) and 10-20 cm (147 mm h -1). In the Vt-Mz-Wt-So system, the mean weight diameter of aggregates was lowest in the 0-5 cm layer (2.39 mm) and highest (3.04 mm) in the Wt-So. The highest cone index values were observed in the Wt-So system, with over 1.5 MPa in the 7.5-22.5 cm layer. The compaction degree was lowest in the Alf-Mz system (0.2 MPa cm). Results were attributed mainly to the role of the crop roots of the systems and to the intensity of machinery traffic. Considering the 0-20 cm layer as a whole, the capacity to promote soil structural quality improvements was greater for the semi-perennial Alf-Mz system than for systems based on annual species. Bi-annual rotation systems, based on cover crops such as black oat and vetch, promote soil structural quality improvements compared to the wheat - soybean succession.
  • Authors:
    • Khan, M.
    • Said, G.
    • Khan, M.
    • Khan, S.
    • Inayat, U.
    • Khalid, U.
  • Source: Journal of Integrative Agriculture
  • Volume: 11
  • Issue: 6
  • Year: 2012
  • Summary: Conservational tillage (CT) in combination with broad spectrum herbicide may be more efficient and economical in controlling weeds, reducing cost of cultivation, and enhancing wheat yield. Field experiments were carried out to evaluate the effect of tillage and herbicides on weeds and wheat yield under rice-wheat cropping system (RWCS). The results indicated that broad spectrum herbicides particularly, carfentrazone ethyl ester+isoproturon (Affinity 50 WDG) reduced weeds density by 93 and 95% compared to control and also produced the maximum grain yield (6818 and 6996 kg ha -1) and HI (harvest index, 44.7 and 44.6%) in 2007-2008 and 2008-2009 growing seasons, respectively. The maximum weeds infestation and the lowest yield were recorded in control. Tillage methods significantly influenced grain yield and HI, while no significant effect on all other parameters. The overall mean yield was significantly higher in zero tillage (5575 kg ha -1) and reduced tillage (5584 kg ha -1) compared to CT (5479 kg ha -1). Besides increasing wheat yield, Affinity 50 WDG and zero tillage are important weed management practices that can be integrated into wheat production in RWCS. However, in case of perennial weeds or insect pests' infestation, CT in combination with Affinity 50 WDG would be more productive than conservation tillage.
  • Authors:
    • Khan, M.
    • Said, G.
    • Inayatullah, A.
    • Khan, S.
    • Khalid, U.
    • Aziz-ur-Rehman
    • Khan, M.
  • Source: Philippine Agricultural Scientist
  • Volume: 95
  • Issue: 2
  • Year: 2012
  • Summary: Conservation tillage practices with an appropriate seed rate recover the declining wheat ( Triticum aestivum L.) yield and soil quality using conventional tillage in poorly drained silty clay soil (calcareous, hyperthermic and Typic Torrifluvents) in rice-wheat cropping system. Field experiments were conducted for 2 consecutive yr to study the impact of three tillage techniques [zero (ZT), reduced (RT) and conventional tillage (CT)] and four seed rates viz. 70, 100, 130 and 160 kg ha -1 on wheat yield, soil organic matter and total soil nitrogen in rice-wheat cropping system in northwestern Pakistan. Mean values for tillage revealed that conservation tillage (ZT and RT) resulted in higher spikes per m 2, biological yield, grain yield, soil organic matter and total soil nitrogen compared with CT. Mean values for seed rates displayed the highest yield and yield components at 130 kg ha -1 and showed the lowest values at 70 kg ha -1 seed rate. The results revealed that ZT/RT in combination with 130 kg ha -1 seed rate produced higher grain yield compared with CT in the first growing season. In contrast, CT in combination with 130 kg ha -1 seed rate gave the highest grain yield in the second growing season. The results emphasized the necessity of using 130 kg ha -1 seed rate in ZT for improving soil organic matter and total soil nitrogen, and sustaining wheat yield in poorly drained silty clay soil. However, in case of severe infestation with weeds or insect pests, CT in combination with 130 kg ha -1seed rate may be the best alternative.
  • Authors:
    • Rosa, D.
    • Mauli, M.
    • Coelho, S.
    • Nobrega, L.
    • Lima, G.
  • Source: Journal of Food Agriculture and Environment
  • Volume: 10
  • Issue: 2 Part 1
  • Year: 2012
  • Summary: It is known that cover crops can influence on seed quality, as well as on yield cropping. This trial analyzed possible allelopathic interferences of black oat ( Avena strigosa Schreb.) remains and a consortium of black oat, forage turnip ( Raphanus sativus L.) and vetch ( Vicia sativa L.) on cropped seeds quality and soybean yield according to different intervals between the drying of some cover crops with Glyphosate 480 (3 L ha -1) herbicide and seeding with BRS 232 cultivar. Plots of 5.0 m * 2.5 m were established, plus 1 m of edge between each of them. The cover crop was sown in August, 2006, with 0.15 m of width among rows; the parcels were dried in intervals of one, ten, twenty and thirty days before the soybean seedling. Four treatments were arranged for black oat cover, four for consortium and one control for each cover, all randomized, with five replications. The soybean was seeded in November, 2006, with 0.45 m width among seeding rows. Data as yield, adjusted to 13% of moisture content on cropped seeds; seedling rate; weight of 100 seeds; moisture content and seeds vigor were recorded by the accelerated aging test. All the tests were submitted to an experimental design, with subdivided plots (split plot), completely randomized; the averages were also compared using Scott-Knott test at 5% of probability. The data showed a possible allelopathic interference of cover crops on soybean seed quality. The greatest weight of 100 seeds was obtained when soybean was sown under black oat cover compared to the consortium. On the other hand, when it was sown under consortium, it showed the best vigor, evaluated by the accelerated aging test. The yield did not differ between both covers. The intervals between drying and sowing interfered on weight of 100 seeds and soybean yield. The interval between drying and sowing of one day had a positive effect on weight of 100 seeds, but soybean yield decreased. Hence, it is not well recommended to sow soybean next to the drying management of a cover crop.
  • Authors:
    • Rodrigues, J. G. L.
    • Fernandes, D. M.
    • Bicudo, S. J.
    • Nascimento, F. M.
    • Fernandes, J. C.
    • Furtado, M. B.
  • Source: Revista Brasileira de Ciencias Agrarias
  • Volume: 7
  • Issue: 1
  • Year: 2012
  • Summary: The main goal of this research was to evaluate the response of maize crop in succession to maize+oat crops, with the anticipation of the increasing doses of nitrogen application in the oat culture, in no-tillage system. The experiment was carried out under field conditions at FCA/UNESP, Botucatu Campus, Sao Paulo, Brazil. The experimental design was arranged in randomized blocks with four replications, in split-plots. The plots were the nitrogen doses applied on the oat crop (0, 20, 40 e 60 kg ha -1), and split-plots, the nitrogen doses applied in the cover (60, 80, 100 e 120 kg ha -1), divided into two different crop stages of the maize crop. The dry matter weight and the C/N ratio were assessed on the oat and maize crops. On the maize crop, the plant nitrogen was quantified before the first covering and 15 days after the second covering, when the dry matter weight of the maize plants was determined. After the harvest, the yield was also calculated. Results indicate that the maize development and yield under no-till system were related to the straw C/N ratio, and the maize crop response to the anticipated N fertilization anticipation varied according to the N doses and application periods. The dry matter weight of the maize plants were influenced by the rates and periods of N applications.
  • 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:
    • Fontoura, S. M. V.
    • Bayer, C.
    • Rojas, C. A. L.
    • Weber, M. A.
    • Vieiro, F.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 36
  • Issue: 1
  • Year: 2012
  • Summary: Nitrogen losses from urea by ammonia volatilization are higher from no-tillage than from conventional tillage. The objective of this study was to evaluate the magnitude of this process under cool and wet spring conditions in the South-Central region of the State of Parana and to evaluate the influence of two winter cover crops (black oat and common vetch) on ammonia volatilization in no-tillage. The tillage systems were compared in a long-term tillage experiment (28 years) and the cover crops tested separately in a long-term (>15 yr) no-tillage area. Maize was grown in both experiments. Urea was applied at rates of 0, 80 and 160 kg ha -1 N in a single application in the tillage experiment and at rates of 0, 100 and 200 kg ha -1 N, split in two applications, in the cover crop experiment. Volatilization of NH 3 was measured for 20 days after urea application in a semi-open static system. Urease activity was evaluated in both experiments. The NH 3 loss rates were highest 5 days after urea application. Cumulative ammonia losses reached 18% of the applied N in no-tillage and 3% in conventional tillage. The higher losses from no-tillage may be partially related to the greatest urease activity in the soil surface layer. Ammonia volatilization was not affected by cover crops. As an isolated practice, split surface N fertilization does not ensure a decrease of NH 3 losses, which are primarily related to rain events immediately after urea application.
  • Authors:
    • Calegari, A.
    • Santos, D.
    • Tiecher, T.
  • Source: Soil & Tillage Research
  • Volume: 124
  • Year: 2012
  • Summary: Organic phosphorus (P) is an important source of phosphate for plants both in natural environments and in cultivated soils. Growing plants with high P recycling capacity may increase the importance of organic forms in phosphate availability mainly in undisturbed soils. The aim of this study was to evaluate the effect of long period of cultivation of different winter species under different soil management systems in the distribution of soil organic P forms, in the P content stored into the soil microbial biomass (SMB) and in the acid phosphatase enzyme activity. The experiment was established in 1986 with six winter treatments (blue lupine, hairy vetch, oat, radish, wheat and fallow) implanted in a Rhodic Hapludox in southern Brazil, under no-tillage system (NT) and conventional tillage system (CT). The crops were cultivated with rational use of chemical phosphate fertilizer, according to plant needs and soil type maintaining high levels of soil organic carbon leading to P organic form accumulation. Growing crops during the winter period in highly weathered subtropical soil increases the importance of microbial interactions in the P cycle, especially in the NT, where a large amount of crop residues is annually added to the soil surface, increasing soil organic P level, P content stored into the SMB and acid phosphatase enzyme activity.
  • 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:
    • Villalobos, F.
    • Gomez-Macpherson, H.
    • Boulal, H.
  • Source: Field Crops Research
  • Volume: 130
  • Year: 2012
  • Summary: In the Mediterranean region, conservation agriculture principles like minimum soil disturbance or retaining residues on soil surface are rarely applied in irrigated annual cropping systems. This paper compares a conservation agriculture practice, permanent bed planting (PB), with a conventional system in which the ridges are reformed annually (CB). Comparisons were made throughout a crop sequence of cotton (Gossypium hirsutum L)-maize (Zea mays L) - cotton in which PB was introduced before the maize cropping. Traffic was controlled during the study. Both maize and cotton crops produced higher leaf area index and biomass under PB than CB and Sand 24% higher yield respectively though the yield benefit for maize was not significant. The PB system did not improve Water-use Efficiency but delayed water use until the later growth stages. Soil organic matter (SUM) was significantly higher in PB compared to CB one year after the introduction of the system, and this difference was due to higher SUM in the 0-0.05 m layer, particularly in the furrows. The lack of negative effects of PB on yield and the positive effects on SUM, coupled with increased water infiltration and reduced erosion shown in previous studies, point to the beneficial adoption of PB in the region assuming the patterns are confirmed in the longer term. (C) 2012 Elsevier B.V. All rights reserved.