• Authors:
    • Brainard, D.
  • Source: Acta Horticulturae
  • Issue: 950
  • Year: 2012
  • Summary: In response to declines in yield and stand longevity, Michigan asparagus growers are experimenting with multiple cultural practices including irrigation, shallow tillage, and "living-mulches" sown immediately following harvest in late June. Drought stress may play an important role in limiting fern growth and increasing fern susceptibility to pests. Living mulches are thought to reduce soil degradation and suppress weeds, but may also suppress asparagus through competition for water. Research was initiated in Hart, Michigan, USA, in 2008 with the following long-term objectives: (1) to evaluate the effects of irrigation on asparagus yields and weed management under two cropping systems; and (2) to determine the effects of cereal rye ( Secale cereal) living-mulch on soil moisture, weed growth, and asparagus yield. In a research farm field experiment, 4 treatments were examined: (1) no-till with standard herbicides; (2) no-till with standard herbicides plus irrigation; (3) shallow-tillage with rye living-mulch; (4) shallow tillage with rye living-mulch plus irrigation. Irrigation increased weed density and weed dry weight but had no detectable effect on asparagus yields. Rye living mulch (1) reduced soil volumetric water content by approximately 2-3% at 60 cm; (2) suppressed weeds compared to weedy control treatments, but resulted in increased weed density and dry weight compared to conventional herbicide treatments; and (3) had no detectable effect on asparagus yield.
  • Authors:
    • Noyes, D. C.
    • Bakker, J.
    • Brainard, D. C.
    • Myers, N.
  • Source: HortScience
  • Volume: 47
  • Issue: 1
  • Year: 2012
  • Summary: Living mulches growing below asparagus ( Asparagus officinales) fern can improve soil health and suppress weeds but may also suppress asparagus through competition for water or nutrients. The central objective of this research was to test whether cereal rye ( Secale cereale) living mulch, in combination with overhead irrigation, could provide comparable weed suppression to standard residual herbicides without reducing asparagus yields. A field experiment was conducted from 2008 to 2010 in a mature asparagus planting on sandy soils in western Michigan to evaluate the effects of irrigation (none vs. overhead) and weed management systems (standard herbicides vs. rye living mulch) on weed suppression, soil moisture content, and asparagus yield. Rye living mulch and herbicide treatments were established immediately after asparagus harvest in late June of each year. Rye living mulch reduced soil-available water in early August by 26% to 52% compared with herbicide treatments but had no detectable effect on asparagus yields. Compared with herbicide treatments, rye living mulch reduced fall-germinating weed emergence and resulted in lower densities of horseweed ( Conyza canadensis) during asparagus harvest. However, in 2 of 3 years, the living mulch system resulted in higher densities of summer annual weeds - including Powell amaranth ( Amaranthus powellii) and longspine sandbur ( Cenchrus longispinus) - during the fern growth period compared with herbicide treatments. After 3 years, the density of summer annual weeds was more than 10-fold greater in rye living mulch treatments compared with standard residual herbicides treatments. Our results suggest that (1) soil-improving rye cover crops can partially suppress weeds but may also compete with asparagus for soil moisture in dry years unless irrigation is used; and (2) successful use of rye living mulches for weed management will depend on identification of complementary weed management practices to avoid build-up of the summer annual weed seedbank.
  • Authors:
    • Connell, T.
    • Knuteson, D. L.
    • MacGuidwin, A. E.
    • Bland, W. L.
    • Bartelt, K. D.
  • Source: Phytopathology
  • Volume: 102
  • Issue: 5
  • Year: 2012
  • Summary: We used cover crops with demonstrated efficacy against Verticillium dahliae and Pratylenchus penetrans in combination with the biocidal practice of solarization to determine the importance of targeting both organisms for managing potato early dying, an issue relevant to the search for alternatives to soil fumigation. Two experiments were conducted in commercial fields using a split-plot design with cover crop treatments of rapeseed, marigold, forage pearl millet, sorghum-sudangrass, and corn as the main plot factor and solarization as the subplot factor. Cover crops were grown and solarization applied in year one, followed by potato in year two. The main effect of solarization was significant for reduced inoculum levels of both organisms in year two and increased tuber yields. The main effect of cover crop was also significant with lower population densities of P. penetrans following the marigold and millet treatments and of V. dahliae following rape and sorghum-sudangrass. The cover crop treatments influenced yield in only one of the experiments in the absence of solarization. The combinatorial effect of cover crops and solarization resulted in a wide range of pathogen population densities. Mean soil inoculum levels were negatively related to yield for V. dahliae in experiment 1, and for P. penetrans and the P. penetrans x V. dahliae interaction in both experiments.
  • Authors:
    • Horwath, W. R.
    • Wroble, J. F.
    • Munk, D. S.
    • Wallender, W. W.
    • Singh, P. N.
    • Mitchell, J. P.
    • Hogan, P.
    • Roy, R.
    • Hanson, B. R.
  • Source: California Agriculture
  • Volume: 66
  • Issue: 2
  • Year: 2012
  • Summary: Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%). However, practical factors, including the need for different equipment and management approaches, will need to be considered before adopting these practices.
  • Authors:
    • Twomlow, S.
    • Mupangwa, W.
    • Walker, S.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Proponents of conservation agriculture (CA) argue that the CA approach offers the greatest opportunity to increase the productivity in smallholder agro-ecosystems. This study was designed to assess (1) first year maize, cowpea and sorghum yield responses to a combination of reduced tillage and mulching and (2) maize yield responses to rotation with cowpea and sorghum in reduced tillage systems. Two conservation tillage methods (ripping and planting basins) combined factorially with seven mulch levels (0, 0.5, 1, 2, 4, 8 and 10 t ha -1) were compared with conventional mouldboard ploughing. The experiment was run for four consecutive growing seasons allowing for a rotation of maize, cowpea, sorghum and maize in some fields used in the study. Crop yields were determined across all tillage and mulch combinations in each year. Tillage system had no significant effect on maize yield while maize grain yield increased with increase in mulch cover in seasons that had below average rainfall. Mulching at 2-4 t ha -1 gave optimum yields in seasons with below average rainfall. Tillage system and mulching had no significant effect on cowpea yield when soil moisture was not limiting. However, the ripper and basin systems had 142 and 102% more cowpea grain than the conventional system in 2006/2007 because of differences in planting dates used in three systems and poor rainfall distribution. The conventional and ripper systems gave 26 and 38% more sorghum grain than the basin system. Rotating maize with cowpea and sorghum resulted in 114, 123 and 9% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize in the conventional system. In the ripper system, maize-cowpea-sorghum-maize rotation gave 98, 153 and 39% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. In the basin system, maize-cowpea-sorghum-maize rotation gave 274, 240 and 43% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. However, long term studies under different soil, climatic and socio-economic conditions still need to be conducted to substantiate the observations made in the reported study.
  • Authors:
    • Zhang, J.
    • Li, B.
    • Xie, G.-L.
    • Cui, Z.-Q.
    • Ojaghian, M. R.
  • Source: Australasian Plant Pathology
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: This study was conducted to evaluate the potential of biofumigation in three Brassica crops including Brassica napus, Brassica juncea and Brassica campestris against potato stem rot caused by Sclerotinia sclerotiorum in field tests. Results from field trials carried out in three naturally infected potato fields during three cropping seasons of 2008-2010 showed that the Brassica crops used as green manure cover crops were able to significantly reduce disease incidence and mean percentage of dead plants (as a proportion of infected plants). Although results varied somewhat by field site and year, B. juncea generally provided the highest level of control, averaging greater than 55.6 % reduction in disease incidence over all fields and years, compared to average disease reductions of 31.6 and 45.8 % for the B. napus and B. campestris crop treatments, respectively. Furthermore reduction of dead plants averaged 61.6, 39.2 and 32.1 % for B. juncea, B. napus, and B. campestris, respectively. In this study, Brassica crops showed various significant inhibitory effects in different fields and years indicating that disease development is affected by other factors including environmental conditions.
  • Authors:
    • Van Eerd, L. L.
    • Vyn, R. J.
    • Lauzon, J. D.
    • O'Reilly, K. A.
  • Source: Canadian Journal of Soil Science
  • Volume: 92
  • Issue: 2
  • Year: 2012
  • Summary: In order to improve N best management practices in southwestern Ontario vegetable farming, the effect of cover crops on N dynamics in the fall and spring prior to sweet corn planting and during sweet corn season was assessed. The experiment was a split plot design in a fresh green pea - cover crop - sweet corn rotation that took place over 2 site-years at Bothwell and Ridgetown in 2006-2007 and 2007-2008, respectively. The main plot factor was fall cover crop type with five treatments including oat (Avena saliva L.), cereal rye (Secale cereal L.), oilseed radish (OSR; Raphanus sativus L. var. oleoferus Metzg Stokes), mixture OSR plus cereal rye (OSR&rye) and a no cover crop control. Compared with no cover crop, sweet corn profit margins were higher by $450 ha(-1) for oat at Bothwell and $1300 and $760 ha(-1) for OSR and OSR&rye, respectively, at Ridgetown. By comparing plant available N over the cover crop season, the cover crops tested were more effective at preventing N loss at Bothwell than at Ridgetown likely due to higher precipitation and sandier soil at Bothwell. Despite differences in site characteristics, cover crops did not result in increased plant available N compared with no-cover during the sweet corn season at either site, indicating that these cover crops will not provide an N credit to the following crop and growers should not modify N fertilizer applications based on cover crops.
  • Authors:
    • Shah, S. C.
    • Chen, Z. S.
    • Adhikari, K. R.
    • Ghimire, R.
    • Dahal, K. R.
  • Source: Paddy and Water Environment
  • Volume: 10
  • Issue: 2
  • Year: 2012
  • Summary: Despite being a major domain of global food supply, rice-wheat cropping system is questioned for its contribution to carbon flux. Enhancing the organic carbon pool in this system is therefore necessary to reduce environmental degradation and maintain agricultural productivity. A field experiment (November 2002-March 2006) evaluated the effects of soil management practices such as tillage, crop residue, and timing of nitrogen (N) application on soil organic carbon (SOC) sequestration in the lowland of Chitwan Valley of Nepal. Rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) were grown in rotation adding 12 Mg ha -1 y -1 of field-dried residue. Mung-bean ( Vigna radiata L.) was grown as a cover crop between the wheat and the rice. Timing of N application based on leaf color chart method was compared with recommended method of N application. At the end of the experiment SOC sequestration was quantified for five depths within 50 cm of soil profile. The difference in SOC sequestration between methods of N application was not apparent. However, soils sequestered significantly higher amount of SOC in the whole profile (0-50 cm soil depth) with more pronounced effect seen at 0-15 cm soil depth under no-tillage as compared with the SOC under conventional tillage. Crop residues added to no-tillage soils outperformed other treatment interactions. It is concluded that a rice-wheat system would serve as a greater sink of organic carbon with residue application under no-tillage system than with or without residue application when compared to the conventional tillage system in this condition.
  • Authors:
    • Oliveira, E. B. de
    • Moraes, A. de
    • Pelissari, A.
    • Reis, E. F. dos
    • Ruaro, L.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 47
  • Issue: 4
  • Year: 2012
  • Summary: The objective of this work was to assess the effect of soil management systems and winter cover crops on the number of propagules of Fusarium spp. in soil, the incidence of sudden death syndrome (SDS), and the productivity of the soybean cultivars CD 206 and FT Fenix. Two experiments were carried out in the 2006/2007 and 2007/2008 crop years. The experimental design was a randomized complete block in a split-split plot arrangement, with three replicates. Two soil tillage systems were evaluated: no-tillage and plowed soil at a depth of 25 cm. The soil covers used were: black oat, with two planting densities; black oat+vetch; ryegrass; and fallow. The incidence of the disease in the 2006/2007 crop year in the cultivar FT Fenix was lower than in CD 206. In the 2007/2008 crop, there was no significant difference. There was an increase in productivity, of 125 kg ha -1, in the plowed treatment, when compared to no-tillage. The cover with black oat+vetch showed a higher number of propagules of Fusarium spp. in soil in the 2006/2007 crop year. However, in the second year, this difference was not observed. The soil management systems and winter cover crops used do not influence the incidence of SDS in soybean cultivars or the number of Fusarium spp. propagules in soil. The plowed system provides an increase in soybean yield in the second year of management.
  • Authors:
    • Portela, S. I.
    • Andriulo, A. E.
    • Restovich, S. B.
  • Source: Field Crops Research
  • Volume: 128
  • Year: 2012
  • Summary: The agricultural system of the Humid Pampas consists of continuous cropping of soybean and maize under no tillage. This system may loose nitrogen (N) through leaching during the early and final stages of summer crops and during fallow. In this study (2005-2011) we evaluated the effect of fall-winter species (rescue grass, ryegrass, oats, barley, vetch, rape seed and forage radish) and a mixture of vetch and oats used as cover crops on water and N dynamics and main crop yield. Above-ground biomass production and N uptake by cover crops ranged from 1.1 to 11.9 Mg ha(-1) and from 17 to 223 kg N ha(-1), respectively, depending on sowing and killing dates and on the preceding crop. At killing, soil nitrate content in treatments with cover crops was 50-90% lower than in the control, reducing spring N leaching risk. When preceding maize, cover crops were killed in winter or early spring and their low C/N ratio (12-38) favored N release through residue decomposition. Vetch and rape seed as predecessors of fertilized maize increased residual N by approximate to 50 kg NO3-N compared to the control, posing the risk of fall N leaching. When preceding soybean, cover crops were killed in spring and, although their C/N ratios were higher (13-85), crucifers and legumes increased soil nitrate content. Maize yield was related to soil N availability at sowing (control and legumes > crucifers > grasses) which was inversely related to the preceding cover crop C/N ratio at killing. In normal to high rainfall years there were no differences in soybean yield among treatments. Water use by cover crops did not affect the main crop production except during an exceptionally dry year. Best synchronicity between N release from cover crop residues and harvest crop demand was achieved with the oats-vetch mixture before maize and with grasses before soybean. (C) 2011 Elsevier B.V. All rights reserved.