• Authors:
    • Handoo, Z. A.
    • Cram, M. M.
    • Fraedrich, S. W.
    • Zarnoch, S. J.
  • Source: Nematology
  • Volume: 14
  • Issue: 4
  • Year: 2012
  • Summary: Tylenchorhynchus ewingi, a stunt nematode, causes severe injury to slash pine seedlings and has been recently associated with stunting and chlorosis of loblolly pine seedlings at some forest tree nurseries in southern USA. Experiments confirmed that loblolly pine is a host for T. ewingi, and that the nematode is capable of causing severe damage to root systems. Initial population densities as low as 60 nematodes (100 cm 3 soil) -1 were sufficient to damage the root systems of loblolly pine seedlings. Populations of T. ewingi increased on pine from two- to 16-fold, depending on the initial population density. Evaluations of various cover crops used in southern forest tree nurseries indicated that legumes, rye and several varieties of sorghum were excellent hosts for T. ewingi. Other small grains such as ryegrass, oats and wheat were poorer hosts. A cultivar of pearl millet was a non-host for T. ewingi, and a cultivar of brown top millet appeared to be either a very poor host or a non-host. Nurseries that have seedling production losses caused by T. ewingi should consider rotating with non-host cover crops such as pearl millet or leaving fields fallow as part of their pest management programme.
  • 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:
    • 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:
    • 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:
    • Xu, Z.
    • Wu, H.
    • Rui, Y.
    • Lu, S.
    • Chen, C.
    • Zhou, X.
  • Source: Biology and Fertility of Soils
  • Volume: 48
  • Issue: 2
  • Year: 2012
  • Summary: Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia. In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were taken in December 2009 to investigate the short-term effects of cover crops on soil pH, moisture, NH 4+-N, NO 3--N, soluble organic C and nitrogen (N), total organic C and N, and C mineralization in comparison with a nil-crop control (CK). The soil is a Chromic Luvisol according to the FAO classification with 48.42.2% sand, 19.52.1% silt, and 32.12.1% clay. An exponential model fitting was employed to assess soil potentially labile organic C ( C0) and easily decomposable organic C for all treatments based on 46-day incubations. The results showed that crop residue biomass significantly decreased over the course of 2-month decomposition. The cover crop treatments had significantly higher soil pH, soluble organic C and N, cumulative CO 2-C, C0, and easily decomposable organic C, but significantly lower NO 3--N than the CK. However, no significant differences were found in soil moisture, NH 4+-N, and total organic C and N contents among the treatments. Our results indicated that the short-term cover crops increased soil labile organic C pools, which might have implications for local agricultural ecosystem managements in this region.
  • Authors:
    • Xu, Z.
    • Wu, H.
    • Chen, C.
    • Zhou, X.
  • Source: Journal of Soils and Sediments
  • Volume: 12
  • Issue: 6
  • Year: 2012
  • Summary: Purpose: Cover crop residue is generally applied to improve soil quality and crop productivity. Improved understanding of dynamics of soil extractable organic carbon (EOC) and nitrogen (EON) under cover crops is useful for developing effective agronomic management and nitrogen (N) fertilization strategies. Materials and methods: Dynamics of soil extractable inorganic and organic carbon (C) and N pools were investigated under six cover crop treatments, which included two legume crops (capello woolly pod vetch and field pea), three non-legume crops (wheat, Saia oat and Indian mustard), and a nil-crop control (CK) in southeastern Australia. Cover crops at anthesis were crimp-rolled onto the soil surface in October 2009. Soil and crop residue samples were taken over the periods October-December (2009) and March-May (2010), respectively, to examine remaining crop residue biomass, soil NH 4++N and NO 3--N as well as EOC and EON concentrations using extraction methods of 2 M KCl and hot water. Additionally, soil net N mineralization rates were measured for soil samples collected in May 2010. Results and discussion The CK treatment had the highest soil inorganic N (NH 4+-N+NO 3--N) at the sampling time in December 2009 but decreased greatly with sampling time. The cover crop treatments had greater soil EOC and EON concentrations than the CK treatment. However, no significant differences in soil NH 4+-N, NO 3--N, EOC, EON, and ratios of EOC to EON were found between the legume and non-legume cover crop treatments across the sampling times, which were supported by the similar results of soil net N mineralization rates among the treatments. Stepwise multiple regression analyses indicated that soil EOC in the hot water extracts was mainly affected by soil total C ( R2=0.654, P
  • 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:
    • Carr, P. M.
    • Anderson, R. L.
    • Lawley, Y. E.
    • Miller, P. R.
    • Zwinger, S. F.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: Special Issue 01
  • Year: 2012
  • Summary: The use of killed cover crop mulch for weed suppression, soil erosion prevention and many other soil and crop benefits has been demonstrated in organic no-till or zero-till farming systems in eastern US regions and in Canada. Implements have been developed to make this system possible by terminating cover crops mechanically with little, if any, soil disturbance. Ongoing research in the US northern Great Plains is being conducted to identify cover crop species and termination methods for use in organic zero-till (OZ) systems that are adapted to the crop rotations and climate of this semi-arid region. Current termination strategies must be improved so that cover crop species are killed consistently and early enough in the growing season so that subsequent cash crops can be grown and harvested successfully. Delaying termination until advanced growth stages improves killing efficacy of cover crops and may provide weed-suppressive mulch for the remainder of the growing season, allowing no-till spring seeding of cash crops during the next growing season. Excessive water use by cover crops, inability of legume cover crops to supply adequate amounts of N for subsequent cash crops and failure of cover crops to suppress perennial weeds are additional obstacles that must be overcome before the use of killed cover crop mulch can be promoted as a weed control alternative to tillage in the US northern Great Plains. Use of vegetative mulch produced by killed cover crops will not be a panacea for the weed control challenges faced by organic growers, but rather one tool along with crop rotation, novel grazing strategies, the judicious use of high-residue cultivation equipment, such as the blade plow, and the use of approved herbicides with systemic activity in some instances, to provide organic farmers with new opportunities to incorporate OZ practices into their cropping systems. Emerging crop rotation designs for organic no-till systems may provide for more efficient use of nutrient and water resources, opportunities for livestock grazing before, during or after cash crop phases and improved integrated weed management strategies on organic farms.
  • Authors:
    • Djigal, D.
    • Saj, S.
    • Rabary, B.
    • Blanchart, E.
    • Villenave, C.
  • Source: Soil & Tillage Research
  • Volume: 118
  • Year: 2012
  • Summary: Conservation agriculture (CA) is rapidly developing in Madagascar but little is known about its effects on local soil functioning. To assess some of those effects, we investigated the effects of three CA systems and two levels of fertilization on soil functioning using nematofauna as indicator. The systems consisted in (i) soybean (Glycine max L.)-maize (Zea mays L) rotation with mulch of residues, CA-R; (ii) bean (Phaseolus vulgaris L.)-soybean rotation with living mulch of Pennisetum clandestinum, CA-K; (iii) continuous maize with living mulch of Desmodium uncinatum, CA-D and were compared with soybean-maize under conventional tillage (CT) and natural fallow (NF). The fertilization levels consisted in ( i) farmyard manure, FYM; and (ii) farmyard manure + mineral fertilizers, FYM + NPK. Located in the Highlands of Madagascar, the experiment was setup in 1991 and andic Dystrustept soil had been sampled in 2005-2007. We measured nematode abundances and ecological indices as well as the abundance and biomass of soil macrofauna, soil water and organic C and N contents and plant yields. We hypothesized that (1) CA including maize in monoculture would lead to higher abundance of plant-parasitic nematodes; (2) both dead-residue mulch and inorganic fertilization would lead to a more basal nematode community structure; and (3) that the combination of system effects on soil nematode community would be able to forecast differential crop yields for the CA systems. Our results show that CA systems tested were able to support better/comparable maize and soybean yields compared with CT, provided that crop rotation is correctly managed. Supporting our first hypothesis, abundance of plant parasitic nematodes was (40-150 times) higher under maize monoculture. Abundance of soil nematofauna and trophic groups (excepted carnivores and omnivores) was stable during the three years. Inorganic fertilization increases carnivorous and omnivorous nematodes to 122% and 140%, respectively. Ecological indices showed that soil functioning of CA systems was intermediate between that NF and CT. CA systems were characterized by a highly structured soil food-web compared with CT. Yet, soil processes intensity revealed to be lower in CA with dead mulch compared with CA with living mulch, contrasting with our second hypothesis. The characterization of nematofauna discriminated well the different systems and supports our third hypothesis. Nematode structure and enrichment indices were significantly correlated to soil organic C and N content as well as grain yields. They proved to be powerful bio-indicators of soil functioning in the CA systems studied.